PEPTIDES FROM DOLLAR I(VARICELLA-ZOSTER) AND OTHER VIRUSES FOR HIV-2 DIAGNOSIS AND THERAPY

Abstract: Viral chimeric peptides useful for HIV diagnostic testing and therapy of HIV are described which comprise a loop sequence from a Varicella-Zoster virus protein and additional portion(s) that enhance antigenic reactivity of the loop with anti-HIV antibody. The peptides typically are at least 16 amino acid residues long and advantageously contain additional portions that have some sequence identity with peptide sequences adjacent to a cystine loop of HIV-1 gp41. The peptides immunologically cross-react with protein from a wide variety of HIV-2 strains. Peptides according to some embodiments of the invention are less hydrophobic and more basic for improved water solubility compared to peptides from naturally occurring strains of HIV. These chimeric peptides differ greatly from the naturally occurring sequences and are not identified as corresponding to any particular viral species or strain.

Description: Peptides from Varicella-Zoster and other Viruses for HTV-2 Diagnosis and Therapy Field of the Invention The invention relates to diagnostic tests and antigens used in such tests. More specifically, the invention relates to peptide sequences and sequence modifications of peptides that comprise sequences from the open reading frame protein 51 of Varicella-Zoster and which have utility for the detection of HIV-2 infection. Background of the Invention The retrovirus known as Human Immunodeficiency Virus (HIV, also HTLV-LLI), causes Acquired Immunodeficiency Syndrome (AIDS) in humans (Gallo, et al., Science 224:500 (1984); Sarngadharan, et al. , Science. 224:506 (1984), Popovic, et al. , Science 224:497 (1984). Infection by this virus results in the appearance of antibodies in the blood that react against various molecular parts of the virus, particularly the envelope proteins. The antibody-based binding reaction between antibodies from an infected patient and a viral antigen(s) is used in various methods for detection of HIV infection, such as latex agglutination and ELISA. Of the retroviruses, HIV has received the most attention recently because of the widespread damage caused by this virus. Initially, tests developed for detecting HIV infection contained antigens corresponding to protein of the first discovered strains of this virus, termed "HIV-1" as described, for example, by U.S. patent Nos. 4,708,818; 4,647,773 and 5,135,864. Later tests have used additional antigens that, although cross-reacting with HIV-1 types of this virus, generally react more specifically with a later discovered type of HTV termed "HTV-2" as described, for example, by U.S. patent Nos. 5,055,391; 4,839,288 and 5,066,782. The discovery of yet further strains of this virus species, such as those termed "HIV-3" or "HIV-1 Group O" has prompted the use of additional antigens for detecting HIV infection that react preferably with these samples as described, for example, by U.S. patent Nos. 5,567,603 and 5,304,466. When used in screening for prior HIV exposure, a blood sample typically is contacted with test antigen(s), followed by detection of binding between test antigen and sample antibody. Such detection is complicated not only by the classification of HTV into various strains such as HIV-1, HIV-2, HIV-3 and their various "clades," based on antibody reactivity, but also by the rapid mutation of HTV, even within the same infected individual. A central challenge of HIV testing and therapy is in finding antigens that cross react with these different antigenic types. One solution to the diversity problem in the diagnostic area has been to include multiple protein antigens in a diagnostic test. In this way separate antigens, each having multiple epitopes from diverse regions of HIV protein can, as a mixture, react with diverse sera of patients infected with HIV. Drawbacks of this strategy include, among other tilings, a higher degree of non-specific binding reactions due to the variety of proteins used and a limitation in the amount of total antigen that can be added to a test, which typically has a small solid phase surface or reaction volume The HIV antigen diversity problem is a major challenge to successful HIV diagnosis and therapy, and directly causes false test results. Unpublished co-pending applications 60/091,659 filed July 2, 1998 (attorney docket No. 073294/0160), 60/072,863 filed January 28, 1998 (attorney docket No. 073294/0161), 60/072,981 filed January 29, 1998 (attorney docket No. 073294/0162), 60/088,229 filed June 5, 1998 (attorney docket No. 073294/0172), 60/100,422 filed September 15, 1998 (attorney docket No. 073294/0191), 60/112,026 filed December 11, 1998 (attorney docket No. 073294/0178), 60/(1104,686) filed October 16, 1998 (attorney docket No. 073294/0197) and 60/104,685 filed October 16, 1998 (attorney docket No. 073294/0198), which are herein incorporated in their entireties by reference, teach how to engineer "Universal" peptides that react more broadly with various strains of HIV to address this problem. Those applications also describe an approach that replaces a large recombinant protein having many different epitopes from various regions of HTV with one or more peptides that correspond to a single epitopic region of HIV. In this approach, alternate peptides from a common region are engineered to approximate various epitopes that HIV may differentiate into. This strategy of employing diversity within one immunologically important point of an HIV protein, in contrast to combining diversity between epitopes from various regions, yields improved assays and therapy, as detailed in the above-referenced unpublished applications. For example, U.S. No. 60/104,685 describes an SP and HIV-1 chimera that simulates a primordial HIV protein epitope sequence that cross- reacts with a surprisingly broad range of HIV strains. Because of the close genetic relationship between HIV-1 and HIV-2 strains, antigens that resemble HIV-1 protein epitope(s) may react with antibodies made from exposure to HTV-2 strains. Conversely, antigens designed from lysates, proteins and peptides from HTV- 2 may cross-react with HIV-1 strains. Accordingly, there is a need for antigens that react more specifically with HIV-2 strains in order to classify an infection as originating from an HIV-1 strain or an HIV-2 strain. The sensitivity of HIV detection is another important problem in HIV detection that is influenced by the test antigen used. If a test could be made more sensitive by use of a more reactive antigen, the test could detect HIV detection at an earlier time, and thus allow earlier treatment. Thus, there is a continuing need for HIV antigens that react more strongly with antibodies in test samples. Of course, there is an urgent need for antigens that are potent for HIV therapy as well as for HIV detection. The rapid mutation of HIV allows the virus a quick genetic response to escape destruction by the immune system. Thus, new HIV antigens, particularly antigens modeled after broader features that are not limited to a specific type of virus and that display new epitopes can directly be used for therapy and prophylaxis against HIV infection as well. Summary of the Invention It is an object of the invention to improve the test specificity of HIV detection by providing a peptide sequence that reacts well with sera from patients infected with HTV-2 strains and that reacts less well with sera from patients infected with HIV-1 strains. It is another object of the invention to provide peptide sequences that improve HTV-2 test sensitivity over existing tests using previously known antigens. It is yet another object of the invention to provide peptide vaccines against infectious agents. It is another object of the invention to provide methods for deriving HIV-2 antigen cross-reactive peptides and methods for testing HIV-2 infection. Further objects of the invention readily will be apparent from the disclosure herein. One embodiment of the invention is a peptide useful for detecting HTV-2 infection, preferably having a length of at least 16 amino acid residues, and comprising a core Varicella-Zoster protein 51 sequence of SEQ ID NO: 1 (C-A-F-R-Q-Xl-C) wherein XI is selected from the group consisting of R, I, L. V. T, H, Q, C, W, F, and Y. Another embodiment of the invention is a peptide useful for detecting HTV-2 infection, having a length of at least 16 amino acid residues, and comprising a core sequence A-W-G-C-A-F-R-Q combined with a sequence from the immunodominant region of gp41 from HIV-1. Another embodiment of the invention is a method for improving a peptide useful for HTV-2 testing, comprising replacing a hydrophobic amino acid of the peptide with a less hydrophobic amino acid. Yet another embodiment of the invention is a method for improving a peptide useful for HIV-2 testing, comprising increasing the alpha helix content of the peptide. In yet another embodiment, the increase in alpha helix content is made outside of a cystine loop immunodominant region. Another embodiment of the invention is a reagent for immunological detection of anti- HTV antibody in a blood sample, comprising a dried antigen that, upon rewetting with water or a clinical sample, substantially reacts with antibodies from patients exposed to HTV-2, wherein said antigen is between 16-50 amino acids long and possesses a sequence described herein. Another embodiment is a method of detecting HTV-2 infection, comprising incubating a blood sample or blood derivative with a peptide described herein, followed by determination of binding between antibody in the blood sample or blood derivative and the peptide. Yet another embodiment is a kit for determining infection with HTV-2, comprising instructions for how to use (for example, an instruction booklet, label or electronic message) and a device for detecting the presence of anti-HIV-2 antibody in a blood sample or blood derivative, wherein the device comprises a peptide described herein. Yet another embodiment of the invention is a method of improving reactivity of an antigenic peptide for a diagnostic test of HIV. comprising replacing a seven amino acid long cystine loop segment of the HIV-1 gp41 protein or the HIV-2 gp36 protein with a sequence selected from the group consisting of SEQ ID NO: 3 CAFRQRC; SEQ ID NO: 19 CAFRQIC; SEQ ID NO: 20 CAFRQQC; SEQ ID NO: 21 CAFRQTC; SEQ ID NO: 22 CAFRQCC; SEQ ID NO: 23 CAFRQLC; SEQ ID NO: 24 CAFRQWC; SEQ ID NO: 25 CAFRQHC; SEQ ID NO: 26 CAFRQFC and SEQ ID NO: 27 CAFRQYC. Yet another embodiment of the invention is a method of increasing HTV-2 cross- reactivity of an antigenic peptide for a diagnostic test of HIV. comprising replacing a seven amino acid long cystine loop segment of the HIV-1 gp41 protein with a sequence selected from the group consisting of SEQ ID NO: 99 C-A-G-R-Q-V-C: SEQ ID NO: 100 C-A-G-K- Q-V-C; SEQ ID NO: 101 C-A-G-R-L-V-C; SEQ ID NO: 102 C-A-D-R-Q-V-C; SEQ ID NO: 103 C-A-N-R-Q-V-C; and SEQ ID NO: 104 C-A-G-K-L-V-C. Another embodiment of the invention is a method of improving reactivity of an antigenic peptide for a diagnostic test of HTV-2, comprising replacing a leucine ("L"), isoleucine ("I") or valine ("V") from the peptide with a hydrophilic amino acid. A further embodiment is a method of detecting HIV-2 infection from a blood sample with a whole blood assay device, the device comprising a blood filter that contacts a reagent layer that contains at least one peptide described herein, wherein the method comprises applying one or more drops of whole blood to the blood filter and determining the presence of one or more visual reactions in response to the presence of anti-HIV antibody in the blood sample. Brief Description of the Figures Figure 1 shows representative peptides in accordance with embodiments of the invention and comparison peptides. Figure 2 shows data obtained from testing HIV-1, HIV-2 and HIV-3 (HTV-1 Group O) infected blood samples with peptides according to the invention, having lengths of 18, 23 and 28 amino acid residues (SEQ ID NO: 5, 7 and 10 respectively). Data are presented as: N" to denote no visual reaction: " 1 + , 1 + + , 2 + , 2+ + " etc to denote progressively increasing visual reaction: "ST" to denote slight tinge of color reaction; "SH" to denote shadow coloration of a weak reaction; and "ND" to denote not done. Figure 3 shows data obtained from testing HIV-1, HIV-2 and HIV-3 infected blood samples with two 18 mer peptides of SEQ ID NO: 5 and 6, that differ by an isoleucine substitution for an arginine within a cystine loop region. Figure 4 shows data obtained from testing HIV-1, HIV-2 and HTV-3 infected blood samples with a mixture of peptides of SEQ ID NO: 5, 9 and 15 and also