SYSTEM FOR THE IN VIVO DELIVERY AND EXPRESSION OF HETEROLOGOUS GENES IN THE BONE MARROW

Abstract: The present invention provides a method of delivering immunogenic or therapeutic proteins to bone marrow cells using alphavirus vectors. The alphavirus vectors disclosed herein target specifically to bone marrow tissue, and viral genomes persist in bone marrow for at least three months post-infection. No or very low levels of virus were detected in quadricep, brain, and sera of treated animals. The sequence of a consensus Sindbis cDNA clone, pTR339, and infectious RNA transcripts, infectious virus particles, and pharmaceutical formulations derived therefrom are also disclosed. The sequence of the genomic RNA of the Girdwood S.A. virus, and cDNA clones, infectious RNA transcripts, infectious virus particles, and pharmaceutical formulations derived therefrom are also disclosed.

Description: SYSTEM FOR THE IN VIVO DELIVERY AND EXPRESSION OF HETEROLOGOUS GENES IN THE BONE MARROW FEDERALLY SPONSORED RESEARCH This invention was made with Government support under Grant Number 5 ROl AI22186 from the National Institutes of Health. The Government has certain rights to this invention. FIELD OF THE INVENTION The present invention relates to recombinant DNA technology, and in particular to introducing and expressing foreign DNA in a eukaryotic cell. BACKGROUND OF THE INVENTION The Alphavirus genus includes a variety of viruses all of which are members of the Togaviridae family. The alphaviruses include Eastern Equine Encephalitis virus (EEE) , Vene2πιelan Equine Encephalitis virus (VEE) , Everglades virus, Mucambo virus, Pixuna virus, Western Equine Encephalitis virus (WEE), Sindbis virus, South African Arbovirus No. 86 (S.A.AR 86), Girdwood S.A. virus, Ockelbo virus, Semliki Forest virus, Middelburg virus, Chikungunya virus, O'Nyong-Nyong virus, Ross River virus, Barmah Forest virus, Getah virus, Sagiyama virus, Bebaru virus, Mayaro virus, Una virus, Aura virus, Whataroa virus, Babanki virus, Kyzylagach virus, Highlands J virus, Fort Morgan virus, Ndumu virus, and Buggy Creek virus. The alphavirus genome is a single-stranded, messenger-sense RNA, modified at the 5 '-end with a methylated cap, and at the 3'-end with a variable- length poly (A) tract. The viral genome is divided into two regions: the first encodes the nonstructural or replicase proteins (nsPl-nsP4) and the second encodes the viral structural proteins. Strauss and Strauss, Microbiological Rev. 58, 491- 562, 494 (1994). Structural subunits consisting of a single viral protein, C, associate with themselves and with the RNA genome in an icosahedral nucleocapsid. In the virion, the capsid is surrounded by a lipid envelope covered with a regular array of transmembranal protein spikes, each of which consists of a heterodimeric complex of two glycoproteins, El and E2. See Paredes et al., Proc. Natl. Acad. Sci. USA 90, 9095-99 (1993); Paredes et al., Virology 187, 324- 32 (1993); Pedersen et al., J. Virol. 14:40 (1974). Sindbis virus, the prototype member of the alphavirus genus of the family Togaviridae, and viruses related to Sindbis are broadly distributed throughout Africa, Europe, Asia, the Indian subcontinent, and Australia, based on serological surveys of humans, domestic animals and wild birds. Kokernot et al., Trans. R. Soc. Trop Med. Hyg. 59, 553-62 (1965); Redaksie, S. Afr. Med. J. 42, 197 (1968); Adekolu-John and Fagbami, Trans. R. Soc. Trop. Med. Hyg. 77, 149- 51 (1983); Darwish et al., Trans. R. Soc. Trop. Med. Hyg. 11, 442-45 (1983); Lundstrδm et al., Epidemiol. Infect. 106, 567-74 (1991); Morrill et al., J. Trop. Med. Hyg. 94, 166-68 (1991). The first isolate of Sindbis virus (strain AR339) was recovered from a pool of Culex sp. mosquitoes collected in Sindbis, Egypt in 1953 (Taylor et al., Am. J. Trop. Med. Hyg. 4, 844-62 (1955)), and is the most extensively studied representative of this group. Other members of the Sindbis group of alphaviruses include South African Arbovirus No. 86, Ockelbo82, and Girdwood S.A. These viruses are not strains of the Sindbis virus; they are related to Sindbis AR339, but they are more closely related to each other based on nucleotide sequence and serological comparisons. Lundstrδm et al., J. Wildl. Dis. 29, 189-95 (1993); Simpson et al., Virology 222, 464-69 (1996). Ockelbo82, S.A.AR86 and Girdwood S.A. are all associated with human disease, whereas Sindbis is not. The clinical symptoms of human infection with Ockelbo82, S.A.AR86, or Girdwood S.A. are a febrile illness, general malaise, macropapular rash, and joint pain that occasionally progresses to a polyarthralgia sometimes lasting from a few months to a few years. The study of these viruses has led to the development of beneficial techniques for vaccinating against the alphavirus diseases, and other diseases through the use of alphavirus vectors for the introduction of foreign DNA. See United States Patent No. 5,185,440 to Davis et al., and PCT Publication WO 92/10578. It is intended that all United States patent references be incorporated in their entirety by reference. It is well known that live, attenuated viral vaccines are among the most successful means of controlling viral disease. However, for some virus pathogens, immunization with a live virus strain may be either impractical or unsafe. One alternative strategy is the insertion of sequences encoding immunizing antigens of such agents into a vaccine strain of another virus. One such system utilizing a live VEE vector is described in United States Patent No. 5,505,947 to Johnston et al. Sindbis virus vaccines have been employed as viral carriers in virus constructs which express genes encoding immunizing antigens for other viruses. See United States Patent No. 5,217,879 to Huang et al. Huang et al. describes Sindbis infectious viral vectors. However, the reference does not describe the cDNA sequence of Girdwood S.A. and TR339, nor clones or viral vectors produced therefrom. Another such system is described by Hahn et al., Proc. Natl. Acad. Sci. USA 89:2679 (1992), wherein Sindbis virus constructs which express a truncated form of the influenza hemagglutinin protein are described. The constructs are used to study antigen processing and presentation in vitro and in mice. Although no infectious challenge dose is tested, it is also suggested that such constructs might be used to produce protective B- and T-cell mediated immunity. London et al., Proc. Natl. Acad. Sci, USA 89, 207-11 (1992), disclose a method of producing an immune response in mice against a lethal Rift Valley Fever (RVF) virus by infecting the mice with an infectious Sindbis virus containing an RVF epitope. London does not disclose using Girdwood S.A. or TR339 to induce an immune response in animals. Viral carriers can also be used to introduce and express foreign DNA in eukaryotic cells. One goal of such techniques is to employ vectors that target expression to particular cells and/or tissues. A current approach has been to remove target cells from the body, culture them ex vivo, infect them with an expression vector, and then reintroduce them into the patient. PCT Publication No. WO 92/10578 to Garoff and Liljestrδm provide a system for introducing and expressing foreign proteins in animal cells using alphaviruses. This reference discloses the use of Se liki Forest virus to introduce and express foreign proteins in animal cells. The use of Girdwood S.A. or TR339 is not discussed. Furthermore, this reference does not provide a method of targeting and introducing foreign DNA into specific cell or tissue types. Accordingly, there remains a need in the art for full-length cDNA clones of positive-strand RNA viruses, such as Girdwood S.A and TR339. In addition, there is an ongoing need in the art for improved vaccination strategies. Finally, there remains a need in the art for improved methods and nucleic acid sequences for delivering foreign DNA to target cells. SUMMARY OF THE INVENTION A first aspect of the present invention is a method of introducing and expressing heterologous RNA in bone marrow cells, comprising: (a) providing a recombinant alphavirus, the alphavirus containing a heterologous RNA segment, the heterologous RNA segment comprising a promoter operable in bone marrow cells operatively associated with a heterologous RNA to be expressed in bone marrow cells; and then (b) contacting the recombinant alphavirus to the bone marrow cells so that the heterologous RNA segment is introduced and expressed therein. As a second aspect, the present invention provides a helper cell for expressing an infectious, propagation defective, Girdwood S.A. virus particle, comprising, in a Girdwood S.A.-permissive cell: (a) a first helper RNA encoding (i) at least one Girdwood S.A. structural protein, and (ii) not encoding at least one other Girdwood S.A. structural protein; and (b) a second helper RNA separate from the first helper RNA, the second helper RNA (/) not encoding the at least one Girdwood S.A. structural protein encoded by the first helper RNA, and (ii) encoding the at least one other Girdwood S.A. structural protein not encoded by the first helper RNA, and with all of the Girdwood S.A. structural proteins encoded by the first and second helper RNAs assembling together into Girdwood S.A. particles in the cell containing the replicon RNA; and wherein the Girdwood S.A. packaging segment is deleted from at least the first helper RNA. A third aspect of the present invention is a method of making infectious, propagation defective, Girdwood S.A. virus particles, comprising: transfecting a Girdwood S.A.-permissive cell with a propagation defective replicon RNA, the replicon RNA including the Girdwood S.A. packaging segment and an inserted heterologous RNA; producing the Girdwood S.A. virus particles in the transfected cell; and then collecting the Girdwood S.A. virus particles from the cell. Also disclosed are infectious Girdwood S.A. RNAs, cDNAs encoding the same, infectious Girdwood S.A. virus particles, and pharmaceutical formulations thereof. As a fourth aspect, the present invention provides a helper cell for expressing an infectious, propagation defective, TR339 virus particle, comprising, in a TR339-permissive cell: (a) a first helper RNA encoding (i) at least one TR339 structural protein, and (ii) not encoding at least one other TR339 structural protein; and (b) a second helper RNA separate from the first helper RNA, the second helper RNA (i) not encoding the at least one TR339 structural protein encoded by the first helper RNA, and (ii) encoding the at least one other TR339 structural protein not encoded by the first helper RNA, and with all of the TR339 structural proteins encoded by the first and second helper RNAs assembling together into TR339 particles in the cell containing the replicon RNA; and wherein the TR339 packaging segment is deleted from at least the first helper RNA. A fifth aspect of the present invention is a method of making infectious, propagation defective, TR339 virus particles, comprising: transfecting a TR339-permissive cell with a propagation defective replicon RNA, the replicon RNA including the TR339 packaging segment and an inserted heterologous RNA; producing the TR339 virus particles in the transfected cell; and then collecting the TR339 virus particles from the cell. Also disclosed are infectious TR339 RNAs, cDNAs encoding the same, infectious TR339 virus particles, and pharmaceutical formulations thereof. As a sixth aspect, the present invention provides a recombinant DNA comprising a cDNA coding for .an infectious Girdwood S.A. virus RNA transcript, and a heterologous promoter positioned upstream from the cDNA and operatively associated therewith. The present invention also provides infectious RNA transcripts encoded by the above-mentioned cDNA and infectious viral particles containing the infectious RNA transcripts. As a seventh aspect, the present invention provides a recombinant DNA comprising a cDNA coding for a Sindbis strain TR339 RNA transcript, and a heterologous promoter positioned upstream from the cDNA and operatively associated therewith. The present invention also provides infectious RNA transcripts encoded by the above-mentioned cDNA and infectious viral particles containing the infectious RNA transcripts. The foregoing and other aspects of the present invention are described in the detailed description set forth below. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 presents the cDNA sequence (SEQ ID NO:l) of S.A.AR86. The RNA sequence of the 5' 40 nucleotides was obtained by direct sequencing of the genomic RNA. The rest of the genome was sequenced by RT- PCR of fragments amplified from virion RNA. Nucleotides 1 through 59 represent the 5' UTR, the non-structural polyprotein is encoded by nucleotides 60 through 7559 (nsPl~nt60 through ntl679; nsP2-ntl680 through nt4099; nsP3- nt4100 through nt5729; nsP4-nt5730 through nt7559), the structural polyprotein is encoded by nucleotides 7608 through 11342 (capsid--nt7608 through nt8399; E3- -nt8400 through nt8591; E2-nt8592 through nt9860; 6K-nt9861 through ntl0025; El~ntl0026 through ntll342), and the 3' UTR is represented by nucleotides 11346 through 11663. Figure 1A shows nucleotides 1 through 3800 of the cDNA sequence of S.A.AR86. Figure IB shows nucleotides 3801 through 7900 of the cDNA sequence of S.A. AR86. Figure IC shows nucleotides 7901 through 11663 of the cDNA sequence of S.A.AR86. Figure 2 presents the putative amino acid sequences of the S.A.AR86 polyproteins (SEQ ID NO:2 and SEQ ID NO:3). The amino acids were derived from the S.A.AR86 cDNA sequence given in Figure 1 (SEQ ID NO:l). Figure 2A shows the amino acid sequence of the non-structural polyprotein of S.A.AR86 (SEQ ED NO:2). Figure 2B shows the amino acid sequence of the structural polyprotein of S.A.AR86 (SEQ ED NO:3). Figure 3 presents the cDNA sequence (SEQ ED NO:4) of Girdwood S.A. The RNA sequence of the 5' 40 nucleotides was obtained by direct sequencing of the genomic RNA. The rest of the genome sequence was obtained by sequencing of fragments amplified by RT-PCR from virion RNA. An "N" in the sequence indicates that the identity of the nucleotide at that position is unknown. Nucleotides 1 through 59 represent the 5' UTR, the non-structural polyprotein is encoded by nucleotides 60 through 7613 (nsPl-nt60 through ntl679; nsP2~ntl680 through nt4099; nsP3-nt4100 through nt5762 or nt5783; nsP4— nt5784 through nt7613), the structural polyprotein is encoded by nucleotides 7662 through 11396 (capsid~nt7662 through nt8453; E3-nt8454 through nt8645; E2~nt8646 through nt9914, 6K--9915 through ntl0079; El~ntl0080 through ntll396), and the 3' UTR is represented by nucleotides 11400 through 11717. There is an opal termination codon at nucleotides 5763 through 5765. Figure 3 A shows nucleotides 1 through 3800 of the cDNA sequence of Girdwood S.A. Figure 3B shows nucleotides 3801 through 7900 of the cDNA sequence of Girdwood S.A. Figure 3C shows nucleotides 7901 through 11717 of the cDNA sequence of Girdwood S.A. Figure 4 illustrates the putative amino acid sequences of the Girdwood S.A. polyproteins (SEQ ED NO:5 and SEQ ED NO:6). The amino acids were derived from the Girdwood S.A. cDNA sequence given in Figure 3 (SEQ ED NO:4). Figure 4A shows the amino acid sequence of the non-structural polyprotein of Girdwood S.A. The sequence terminates at the opal termination codon. The complete amino acid sequence is presented in SEQ ED NO:5. Figure 4B shows the amino acid sequence of the structural polyprotein of Girdwood S.A. (SEQ ED NO:6). Figure 5 illustrates the nucleotide sequence (SEQ ED NO:7) of clone pS55, a cDNA clone of the S.A.AR86 genomic RNA. Figure 5A shows nucleotides 1 through 6720 of the cDNA sequence of pS55. Figure 5B shows nucleotides 6721 through 11663 of the cDNA sequence of pS55. Figure 6 presents the cDNA sequence (SEQ ED NO: 8) of clone pTR339. The TR339 virus is derived from this clone. Nucleotides 1 through 59 represent the 5' UTR, the non-structural polyprotein is encoded by nucleotides 60 through 7598 (nsPl-nt60 through ntl679; nsP2-ntl680 through nt4099; nsP3- nt4100 through nt5747 or 5768; nsP4~nt5769 through nt7598), the structural polyprotein is encoded by nucleotides 7647 through 11381 (capsid~nt7647 through nt8438; E3-nt8439 through nt8630; E2-nt8631 through nt9899; 6K-nt9900 through ntl0064; El-ntl0065 through ntll381), and the 3' UTR is represented by nucleotides 11382 through 11703. There is an opal termination codon at nucleotides 5748 through 5750. Figure 6A shows nucleotides 1 through 6720 of the cDNA sequence of pTR339. Figure 6B shows nucleotides 6721 through 11703 of the cDNA sequence of pTR339. DETAILED DESCRIPTION OF THE INVENTION The production and use of recombinant DNA, vectors, transformed host cells, selectable markers, proteins, and protein fragments by genetic engineering are well-known to those skilled in the art. See, e.g. , United States Patent No. 4,761,371 to Bell et al. at Col. 6 line 3 to Col. 9 line 65; United States Patent No. 4,877, 729 to Clark et al. at Col. 4 line 38 to Col. 7 line 6; United States Patent No. 4,912,038 to Schilling at Col 3 line 26 to Col 14 line 12; and United States Patent No. 4,879,224 to Wallner at Col. 6 line 8 to Col. 8 line 59. The term "alphavirus" has its conventional meaning in the art, and includes the various species of alphaviruses such as Eastern Equine Encephalitis virus (EEE), Venezuelan Equine Encephalitis virus (VEE), Everglades virus, Mucambo virus, Pixuna virus, Western Encephalitis virus (WEE), Sindbis virus, South African Arbovirus No. 86, Girdwood S.A. virus, Ockelbo virus, Semliki Forest virus, Middelburg virus, Chikungunya virus, O'Nyong-Nyong virus, Ross River virus, Barmah Forest virus, Getah virus, Sagiyama virus, Bebaru virus, Mayaro virus, Una virus, Aura virus, Whataroa virus, Babanki virus, Kyzlagach virus, Highlands J virus, Fort Morgan virus, Ndumu virus, Buggy Creek virus, and any other virus classified by the International Committee on Taxonomy of Viruses (ICTV) as an alphavirus. The preferred alphaviruses for use in the present invention include Sindbis virus strains (e.g. , TR339), Girdwood S.A., S.A.AR86, and Ockelbo82. An "Old World alphavirus" is a virus that is primarily distributed throughout the Old World. Alternately stated, an Old World alphavirus is a virus that is primarily distributed throughout Africa, Asia, Australia and New Zealand, or Europe. Exemplary Old World viruses include SF group alphaviruses and SIN group alphaviruses. SF group alphaviruses include Semliki Forest virus, Middelburg virus, Chikungunya virus, O'Nyong-Nyong virus, Ross River virus, Barmah Forest virus, Getah virus, Sagiyama virus, Bebaru virus, Mayaro virus, and Una virus. SIN group alphaviruses include Sindbis virus, South African Arbovirus No. 86, Ockelbo virus, Girdwood S.A. virus, Aura virus, Whataroa virus, Babanki virus, and Kyzylagach virus. Acceptable alphaviruses include those containing attenuating mutations. The phrases "attenuating mutation" and "attenuating amino acid," as used herein, mean a nucleotide sequence containing a mutation, or an amino acid encoded by a nucleotide sequence containing a mutation, which mutation results in a decreased probability of causing disease in its host (i.e. , a loss of virulence), in accordance with standard terminology in the art, whether the mutation be a substitution mutation or an in-frame deletion mutation. See, e.g., B. DAVIS ET AL., MICROBIOLOGY 132 (3d ed. 1980). The phrase "attenuating mutation" excludes mutations or combinations of mutations which would be lethal to the virus. Appropriate attenuating mutations will be dependent upon the alphavirus used. Suitable attenuating mutations within the alphavirus genome will be known to those skilled in the art. Exemplary attenuating mutations include, but are not limited to, those described in United States Patent No. 5,505,947 to Johnston et al., copending United States application 08/448,630 to Johnston et al., and copending United States application 08/446,932 to Johnston et al. It is intended that all United States patent references be incorporated in their entirety by reference. Attenuating mutations may be introduced into the RNA by performing site-directed mutagenesis on the cDNA which encodes the RNA, in accordance with known procedures. See, Kunkel, Proc. Natl. Acad. Sci. USA 82, 488 (1985), the disclosure of which is incorporated herein by reference in its entirety. Alternatively, mutations may be introduced into the RNA by replacement of homologous restriction fragments in the cDNA which encodes for the RNA, in accordance with known procedures. I. Methods for Introducing and Expressing Heterologous RNA in Bone Marrow Cells. The present invention provides methods of using a recombinant alphavirus to introduce and express a heterologous RNA in bone marrow cells. Such methods are useful as vaccination strategies when the heterologous RNA encodes an immunogenic protein or peptide. Alternatively, such methods are useful in introducing and expressing in bone marrow cells an RNA which encodes a desirable protein or peptide, for example, a therapeutic protein or peptide. The present invention is carried out using a recombinant alphavirus to introduce a heterologous RNA into bone marrow cells. Any alphavirus that targets and infects bone marrow cells is suitable. Preferred alphaviruses include Old World alphaviruses, more preferably SF group alphaviruses and SIN group alphaviruses, more preferably Sindbis virus strains (e.g. , TR339), S.A.AR86 virus, Girdwood S.A. virus, and Ockelbo virus. In a more preferred embodiment, the alphavirus contains one or more attenuating mutations, as described hereinabove. Two types of recombinant virus vector are contemplated in carrying out the present invention. In one embodiment employing "double promoter vectors," the heterologous RNA is inserted into a replication and propagation competent virus. Double promoter vectors are described in United States Patent No. 5,505,947 to Johnston et al. With this type of viral vector, it is preferable that heterologous RNA sequences of less than 3 kilobases are inserted into the viral vector, more preferably those less than 2 kilobases, and more preferably still those less than 1 kilobase. In an alternate embodiment, propagation-defective "replicon vectors," as described in copending United States application 08/448,630 to Johnston et al. , will be used. One advantage of replicon viral vectors is that larger RNA inserts, up to approximately 4-5 kilobases in length can be utilized. Double promoter vectors and replicon vectors are described in more detail hereinbelow. The recombinant alphaviruses of the claimed method target die heterologous RNA to bone marrow cells, where it expresses the encoded protein or peptide. Heterologous RNA can be introduced and expressed in any cell type found in the bone marrow. Bone marrow cells that may be targeted by the recombinant alphaviruses of the present invention include, but are not limited to, polymorphonuclear cells, hemopoietic stem cells (including megakaryocyte colony foπning units (CFU-M), spleen colony forming units (CFU-S), erythroid colony forming units (CFU-E), erythroid burst forming units (BFU-E), and colony forming units in culture (CFU-C), erythrocytes, macrophages (including reticular cells), monocytes, granulocytes, megakaryoctyes, lymphocytes, fibroblasts, osteoprogenitor cells, osteoblasts, osteoclasts, marrow stromal cells, chondrocytes and other cells of synovial joints. Preferably, marrow cells within the endosteum are targeted, more preferably osteoblasts. Also preferred are methods in which cells in the endosteum of synovial joints (e.g. , hip and knee joints) are targeted. By targeting to the cells of the bone marrow, it is meant