with peptide of SEQ ID NO: 5 alone. Figure 5 depicts the relative bulk hydrophobic profiles for peptides of SEQ ID NO: 16 and 17. The thick line in this graph represents a primate gp36 immunodominant region sequence (SEQ ID NO. 16) from SIV and is similar to that from HIV-2. SEQ ID NO. 17 is from Varicella-Zoster. The y-axis displacement of these lines represents predicted bulk hydrophobicity. Hydrophobicity decreases with an increase in y. Figure 6 depicts the relative bulk hydrophobic profiles for peptides of SEQ ID NO: 16 and 18. The thick line in this graph represents the primate gp36 immunodominant region sequence (SEQ ID NO. 16) from SIV. SEQ ID NO: 18 is a representative sequence according to an embodiment of the invention. The y-axis displacement of these lines represents predicted bulk hydrophobicity. Hydrophobicity decreases with an increase in y. Figure 7 depicts analytical sensitivity of tests that use a primate sequence from gp36 (SEQ ID NO. 44) compared with that of tests having 18, 23 and 28 amino acid long chimeric peptides with increasing alpha helix (SEQ ID NO: 5, 7 and 10). The chimeric peptides have equivalent sensitivity to that of the native peptide. Figure 8 depicts the use of HIV-1- SIV chimera peptides for detecting HIV-2 infected blood specimens with a flow-through test. SEQ ID NO: 44 is a native sequence from the STV gp36 immunodominant region. The other sequences tested are representative embodiments of the invention. Detailed Description of the Preferred Embodiments The inventors have explored chimeric peptides from various viruses and virus strains for the purpose of improving the sensitivity and selectivity of HIV tests and therapeutics. This work led to several discoveries relating to chimeric peptides formed from a Varicella- Zoster protein and peptide sequences of HIV-1 protein, which provide unexpected improvements in HIV testing and therapy, particularly for HIV-2 testing. This work also led to a discovery of broadly reactive peptide sequences that contain epitopes which represent epitopes of an evolutionary precursor of primate immunodeficiency virus. Peptides according to this embodiment cross-react with a variety of strains that infect human that are classified as HTV-1, HTV-1 Group O and HIV-2 These discoveries are discussed separately below, together with related embodiments of the invention Varicella-zoster - HTV-1 Chimeric Peptides with Superior Properties for Detecting HTV (1) Combine a V. zoster Gene 51 cystine loop with an HIV-1 Antigen-loop Enhancer The inventors explored cystine loop regions of viral proteins and selected a Vancella- zoster ("Varicella-Zoster") virus gene 51 product sequence C-A-F-R-Q-R-C sequence (SEQ ID NO 3) for further study This 7 ammo acid sequence differs from a cystme loop sequence C-A-F-R-Q-V-C (SEQ ID NO 4) common to both simian and human viruses by a hydrophobic (V) to basic (R) amino acid substitution Chimeric peptides comprised of the seven residue Varicella-Zoster sequence and of HIV-1 peptide sequences were prepared and studied for use in HIV detection Peptide chimeras that comprised, along with the Varicella- Zoster sequence, increasing length of HIV-1 peptide showed correspondingly increased reactivity in HTV lmmunoassays, particularly HIV-2 assays The term "chimera as used here, means that the peptide is a composite of peptide sequences that come from two different species or types of viruses, for example the HTV-1 species of virus and the Varicella-Zoster species of virus In some advantageous embodiments, however, the portion from the HIV-1 species of virus differs significantly and is not identifiable as belonging to any particular strain or species Furthermore, the portion from the Varicella-Zoster species can be modified according to certain principles enumerated herein or otherwise apparent to the skilled person, and after modification is not identifiable as belongmg to any particular virus strain or species A chimera according to an embodiment of the invention, comprises a 7 ammo acid Varicella-Zoster segment and at least 9, preferably at least 11 and more advantageously at least 15 or more ammo acid residues attached to at least one end of the Varicella-Zoster segment The Varicella-Zoster protein 51 sequence is taught by Davidson and Scott, /. Gen. Virol 67 1759-1816 (1986) In an embodiment of the invention, the added ammo acids form a sequence that antigemcally enhances a known HTV-1 gp41 immunodominant region sequence The term "antigenically enhances a known HTV-1 gp41 immunodominant region sequence" means an antigen that comprises a sequence which, when combined with a 7 member cystme loop sequence from an HTV-1 strain (for ex. C-K-G-K-L-I-C) enhances that sequence's cross- reactivity with antibodies specific for a known naturally occurring gp41 sequence. Furthermore, an enhancing peptide sequence as termed here, typically shares at least some sequence identity with a corresponding known sequence that is adjacent (contiguous to) the cystine loop of this protein. By way of example, SEQ ID NO: 5 (L-E-D-Q-A-R-L-N-A-W- G-C-A-F-R-Q-R-C) shares 64% sequence homology with the Group O subtype M consensus sequence of SEQ ID NO: 105 (L-K-D-Q-Q-L-L-N-L-W-G-C-K-G-K-L-I-C) because 7 of the 11 amino acids outside the loop have the same identity. In making this comparison, only amino acids within 25 positions of the loop should be considered. In an advantageous embodiment, the amino acids within 25 positions from the loop share less than 70% sequence homology with a known HIV-1 env41 protein. The identity comparison used to select a suitable sequence to link with the Varicella Zoster cystine loop segment is founded on the inventors ' discovery that amino acids positioned near (i.e. within about 25 amino acids, particularly within 21 amino acids) the cystine loop affect the antigenicity of the loop and often have no cross-reactivity with anti- HTV-1 antibodies in the absence of the cystine loop. Generally, the neighboring amino acid residues which affect the loop antigenicity contain at least 30% and more advantageously, at least 50% sequence identity with a corresponding known gp41 protein sequence. When making this comparison, it is advantageous to look at the segment of amino acids adjacent to the amino terminal side of the loop. In another embodiment, however, residues on both the amino terminal side and the carboxyl terminal side of the loop are considered. A large number of "antigenically enhancing" sequences work according to this formula. Co-pending U.S. patent applications 60/091,659 filed July 2, 1998 (attorney docket No. 073294/0160), 60/072,863 filed January 28, 1998 (attorney docket No. 073294/0161), 60/072,981 filed January 29, 1998 (attorney docket No. 073294/0162), 60/098,705 filed September 1, 1998 (attorney docket No. 073294/0168), 60/088,229 filed June 5, 1998 (attorney docket No. 073294/0172), 60/100,422 filed September 15, 1998 (attorney docket No. 073294/0191), 60/(104,686) filed October 16, 1998 (attorney docket No. 073294/0197), PCT application "Universal Peptides" filed June 4, 1999 (attorney docket No. 036034/0106) and 60/104,685 filed October 16, 1998 (attorney docket No. 073294/0198) describe antigenically enhancing sequences according to the meaning used herein. A peptide comprising at least a 7 amino acid long segment of a sequence listed in one of these referenced applications can be combined with a Varicella Zoster loop to form a chimera. This sequence is continuous with the immunodominant loop of gp41, as exemplified by the sequences shown in Figure 1. Each 7 amino acid long or larger sequence from the sequences disclosed in the co-pending applications specifically is contemplated for combining with a Varicella Zoster loop to form a suitable chimera according to the invention. Within the chimera, the HIV-1 enhancing peptide portion facilitates reaction of the cystine loop portion from Varicella Zoster with antibodies from at least some HIV-2 infected blood samples. Preferably, such chimeric peptides cross-react with a large variety of HIV-2 infected samples. Even more preferably, such chimeras do not react well with HIV-1 samples and are useful to distinguish between HTV-1 and HIV-2 infection. In another embodiment, the amino acid sequence(s) added to the Varicella-Zoster sequence are known sequences from HTV-1. particularly HIV-1 Group O, as described by, for example, by Eberle et al. J. Vir. Meth. 67: 85,88 (1997) and U.S. Nos. 5,567,603 and 5,304,466. According to yet further embodiments, a naturally occurring sequence is further modified as described in one or more of the co-pending applications referred to above. Chimeras in accordance with the invention may include an antigenically enhancing HTV-1 sequence on the amino terminal side of the Varicella-Zoster loop and/or an antigenically enhancing HIV-1 sequence on the carboxyl terminal side of the Varicella-Zoster loop. Most advantageously, the chimera comprises an enhancing sequence portion of at least 11 amino acids long on the amino terminal side and contiguous with the loop. It is emphasized that the claimed peptides and peptides constructed according to principles of the invention differ significantly from naturally occurring forms and are not identified as belonging to any particular viral species or strain. Furthermore, these chimeras were found to have new and advantageous properties for HIV tests, and particularly for tests of infection by HIV-2. (2) Preferred Helix Turn Profile for the Di-cysteine Loop Region of the Chimera The cystine loop sequence taken from the Varicella-Zoster protein may be modified according to certain principles. Derivatives of the cystine sequence of Varicella-Zoster ORF 51 protein which evince a "s-s-s-s-h-s-s" helix turn profile, when modeled by the peptide analysis software program, "Peptide Companion Version 1.24 for Windows" from Peptides International, Inc. Louisville, Kentucky 40299 U.S.A. are particularly useful. As revealed by output from this program, the Varicella-Zoster cystine loop structure differs conformationally from the HIV-1 gp41 immunodominant region loop, which lacks a helix twist. The inventors discovered that the different conformation of the Varicella-Zoster loop is advantageous for engineering peptides for HTV tests and therapy. Furthermore, changes to this loop sequence which maintain the s-s-s-s-h-s-s mrn profile, as determined by use of the referenced software, are useful for peptides in accordance with further embodiments of the invention. For example, the following sequences have the advantageous peptide mrn profile and represent further embodiments: SEQ ID NO: 19 CAFRQIC; SEQ ID NO: 20 CAFRQQC; SEQ ID NO: 21 CAFRQTC; SEQ ID NO: 22 CAFRQCC; SEQ ID NO: 23 CAFRQLC; SEQ ID NO: 24 CAFRQWC; SEQ ID NO: 25 CAFRQHC; SEQ ID NO: 26 CAFRQFC and SEQ ID NO: 27 CAFRQYC. According to an embodiment of the invention, a chimeric peptide advantageously comprises a Varicella-Zoster sequence chosen from this list linked with one or more peptide sequences that antigenically enhance the HTV-1 loop. The namral Varicella-Zoster sequence of CAFRQRC, however, is preferred because peptides having this sequence give superior performance under some conditions. For example, replacing the arginine in this sequence with isoleucine caused greater non-specific background when used in an immunoassay. as seen by the data of Figure 3. and the naturally occurring arginine is advantageous at this position. (3) Decrease Bulk Hydrophobicity within the Varicella-Zoster Loop Sequence Another discovery from the study of Varicella Zoster protein sequences was that peptides having a lower bulk hydrophobicity within the cystine loop region cross-react more specifically with HIV-2 antigens. Figure 5 depicts the hydrophobicity scale of a representative (HTV/SIV) primate gp36 immunodominant loop sequence (SEQ ID NO. 16) and of a more hydrophilic (less hydrophobic) sequence of Varicella Zoster (SEQ ID NO. 17) according to this embodiment of the invention. Figure 6 shows, for example, a comparison profile of another sequence in accordance with the invention (SEQ ID NO. 18) with the primate loop sequence SEQ ID NO. 16. These figures show predicted bulk hydrophobicity of sequences obtained with the software cited above. Most advantageous embodiments of the invention according to this discovery are peptides comprising a cystine loop region that comprises an arginine adjacent to the amino terminal side of the loop amino terminal cysteine residue, as shown by, for example, SEQ ID NO. 3. Without wishing to be bound by a particular theory of this embodiment of their invention, the inventors theorize that the antigenically active cysteine loop portion of a peptide in accordance with