that the primary site in which the virus will be localized in vivo is the cells of the bone marrow. Alternately stated, the alphaviruses of the present invention target bone marrow cells, such that titers in bone marrow two days after infection are greater than 100 PFU/g crushed bone, preferably greater than 200 PFU/g crushed bone, more preferably greater than 300 PFU/g crushed bone, and more preferably still greater than 500 PFU/g crushed bone. Virus may be detected occasionally in other cell or tissue types, but only sporadically and usually at low levels. Virus localization in the bone marrow can be demonstrated by any suitable technique known in the art, such as in situ hybridization. Bone marrow cells are long-lived and harbor infectious alphaviruses for a prolonged period of time, as demonstrated in the Examples below. These characteristics of bone marrow cells render the present invention useful not only for the purpose of supplying a desired protein or peptide to skeletal tissue, but also for expressing proteins or peptides in vivo that are needed by other cell or tissue types. The present invention can be carried out in vivo or with cultured bone marrow cells in vitro. Bone marrow cell cultures include primary cultures of bone marrow cells, serially-passaged cultures of bone marrow cells, and cultures of immortalized bone marrow cell lines. Bone marrow cells may be cultured by any suitable means known in the art. The recombinant alphaviruses of the present invention carry a heterologous RNA segment. The heterologous RNA segment encodes a promoter and an inserted heterologous RNA. The inserted heterologous RNA may encode any protein or a peptide which is desirably expressed by the host bone marrow cells. Suitable heterologous RNA may be of prokaryotic (e.g. , RNA encoding the Botulinus toxin C), or eukaryotic (e.g. , RNA encoding malaria Plasmodium protein csl) origin. Illustrative proteins and peptides encoded by the heterologous RNAs of the present invention include hormones, growth factors, terleukins, cytokines, chemokines, enzymes, and ribozymes. Alternately, the heterologous RNAs encode any therapeutic protein or peptide. As a further alternative, the heterologous RNAs of the present invention encode any immunogenic protein or peptide. An immunogenic protein or peptide, or "immunogen," may be any protein or peptide suitable for protecting the subject against a disease, including but not limited to microbial, bacterial, protozoal, parasitic, and viral diseases. For example, the immunogen may be an orthomyxovirus -immunogen (e.g. , an influenza virus immunogen, such as the influenza virus hemagglutinin (HA) surface protein or the influenza virus nucleoprotein gene, or an equine influenza virus immunogen), or a lentivirus immunogen (e.g. , an equine infectious anemia virus immunogen, a Simian Immunodeficiency Virus (SIV) immunogen, or a Human Immunodeficiency Virus (HIV) immunogen, such as the HIV envelope GP160 protein and the HIV matrix/capsid proteins). The immunogen may also be an arenavirus immunogen (e.g. , Lassa fever virus immunogen, such as the Lassa fever virus nucleocapsid protein gene and the Lassa fever envelope glycoprotein gene), a poxvirus immunogen (e.g. , vaccinia), a flavivirus immunogen (e.g. , a yellow fever virus immunogen or a Japanese encephalitis virus immunogen), a filovirus immunogen (e.g. , an Ebola virus immunogen, or a Marburg virus immunogen), a bunyavirus immunogen (e.g. , RVFV, CCHF, and SFS viruses), or a coronavirus immunogen (e.g. , an infectious human coronavirus immunogen, such as the human coronavirus envelope glycoprotein gene, or a transmissible gastroenteritis virus immunogen for pigs, or an infectious bronchitis virus immunogen for chickens). Alternatively, the present invention can be used to express heterologous RNAs encoding antisense oligonucleotides. In general, "antisense" refers to the use of small, synthetic oligonucleotides to inhibit gene expression by inhibiting the function of the target rnRNA containing the complementary sequence. Milligan, J.F. et al., J. Med. Chem. 36(14), 1923-1937 (1993). Gene expression is inhibited through hybridization to coding (sense) sequences in a specific mRNA target by hydrogen bonding according to Watson-Crick base pairing rules. The mechanism of antisense inhibition is that the exogenously applied oligonucleotides decrease the mRNA and protein levels of the target gene. Milligan, J.F. et al., J. Med. Chem. 36(14), 1923-1937 (1993). See also Helene, C. and Toulme, J., Biochim. Biophys. Acta 1049, 99-125 (1990); Cohen, J.S., Ed., OLIGODEOXYNUCLEOTIDES AS ANTISENSE INHIBITORS OF GENE EXPRESSION, CRC Press:Boca Raton, FL (1987). Antisense oligonucleotides may be of any suitable length, depending on the particular target being bound. The only limits on the length of the antisense oligonucleotide is the- capacity of the virus for inserted heterologous RNA. Antisense oligonucleotides may be complementary to the entire mRNA transcript of the target gene or only a portion thereof. Preferably the antisense oligonucleotide is directed to an mRNA region containing a junction between intron and exon. Where the antisense oligonucleotide is directed to an intron/exon junction, it may either entirely overlie the junction or may be sufficiently close to the junction to inhibit splicing out of the intervening exon during processing of precursor mRNA to mature mRNA (e.g. , with the 3' or 5' terminus of the antisense oligonucleotide being positioned within about, for example, 10, 5, 3 or 2 nucleotides of the intron/exon junction). Also preferred are antisense oligonucleotides which overlap the initiation codon. When practicing the present invention, the antisense oligonucleotides administered may be related in origin to the species to which it is administered. When treating humans, human antisense may be used if desired. Promoters for use in carrying out the present invention are operable in bone marrow cells. An operable promoter in bone marrow cells is a promoter that is recognized by and functions in bone marrow cells. Promoters for use with the present invention must also be operatively associated with the heterologous RNA to be expressed in the bone marrow. A promoter is operably linked to a heterologous RNA if it controls the transcription of the heterologous RNA, where the heterologous RNA comprises a coding sequence. Suitable promoters are well known in the art. The Sindbis 26S promoter is preferred when the alphavirus is a strain of Sindbis virus. Additional preferred promoters beyond the Sindbis 26S promoter include the Girdwood S.A. 26S promoter when the alphavirus is Girdwood S.A., the S.A.AR86 26S promoter when the alphavirus is S.A.AR86, and any other promoter sequence recognized by alphavirus polymerases. Alphavirus promoter sequences containing mutations which alter the activity level of the promoter (in relation to the activity level of the wild-type) are also suitable in the practice of the present invention. Such mutant promoter sequences are described in Raju and Huang, J. Virol. 65, 2501-2510 (1991), the disclosure of which is incorporated in its entirety by reference. The heterologous RNA is introduced into the bone marrow cells by contacting the recombinant alphavirus carrying the heterologous RNA segment to the bone marrow cells. By contacting, it is meant bringing the recombinant alphavirus and the bone marrow cells in physical proximity. The contacting step can be performed in vitro or in vivo. In vitro contacting can be carried out with culmres of immortalized or non- immortalized bone marrow cells. In one particular embodiment, bone marrow cells can be removed from a subject, cultured in vitro, infected with the vector, and then introduced back into the subject. Contacting is performed in vivo when the recombinant alphavirus is administered to a subject. Pharmaceutical formulations of recombinant alphavirus can be administered to a subject parenterally (e.g. , subcutaneous, intracerebral, intradermal, intramuscular, intravenous and intraarticular) administration. Alternatively, pharmaceutical formulations of the present invention may be suitable for administration to the mucus membranes of a subject (e.g. , intranasal administration, by use of a dropper, swab, or inhaler). Methods of preparing infectious virus particles and pharmaceutical formulations thereof are discussed in more detail hereinbelow. By "introducing" the heterologous RNA segment into the bone marrow cells it is meant infecting the bone marrow cells with recombinant alphavirus containing the heterologous RNA, such that the viral vector carrying the heterologous RNA enters the bone marrow cells and can be expressed therein. As used with respect to the present invention, when the heterologous RNA is "expressed," it is meant that the heterologous RNA is transcribed. In particular embodiments of the invention in which it is desired to produce a protein or peptide, expression further includes the steps of post-transcriptional processing and translation of the mRNA transcribed from the heterologous RNA. In contrast, where the heterologous RNA encodes an antisense oligonucleotide, expression need not include post-transcriptional processing and translation. With respect to embodiments in which the heterologous RNA encodes an immunogenic protein or a protein being administered for therapeutic purposes, expression may also include the further step of post-translational processing to produce an immunogenic or therapeutically-active protein. The present invention also provides infectious RNAs, as described hereinabove, and cDNAs encoding the same. Preferably the infectious RNAs and cDNAs are derived from the S.A.AR86, Girdwood S.A., TR339, or Ockelbo viruses. The cDNA clones can be generated by any of a variety of suitable methods known to those skilled in the art. A preferred method is the method set forth in United States Patent No. 5,185,440 to Davis et al., the disclosure of which is incorporated in its entirety by reference, and Gubler et al., Gene 25:263 (1983). RNA is preferably synthesized from the DNA sequence in vitro using purified RNA polymerase in the presence of ribonucleotide triphosphates and cap analogs in accordance with conventional techniques. However, the RNA may also be synthesized intracellularly after introduction of the cDNA. A. Double Promoter Vectors. In one embodiment of the invention, double promoter vectors are used to introduce the heterologous RNA into the target bone marrow cells. A double promoter virus vector is a replication and propagation competent virus. Double promoter vectors are described in United States Patent No. 5,505,947 to Johnston et al., the disclosure of which is incorporated in its entirety by reference. Preferred alphaviruses for constructing the double promoter vectors are S. A.AR86, Girdwood S.A., TR339 and Ockelbo viruses. More preferably, the double promoter vector contains one or more attenuating mutations. Attenuating mutations are described in more detail hereinabove. The double promoter vector is constructed so as to contain a second subgenomic promoter (i.e. , 26S promoter) inserted 3' to the virus RNA encoding the structural proteins. The heterologous RNA is inserted between the second subgenomic promoter, so as to be operatively associated therewith, and the 3' UTR of the virus genome. Heterologous RNA sequences of less than 3 kilobases, more preferably those less than 2 kilobases, and more preferably still those less than 1 kilobase, can be inserted into the double promoter vector. In a preferred embodiment of the invention, the double promoter vector is derived from Girdwood S.A., and the second subgenomic promoter is a duplicate of the Girdwood S.A. subgenomic promoter. In an alternate preferred embodiment, the double promoter vector is derived from TR339, and the second subgenomic promoter is a duplicate of the TR339 subgenomic promoter. B. Replicon Vectors. Replicon vectors, which are propagation-defective virus vectors can also be used to carry out the present invention. Replicon vectors are described in more detail in copending United States Application 08/448,630 to Johnston et al., the disclosure of which is incorporated in its entirety by reference. Preferred alphaviruses for constructing the replicon vectors are S.A.AR86, Girdwood S.A., TR339, and Ockelbo. In general, in the replicon system, a foreign gene to be expressed is inserted in place of at least one of the viral structural protein genes in a transcription plasmid containing an otherwise full-length cDNA copy of the alphavirus genome RNA. RNA transcribed from this plasmid contains an intact copy of the viral nonstructural genes which are responsible for RNA repUcation and transcription. Thus, if the transcribed RNA is transfected into susceptible cells, it will be replicated and translated to give the nonstructural proteins. These proteins will transcribe the transfected RNA to give high levels of subgenomic mRNA, which will then be translated to produce high levels of the foreign protein. The autonomously replicating RNA (i.e. , replicon) can only be packaged into virus particles if the alphavirus structural protein genes are provided on one or more "helper" RNAs, which are cotransfected into cells along with the replicon RNA. The helper RNAs do not contain the viral nonstructural genes for replication, but these functions are provided in trans by the replicon RNA. Similarly, the transcriptase functions translated from the replicon RNA transcribe " the structural protein genes on the helper RNA, resulting in the synthesis of viral structural proteins and packaging of the replicon into virus-like particles. As the packaging or encapsidation signal for alphavirus RNAs is located within the nonstructural genes, the absence of these sequences in the helper RNAs precludes their incorporation into virus particles. Alphavirus-permissive cells employed in the methods of the present invention are cells which, upon transfection with the viral RNA transcript, are capable of producing viral particles. Preferred alphavirus-permissive cells are TR339-permissive cells, Girdwood S.A.-permissive cells, S.A.AR86-permissivecells, and Ockelbo-permissive cells. Alphaviruses have a broad host range. Examples of suitable host cells include, but are not limited to Vero cells, baby hamster kidney (BHK) cells, and chicken embryo fibroblast cells. The phrase "structural protein" as used herein refers to the encoded proteins which are required for encapsidation (e.g. , packaging) of the RNA replicon, and include the capsid protein, El glycoprotein, and E2 glycoprotein. As described hereinabove, the structural proteins of the alphavirus are distributed among one or more helper RNAs (i.e. , a first helper RNA and a second helper RNA). In addition, one or more structural proteins may be located on the same RNA molecule as the replicon RNA, provided that at least one structural protein is deleted from the replicon RNA such that the resulting alphavirus particle is propagation defective. As used herein, the terms "deleted" or "deletion" mean either total deletion of the specified segment or the deletion of a sufficient portion of the specified segment to render the segment inoperative or nonfunctional, in accordance with standard usage. See, e.g., U.S. Patent No. 4,650,764 to Temin et al. The term "propagation defective" as used herein, means that the replicon RNA cannot be encapsidated in the host cell in the absence of the helper RNA. The resulting alphavirus replicon particles are propagation defective inasmuch as the replicon RNA in these particles does not include all of the alphavirus structural proteins required for encapsidation, at least one of the required structural proteins being deleted therefrom, such that the replicon RNA initiates only an abortive infection; no new viral particles are produced, and there is no spread of the infection to other cells. The helper cell for expressing the infectious, propagation defective alphavirus particle comprises a set of RNAs, as described above. The set of RNAs principally include a first helper RNA and a second helper RNA. The first helper RNA includes RNA encoding at least one alphavirus structural protein but does not encode all alphavirus structural proteins. In other words, the first helper RNA does not encode at least one alphavirus structural protein; the at least one non-coded alphavirus structural protein being deleted from the first helper RNA. In one embodiment, the first helper RNA includes RNA encoding the alphavirus El glycoprotein, with the alphavirus capsid protein and the alphavirus E2 glycoprotein being deleted from the first helper RNA. In another embodiment, the first helper RNA includes RNA encoding the alphavirus E2 glycoprotein, with the alphavirus capsid protein and the alphavirus El glycoprotein being deleted from the first helper RNA. In a third, preferred embodiment, the first helper RNA includes RNA encoding the alphavirus El glycoprotein and the alphavirus E2 glycoprotein, with the alphavirus capsid protein being deleted from the first helper RNA. The second helper RNA includes RNA encoding at least one alphavirus structural protein which is different from the at least one structural protein encoded by the first helper RNA. Thus, the second helper RNA encodes at least one alphavirus structural protein which is not encoded by the first helper RNA. The second helper RNA does not encode the at least one alphavirus structural protein which is encoded by the first helper RNA, thus the first and second helper RNAs do not encode duplicate structural proteins. In the embodiment wherein the first helper RNA includes RNA encoding only the alphavirus El glycoprotein, the second helper RNA may include RNA encoding one or both of the alphavirus capsid protein and the alphavirus E2 glycoprotein which are deleted from the first helper RNA. In the embodiment wherein, the first helper RNA includes RNA encoding only the alphavirus E2 glycoprotein, the second helper RNA may include RNA encoding one or both of the alphavirus capsid protein and the alphavirus El glycoprotein which are deleted from me first helper RNA. In the embodiment wherein the first helper RNA includes RNA encoding both the alphavirus El glycoprotein and the alphavirus E2 glycoprotein, the second helper RNA may include RNA encoding the alphavirus capsid protein which is deleted from the first helper RNA. In one embodiment, the packaging segment (RNA comprising me encapsidation or packaging signal) is deleted from at least the first helper RNA. In a preferred embodiment, the packaging segment is deleted from both the first helper RNA and the second helper RNA. In the preferred embodiment wherein the packaging segment is deleted from both the first helper RNA and the second helper RNA, the helper cell is co-transfected with a replicon RNA in addition to the first helper RNA and me second helper RNA. The replicon RNA encodes the packaging segment and an inserted heterologous RNA. The inserted heterologous RNA may be RNA encoding a protein or a peptide. In a preferred embodiment, the replicon RNA, the first helper RNA and the second helper RNA are provided on separate molecules such that a first molecule, i.e. , the replicon RNA, includes RNA encoding the packaging segment and the inserted heterologous RNA, a second molecule, i.e. , the first helper RNA, includes RNA encoding at least one but not all of the required alphavirus structural proteins, and a third molecule, i.e. , the second helper RNA, includes RNA encoding at least one but not all of the required alphavirus structural proteins. For example, in one preferred embodiment of the present invention, the helper cell includes a set of RNAs which include (a) a replicon RNA including RNA encoding an alphavirus packaging sequence and an inserted heterologous RNA, (b) a first helper RNA including RNA encoding the alphavirus El glycoprotein and the alphavirus E2 glycoprotein, and (c) a second helper RNA including RNA encoding the alphavirus capsid protein so that the ' alphavirus El glycoprotein, the alphavirus E2 glycoprotein and the capsid protein assemble together into alphavirus particles in the host cell. In an alternate embodiment, the replicon RNA and the first helper RNA are on separate molecules, and the replicon RNA and RNA encoding a structural gene not encoded by the first helper RNA are on another single molecule together, such that a first molecule, i.e. , the first helper RNA, including RNA encoding at least one but not all of the required alphavirus structural proteins, and a second molecule, i.e. , the replicon RNA, including RNA encoding the packaging segment, the inserted heterologous RNA, and the remaining structural proteins not encoded by the first helper RNA. For example, in one preferred embodiment of the present invention, the helper cell includes a set of RNAs including (a) a replicon RNA including RNA encoding an alphavirus packaging sequence, an inserted heterologous RNA, and an alphavirus capsid protein, and (b) a first helper RNA including RNA encoding the alphavirus El glycoprotein and the alphavirus E2 glycoprotein so that the alphavirus El glycoprotein, the alphavirus E2 glycoprotein and the capsid protein assemble together into alphavirus particles in the host cell, with the replicon RNA packaged therein. In one preferred embodiment of the present invention, the RNA encoding the alphavirus structural proteins, i.e. , the capsid, El glycoprotein and E2 glycoprotein, contains at least one attenuating mutation, as described hereinabove. Thus, according to this embodiment, at least one of the first helper RNA and the second helper RNA includes at least one attenuating mutation. In a more preferred embodiment, at least one of the first helper RNA and the second helper RNA includes at least two, or multiple, attenuating mutations. The multiple attenuating mutations may be positioned in either the first helper RNA or in the second helper RNA, or they may be distributed randomly with one or more attenuating mutations being positioned in the first helper RNA and one or more attenuating mutations positioned in the second helper RNA. Alternatively, when the replicon RNA and the RNA encoding the structural proteins not encoded by the first helper RNA are located on the same molecule, an attenuating mutation may be positioned in the RNA which codes for the structural protein not encoded by the first helper RNA. The attenuating mutations may also be located within the RNA encoding non-structural proteins (e.g. , the replicon RNA). Preferably, the first helper RNA and the second helper RNA also include a promoter. It is also preferred that the replicon RNA also includes a promoter. Suitable promoters for inclusion in the first helper RNA, second helper RNA and replicon RNA are well known in the art. One preferred promoter is the Girdwood S.A. 26S promoter for use when the alphavirus is Girdwood S.A. Another preferred promoter is the TR339 26S promoter for use when the alphavirus is TR339. Additional promoters beyond the Girdwood S.A. and TR339 promoters include the VEE 26S promoter, the Sindbis 26S promoter, the Semliki Forest 26S promoter, and any other promoter sequence recognized by alphavirus polymerases. Alphavirus promoter sequences containing mutations which alter the activity level of the promoter (in relation to the activity level of the wild-type) are also suitable in the practice of the present invention. Such mutant promoter sequences are described in Raju and Huang, J. Virol. 