the embodiment is solvated better and reacts better with components of the immune system by virtue of its better water solubility. Furthermore, this feature is particularly important when the peptide is attached to a particle or other solid phase such as a membrane used in diagnostic tests. Keeping the cystine loop off the solid phase surface helps the loop react faithfully with antibodies and other components of the immune system. The claimed peptides described herein, in fact, are particularly useful for solid phase binding assays wherein a peptide is immobilized onto a solid phase. Thus, having an arginine, or other amino acid that is less hydrophilic than valine, in the 6 th position of this loop provides an advantageous peptide, particularly when the amino acid is chosen to maintain a predicted s-s-s-s-h-s-s helix mm profile, and also particularly when it is desired to keep the loop in solution with the non-loop portion attached, directly, or indirectly via a conjugated moiety, to a solid phase. (4) Increase Bulk Hydrophobicity in the Region Adjacent to the Amino Terminal Side of the Varicella-Zoster Loop Sequence Yet another discovery from a study of the Varicella-Zoster sequence is that increasing the bulk hydrophobicity character of the peptide portion adjacent to the amino terminal side of the cystine loop portion yields a peptide antigen with improved characteristics such as sensitivity or selectivity in HIV-2 infection tests. Figure 5 depicts a comparison between this portion of the HIV-2/SIV primate sequence and the Varicella-Zoster sequence. The Varicella Zoster sequence is significantly more hydrophobic than the HIV-2 sequence in this region. Figure 6 compares this portion of primate sequence with the corresponding portion of a chimeric peptide in accordance with the invention. Without wishing to be bound by any particular theory of this embodiment of the invention, the inventors theorize that the increased hydrophobic character of the portion adjacent to the amino terminal side of the loop helps stabilize the alpha helix there because that portion forms less hydrogen bonding and ionic binding with water and other molecules, which could interfere with its structure. Furthermore, the hydrophobic character helps orient the cysteine loop region into the aqueous medium by binding to a solid surface when used in immunoassays. In one embodiment, a more hydrophobic portion from 1 to 6 amino acids off of the amino terminal side of the cystine is particularly advantageous when the peptide is used as an immobilized binding partner in an immunoassay. In this use, the more hydrophobic region is at least 6 amino acids long, and is "more hydrophobic" than the corresponding portion of a naturally occurring peptide sequence such as the HIV-2/STV sequence exemplified in Figure 5 and as determined by prediction of bulk hydrophobicity with the above-referenced software program. Each chimeric peptide according to an embodiment of the invention is useful for detecting HIV infection. That is, each chimera has the biochemical quality of binding at least some antibody from at least one sample of HIV infected blood. Most advantageously, in this respect is the quality of antibody binding to peptides. Thus, each chimera according to this embodiment can be used in an HIV test that reacts with at least one HIV-2 infectious sample to yield a positive test result. Binding assays used for this purpose are well known, and can be carried out by various procedures, such as an ELISA test or dot-blot assay described herein. (5) Increase Secondary Structure of the Chimeric Peptide It was further discovered that increasing the amount of secondary structure of the chimeric peptide, particularly outside the cystine loop region provides improved HTV-2 detection. Secondary structure in this context refers to polypeptide helix or pleated sheet that forms primarily by multiple hydrogen bonding between peptide bond hydrogen and oxygen. Most advantageous is alpha helix strucmre that forms within a stretch of the peptide to the amino teπninal side of the loop. The inventors discovered that placing or increasing alpha helix on the amino terminal side of the cystine loop Varicella-Zoster portion in particular stabilizes the antigen structure. The degree of stabilization has a great influence on performance of a peptide used in diagnosis or therapy. For example, the inventors discovered that adding a five amino acid long helix portion "A-W-E-K-T" to the amino terminal end of an 18 mer chimera comprised of a Varicella-Zoster sequence with an antigenically enhancing HIV-1 sequence provided greater test sensitivity. These data are shown in Figures 2 and 3. Without wishing to be bound by any one theory of an embodiment of the invention, the inventors theorize that adding this 5 amino acid long helix, which is not a known epitope of HTV, increases structural stability of the peptide when used in an aqueous environment for binding reactions with anti-HIV-2 antibodies. The increased stability allows the peptide to react more favorably to give more sensitive tests but also changes the immunological characteristics of the antigen. In particular, placement of a tryptophan ("W") at this position 15 residues from the amino terminal side of the cystine loop, decreases cross-reactivity with HTV-1 while maintaining the tendency of this portion of the peptide to form alpha helix and is a particularly advantageous embodiment. The theory of increased stability derives further support from the experimental observation that when this same peptide helix was lengthened by an additional 5 amino acids (to 10 amino acids at the amino terminal portion), the antigen thus formed showed yet even better sensitivity for testing HIV-2. These data are shown in Figure 2. In alternative embodiments, the alpha helix portion may be 6. 7, 8, 9, 10, 11, 12 or more amino acids long. In other advantageous embodiments alpha helix is added to the carboxyl terminal side of the Varicella-Zoster loop. Of course, other amino acid combinations, for example, that provide alpha helix extending further away from the amino terminal side of the HIV-1 cystine loop region are advantageous and are contemplated. For example, in preferred embodiments, the following substitutions of the first 16 positions beginning 21 amino acids to the amino terminal side of the loop are used to form predicted alpha helix structure: TABLE 1 Position Number Amino Acid Possible Amino Acid Substitutions 1 R QMWANDEGHILKFPST 2 A MRDEHK 3 R MADEHK 4 L QMRANDEGHKFPS 5 Q MRADEGHLKPS 6 A MDEK 7 W LQMRANDCEGHKFPST 8 E KD 9 K QTMWRANDEH 10 T QMWRAND 11 L QMWRAEHKFST 12 E KHDAM 13 D NKRHEQWFMILTSCGP 14 Q MRADEHLKS 15 A ME 16 R QMADEHLKFS Chimeric peptides that comprise one or more of these combinations are contemplated for the invention. Of course, further extensions of the peptide chain on either side of the immunodominant region are possible and form advantageous antigens in accordance with these principles. Advantageous amino acids in this regard may be determined by prediction from a peptide analysis software program, "Peptide Companion Version 1.24 for Windows" from Peptides International, Inc. Louisville, Kenmcky 40299 U.S.A. The Chou-Fasman Conformational parameters are used in determining which amino acids can be changed within the helix in a manner to preserve the helix, with corresponding advantageous antigenicity of the peptide. When selecting a sequence to form a helix on the amino terminal side of the loop, it is particularly helpful to use a sequence from an HIV-1 "O" type strain that naturally has more alpha helix in this region compared to other non-O strains of HIV. Advantageous chimeras in accordance with this embodiment of the invention comprise at least one antigenically enhancing sequence that has at least 50%, and more advantageously at least 65% sequence similarity to a known O-type sequence. (6) Change a Hydrophobic Amino Acid in the Chimera to a Hydrophilic Amino Acid Variations of the chimeric peptides having altered and useful immunological characteristics can be prepared by changing a hydrophobic amino acid of the Varicella-Zoster portion or of the antigenically enhancing HTV-1 portion (for example, leucine) to a hydrophilic amino acid (for example, glutamine or arginine). It was further discovered that such a modification could be made outside the immunodominant region, outside the cysteine loop but within the immunodominant region, or even within the cysteine loop itself. Altering a hydrophobic amino acid to a hydrophilic amino acid in the chimera can improve its solubility in water. An increase in water solubility leads directly to improved diagnostic assay or vaccine performance by allowing a greater amount of peptide to be used. This attribute also facilitates the use of more than one peptide together in the same solution without causing a precipitate at higher concentrations of one or more of the peptides. As a result, an antigen mixmre for testing of multiple variants of the HIV protein epitopes is more possible. In other words, the embodiments that provide peptides of greater solubility in water solution allow multiple species of peptides with alternative epitopes to be mixed and used more advantageously together in the same aqueous solution. The ability to present multiple variants (i.e. epitopes that react with multiple types of a virus) is an intended consequence of the invention, and which can allow improved testing and therapy, compared to materials and procedures that use proteins or larger polypeptides. Data was obtained, for example, showing that a recombinant antigen for HIV-2 used at 200 ng per spot gave false positives, but that a chimera peptide according to an embodiment of the invention when used at 225 ng per spot did not give false positives with the same clinical samples. A peptide antigen according to one embodiment of the invention advantageously is greater than 16 amino acid residues long but smaller than 100 amino acid residues long and particularly less than 50 amino acids long. This size range is teπned "intermediate size." The upper size limit reflects the fact that an intermediate size peptide according to the invention is shorter than most proteins, which have tertiary strucmre due to folding of the peptide sequence. In a protein, the polypeptide chain folds upon itself (forms tertiary structure) to, among other things, allow mutual association of hydrophobic residues in order to maximize entropy of a water solution that contains the polypeptide. Intermediate sized peptides in accordance with the invention on the other hand, generally are smaller, generally fold less and have less tertiary strucmre than an intact protein but have secondary structure. Their minimum size limit of 16 amino acids reflects the fact that peptides smaller than 16 residues long generally have little structure outside the primary strucmre of amino acid sequence and are less improved by making an alteration according to the claimed embodiment Although not wishing to be bound by any one theory of this embodiment of their mvention. the inventors theorize that altering a hydrophobic ammo acid such as leucme, valine and isoleucine etc to a hydrophilic amino acid such as glutamine, arginine, asparagine. seπne. threonine etc , particularly in the immunodominant region, helps prevent structural instability when present in an intermediate sized (16-100 residue-long) peptide that lacks complex protein (1 e tertiary structure) The inventors theorize that hydrophobic ammo acid residues in a large protein come together to form an interior oily pocket that excludes water and stabilize the strucmre of the complete large protein However, when a peptide antigen less than about 100 amino acids (e g less than 100 ammo acids), particularly less than about 75 ammo acids (e g less than 75 amino acids) and more particularly less than about 50 amino acids (e g less than 50 ammo acids) is prepared to mimic antigenically this same protein, individual hydrophobic lesidues no longer can avoid water by optimally coming together and instead randomly are exposed to water and increase disorder of the peptide in water The disorder contributes to less stable and unrecognizable epitopic structures which leact less well or react less specifically with antibodies directed against the native undenatured protein, which is more ordered The increased disorder is alleviated by decreasing the hydrophobic character of the hydrophobic residue, preferably by substituting the ammo acid with a more hydrophilic lesidue Of the proposed ammo acid changes, it is particularly advantageous to alter leucine or isoleucine to glutamine or arginine because of the similarity in sizes of these