65, 2501-2510 (1991), the disclosure of which is incorporated herein in its entirety. In the system wherein the first helper RNA, the second helper RNA, and the replicon RNA are all on separate molecules, the promoters, if the same promoter is used for all three RNAs, provide a homologous sequence between the three molecules. It is preferred that the selected promoter is operative with the non-structural proteins encoded by the replicon RNA molecule. In cases where vaccination with two immunogens provides improved protection against disease as compared to vaccination with only a single immunogen, a double-promoter replicon would ensure that both immunogens are produced in the same cell. Such a replicon would be the same as the one described above, except that it would contain two copies of the 26S RNA promoter, each followed by a different multiple cloning site, to allow for the insertion and expression of two different heterologous proteins. Another useful strategy is to insert the IRES sequence from the picornavirus, EMC virus, between the two heterologous genes downstream from the single 26S promoter of the replicon described above, thus leading to expression of two immunogens from the single replicon transcript in the same cell. C. Uses of the Present Invention. The alphavirus vectors, RNAs, cDNAs, helper cells, infectious virus particles, and methods of the present invention find use in in vitro" expression systems, wherein the inserted heterologous RNA encodes a protein or peptide which is desirably produced in vitro. The RNAs, cDNAs, helper cells, infectious virus particles, methods, and pharmaceutical formulations of the present invention are additionally useful in a method of administering a protein or peptide to a subject in need of the protein or peptide, as a method of treatment or otherwise. In this embodiment of the invention, the heterologous RNA encodes the desired protein or peptide, and pharmaceutical formulations of the present invention are administered to a subject in need of the desired protein or peptide. In this manner, the protein or peptide may thus be produced in vivo in the subject. The subject may be in need of the protein or peptide because the subject has a deficiency thereof, or because the production of the protein or peptide in the subject may impart some therapeutic effect, as a method of treatment or otherwise. Alternately, the claimed methods provide a vaccination strategy, wherein the heterologous RNA encodes an immunogenic protein or peptide. The methods and products of the invention are also useful as antigens and for evoking the production of antibodies in animals such as horses and rabbits, from which the antibodies may be collected and then used in diagnostic assays in accordance with known techniques. A further aspect of the present invention is a method of introducing and expressing antisense oligonucleotides in bone marrow cell cultures to regulate gene expression. Alternately, the claimed method finds use in introducing and expressing a protein or peptide in bone marrow cell cultures. π. Girdwood S.A. and TR339 Clones. Disclosed hereinbelow are genomic RNA sequences encoding live Girdwood S.A. virus, live S.A.AR86 virus, and live Sindbis strain TR339 virus, cDNAs derived therefrom, infectious RNA transcripts encoded by the cDNAs, infectious viral particles containing the infectious RNA transcripts, and pharmaceutical formulations derived therefrom. The cDNA sequence of Girdwood S.A. is given herein as SEQ ED NO:4. Alternatively, the cDNA may have a sequence which differs from the cDNA of SEQ ED NO:4, but which has the same protein sequence as the cDNA given herein as SEQ ED NO:4. Thus, the cDNA may include one or more silent mutations. The phrase "silent mutation" as used herein refers to mutations in the cDNA coding sequence which do not produce mutations in the corresponding protein sequence translated therefrom. Likewise, the cDNA sequence of TR339 is given herein as SEQ ED NO:8. Alternatively, the cDNA may have a sequence which differs from the cDNA of SEQ ED NO:8, but which has the same protein sequence as the cDNA given herein as SEQ ED NO:8. Thus, the cDNA may include one or more silent mutations. The cDNAs encoding infectious Girdwood S.A. and TR339 virus RNA transcripts of the present invention include those homologous to, and having essentially the same biological properties as, the cDNA sequences disclosed herein as SEQ ED NO:4 and SEQ ED NO:8, respectively. Thus, cDNAs that hybridize to cDNAs encoding infectious Girdwood S.A. or TR339 virus RNA transcripts disclosed herein are also an aspect of this invention. Conditions which will permit other cDNAs encoding infectious Girdwood S.A. or TR339 virus transcripts to hybridize to the cDNAs disclosed herein can be deteπnined in accordance with known techniques. For example, hybridization of such sequences may be carried out under conditions of reduced stringency, medium stringency, or even high stringency conditions (e.g. , conditions represented by a wash stringency of 35-40% formamide with 5X Denhardt's solution, 0.5% SDS and IX SSPE at 37°C; conditions represented by a wash stringency of 40-45% formamide with 5X Denhardt's solution, 0.5% SDS, and IX SSPE at 42 °C; and conditions represented by a wash stringency of 50% formamide with 5X Denhardt's solution, 0.5% SDS and IX SSPE at 42°C, respectively, to cDNA encoding infectious Girdwood S.A. or TR339 virus RNA transcripts disclosed herein in a standard hybridization assay. See J. SAMBROOK ET AL., MOLECULAR CLONING: A LABORATORY MANUAL (2d ed. 1989)). In general, cDNA sequences encoding infectious Girdwood S.A. or TR339 virus RNA transcripts that hybridize to the cDNAs disclosed herein will be at least 30% homologous, 50% homologous, 75% homologous, and even 95% homologous or more with the cDNA sequences encoding infectious Girdwood S.A. or TR339 virus RNA transcripts disclosed herein. Promoter sequences and Girdwood S.A. virus or Sindbis virus strain TR339 cDNA clones are operatively associated in the present invention such that the promoter causes the cDNA clone to be transcribed in the presence of an RNA polymerase which binds to the promoter. The promoter is positioned on the 5' end (with respect to the virion RNA sequence), of the cDNA clone. An excessive number of nucleotides between the promoter sequence and the cDNA clone will result in the inoperability of the construct. Hence, the number of nucleotides between the promoter sequence and the cDNA clone is preferably not more than eight, more preferably not more than five, still more preferably not more than three, and most preferably not more than one. Examples of promoters which are useful in the cDNA sequences of the present invention include, but are not limited to T3 promoters, T7 promoters, cytomegalovirus (CMV) promoters, and SP6 promoters. The DNA sequence of the present invention may reside in any suitable transcription vector. The DNA sequence preferably has a complementary DNA sequence bound thereto so that the double-stranded sequence will serve as an active template for RNA polymerase. The transcription vector preferably comprises a plasmid. When the DNA sequence comprises a plasmid, it is preferred that a unique restriction site be provided 3' (with respect to the virion RNA sequence) to the cDNA clone. This provides a means for linearizing the DNA sequence to allow the transcription of genome- length RNA in vitro. The cDNA clones can be generated by any of a variety of suitable methods known to those skilled in the art. A preferred method is the method set forth in United States Patent No. 5,185,440 to Davis et al., the disclosure of which is incorporated in its entirety by reference, and Gubler et al., Gene 25:263 (1983). RNA is preferably synthesized from the DNA sequence in vitro using purified RNA polymerase in the presence of ribonucleotide triphosphates and cap analogs in accordance with conventional techniques. However, the RNA may also be synthesized intracellularly after introduction of the cDNA. The Girdwood S.A. and TR339 cDNA clones and the infectious RNAs and infectious virus particles produced therefrom of the present invention are useful for the preparation of pharmaceutical formulations, such as vaccines. In addition, the cDNA clones, infectious RNAs, and infectious viral particles of the present invention are useful for administration to animals for the purpose of producing antibodies to the Girdwood S.A. virus or the Sindbis virus strain TR339, which antibodies may be collected and used in known diagnostic techniques for the detection of Girdwood S.A. virus or Sindbis virus strain TR339. Antibodies can also be generated to the viral proteins expressed from the cDNAs disclosed herein. As another aspect of the present invention, the claimed cDNA clones are useful as nucleotide probes to detect the presence of Girdwood S.A. or TR339 genomic RNA or transcripts. IU. Infectious Virus Particles and Pharmaceutical Formulations. The infectious virus particles of the present invention include those containing double promoter vectors and those containing replicon vectors as described hereinabove. Alternately, the infectious virus particles contain infectious RNAs encoding the Girdwood S.A. or TR339 genome. When the infectious RNA comprises the Girdwood S.A. genome, preferably the RNA has the sequence encoded by the cDNA given as SEQ ED NO:4. When the infectious RNA comprises the TR339 genome, preferably the RNA has the sequence encoded by the cDNA given as SEQ ED NO:8. The infectious, alphavirus particles of the present invention may be prepared according to the methods disclosed herein in combination with techniques known to those skilled in the art. These methods include transfecting an alphavirus-permissive cell with a replicon RNA including the alphavirus packaging segment and an inserted heterologous RNA, a first helper RNA including RNA encoding at least one alphavirus structural protein, and a second helper RNA including RNA encoding at least one alphavirus structural protein which is different from that encoded by the first helper RNA. Alternately, and preferably, at least one of the helper RNAs is produced from a cDNA encoding the helper RNA and operably associated with an appropriate promoter, the cDNA being stably transfected and integrated into the cells. More preferably, all of the helper RNAs will be "launched" from stably transfected cDNAs. The step of transfecting the alphavirus-permissive cell can be carried out according to any suitable means known to those skilled in the art, as described above with respect to propagation- competent viruses. Uptake of propagation-competent RNA into the cells in vitro can be carried out according to any suitable means known to those skilled in the art. Uptake of RNA into the cells can be achieved, for example, by treating the cells with DEAE-dextran, treating the RNA with LIPOFECTIN ® before addition to the cells, or by electroporation, with electroporation being the currently preferred means. These techniques are well known in the art. See e.g. , United States Patent No. 5,185,440 to Davis et al., and PCT Publication No. WO 92/10578 to Bioption AB, the disclosures of which are incorporated herein by reference in their entirety. Uptake of propagation-competent RNA into the cell in vivo can be carried out by administering the infectious RNA to a subject as described in Section I above. The infectious RNAs may also contain a heterologous RNA segment, where the heterologous RNA segment contains a heterologous RNA and a promoter operably associated therewith. It is preferred that the infectious RNA introduces and expresses the heterologous RNA in bone marrow cells as described in Section I above. According to this embodiment, it is preferable that the promoter operatively associated with the heterologous RNA is operable in bone marrow cells. The heterologous RNA may encode any protein or peptide, preferably an immunogemc protein or peptide, a therapeutic protein or peptide, a hormone, a growth factor, an interleukin, a cytokine, a chemokine, an enzyme, a ribozyme, or an antisense oligonucleotide as described in more detail in Section I above. The step of facilitating the production of the infectious viral particles in the cells may be carried out using conventional techniques. See e.g. , United States Patent No. 5,185,440 to Davis et al., PCT Publication No. WO 92/10578 to Bioption AB, and United States Patent No. 4,650,764 to Temin et al. (although Temin et al. , relates to retroviruses rather than alphaviruses). The infectious viral particles may be produced by standard cell culture growth techniques. The step of collecting the infectious virus particles may also be carried out using conventional techniques. For example, the infectious particles may be collected by cell lysis, or collection of the supernatant of the cell culture, as is known in the art. See e.g. , United States Patent No. 5,185,440 to Davis et al., PCT Publication No. WO 92/10578 to Bioption AB, and United States Patent No. 4,650,764 to Temin et al. Other suitable techniques will be known to ose skilled in the art. Optionally, the collected infectious virus particles may be purified if desired. Suitable purification techniques are well known to those skilled in the art. Pharmaceutical formulations, such as vaccines, of the present invention comprise an immunogenic amount of the infectious, virus particles in combination with a pharmaceutically acceptable carrier. An "immunogenic amount" is an amount of the infectious virus particles which is sufficient to evoke an immune response in the subject to which the pharmaceutical formulation is administered. An amount of from about 10 3 to about 10 7 particles, and preferably about 10 4 to 10 δ particles per dose is believed suitable, depending upon the age and species of the subject being treated, and the immunogen against which the immune response is desired. Pharmaceutical formulations of the present invention for therapeutic use comprise a therapeutic amount of the infectious virus particles in combination with a pharmaceutically acceptable carrier. A "therapeutic amount" is an amount of the infectious virus particles which is sufficient to produce a therapeutic effect (e.g. , triggering an immune response or supplying a protein to a subject in need thereof) in the subject to which the pharmaceutical formulation is administered. The therapeutic amount will depend upon the age and species of the subject being treated, and the therapeutic protein or peptide being administered. Typical dosages are an amount from about 10 1 to about 10 s infectious units. Exemplary pharmaceutically acceptable carriers include, but are not limited to, sterile pyrogen-free water and sterile pyrogen-free physiological saline solution. Subjects which may be adininistered immunogenic amounts of the infectious virus particles of the present invention include but are not limited to human and animal (e.g. , pig, cattle, dog, horse, donkey, mouse, hamster, monkeys) subjects. Pharmaceutical formulations of the present invention include those suitable for parenteral (e.g. , subcutaneous, intracerebral, intradermal, intramuscular, intravenous and intraarticular) administration. Alternatively, pharmaceutical formulations of the present invention may be suitable for .administration to the mucus membranes of a subject (e. g. , intranasal administration by use of a dropper, swab, or inhaler). The formulations may be conveniently prepared in unit dosage form and may be prepared by any of the methods well known in the art. The following examples are provided to illustrate the present invention, and should not be construed as limiting thereof. In these examples, PBS means phosphate buffered saline, EDTA means ethylene diamine tetraacetate, ml means milliliter, μl means microliter, mM means millimolar, μM means micromolar, u means unit, PFU means plaque forming units, g means gram, mg means milligram, μg means microgram, cpm means counts per minute, ic means intracerebral or intracerebrally, ip means intraperitoneal or intraperitoneally, iv means intravenous or intravenously, and sc means subcutaneous or subcutaneously. Amino acid sequences disclosed herein are presented in the amino to carboxyl direction, from left to right. The amino and carboxyl groups are not presented in the sequence. Nucleotide sequences are presented herein by single strand only in the 5' to 3' direction, from left to right. Nucleotides and amino acids are represented herein in the manner recommended by the IUPAC-IUB Biochemical Nomenclature Commission, or (for amino acids) by either one letter or three letter code, in accordance with 37 CFR § 1.822 and established usage. Where one letter amino acid code is used, the same sequence is also presented elsewhere in three letter code. EXAMPLE I Cells and Virus Stocks S. A.AR86 was isolated in 1954 from a pool of Culex sp. mosquitoes collected near Johannesburg, South Africa. Weinbren et al., S. Afr. Med. J. 30, 631-36 (1956). Ockelbo82 was isolated from Culiseta sp. mosquitoes collected in Edsbyn, Sweden in 1982 and was associated serologically with human disease. Niklasson et al., Am. J. Trop. Med. Hyg. 33, 1212-17 (1984). Girdwood S.A. was isolated from a human patient in the Johannesburg area of South.Africa in 1963. Malherbe et al., S. Afr. Med. J. 37, 547-52 (1963). Molecularly cloned virus TR339 represents the deduced consensus sequence of Sindbis AR339. McKnight et al., J. Virol. 70, 1981-89 (1996); William Klimstra, personal communication. TRSB is a laboratory strain of Sindbis isolate AR339 derived from a cDNA clone pTRSB and differing from the AR339 consensus sequence at three codons. McKnight et al., J. Virol. 70, 1981-89 (1996). pTR5000 is a full- length cDNA clone of Sindbis AR339 following the SP6 phage promoter and containing mostly Sindbis AR339 sequences. Stocks of all molecularly cloned viruses were prepared by electroporating genome length in vitro transcripts of their respective cDNA clones in BHK-21 cells. Heidner et al., J. Virol. 68, 2683-92 (1994). Girdwood S.A. (Malherbe et al., S. Afr. Med. J. 37, 547-52 (1963)) and Ockelbo82 (Espmark and Niklasson, Am. J. Trop. Med. Hyg. 33, 1203-11 (1984); Niklasson et al., Am. J. Trop. Med. Hyg. 33, 1212-17 (1984)) were passed one to three times in BHK-21 cells in order to produce amplified stocks of virus. All virus stocks were stored at -70 °C until needed. The titers of the virus stocks were determined on BHK-21 cells from aliquots of frozen virus. EXAMPLE 2 Cloning the S.A.AR86 and Girdwood S.A. Genomic Sequences The sequences of S.A.AR86 (Figure 1, SEQ ED NO: 1) and Girdwood S.A. (Figure 3, SEQ ED NO:4) were determined from uncloned reverse transcriptase-polymerase chain reaction (RT-PCR) fragments amplified from virion RNA. Heidner et al., J. Virol. 68, 2683-92 (1994). The sequence of the 5' 40 nucleotides was determined by directly sequencing the genomic RNA. Sanger et al., Proc. Natl. Acad. Sci. USA 74, 5463-67 (1977); Zimmern and Kaesberg, Proc. Natl. Acad. Sci. USA 75, 4257-61 (1978); Ahlquist et al., Ce// 23, 183-89 (1981). The S.A.AR86 genome was 11,663 nucleotides in length, excluding the 5' CAP and 3'poly(A) tail, 40 nucleotides shorter than the alphavirus prototype Sindbis strain AR339. Strauss et al., Virology 133, 92-110 (1984). Compared with the consensus sequence of Sindbis virus AR339 (McKnight et al., J. Virol. 70 1981-89 (1996)), S.A.AR86 contained two separate 6-nucleotide insertions, and one 3-nucleotide insertion in the 3' half of the nsP3 gene, a region not well conserved among alphaviruses. The two 6-nucleotide insertions were found immediately 3' of nucleotides 5403 and 5450, and the 3-nucleotide insertion was immediately 3 ' of nucleotide 5546 compared with the AR339 genome. In addition, S.A.AR86 contained a 54-nucleotide deletion in nsP3 which spanned nucleotides 5256 to 5311 of AR339. As a result of these deletions and insertions, S.A.AR86 nsP3 was 13 amino acids smaller than AR339, containing an 18-amino acid deletion and a total of 5 amino acids inserted. The 3' untranslated region of S.A.AR86 contained, with respect to AR339, two 1-nucleotide deletions at nucleotides 11,513 and 11,602, and one 1-nucleotide insertion following nucleotide 11,664. The total numbers of nucleotides and predicted amino acids comprising the remaining genes of S.A.AR86 were identical to those of AR339. A notable feature of the deduced amino acid sequence of S. A.AR86 (Figure 2, SEQ ED NO:2 and SEQ ED NO:3) was the cysteine codon in place of an opal termination codon between nsP3 and nsP4. S.A.AR86 is the only alphavirus of the Sindbis group, and one of just three alphavirus isolates sequenced to date, which do not contain an opal termination codon between nsP3 and nsP4. Takkinen, K., Nucleic Acids Res. 14, 5667-5682 (1986); Strauss et al., Virology 164, 265-74 (1988). The genome of Girdwood S.A. was 11,717 nucleotides long excluding the 5' CAP and 3' poly (A) tail. The nucleotide sequence (SEQ ED NO:4) of the Girdwood S.A. genome and the putative amino acid sequence (SEQ ED NO:5 and SEQ ED NO:6) of the Girdwood S.A. gene products are shown in Figure 3 and Figure 4, respectively. The asterisk at position 1902 in SEQ ED NO: 5 indicates the position of the opal termination codon in the coding region of the nonstructural polyprotein. The extra nucleotides relative to AR339 were in the nonconserved half of nsP3, which contained insertions totalling 15 nucleotides, and in the 3' untranslated region which contained two 1-nucleotide deletions and a 1- nucleotide insertion with respect to the consensus Sindbis AR339 genome. The insertions found in the nsP3 gene of Girdwood S.A. were identical in position and content to those found in S.A.AR86, although Girdwood S.A. did not have the large nsP3 deletion characteristic of S.A.AR86. The remaining portions of the genome contained the same number of nucleotides and predicted amino acids as Sindbis AR339. Overall, Girdwood S.A. was 94.5% identical to the consensus Sindbis AR339 sequence, differing at 655 nucleotides not including the insertions and deletions. These nucleotide differences resulted in 88 predicted amino acid changes or a difference of 2.3%. A plurality of amino acid differences were concentrated in the nsP3 gene, which contained 32 of the amino acid changes, 25 of which were in the nonconserved 3' half. The Girdwood S.A. nucleotides at positions 1, 3, and 11,717 could not be resolved. Because the primer used during the RT-PCR amplification of the 3' end of the genome assumed a cytosine in the 3' terminal position, the identity of this nucleotide could not be determined with certainty. However, in all alphaviruses sequenced to date there is a cytosine in this position. This, combined with the fact that no difficulty was encountered in obtaining RT-PCR product for this region with an oligo(dT) primer ending with a 3'G, suggested that Girdwood S.A. also contains a cytosine at this position. The ambiguity at nucleotide positions 1 and 3 resulted from strong stops encountered during the RNA sequencing. EXAMPLE 3 Comparison of S.A.AR86 and Girdwood S.A. Sequences With Other Sindbis-Related Virus Sequences Table 1 examines the relationship of S.A.AR86 and Girdwood S.A. to each other and to other Sindbis-related viruses. This was accomplished by aligning the nucleotide and .deduced amino acid sequences of Ockelbo82, AR339 and Girdwood S.A. to those of S.A.AR86 and then calculating the percentage identity for each gene using the programs contained within the Wisconsin GCG package (Genetics Computer Group, 575 Science Drive, Madison WI 53711)1 as described in more detail in McKnight et al., J. Virol. 