ammo acids, although other related changes are desirable and contemplated as described elsewhere The embodiment of replacing one oi more hydrophobic am o acids with one or more hydrophilic ammo acids particularly relates to intermediate sized peptides from 16 ammo acids to 100 amino acids m length, and more particularly to peptides between 25 to 50 ammo acids, 36 to 50 ammo acids and 41 to 50 ammo acids The unproved effect is seen particularly with intermediate sized peptides because, at very small sizes of less than about 16 (e.g , 16), and particularly less than 10 amino acids, the epitope recognized by an antibody more closely resembles the primary strucmre of the short segment, namely, the individual ammo acid residues themselves That is, antibody reactivity (if any) to such a short peptide arises primarily Irom chemical characteristics of the ammo acid residues themselves In contrast, secondary structures such as alpha helix and beta pleated sheet, and tertiary structure, such as that resulting from ionic bonding, hydrogen bonding and hydrophobic effect "bonding" (actually, association driven by an increase in entropy) between residues of the same chain have little role in these small peptides. In making a chimeric peptide according to the invention, it is advantageous to add one or more positively charged amino acid residues. Preferred chimeras contain at least one extra basic amino acid residue compared to an antigenically enhancing HIV-1 sequence from this portion of the gp41 immunodominant region. Because of the decreased hydrophobic amino acid content and increased charged amino acid content, such embodiments of the invention advantageously allow an increase in the amount of antigen used in an immunodiagnostic assay (or therapy) by comparison with other peptides used for such assays via making the antigen more hydrophilic. The increase in antigen amount provides more advantageous sensitivity. The increase in total amount of peptide that can be used also allows for an "all variants" approach whereby multiple (allelic) peptides of the same epitopic region of a viral protein are used simultaneously, in order to anticipate multiple epitopic forms of an immunodominant site that the virus may evolve during infection. This "all variants" approach is particularly important for RNA viruses that mutate rapidly and is made possible by applicant's engineering of peptide antigens having greater solubility in water. The "all variants" method was tested using 69 blood samples, including problematic blood samples as listed in Figure 4. This figure shows that an antigen of SEQ ID NO. 5, which cross-reacts with HIV-2 antigen, could be combined with two other peptides that cross react with HTV-1 antigen to successfully detect a set samples from HIV infected patients. Peptides that Appear to Resemble an Evolutionary Precursor of Primate Virus Antigen The inventors further realized that an antigen of a putative genetic forerunner to present day primate immunodeficiency viruses would react with a broad range of HTV strains that have evolved from this precursor virus. In this context, the inventors reviewed sequences that cross-react with a wide variety of HIV-1 viruses to ascertain what features of an envelope protein immunodominant sequence may have existed in the precursor virus. By "features" is meant individual amino acids at particular positions in the immunodominant sequence and small stretches in the sequence of less than six amino acids long and that are smaller than an epitope. The inventors also studied the simian immunodeficiency virus to obtain sequence information that reveals features of a precursor immunodominant loop. With the help of peptide analysis software specified above, and data obtained from studying sequences with defined sub-epitopic changes, the inventors realized the secondary structure of the immunodominant loop and other features, finding sequences and changes that can form secondary peptide strucmre as well as form more soluble peptides. The inventors blended the desired features of primate virus envelope protein obtained from HIV-1 Group O and from simian viruses into useful peptides to resemble a putative envelope protein sequence from a distant precursor virus. The blended primordial sequences made were shown to be more broadly reactive with modern day HIV strains compared to peptides having natural sequences. One embodiment of the invention is a peptide having an amino acid immunodominant loop sequence as revealed in the simian line of immunodeficiency virus and exemplified by the SIV gp36 immunodominant sequence. This peptide also has sequence similarity to the HIV-1 Group O gp41 immunodominant region. In another embodiment a 7mer immunodominant loop region of simian virus that corresponds to a distant evolutionary strain is merged with flanking portion(s) of peptide that reacts broadly with HIV-1 strains. In yet a further embodiment, a section of SIV sequence that is 10 amino acids long and which contains a characteristic alanine at 3 positions to the amino terminal side of the immunodominant loop is sandwiched between two portions of peptide having a sequence that resembles an HIV-1 "Universal sequence" as described in co-pending applications 60/091,659 filed July 2, 1998 (attorney docket No. 073294/0160), 60/072,863 filed January 28, 1998 (attorney docket No. 073294/0161), 60/072,981 filed January 29, 1998 (attorney docket No. 073294/0162), 60/098,705 filed September 1, 1998 (attorney docket No. 073294/0168), 60/088,229 filed June 5, 1998 (attorney docket No. 073294/0172), 60/100,422 filed September 15, 1998 (attorney docket No. 073294/0191), 60/112,026 filed December 12, 1998 (attorney docket No. 073294/0178) and 60/104,685 filed October 16, 1998 (attorney docket No. 073294/0198), which are herein incorporated in their entireties by reference. In yet another embodiment, the SIV immunodominant loop sequence is replaced by another sequence that conserves the characteristic secondary strucmre of this sequence. The inventors further discovered that putative precursor virus peptides which contain certain conformational constraints work better as antigens with anti-HIV antibodies. That is, peptides in accordance with this embodiment of the claimed invention advantageously contain secondary peptide strucmre such as beta-pleated sheet, or even more advantageously, some alpha helix strucmre. When merging or combining an SIV evolutionary immunodominant loop region with a Universal HIV-1 sequence to simulate the evolutionary precursor, it is best to make one or more amino acid substitutions as needed to maintain, or even increase the size of an alpha helix (or beta pleated sheet) strucmre that forms from the sequence. In the case of the env protein membrane spanning immunodominant region termed gp41 in HIV-1 and gp36 in SIV, an alpha helix may form on the amino terminal side of the cystine loop. The inventors discovered that increasing the size of this helix in an intermediate-sized peptide will improve performance of the peptide as an antigen. A peptide analysis software program can be used to select which amino acid substitution(s) will maintain or. more advantageously increase the alpha helix strucmre. Table 1 (above) shows some representative examples of alternative sequences useful for making or extending alpha helix strucmre in the gp41 (or gp36) immunodominant region to improve the efficacy of the peptide antigen for detection or treatment of HIV infection. Representative sequences according to this embodiment of the invention are provided as SEQ ID NO: 45 through 105 in Figure 1. These peptides can react with a broad range of HIV infected blood specimens. SEQ ID NO: 57 is a 36 mer that has a 16 amino acid long portion, which forms an alpha helix. Six residues of the helix at its amino terminus end are from a sequence of HIV-1 that resembles a primordial sequence in that the peptide cross- reacts with a wide variety of HIV strains (described, for example, in PCT application "Universal Peptides" filed June 4, 1999 attorney docket No. 036034/0106), and the next 8 residues are from the putative evolutionary SIV immunodominant loop. This example demonstrates a blend of SIV epitope(s) with a Universal HIV-1 Group O epitope that represents a more broadly cross-reactive peptide. Some of the cross-reacting antibodies will bind to epitopes found on HIV-1, HIV-2 and SIV proteins (i.e. one antibody by itself has specificity for binding HIV-1 protein, HIV-2 protein and also SIV protein). However, of course, some of these antibodies will only bind HIV-1, HIV-2 or SIV protein. SEQ ID NO: 56 is a 36 mer peptide having a 16 residue helix comprising an 8 mer Universal HIV-1 Group O portion and a 7 mer portion from SIV, separated by a break (non- helix forming amino acid) between the two portions. The peptide formed from this sequence contains a 15 amino acid long portion of STV peptide sandwiched between two approximately equal sized portions of Umversal HIV-1 Group O peptide Sequences depicted as SEQ ID NO 45 through 55 and 58 through 98 in Figure 1 blend features of an SIV immunodominant loop sequence with one or more HTV-1 Universal peptide sequences When merging sequences to form an antigen, it is best to preserve the helix structure at the ammo terminal side ot the cystine loop by making an acceptable a mo acid substitution such as described below A peptide that comprises one or more sequences depicted as SEQ ID NO 99 through SEQ ID NO 104 contain predicted secondary strucmre that characterizes a putative HTV immunodominant loop region The inventors found that these sequences form peptides that have a predicted characteristic mrn in the helix of this region In another advantageous embodiment, this region forms a continuous helix with the flanking region at the ammo terminal side of the immunodominant loop Sequences depicted as SEQ ID NO 65 through SEQ ID NO 98 represent further embodiments which diverge generally more from known sequences in order to better approximate an evolutionary sequence, and can have broader reactivity with known strains. For example, the tryptophan (W) located 15 positions on the amino terminal side of the cystine loop in many of these sequences has been found to give a broader antigemc specificity compared to a sequence that has an isoleucine (I) at this site An isoleucine is found in both SIV and HIV-2 types, and replacing this isoleucine with tryptophan can facilitate more cross- reaction with other strains such as those classified as HIV-1, if desired Native modern HIV gp41 envelope peptides typically have a helix at the ammo terminal side of the cystine loop The inventors realized that lengthening this helix region can improve reactivity of peptides used for HIV diagnosis Furthermore, the mventors discovered that terminating this helix with at least one, and preferably multiple basic ammo acids provides antigens that bind to solid surfaces in an optimal manner to give diagnostic assays of high sensitivity For example, the inventors have obtained data showmg that terminating the peptide with "R-A-R" provides much greater sensitivity Of course, in addition to merging SIV with a Universal HIV-1 Group O sequence, and altering ammo acids to extend the alpha helix, other amino acid changes can be made. For example, the inventors discovered that changmg a hydrophobic amino acid (for example, leucine) to a hydrophilic amino acid (for example, glutamme or arginine group) in HTV peptide antigens allows detection of a wider range of samples, as described above Sequences that are formed from SIV and an HIV Universal peptide can work better than the coi responding sequences of naturally occurring proteins for detecting (and analogously lmmunizmg against) a wide range of HIV infections. Although not wishmg to be bound by a particular theory of this embodiment ot their invention, the inventors theorize that the simian immunodominant loop represents an early version of the primate virus and that present day so called "HIV-1 " viruses have an immunodominant loop that has diverged from the more representative sequence now existing in the simian virus Although not wishmg to be bound by any one theory, the mventors theorize that combimng the immunodominant loop region from the SIV with flanking epιtope(s) from their broadly reactive Umveisal "HIV-1 " antigen produces an antigen that resembles more closely, an antigen of a virus that represents a common ancestor ot both HIV-1 and SIV, (and consequently HIV-2) This antigen thus cross reacts with a wider variety of HIV types than any particular antigen derived from sequencing HIV specimens The sequences in accordance with this embodiment ot the invention may have one or more altered hydrophobic amino acids such as leucine, va ne and isoleucine etc to a hydrophilic amino acid such as glutamine. asparagine, serme, threonine etc , particularly m the immunodominant region Such alteration, as descnbed in the above-cited co-pendmg applications helps prevent structural instability when a small (16-100 residue-long, advantageously 25-50 residues long) amino acid long peptide, lacking complex protem strucmre is used Of the proposed amino acid changes, the inventors prefer altering leucme to glutamine because ot the similarity in sizes ot these amino acids, although other related changes are desirable and contemplated as described elsewhere The alterations discussed above for the chimeric Herpes zoster peptide apply equally well for engineering sequences of a putative precursor virus and although not recited again, are contemplated for these embodiments as well Antigens that cross-react with the immunodominant region of the gp41 envelope protem of HIV-1 are contemplated as embodiments of the claimed invention as exemplified above Combinations of substitutions are particularly advantageous. Specific examples of these antigens are peptides that comprise (I e contain in whole or in part) peptide sequences SEQ ID NO 45 through 106 The inventors realized that they could mix one or more peptide antigens according to this embodiment of the invention with recombinant antigen at a higher concentration if the peptide is made more hydrophilic by amino acid substitution as described herein. For example, a peptide made by replacing one or more hydrophobic amino acids with less hydrophobic amino acids can be mixed with another peptide or with a recombinant antigen used for HIV-1 tests (Viro-1, Catalog #00113-V ViroGen Corp., Watertown, Massachusetts) at a higher concentration without precipitation compared to the unmodified native sequence Of course, other antigens can be devised and used for diagnostics and/or therapy of HTV infection by following the selection methods described above In this context, antigens that have at least one substimtion of a hydrophilic amino acid (such as glutamine or arginine) for an aliphatic amino acid (such as leucme. isoleucine or vahne) from a naturally occurring sequence are particularly advantageous An ammo acid substimtion as described herein often may alter the lmmunoreactivity of the peptide sequence with respect to the native (unmodified) form Experimental data have been obtained that indicate such alteration can broaden lmmunoreactivity from the native sequence, in agreement with the theory that a primordial sequence would react more broadly with the evolved present-day strains For example it was shown that two alterations of glutamine to leucme and alteration ot glutamine to arginine m a 36 mer peptide can add STV epitope reactivity to an HIV-1 peptide and was experimentally tound to allow the peptide to cross-react with an entire group of HIV-2 infected samples That is. some antibodies which recognize an HIV-1 protem can also recognize HIV-2 and SIV proteins, although usually to different extents This embodiment ot the invention increases binding of HIV-1 antibody to SIV or HIV-2 protein by blending the HIV epitope with an SIV epitope. Making alterations in accordance with an embodiment of the invention allows antibodies that already bind to HTV-1 also bind to SIV and HIV-2 In this context, it was also found that substimtion of a valine for an isoleucine within the cysteine loop region of the HIV-1 gp 41 protem, and substimtion of a basic amino acid such as arginine or lysine at the eighth position to the carboxy terminal side of the cystine loop is particularly advantageous and can lead to a peptide havmg altered immunological characteristics. Sequences of representative altered peptides having these and related changes are shown in Figure 1 and described more generally by the claims. Of course, other alterations are contemplated in accordance with the discoveries detailed herein. In the case of the SIV immunodominant region exemplified here, it was realized that an antigen works better if it includes at least about 5 amino acids (e.g. five) to the amino terminal side of the immunodominant region. In alternative embodiments, this portion may be 6, 7, 8, 9, 10, 11, 12 or more ammo acids long. In another embodiment this added portion, or at least a part of it, which is adjacent to the immunodominant region is m the form of a helix In such case of an intermediate size (25-100 amino acids long, particularly 25-50 ammo acids long) peptide, a hydrophobic residue such as a leucine within the immunodommant region tends to disturb the rest of the peptide. The hydrophobic leucine residue disturbs the secondary strucmre. because the hydrophobic effect of the leucine requires a much larger protem to reach stability in water solution (i.e. come together with enough tra peptide hydrophobic residues to maximize overall entropy ) One embodiment of the invention is exemplified with a leucine to glutamme shift within a 25-50 amino acid long peptide, but works well with shifts of other hydrophobic amino acids such as I, V, M, F and W to hydrophilic amino acids, and even hydrophilic charged amino acids In making these substimtions, it is particularly advantageous to replace a hydrophobic amino acid residue with a hydrophilic (preferably uncharged) amino acid residue having a similar overall size. Most advantageous in this aspect is to replace a leucine, which has a three carbon long residue with a methyl group attached, with a glutamme, which also has a three carbon long residue with an additional amine group attached. In another embodiment, a peptide ot between 25-50 amino acids long has only one hydrophobic residue within an 8 residue long portion Altering this hydrophobic residue to a hydrophilic residue will improve reactivity (increased sensitivity or broadened selectivity or both). In yet another embodiment, 2 hydrophobic residues within an 8 amino acid long portion exist and at least one of these is altered to a hydrophilic ammo acid to provide the benefit. In yet another embodiment, an isoleucine, leucine, valine, or methionine is replaced with glutamine In another embodiment, any of these hydrophobic ammo acids is replaced with asparagine. In another embodiment, any of these hydrophobic amino acids is replaced with threomne, seπne, alanine or glycine. In another embodiment, any of these hydrophobic amino acids is replaced with histidine or proline. In another embodiment, any of these hydrophobic ammo acids is replaced with aspartic acid, glutamic acid, arginine or lysine. Other hydrophobic to hydrophilic ammo acid changes are possible in accordance with the claimed invention. For example, in one embodiment, a phenyl alanine can be converted to a glutamine. In another embodiment, a phenyl alanine can be converted to any of the other hydrophilic amino acids. In considering any specific alteration, a computer modeling software program, such as "Peptide Companion" advantageously is used and a specific alteration is chosen, using the program, to maintain the predicted pre-existing secondary or tertiary structure of the protein. Preparation of Peptide The peptides of the invention can be prepared using any suitable means. Because of their relatively short size (generally, less than 100 amino acids, advantageously less than 75, more advantageously less than 50 and conveniently less than 40), the peptides can be synthesized in solution or on a solid support in accordance with conventional peptide synthesis techniques. Various automatic synthesizers are commercially available (for example, from Applied Biosy stems) and can be used in accordance with known protocols. See, for example, Stewart and Young, SOLID PHASE PEPTIDE SYNTHESIS (2d. ed., Pierce Chemical Co., 1984); Tarn et. al. , J. Am. Chem. Soc, 105, 6442 (1983); Merrifield, Science, 232, 341-347 (1986); and Barany and Merrifield. THE PEPTIDES (Gross and Meienhofer, eds.. Academic Press, New York, 1979). 1-284. Alternatively, suitable recombinant DNA technology may be employed for the preparation of the peptides of the invention, wherein a nucleotide sequence that encodes a peptide of interest is inserted into an expression vector, transformed or transfected into a suitable host cell and cultivated under conditions suitable for expression. These procedures are generally known in the art, as described generally in Sambrook et. al., MOLECULAR CLONING, A LABORATORY MANUAL (2d ed., Cold Spring Harbor Press, Cold Spring Harbor, New York, 1989), and CURRENT PROTOCOLS IN MOLECULAR BIOLOGY (Ausubel et. al., eds., John Wiley and Sons, Inc., New York, 1987), and U.S. Pat. Nos. 4,237,224, 4, 273,875, 4,431,739, 4,363.877 and 4,428,941, for example. Thus, recombinant DNA-derived proteins or peptides. which comprise one or more peptide sequences of the invention, can be used to prepare the HIV cytotoxic T cell epitopes identified herein or identified using the methods disclosed herein. For example, a recombinant peptide of the invention is prepared in which the amino acid sequence is altered so as to present more effectively epitopes of peptide regions described herein to stimulate a cytotoxic T lymphocyte response. By this means, a polypeptide is used that incorporates several T cell epitopes into a single polypeptide. As the coding sequence for peptides of the length contemplated herein can be synthesized by chemical techniques, for example, the phosphotriester method of Matteucci et. al., J. Am. Chem. Soc, 103, 3185 (1981), modification can be made simply by substituting the appropriate base(s) for those encoding the native peptide sequence. The coding sequence can then be provided with appropriate linkers and ligated into expression vectors commonly available in the art, and the vectors used to transform suitable hosts to produce the desired fusion protein. A number of such vectors and suitable host systems are now available. For expression of the fusion proteins, the coding sequence will be provided with operably linked start and stop codons, promoter and terminator regions and usually a replication system to provide an expression vector for expression in a suitable cellular host. For example, promoter sequences compatible with bacterial hosts are provided in plasmids containing convenient restriction sites for insertion of the desired coding sequence. The resulting expression vectors are transformed into suitable bacterial hosts. Yeast or mammalian cell hosts may also be used, employing suitable vectors and control sequences. Funher Modifications to the Peptide In another embodiment at least one additional amino acid is added to at least one terminus of a peptide of the invention. Such added amino acid(s) facilitates linking the peptide to another peptide, coupling to a carrier, or coupling to a support. The added amino acid(s) also can be chosen to alter the physical, chemical or biological properties of the peptide, such as, for example adding another epitope for T-cell stimulation. Suitable amino acids, such as tyrosine, cysteine. lysine, glutamic or aspartic acid, and the like, can be introduced at the C- or N-terminus of the peptide. In another embodiment, a peptide of the invention can differ from the natural sequence by being modified by terminal-NH sub 2 acylation, e.g., acetylation, or thioglycolic acid amidation, terminal-carboxyl amidation, e.g., ammonia, methylamine, etc. In some instances these modifications may provide sites for linking to a support or other molecule, thereby providing a linker function. It is understood that the peptides of the invention or analogs or homologs thereof may be further modified beyond the sequence considerations given above, as necessary to provide certain other desired attributes, e.g., improved pharmacological characteristics, while increasing or at least retaining substantially the biological activity of the unmodified peptide. For instance, the peptides can be modified by extending, decreasing or substituting amino acids in the peptide sequence by, for example, the addition or deletion of suitable amino acids on either the amino terminal or carboxyl terminal end, or both, of peptides derived from the sequences disclosed herein. Thus, although preferred amino acid substimtions for HIV-1 testing are described by, for example, SEQ ID Nos. 1-6, further conservative substimtions are possible and sometimes desirable for HIV-1 testing. By "conservative" substitutions is meant replacing an amino acid residue with another that is biologically and/or chemically similar, e.g., one hydrophobic residue for another, or one polar residue for another. The substimtions include combinations such as Gly, Ala: Val. He, Leu; Asp, Glu; Asn. Gin; Ser, Thr; Lys, Arg; and