70, 1981-89 (1996). The analysis suggests that S.A.AR86 is most similar to the other South African isolate, Girdwood S.A. , and that the South African isolates are more similar to the Swedish Ockelbo82 isolate than to the Egyptian Sindbis AR339 isolate. These results also suggest that it is unlikely that S.A.AR86 is a recombinant virus like WEE virus. Hahn et al., Proc. Natl. Acad. Sci. USA 85, 5997-6001 (1988). TABLE 1 Comparison of the Nucleotide and Amino Acid Sequences of S.A.AR86 Virus with Those of Sindbis AR339, Ockelbo82, and Girdwood S.A. Viruses 3 Nucleotide Differences" Amino Acid Differences" AR339 OCK82 GIRD AR339 OCK82 GIRD Regions Number (%) Number (%) 5' untranslated 0 (0.0) 0 (0.0) 1 (1.7) -- -- -- nsPl 76 (4.7) 37 (2.3) 15 (0.9) 9 (1.7) (0 6 (1.1) 2(0.4) c ID nsP2 137 (5.7) 86 (3.6) 45 (1.9) 15 (1.9) 8 (1.0) 12(1.5) nsP3 H C Conserved 0 51 (5.7) 35 (3.9) 13 (1.6) 6 (2.0) 1 (0.3) 1 (0.4) H m Nonconserved d 116 (6.6) 83 (4.4) 70 (2.2) 45 (9.7) 34 (7.0) 27 (3.7) co x nsP4 111 (6.1) 68 (3.7) 19 (1.1) 8 (1.3) 2 (0.3) 4 (0.6) m 26s junction 1 (2.1) 0 (0.0) 1 (2.1) -- -- -- «» 3 ) C Capsid 36 (4.5) 26 (3.3) 7 (0.9) 1 (0.4) 3 (1.1) 0 (0.0) E3 17 (8.9) 5 (2.6) 4(2.1) 1 (1.6) 0 (0.0) 0 (0.0) ro E2 71 (5.6) 43 (3.4) 18 (1.4) 12 (2.6) 6 (1.4) 2 (0.5) 6K 10 (6.1) 9 (5.4) 4 (2.4) 2 (3.6) 2 (3.6) 1 (1.8) E1 49 (3.7) 31 (2.3) 16 (1.2) 7 (1.6) 6 (1.4) 2 (0.9) 3' untranslated 14 (4.5) 8 (2.5) 1 (0.3) - -- -- Totals 689 (5.5) 431 (3.3) 214 (1.4) 106 (2.3) 68 (1.4) 51 (0.9) a. All nucleotide positions and gene boundaries are numbered according to those used for the Sindbis AR339, HR $P variant Genebank Accession No. J02363; Strauss et al., Virology 133, 92-110 (1984). b. Differences include insertions and deletions. c. Conserved region nucleotides 4100 to 5000 (aa 1 to aa300). d. Nonconserved region nucleotides 5001 to 5729 (aa301 to aa542, S.A.AR86 numbering). EXAMPLE 4 Neurovirulence of S.A.AR86 and Girdwood S.A. Girdwood S.A. , Ockelbo82, and S.A.AR86 are related by sequence; in contrast, it has previously been reported that only S.A.AR86 displayed the adult mouse neurovirulence phenotype. Russell et al. , J. Virol. 63, 1619-29 (1989). These findings were confirmed by the present investigations. Briefly, groups of four female CD-I mice (3-6 weeks of age) were inoculated ic with 10 3 plaque- forming units (PFU) of S. A. AR86, Girdwood S.A. , or Ockelbo82. Neither Girdwood S.A. nor Ockelbo82 infection produced any clinical signs of infection. Infection with S.A. AR86 produced neurological signs within four to five days and ultimately killed 100% of the mice as previously demonstrated. Table 2 lists those amino acids of S.A.AR86 which might explain the neurovirulence phenotype in adult mice. A position was scored as potentially related to the S.A.AR86 adult neurovirulence phenotype if the S.A.AR86 amino acid differed from that which otherwise was absolutely conserved at that position in the other viruses. TABLE 2 Divergent Amino Acids in S.A.AR86 Potentially Related to the Adult Neurovirulence Phenotype Position in S.A.AR86 Conserved S.A.AR86 Amino Acid Amino Acid nsP1 583 Thr lie nsP2 256 Arg Ala 648 lie Val 651 Lys Glu nsP3 344 Gly Glu 386 Tyr Ser 441 Asp Gly 445 lie Met 537 Cys Opal E2 243 Ser Leu 6K 30 Val He E1 1 1 2 Val Ala 1 69 Leu Ser EXAMPLE 5 t>S55 Molecular Clone of S.A.AR86 As a first step in investigating the unique adult mouse neurovirulence phenotype of S.A.AR86, a full-length cDNA clone of the S.A.AR86 genome was constructed. The sources of cDNA included conventional cDNA clones (Davis et al., Virology 111, 189-204 (1989)) as well as uncloned RT-PCR fragments derived from the S . A. AR86 genome. As described previously, these were substituted, starting at the 3' end, into pTR5000 (McKnight et al., J. Virol. 70, 1981-89 (1996)), a full-length Sindbis clone from which infectious genomic replicas could be derived by transcription with SP6 polymerase in vitro. The end result was pS55, a molecular clone of S.A.AR86 from which infectious transcripts could be produced and which contained four nucleotide changes (G for A at nt 215; G for C at nt 3863; G for A at nt 5984; and C for T at nt 9113) but no amino acid coding differences with respect to the S.A.AR86 genomic RNA (amino acid sequence of S.A. AR86 presented in Figure 2 (SEQ ED NO:2 and SEQ ED NO:3)). The nucleotide sequence of clone pS55 is presented in Figure 5 (SEQ ED NO:7). As has been described by Simpson et al. , Virology 222, 464-69 (1996), neurovirulence and replication of the virus derived from pS55 (S55) were compared with those of S.A.AR86. It was found that S55 exhibits the distinctive adult neurovirulence characteristic of S.A.AR86. Like S.A.AR86, S55 produces 100% mortality in adult mice infected with the virus and the survival times of animals infected ; with both viruses were indistinguishable. In addition, S55 and S.A.AR86 were found to replicate to essentially equivalent titers in vivo, and the profiles of S55 and S.A.AR86 virus growth in the central nervous system and periphery were very similar. From these data it was concluded that the silent changes found in virus derived from clone pS55 had little or no effect on its growth or virulence, and that this molecularly cloned virus accurately represents the biological isolate, S.A.AR86. EXAMPLE 6 Construction of the Consensus AR339 Virus TR339 The consensus sequence of the Sindbis virus AR339 isolate, the prototype alphavirus was deduced. The consensus AR339 sequence was inferred by comparison of the TRSB sequence (a laboratory-derived AR339 strain) with the complete or partial sequences of HR,. (the Gen Bank sequence; Strauss et al. , Virology 133, 92-110 (1984)), SV1A, and NSV ( AR339-derived laboratory strains; Lustig et al., J. Virol 62, 2329-36 (1988)), and SIN (a laboratory-derived AR339 strain; Davis et al., Virology 161, 101-108 (1987), Strauss et al., J. Virol. 65, 4654-64 (1991)). Each of these viruses was descended from AR339. Where these sequences differed from each other, they also were compared with the amino acid sequences of other viruses related to Sindbis virus: Ockelbo82, S.A.AR86, Girdwood S.A. , and the somewhat more distantly related Aura virus. Rumenapf et al. , Virology 208, 621-33 (1995). The details of determining a consensus AR339 sequence and constructing the consensus virus TR339 have been described elsewhere. McKnight et al., J. Virol. 70, 1981-89 (1996); Klimstra et al., manuscript in preparation. The nucleotide (SEQ ED NO:8) sequence of pTR339 is presented in Figure 6. The deduced amino acid sequences of the pTR339 non-structural and structural polyproteins are shown as SEQ ED NO:9 and SEQ ED NO:10, respectively. The asterisk at position 1897 in SEQ ED NO:9 indicates the position of the opal ' termination codon in the coding region of the nonstructural polyprotein. The consensus nucleotide sequence diverged from the pTRSB sequence at three coding positions (nsP3'528, E2 1, and El 72). These differences are illustrated in Table 3. TABLE 3 Amino Acid Differences Between Laboratory Strain TRSB and Molecular Clone TR339 EXAMPLE 7 Animals Used for In Vivo Localization Studies Specific pathogen free CD-I mice were obtained from Charles River Breeding Laboratories (Raleigh, North Carolina) at 21 days of age and maintained under barrier conditions until approximately 37 days of age. Intracerebral (ic) inoculations were performed as previously described, Simpson et al., Virol. 222, 464-49 (1996), with 500 PFU of S51 (an attenuated mutant of S55) or 10 3 PFU of S55. Animals inoculated peripherally were first anesthetized with METOFANE®. Then, 25 μl of diluent (PBS, pH 7.2, 1 % donor calf serum, 100 u/ml penicillin, 50 μg/ml streptomycin, 0.9 mM CaCl 2 , and 0.5 mM MgCl 2 ) containing 10 3 PFU of virus were injected either intravenously (iv) into the tail vein, subcutaneously (sc) into the skin above the shoulder blades on the middle of the back, or intraperitoneally (ip) in the lower right abdomen. Animals were sacrificed at various times post-inoculation as previously described. Simpson et al. , Virol. 222, 464-49 (1996). Brains (including brainstems) were homogenized in diluent to 30% w/v, and right quadriceps were homogenized in diluent to 25 % w/v. Homogenates were handled and titered as described previously. Simpson et al. , Virol. 222, 464- 49 (1996). Bone marrow was harvested by crushing both femurs from each animal in sufficient diluent to produce a 30% w/v suspension (calculated as weight of uncrushed femurs in volume of diluent). Samples were stored at -70°C. For titration, samples were thawed and clarified by centrifugation at 1,000 x g for 20 minutes at 4°C before being titered by conventional plaque assay on BHK-21 cells. EXAMPLE 8 Tissue Preparation for In Situ Hybridization Studies Animals were anesthetized by ip injection of 0.5 ml AVERTIN ® at various times post-inoculation followed by perfusion with 60 to 75 ml of 4% paraformaldehyde in PBS (pH 7.2) at a flow rate of 10 ml per minute. The entire carcass was decalcified for 8 to 10 weeks in 4% parafomaldehyde containing 8% EDTA in PBS (pH 6.8) at 4°C. This solution was changed twice during the decalcification period. Selected tissues were cut into blocks approximately 3 mm thick and placed into biopsy cassettes for paraffin embedding and sectioning. Blocks were embedded, sectioned and hematoxylin/eosin stained by Experimental Pathology Laboratories (Research Triangle Park, North Carolina) or North Carolina State University Veterinary School Pathology Laboratory (Raleigh, North Carolina). EXAMPLE 9 In Situ Hybridization Hybridizations were performed using a [ 35 S]-UTP labeled S. A. AR86 specific riboprobe derived from pDS-45. Clone pDS-45 was constructed by first amplifying a 707 base pair fragment from pS55 by PCR using primers 7241 (5'- CTGCGGCGGATTCATCTTGC-3', SEQ ED NO:ll) and SC-3 (5'- CTCCAACTTAAGTG-3 ', SEQ ED NO:12). The resulting 707 base pair fragment was purified using a GENE CLEAN ® kit (BiolOl, CA), digested with Hhal, and cloned into the Smal site of pSP72 (Promega). Linearizing pDS-45 with EcoRV and performing an in vitro transcription reaction with SP6 DNA-dependent, RNA polymerase (Promega) in the presence of [ 35 S]-UTP resulted in a riboprobe approximately 500 nucleotides in length of which 445 nucleotides were complementary to the S.A.AR86 genome (nucleotides 7371 through 7816). A riboprobe specific for the influenza strain PR-8 hemagglutinin (HA) gene was used as a control probe to test non-specific binding. The in situ hybridizations were performed as described previously (Charles et al. , Virol. 