Phe, Tyr. Other amino acid substimtions are provided as groups within individual claims. Preferably, the portion of the peptide sequence that is intended to mimic an antigen of HIV will not differ by more than about 30% from any of the sequences provided herein, except where additional amino acids may be added at either terminus for the purpose of modifying the physical or chemical properties of the peptide for, for example, ease of linking or coupling, and the like. Where regions of the peptide sequences are highly variable, it may be desirable to vary one or more particular amino acids to mimic more effectively differing epitopes of different HTV strains. In addition, the contributions made by the side chains of the residues can be probed via a systematic replacement of individual residues with a suitable amino acid, such as Gly or Ala. Systematic methods for determining which residues of a linear amino acid sequence of a peptide are required for binding to a specific MHC protein, (or other component of the immune system) are known. See, for instance, Allen et. al.. Nature, 327, 713-717; Sette et. al., Nature, 328, 395-399; Takahashi et. al., J. Exp. Med., 170, 2023-2035 (1989); and Maryanski et. al., Cell, 60, 63-72 (1990). A considerable amount of work in this area has provided algorithms to use in making conservative changes to individual amino acids without altering a peptide 's biological activity. For example, the hydropathic index of amino acids may be considered. The importance of the hydropathic amino acid index in conferring interactive biologic function on a protein is generally understood in the art as cited in U.S. No. 5,703,057 (citing Kyte and Doolittle, 1982, incorporated herein by reference). It is accepted that the relative hydropathic character of the amino acid contributes to the secondary strucmre of the resultant peptide which in turn defines the interaction of the peptide with other molecules, for example, receptors, DNA, antibodies, antigens, and the like. Each amino acid has been assigned a hydropathic index on the basis of its hydrophobicity and charge characteristics (Kyte and Doolittle. 1982), these are: isoleucine (+4.5); valine (+4.2); leucine ( + 3.8); phenylalanine ( + 2.8); cysteine/cystine (+2.5); methionine (+ 1.9); alanine ( + 1.8); glycine (-0.4); threonine (-0.7); serine (-0.8); tryptophan (-0.9); tyrosine (-1.3); proline (-1.6); histidine (-3.2); glutamate (-3.5); glutamine (-3.5); aspartate (-3.5); asparagine (-3.5); lysine (-3.9); and arginine (-4.5). It is known in the art that certain amino acids may be substituted by other amino acids having a similar hydropathic index or score and still result in a peptide with similar biological activity, i.e., still obtain a biological functionally equivalent peptide. In making such changes, the substimtion of amino acids whose hydropathic indices are within +- 2 is preferred, those which are within +- 1 are particularly preferred, and those within +- 0.5 are even more particularly preferred. It is also understood in the art that the substimtion of like amino acids can be made effectively on the basis of hydrophilicity. U.S. Pat. No. 4,554.101, incorporated herein by reference, states that the greatest local average hydrophilicity of a protein, as governed by the hydrophilicity of its adjacent amino acids, correlates with a biological property of the protein. As detailed in U.S. Pat. No. 4,554,101, the following hydrophilicity values have been assigned to amino acid residues: arginine (+3.0); lysine ( + 3.0); aspartate (+3.0 +- 1) glutamate (+3.0 +- 1); serine (+0.3); asparagine (+0.2); glutamine (+0.2); glycine (0) threonine (-0.4); proline (-0.5 +- 1); alanine (-0.5); histidine (-0.5); cysteine (-1.0) methionine (-1.3); valine (-1.5); leucine (-1.8); isoleucine (-1.8); tyrosine (-2.3) phenylalanine (-2.5); tryptophan (-3.4). It is understood that an amino acid can be substituted for another having a similar hydrophilicity value and still obtain a biologically equivalent, and in particular, an immunologically equivalent peptide. In such changes, the substimtion of amino acids whose hydrophilicity values are within +- 2 is preferred, those which are within +- 1 are particularly preferred, and those within +- 0.5 are even more particularly preferred. As outlined above, amino acid substimtions are generally therefore based on the relative similarity of the amino acid side-chain substituents, for example, their hydrophobicity, hydrophilicity, charge, size, and the like. Exemplary substimtions which take various of the foregoing characteristics into consideration are well known to those of skill in the art and include: arginine and lysine: glutamate and aspartate; serine and threonine; glutamine and asparagine: and valine, leucine and isoleucine. Peptides that tolerate multiple amino acid substitutions generally incorporate small, relatively neutral molecules, e.g., Ala, Gly, Pro, or similar residues. The number and types of residues that can be substituted, added or subtracted will depend on the spacing necessary between the essential epitopic points and certain conformational and functional attributes that are sought. By types of residues, it is intended, e.g.. to distinguish between hydrophobic and hydrophilic residues, among other attributes. If desired, increased binding affinity of peptide analogs to can also be achieved by such alterations. Generally, any spacer substimtions, additions or deletions between epitopic and/or conformationally important residues will employ amino acids or moieties chosen to avoid stearic and charge interference that might disrupt intramolecular binding of the peptides and intermolecular binding of peptides to other molecules. Peptides that tolerate multiple substimtions while retaining the desired immunological activity also may be synthesized as D-amino acid-containing peptides. Such peptides may be synthesized as "inverso" or "retro-inverso" forms, that is, by replacing L-amino acids of a sequence with D-amino acids, or by reversing the sequence of the amino acids and replacing one or more L-amino acids with D-amino acids. As the D-peptides are substantially more resistant to peptidases. and therefore are more stable in serum and tissues compared to their L-peptide counterparts, the stability of D-peptides under physiological conditions may more than compensate for a difference in affinity compared to the corresponding L-peptide. Further, L-amino acid-containing peptides with or without substimtions can be capped with a D-amino acid to inhibit exopeptidase destruction of the antigenic peptide. An advantageous embodiment is to prepare the peptide by chemical synthesis. In another embodiment, the peptide is made recombinantly. In the latter case, modifications, including conservative modifications, are best carried out by changing a DNA sequence that codes for the peptide. The following is a discussion based upon changing the amino acids of a protein to create an equivalent, or even an improved, second-generation molecule. The amino acid changes may be achieved by changing the codons of the DNA sequence, according to the following codon table: Amino Acids Symbol Codons Alanine Ala A GCA GCC GCG GCU Cysteine Cys C UGC UGU Aspartic acid Asp D GAC GAU Glutamic acid Glu E GAA GAG Phenylalanine Phe F UUC UUU Glycine Gly G GGA GGC GGG GGU Histidine His H CAC CAU Isoleucine lie I AUA AUC AUU Lysine Lys K AAA AAG Leucine Leu L UUA UUG CUA CUC CUG CUU Methionine Met M AUG Asparagine Asn N AAC AAU Proline Pro P CCA CCC CCG CCU Glutamine Gin Q CAA CAG Arginine Arg R AGA AGG CGA CGC CGG CGU Serine Ser S AGC AGU UCA UCC UCG UCU Threonine Thr T ACA ACC ACG ACU Valine Val V GUA GUC GUG GUU Tryptophan Trp W UGG Tyrosine Tyr Y UAC UAU Biologically functional universal peptides can be prepared through specific mutagenesis of the underlying DNA. The technique further provides a ready ability to prepare and test sequence variants, for example, incorporating one or more of the foregoing considerations, by introducing one or more nucleotide sequence changes into the DNA. Site-specific mutagenesis allows the production of mutants through the use of specific oligonucleotide sequences which encode the DNA sequence of the desired mutation, as well as a sufficient number of adjacent nucleotides, to provide a primer sequence of sufficient size and sequence complexity to form a stable duplex on both sides of the deletion junction being traversed. Typically, a primer of about 17 to 25 nucleotides in length is preferred, with about 5 to 10 residues on both sides of the junction of the sequence being altered. The technique of site-specific mutagenesis is well known in the art, as exemplified by various publications. As will be appreciated, the technique typically employs a phage vector which exists in both a single stranded and double stranded form. Typical vectors useful in site-directed mutagenesis include vectors such as the M13 phage. These phage are readily commercially available and their use is generally well known to those skilled in the art. Double stranded plasmids are also routinely employed in site directed mutagenesis which eliminates the step of transferring the gene of interest from a plasmid to a phage. Site-directed mutagenesis in accordance herewith is performed by first obtaining a single-stranded vector or melting apart of two strands of a double stranded vector which includes within its sequence a DNA sequence which encodes the desired peptide. An oligonucleotide primer bearing the desired mutated sequence is prepared, generally synthetically. This primer is then annealed with the single-stranded vector, and subjected to DNA polymerizing enzymes such as E. coli polymerase I Klenow fragment, in order to complete the synthesis of the mutation-bearing strand. Thus, a heteroduplex is formed wherein one strand encodes the original non-mutated sequence and the second strand bears the desired mutation. This heteroduplex vector is then used to transform appropriate cells, such as E. coli cells, and clones are selected which include recombinant vectors bearing the mutated sequence arrangement. The preparation of sequence variants of the selected peptide-encoding DNA segments using site-directed mutagenesis is provided as a means of producing potentially useful species and is not meant to be limiting as there are other ways in which sequence variants of peptides and the DNA sequences encoding them may be obtained. For example, recombinant vectors encoding the desired peptide sequence may be treated with mutagenic agents, such as hydroxylamine, to obtain sequence variants. Use of the Peptides in Test Devices Antigens of the instant invention can be used in a wide variety of diagnostic tests that employ antigen-antibody binding for detection of a disease agent. The peptides are particularly useful in dot blot immunoassays such as. for example, described in co-pending application U.S. App. Ser. No. 09/069,935 "Multiple Readout Immunoassay with Improved Resistance to Interferences" (Attorney Docket No. 073294/0173 filed April 30, 1998, incorporated herein in its entirety by reference) and in ELISA assays. The dot-blot immunoassay described in the 09/069,935 application is especially advantageous for detecting HIV infection using a peptide chimera as herein described. This assay uses a test device which has a housing comprised of a water impermeable material which holds other test components such as an absorbent pad with a reagent layer, filter and a reagent used to obtain a test result. The housing has an opening to admit a fluid sample. The housing comes apart during use so that the user can remove the filter to expose the reagent layer for application of a reagent and/or wash fluid. A sleeve that holds the filter is removably attached to the housing such that contact of the filter is favored over contact of the sleeve with the surface of the reagent layer. The sleeve is attached to the housing by a bayonet mount. After a sample is applied, and an optional wash solution added, the sleeve is removed and further optional reagent solution and a wash solution are added directly to the reagent layer. In some applications a sample is added to the device and further processing is carried out at a separate location or after storage of the device for a few hours. In these situations, the sleeve remains attached to the housing to prevent or delay the release of moisture from the device until the later processing steps are carried out. The housing also may contain a cover to protect the opening and further guard against the release of moisture. Acceptable materials for the device housing include water impermeable plastics such as polystyrene, polypropylene, poly vinyl chloride and the like. Acceptable materials for the filtering portion of the filter, the dispersing portion of the filter, the reagent layer and the absorbent pad are glass fiber, ethyl cellulose, nitrocellulose and ethyl cellulose respectively. When nitrocellulose is used for the reagent layer, however, the material of the filter should be chosen for its ability to premix the test sample and any test reagent that may be present in the filter. Two or more materials can be physically combined to make up a filter, reagent layer or absorbent pad. Two materials are acceptable for the filter, an upper filtering material and a lower dispersal material. Most acceptable is a dispersal layer that passes fluid at a slower flow rate compared to passage of fluid through an upper filtering material. The applicants have found that the use of a dispersal layer is surprisingly superior over the use of a single part filter. Although applicants wish not to be bound by one particular theory of how their dispersal layer works in the assay device, the layer may remove irregularities in the flow that arise from irregular collection of particles in the upper regions of the filter. A second advantage of using a two-part filter is that the dispersal layer, by virtue of its slow fluid flow rate, can prolong one or more reaction times for substances that react before entering the reaction layer, thereby increasing sensitivity. Advantageously, the dispersal layer extends beyond the sleeve that holds the filter such that when the filter is attached to the container, the dispersal layer portion exerts a greater pressure onto the reagent layer than does the sleeve. "Greater pressure" in this context means that the mechanical force per unit area exerted by the filter onto the reagent layer exceeds the mechanical force per unit area exerted by the sleeve onto the reagent layer. Preferably, the filter exerts at least twice as much mechanical pressure onto the reagent layer compared to the sleeve. More preferably, the sleeve does not contact the reagent layer. By relying principally on the filter itself to contact the reagent layer, the sleeve does not deform the reagent layer. This allows a more even and reproducible transfer of fluid from the filter to the reagent layer. Further advantageous feamres of a test device are found in co-pending application No. 08/933,943 filed on September 19, 1997. An antigen is immobilized onto the reagent layer portion of the absorbent pad by absorption, via spotting a water solution of the antigen. The optimum amount of antigen to use is determined by methods accepted in the art. The inventors used approximately 150 ng of antigen per test. Chemically synthesized antigens and recombinant antigens can be immobilized within these and other devices by routine methods, such as by spotting a water solution of the antigen onto a nitrocellulose membrane or membrane layer. Example 1 In this Example peptides of SEQ ID NO: 5 (18 mer), 7 (23 mer), 10 (28 mer) and 28 (18 mer with helix region but lacking a cystine loop) and a primate virus sequence from gp36 (SEQ ID NO: 44) were prepared and tested as antigens with HIV-1 infected, HIV-2 infected and other problematic blood samples. The test method is described in co-pending U.S. patent application "Diagnostic Test Devices with Improved Fluid Movement and Resistance to Interferences" US No. 09/311,143 filed May 13. 1999. Data were obtained as shown in Figure 2, indicating that chimeric peptides of increasing alpha helix strucmre cross-react more strongly and more specifically with HTV-2 antigen. A peptide having the sequence of SEQ ID NO. 28 did not react with samples, indicating that the specific sequence used to form the alpha helix in the peptides did not itself contribute to antibody reactivity. Figure 7 shows data obtained that indicates the analytical sensitivity of tests that use a primate sequence from gp36 (SEQ ID NO. 44) compared with that of tests that use 18, 23 and 28 amino acid long chimeric peptides with increasing alpha helix. This figure shows that the chimeric peptides have sensitivity equivalent to that of the native peptide. Example 2 In this Example peptides of SEQ ID NO: 4 and 5, which differ by an arginine amino acid, were prepared and tested as antigens with HTV-1 infected, HIV-2 infected and other problematic blood samples. The test method is described in co-pending U.S. patent application "Multiple Readout Immunoassay for Improved Resistance to Interferences. " Data were obtained as presented in Figure 3, indicating that a chimeric peptide having an arginine in place of a hydrophobic amino acid at the sixth position of the cystine loop region provide more sensitive and more specific HIV-2 tests. Example 3 In this Example, peptides of SEQ ID NO: 15, 9 and 5 were prepared and used at 200 ng, 300 ng and 225 ng per spot, respectively, as described in Example 1 in dot-blot tests. The peptide of SEQ ID NO. 5 was used at 225 ng per spot, both with the other peptides present and by itself as a separate spot. Data were obtained as presented in Figure 4, indicating that the mixmre of three peptides was reactive with a variety of HIV infected test specimens. Example 4 In this Example, peptides were prepared having sequences shown by SEQ ID NO: 28 and 10. The peptides were incorporated into diagnostic tests according to the procedure of Example 1. HIV-1 and HIV-2 infected samples were tested according to the procedure of Example 1. Tests that contained the antigen of SEQ ID NO. 28 failed to react with any of the HIV positive blood samples examined but tests that contained the peptide of SEQ ID NO. 10 yielded positive results for the HIV-2 positive test samples. Example 5 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 30. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HTV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 6 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 31. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 7 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 32. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1, and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 8 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 33. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 9 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 34. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 10 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 35. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 11 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 36. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HTV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 12 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO- 37 The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the proceduie of Example 1, and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 13 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 38. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1. and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 14 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 39. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 15 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 40. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HTV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 16 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 41. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1, and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 17 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 42. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HTV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 18 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 43. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. Example 19 In this example, a 28 mer chimeric peptide (SEQ ID NO: 10) having some sequence similarity to HTV-1 gp41 immunodominant region, and some sequence similarity to Herpes zoster protein from open reading frame 51 was compared directly with a 23 mer peptide from the immunodominant region of STV gp36 protein (SEQ ID NO: 44) in two test formats for detecting HIV-1 and HIV-2 infection from blood plasma. Results from testing more than 1,500 blood specimens indicated that the chimeric peptide was significantly more specific in distinguishing between HIV-1 and HIV-2 infection, compared with test results from the native HIV-2 peptide. The chimeric peptide was equally effective in detecting HTV-2 infection, but reacted significantly less with HIV-1 infected samples. Peptide-Based ELISA in Microtiter Plate A micro-titer plate based ELISA was carried out by the following procedure. A peptide solution of the chimera in carbonate buffer at pH 9.6 (400ng in 150 microliters) or of the native gp36 peptide were placed into separate wells of a polystyrene plate and incubated at 37°C for 2 hours. After incubation of plate, each well was washed 5 times. The plate was then blotted on a paper towel. Blocking solution of 2% non-fat milk was added to each well and left at 37°C for 2 hours. After blocking, each well was washed 5 times and blotted. Ten microliters of a sample and 90μl of diluent (2% non-fat milk in phosphate buffered saline with 0.5% NaCI) were added to each well, the well sealed with plastic, and incubated at 37°C for 30 minutes. Each well was then washed 5 times (pH 7.4 phosphate buffered saline with 1 % Tween-20) and blotted. One hundred microliters of conjugate (horseradish peroxidase/anti-human IgG) were added to each well and incubated after covering at 37°C for 30 minutes. Each well was washed 5 times and blotted. One hundred microliters of freshly prepared TMB substrate were added to each well and incubated in the dark at 24°C for 20 minutes. A stop reagent was added and 450nm absorbance recorded. Peptide-Based ELISA in Dot-Blot Format One hundred fifty nanograms of the selected peptide were added to a nitrocellulose filter and incorporated into an assay device as described for Example 1. The procedure for a single test was as follows. During use, two drops of buffer solution were added to the device. Then one drop of plasma or serum were added. Three drops of buffer solution were added and allowed to absorb into the filter. The device filter was removed and 2 drops of wash solution added. Two drops of protein- A gold conjugate were added and allowed to completely pass through the membrane. Two drops of wash solution were dispensed and then a test result, which showed up as a colored dot in response to the presence of anti-HIV antibody was immediately determined. For both test formats, the chimeric peptide and the native peptide exhibited non- reactivity with an interfering panel of samples (RF positive. HCV positive, HSV positive, CMV positive, ANA positive, syphilis positive, HBV positive, icteric, lipemic, and hemolyzed). A total of 1,626 blood samples were tested. Of those, 786 were HTV-1 seropositive, 215 were HIV-2 seropositive and 625 were HIV seronegative. A summary of the test results is shown below. Example 20 In this Example, a peptide is prepared having a sequence shown by SEQ ID NO: 106. The peptide is incorporated into a diagnostic test according to the procedure of Example 1. Ten HIV-2 infected samples are tested according to the procedure of Example 1 , and at least one of the test results is positive, indicating the presence of antibodies to HIV-2 virus antigen. In this preferred embodiment, the segment of SEQ ID NO: 28 forms a predicted alpha helix that is contiguous with a cystine loop region as shown in SEQ ID NO: 1. The alpha helix portion is not antigenic primarily because of the substimtion of a tryptophan for a leucine near the amino terminal side of the alpha helix region. This tryptophan, and other changes made to maintain the predicted alpha helix, it is believed, removes HTV-1 cross-reactivity of this sequence. Example 21 In this Example, peptides are prepared having sequence shown by SEQ ID NOs: 47, 48, 56, 57, 65 and 44. Each peptide was incorporated into a diagnostic test as described for Example 1, using 150ng of each peptide in each test. Blood serum samples were tested and results obtained as shown in Figure 8. All publications and applications cited in this disclosure are specifically incorporated by reference in their entireties. It is to be understood that the description, specific examples and data, while indicating exemplary embodiments, are given by way of illustration and are not intended to limit the present invention. Various changes and modifications within the present invention will become apparent to the skilled artisan from the discussion, disclosure and data contained herein, and thus are considered part of the invention.

Claims: We Claim: 1. A peptide for detecting HIV-2 infection, wherein the peptide comprises a core Varicella-Zoster protein 51 sequence of SEQ ID NO. 1 (C-A-F-R-Q-Xl-C) wherein XI is selected from the group consisting of R, I, L. V, T, H, Q, C, W, F, and Y. 2. A peptide as described in claim 1, wherein XI is R. 3. A peptide as described in claim 1, further comprising at least 11 amino acid residues adjacent to the amino terminal side of the Varicella-Zoster protein 51 sequence. 4. A peptide as described in claim 3, wherein at least 11 amino acid residues adjacent to the amino terminal side of the Varicella-Zoster protein 51 sequence are chosen from sequences adjacent to the amino terminal side of the cystine loop from the immunodominant region of HIV-1 Gp 41 protein. 5. A peptide as described in claim 3, wherein at least 11 amino acid residues adjacent to the amino terminal side of the Varicella-Zoster protein 51 sequence are chosen from sequences that antigenically enhance the antibody binding activity of the cystine loop from the immunodominant region of HIV-1 Gp 41 protein. 6. A peptide as described in claim 3. wherein at least 16 amino acid residues adjacent to the amino terminal side of the Varicella-Zoster protein 51 sequence are chosen from sequences adjacent to the amino terminal side of the cystine loop from the immunodominant region of HIV-1 Gp 41 protein. 7. A peptide as described in claim 4, wherein at least 16 amino acid residues adjacent to the amino terminal side of the Varicella-Zoster protein 51 sequence are chosen from sequences that antigenically enhance known sequences that are adjacent to the amino terminal side of the di-cystine loop from the immunodominant region of HIV-1 Gp 41 protein. 8. A peptide as described in claim 1, further comprising L-E-D-Q-A-R-L-N-A-W-G (SEQ ID NO. 29) contiguous to the amino terminal side of the cystine loop. 9. A peptide as described in claim 1, further comprising A-W-E-K-T-L-E-D-Q-A-R-L- N-A-W-G (SEQ ID NO. 8) contiguous to the amino terminal side of the cystine loop. 10. A peptide as described in claim 1, further comprising a section contiguous to the amino terminal side of the cysteine loop having a sequence SEQ ID NO. 2, wherein XI is selected from the group consisting of D, N, Q, G, S, T, and A; X2 is R or K; and X3 is selected from the group consisting of N, Q, G, S, T, H, A, L, I. V. P and M. 11. A peptide as described in claim 10, wherein the X3 residue is selected from the group consisting of I, L, V, H and A. 12. A peptide as described in claim 10, wherein the X3 residue is selected from the group consisting of I. L and V. 13. A peptide as described in claim 10, wherein the X3 residue is L. 14. A peptide as described in claim 10, wherein the X3 residue is Q. 15. A peptide for detecting HIV infection comprising a core sequence SEQ ID NO: 45, wherein XI is selected from the group consisting of N. Q, G. S. T. and A; X2 is R or K; and X3 is selected from the group consisting of N, Q, G, S, T, H. A, L, I, V, P and M. 16. A peptide as described in claim 15, wherein the X3 residues are selected from the group consisting of I, L , V, H and A. 17. A peptide as described in claim 16, wherein the X3 residues are selected from the group consisting of I, L and V. 18. A peptide as described in claim 17, wherein the X3 residues are L. 19. A peptide as described in claim 15, wherein at least one of the X3 residues is Q. 20. A peptide as described in claim 15, further comprising at least 8 additional amino acid residues at the amino terminal end of SEQ ID NO: 45, wherein the eighth additional residue is selected from the group consisting of N, Q. G. S. T, H, and A. 21. A peptide as described in claim 20, wherein the eighth additional residue is Q. 22. A peptide as described in claim 15, comprising at least 12 additional amino acids at the amino terminal end of SEQ ID NO: 45, wherein the twelfth additional residue is arginine or glutamine. 23. A peptide as described in claim 22. wherein the twelfth additional residue is glutamine. 24. A peptide as described in claim 15, further comprising a threonine or tyrosine residue at the carboxyl side of the C residue at the carboxyl terminus of SEQ ID NO: 45. 25. A peptide as described in claim 15, wherein the core 16 residue sequence of SEQ ID NO: 45 comprises a maximum of five hydrophobic residues selected from the group consisting of I, L, V, M and W. 26. A peptide as described in claim 25. wherein the core 16 residue sequence of SEQ ID NO: 45 comprises a maximum of four hydrophobic residues selected from the group consisting of I, L, V, M and W. 27. A peptide as described in claim 26, wherein the core 16 residue sequence of SEQ TD NO: 45 comprises a maximum of three hydrophobic residues selected from the group consisting of I, L, V, M and W. 28. A peptide for detecting HIV infection, having a length between 26 and 100 amino acid residues, and comprising a core sequence SEQ ID NO: 46, wherein X is an alpha helix of at least 5 amino acids, XI is selected from the group consisting of N, Q, G, S, T, D, N, H and A, X2 is R, K, P or E. X3 is selected from the group consisting of I, L, R, and V, X4 is selected from the group consisting ot T, S and A, and X5 is at least one amino acid long. 29 A peptide for detecting HIV infection, having a length between 36 and 100 ammo acid residues, and comprising a core sequence selected from the group consisting of SEQ TD NO: 47, SEQ ID NO 48, SEQ ID NO 49, SEQ ID NO 50, SEQ ID NO 51, SEQ ID NO: 52, SEQ ID NO 53, SEQ ID NO 54 SEQ ID NO 55. SEQ ID NO 56 and SEQ ID NO: 57, and derivatives thereof that contain one or more conservative amino acid substimtions 30 A peptide as described in claim 29, wherein said conservative amino acid substitutions consist of I, L, V, and M for each other, and S, T and A for each other 31 A peptide as described in claim 30, wherein at least one ammo acid selected from the group consisting of L. I, M and V is replaced with an amino acid selected from the group consisting of N, Q, G, S T H. and A 32 A peptide useful for detecting HIV infection, having a length of between 16 and 100 ammo acid residues, and comprising a sequence selected trom the group consisting of SEQ ID NO 58, SEQ ID NO 59 SEQ ID NO 60, SEQ ID NO 61. SEQ ID NO 62, SEQ ID NO 63 and SEQ ID NO 64 and wherein X6 is at least one amino acid residue long 33 A peptide as described in claim 32, wherein X6 compπses the sequence X1-X1-X1- X2-X3-X1, XI is selected trom the group consisting ot N Q G. S T, and A, X2 is R or K, and X3 is selected from the group consisting of N, Q, G, S T H, A, L, I, V, P and M. 34 A peptide as described m claim 33, wherein the carboxyl terminal end of the peptide comprises a Y residue 35 A peptide useful for detecting HIV infection, having a length of between 16 and 100 ammo acid residues, and comprising a core SIV sequence of AXXXAFRQ, a peptide segment of at least 2 amino acids contiguous to the amino terminal side of the core sequence and a peptide segment of at least 4 ammo acids contiguous to the carboxyl terminal side of the core sequence, wherein the non SIV sequence portions comprise homologous HTV-1 sequences from gp 41 protem and X is an ammo acid 36. A peptide as described in claim 35, wherein the SIV core sequence is SEQ ID NO: 97. 37. A peptide as described in claim 36. wherein the peptide is between 25 and 40 amino acids long. 38. A peptide as described in claim 37. wherein the peptide is between 30 and 40 amino acids long. 39. A peptide as described in claim 35, wherein the peptide segment of at least 4 amino acids contiguous to the carboxy terminal side of the core sequence is ICYT. 40. A peptide as described in claim 35, further comprising an alpha helix portion contiguous to and extending from two amino acids contiguous to the amino terminal side of the core sequence, wherein the alpha helix portion comprises at least 5 amino acids. 41. A peptide as described in claim 40, wherein the alpha helix portion comprises at least 8 amino acids. 42. A peptide as described in claim 40. wherein the alpha helix portion comprises at least 10 amino acids. 43. A peptide as described in claim 40, wherein the alpha helix portion comprises at least 12 amino acids. 44. A peptide as described in claim 40. wherein the alpha helix portion comprises at least 14 amino acids. 45. A peptide as described in claim 40, wherein the alpha helix portion comprises at least 16 amino acids. 46. A peptide as described in claim 35, wherein the core SIV sequence comprises K X X X D X X X X X A X X X AFRQ wherein X is an amino acid. 47. A peptide for detecting HIV infection, comprising a core SIV sequence of A X X X AFRQ, a peptide segment of at least 2 amino acids contiguous to the amino terminal side of the core sequence and a peptide segment of at least 4 amino acids contiguous to the carboxy terminal side of the core sequence, wherein the non SIV sequence portions comprise homologous HIV-1 sequences from gp 41 protein with the provisio that at least one L, I or V from the homologous gp 41 protein sequence in the peptide is substituted with a less hydrophobic amino acid and X is an amino acid. 48. A peptide as described in claim 47, wherein the less hydrophobic amino acid is glutamine. 49. A peptide as described in any of claims 1 to 48, further comprising an alpha helix portion contiguous to eight amino acids from the amino terminal side of the core sequence and extending towards the amino terminus, wherein the alpha helix portion comprises at least 3 amino acids. 50. A peptide as described in claim 49. wherein the alpha helix portion comprises at least 5 amino acids. 51. A peptide as described in claim 49, wherein the alpha helix portion comprises at least 8 amino acids. 52. A peptide as described in claim 49, wherein the alpha helix portion comprises at least 10 amino acids. 53. A peptide as described in claim 49, wherein the alpha helix portion comprises at least 12 amino acids. 54. A peptide as described in claim 49, wherein the alpha helix portion comprises at least 13 amino acids. 55. A peptide comprising a first cystine loop portion, wherein the cysteine loop has a sequence selected from the group consisting of SEQ ID NO: 3. SEQ ID NO: 4, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, and SEQ ID NO: 27 and a second portion contiguous to the amino terminal side of the first portion, wherein the second portion has a sequence that gives a predicted alpha helix strucmre. 56. A peptide as described in claim 5, having the sequence SEQ ID NO: 106. 57. A peptide as described in any of claims 1-56, wherein at least one amino acid selected from the group consisting of L. I and V is replaced with an amino acid selected from the group consisting of R, N, Q, G, S, T, H, and A and wherein the peptide has a length of between 16 and 100 amino acids. 58. A peptide as described in claim 57, wherein at least one amino acid selected from the group consisting of L, I and V is replaced with R or Q. 59. A reagent for immunological detection of anti-HIV antibody in a blood sample, comprising a dried antigen that upon rewetting with water or a clinical sample substantially reacts with antibodies from patients exposed to HIV-2, wherein said antigen is between 16-50 amino acids long and possesses a sequence described by any of claims 1-58. 60. A method of detecting HIV-2 infection, comprising incubating a blood sample or blood derivative with a peptide described by any of claims 1-58, followed by determination of binding between antibody in the blood sample or blood derivative and the peptide. 61. A kit for determining infection with HIV-2, comprising instructions and a device for detecting the presence of anti-HIV -2 antibody in a blood sample or blood derivative, wherein the device comprises a peptide described by any of claims 1-58. 62. A method of improving reactivity of an antigenic peptide for a diagnostic test of HTV, comprising replacing a seven amino acid long cystine loop segment of the HIV-1 gp41 protein or the HIV-2 gp36 protein with a sequence selected from the group consisting of CAFRQRC, CAFRQIC, CAFRQQC; CAFRQTC. CAFRQCC, CAFRQLC; CAFRQWC; CAFRQHC. CAFRQFC and CAFRQYC. 63. A method of improving reactivity of an antigenic peptide for a diagnostic test of HTV- 2, comprising replacing a L, I or V from the peptide with a hydrophilic amino acid. 64. A method as described in claim 63, wherein the hydrophilic ammo acid is glutamine or argimne 65. A method of improving reactivity of an antigenic peptide for a diagnostic test of HTV- 2, comprising increasing the amount of alpha helix in the peptide by replacing at least one amino acid with another. 66. A method of improving reactivity ot an antigenic peptide for a diagnostic test of HTV- 2, comprising increasing the amount of alpha helix in the peptide by adding at least one amino acid that participates in formation ot a predicted alpha helix within the peptide. 67. A method of detecting HIV-2 infection trom a blood sample with a whole blood assay device, the device comprising a blood filter positioned on top of a reagent layer that contains at least one peptide described by any of claims 1-58. wherein the method comprises applying one or more drops of whole blood to the blood filter, removing the filter, and deteirnining the presence of one or more visual reactions in response to the presence of anti-HIV antibody in the blood sample. 68. A device for detecting HIV-2 infection from a blood sample, comprising a reagent layer having immobilized at least one peptide as described by any of claims 1-58. 69. A kit for determining infection with HIV-2, comprising instructions and a device for detecting the presence of anti-HIV-2 antibody from a sample, wherein the device comprises a peptide described by any of claims 1-58.

Inventors: BERNSTEIN DAVID, CHOWDHURY A MOHAMMED, KOZHICH ALEXANDER, MOTSENBOCKER MARVIN, BERNSTEIN, DAVID, CHOWDHURY, A., MOHAMMED, KOZHICH, ALEXANDER, MOTSENBOCKER, MARVIN
Applicants: BERNSTEIN DAVID, CHOWDHURY A MOHAMMED, KOZHICH ALEXANDER, MOTSENBOCKER MARVIN, PEPTIDE SOLUTIONS, BERNSTEIN, DAVID, CHOWDHURY, A., MOHAMMED, KOZHICH, ALEXANDER, MOTSENBOCKER, MARVIN
Application year: 1999
Main classification: C07K14
IPC codes: C07K14