208, 662-71 (1995)) using 10 s cpm of probe per slide. EXAMPLE 10 Replication of S.A.AR86 in Bone Marrow Three groups of six adult mice each were inoculated peripherally (sc, ip, or iv) with 1200 PFU of S55 (a molecular clone of S.A.AR86) in 25 μl of diluent. Under these conditions, the infection produced no morbidity or mortality. Two mice from each group were anesthetized and sacrificed at 2, 4 and 6 days post-inoculation by exsanguination. The serum, brain (including brainstem), right quadricep, and both femurs were harvested and titered by plaque assay. Virus was never detected in the quadricep samples of animals inoculated sc (Table 4). A single animal inoculated ip (two days post-inoculation) and two mice inoculated iv (at four and six days post- inoculation) had detectable virus in the right quadricep, but the titer was at or just above the limit of detection (6.25 PFU/s tissue . Virus was present sporadically or at low levels in the brain and serum of animals regardless of the route of inoculation. Virus was detected in the bone marrow of animals regardless of the route of inoculation. However, the presence of virus in bone marrow of animals inoculated sc or ip was more sporadic than animals inoculated iv, where five out of six animals had detectable virus. These results suggest that S55 targets to the bone marrow, especially following iv inoculation. The level and frequency of virus detected in the serum and muscle suggested that virus detected in the bone marrow was not residual virus contamination from blood or connective tissue remaining in bone marrow samples. The following experiment also suggested that virus in bone marrow was not due to tissue or serum contamination. Mice were inoculated ic with 1200 PFU of S55 in 25 μl of diluent. Animals were sacrificed at 0.25, 0.5, 1, 1.5, 2, 3, 4, 5, and 6 days post-inoculation, and the carcasses were decalcified as described in Example 8. Coronal sections taken at approximately 3 mm intervals through the head, spine (including shoulder area), and hips were probed with an S55-specific [ 35 S]-UTP labeled riboprobe derived from pDS-45. Positive in situ hybridization signal was detected by one day post-inoculation in the bone marrow of the skull (data not shown). Weak signal also was present in some of die chondrocytes of the vertebrae, suggesting that S55 was replicating in these cells as well. Although the frequency of positive bone marrow cells was low, the signal was very intense over individual positive cells. This result strongly suggests that S55 replicates in vivo in a subset of cells contained in the bone marrow. EXAMPLE 11 Other Sindbis Group Viruses It was of interest to determine if the ability to replicate in the bone marrow of mice was unique to S55 or was a general feature of other viruses, both Sindbis and non-Sindbis viruses, in the Sindbis group. Six 38-day-old female CD- 1 mice were inoculated iv with 25 μl of diluent containing 10 3 PFU of S55, Ockelbo82, Girdwood S.A., TR339, or TRSB. At 2, 4 and 6 days post- inoculation two mice from each group were sacrificed and whole blood, serum, brain (including brainstem), right quadricep, and both femurs were harvested for virus titration. The results of this experiment were similar to those with S55. TRSB infected animals had no virus detectable in serum or whole blood in any animal at any time, and with the other viruses tested, no virus was detected in the serum or whole blood of any animal beyond two days post-inoculation (detection limit, 25 PFU/ml). Neither TRSB nor TR339 was detectable in me brains of infected animals at any time post-inoculation. S55, Girdwood S.A., and Ockelbo82 were present in the brains of infected animals sporadically with the titers being at or near the 75 PFU/g level of detection. All the tested viruses were found sporadically at or slightly above the 50 PFU/g detection limit in the right quadricep of infected animals except for a single animal four days post-inoculation with TRSB which had nearly 10 5 PFU/g of virus in its quadricep. . The frequency at which the different viruses were detected in bone marrow varied widely, with S55 and Girdwood S.A. being the most frequently isolated (five out of six animals) and Ockelbo82 and TRSB being the least frequently isolated from bone marrow (one out of six animals and two out of six animals, respectively) (Table 4). Girdwood S.A. and S55 gave nearly identical profiles in all tissues. Girdwood S.A., unlike S.A.AR86, is not neurovirulent in adult mice (Example 4), suggesting that the adult neurovirulence phenotype is distinct from the ability of the virus to replicate efficiently in bone marrow. TABLE 4 Titers Following IV Inoculation of Virus TABLE 4 Continued Titers Following IV Inoculation of Virus (0 c σ ω H c Ά H m to x m =1 c r m r en * "N.D." indicates that the virus titers were below the limit of detection. EXAMPLE 12 Virus Persistence in Bone Marrow The next step in our investigations was to evaluate the possibility that S.A.AR86 persisted long-term in bone marrow. S51 is a molecularly cloned, attenuated mutant of S55. S51 differs from S55 by a threonine for isoleucine substitution at amino acid residue 538 of nsPl and is attenuated in adult mice inoculated intracerebrally. Like S55, S51 targeted to and replicated in the bone marrow of 37-day-old female CD-I mice following ic inoculation. Mice were inoculated ic with 500 PFU of S51 and sacrificed at 4, 8, 16, and 30 days post- inoculation for determination of bone marrow and serum titers. At no time post- inoculation was virus detected in the serum above the 6.25 PFU/ml detection limit. Virus was detectable in the bone marrow samples of both animals sampled at four days post-inoculation and in one animal eight days post- inoculation (Table 5). No virus was detectable by titration on BHK-21 cells in any of the bone marrow samples beyond eight days post-inoculation. These results suggested that the attenuating mutation present in S51 , which reduces the neurovirulence of the virus, did not impair acute viral replication in the bone marrow. It was notable that the plaque size on BHK-21 cells of virus recovered on day 4 post-inoculation was smaller than the size of plaques produced by the inoculum virus, and that plaques produced from virus recovered from the day 8 post-inoculation samples were even smaller and barely visible. This suggests a strong selective pressure in the bone marrow for virus that is much less efficient ' in forming plaques on BHK-21 cells. To demonstrate that S51 virus genomes were present in bone marrow cells long after acute infection, four to six-week-old female CD-I mice were inoculated ic with 500 PFU of S51. Three months post-inoculation two animals were sacrificed, perfused with paraformaldehyde and decalcified as described in Example 8. The heads and hind limbs from these animals were paraffin embedded, sectioned, and probed with a S.A.AR86 specific p 5 S]-UTP labeled riboprobe derived from clone pDS-45. In situ hybridization signal was clearly present in discrete cells of the bone and bone marrow of the legs (data not shown). Furthermore, no in situ hybridization signal was detected in an adjacent control section probed with an influenza virus HA gene specific riboprobe. As the relative sensitivity of in situ hybridization is reduced in decalcified tissues (Peter Charles, personal communication), these cells likely contain a relatively high number of viral sequences, even at three months post- inoculation. No in situ hybridization signal was observed in mid-sagital sections of the heads with the S.A.AR86 specific probe, although focal lesions were observed in the brain indicative of the prior acute infection with S51. TABLE 5 a "N.D. " indicates that the virus titers were below the limit of detection. Example 13 Replication of S.A.A.R86 within Bone/Joint Tissue of Adult Mice Several old world alphaviruses, including Ross River Virus, Chikungunya virus, Okelbo82, and S.A.AR86 are associated with acute and persistent arthritis/arthralgia in humans. Molecular clones of several Sindbis group viruses, including S.A.AR86, were used to investigate alphavirus replication within bone/joint tissue. Following intravenous inoculation of S.A.AR86 into adult CD-I mice, viral replication was observed in bone/joint tissue, but not surrounding muscle tissue of the hind limbs. Infectious virus was detectable 24 hrs post-infection; however, viral titer within bone/joint tissue was maximal 72 hours post-infection. Fractionation of hind limbs from infected animals revealed that the hip and knee joints were the predominant sites of viral replication. Replication within bone/joint tissue appears to be a common trait of Sindbis-group viruses, since the laboratory strains TR339 and TRSB also replicated within bone/joint tissue. In situ hybridization and S.A.AR86 based double promoter vectors expressing green fluorescent protein were used to further localize S.A.AR86 infected cells within bone/joint tissue. Green fluorescent protein expression was detected in bone/joint tissue for at least one month post-inoculation. These studies demonstrated that cells within the endosteum of synovial joints were the predominant site of S.AAR86 replication. SEQUENCE LISTINGS

Claims: THAT WHICH IS CLAIMED IS: 1. A method of introducing and expressing heterologous RNA in bone marrow cells, comprising: (a) providing a recombinant alphavirus, said alphavirus containing a heterologous RNA segment, said heterologous RNA segment comprising a promoter operable in said bone marrow cells operatively associated with a heterologous RNA to be expressed in said bone marrow cells; and then (b) contacting said recombinant alphavirus to said bone marrow cells so that said heterologous RNA segment is introduced and expressed therein. 2. A method according to claim 1 , wherein said contacting step is carried out in vitro. 3. A method according to claim 1 , wherein said contacting step is carried out in vivo in a subject in need of such treatment. 4. A method according to claim 1, wherein said heterologous RNA encodes a protein or peptide. 5. A method according to claim 1, wherein said heterologous RNA encodes an immunogenic protein or peptide. 6. A method according to claim 1, wherein said heterologous RNA encodes an antisense oligonucleotide or a ribozyme. 7. A method according to claim 1, wherein said alphavirus is an Old World alphavirus. 8. A method according to claim 1, wherein said alphavirus is selected from the group consisting of SF group and SIN group alphaviruses. 9. A method according to claim 1 , wherein said alphavirus is selected from the group consisting of Semliki Forest virus, Middelburg virus, Chikungunya virus, O'Nyong-Nyong virus, Ross River virus, Barmah Forest virus, Getah virus, Sagiyama virus, Bebaru virus, Mayaro virus, Una virus, Sindbis virus, South African Arbovirus No. 86, Ockelbo virus, Girdwood S.A. virus, Aura virus, Whataroa virus, Babanki virus, and Kyzylagach virus. 10. A method according to claim 1, wherein said alphavirus is South African Arbovirus No. 86. 11. A method according to claim 1, wherein said alphavirus is Girdwood S.A. 12. A method according to claim 1, wherein said alphavirus is Sindbis strain TR339. 13. A helper cell for expressing an infectious, propagation defective, Girdwood S.A. virus particle, comprising, in a Girdwood S.A.- permissive cell: (a) a first helper RNA encoding (i) at least one Girdwood S.A. strucmral protein, and (ii) not encoding at least one other Girdwood S.A. strucmral protein; and (b) a second helper RNA separate from said first helper RNA, said second helper RNA (i) not encoding said at least one Girdwood S.A.. strucmral protein encoded by said first helper RNA, and (ii) encoding said at least one other Girdwood S.A. structural protein not encoded by said first helper RNA, and with all of said Girdwood S.A. structural proteins encoded by said first and second helper RNAs assembling together into Girdwood S.A. particles in said cell containing said replicon RNA; and wherein the Girdwood S.A. packaging segment is deleted from at least said first helper RNA. 14. The helper cell according to claim 13, further containing a replicon RNA; said replicon RNA encoding said Girdwood S.A. packaging segment and an inserted heterologous RNA; wherein said Girdwood S.A. packaging segment is deleted from at least one of said helper RNA; and wherein said replicon RNA, said first helper RNA, and said second helper RNA are all separate molecules from one another. 15. The helper cell according to claim 13, further containing a replicon RNA; said replicon RNA encoding said Girdwood S.A. packaging segment and an inserted heterologous RNA; wherein said replicon RNA and said first helper RNA are separate molecules; and wherein the molecule containing said replicon RNA further contains RNA encoding said at least one Girdwood S.A. structural protein not encoded by said first helper RNA. 16. The helper cell according to claim 13, wherein said first helper RNA encodes bom the Girdwood S.A. El glycoprotein and the Girdwood S.A. E2 glycoprotein, and wherein said second helper RNA encodes the Girdwood S.A. capsid protein. 17. A method of making infectious, propagation defective, Girdwood S.A. virus particles, comprising: transfecting a Girdwood S.A.-permissive cell according to claim 13 wit a propagation defective replicon RNA, said replicon RNA including said Girdwood S.A. packaging segment and an inserted heterologous RNA; producing said Girdwood S.A. virus particles in said transfected cell; and then collecting said Girdwood S.A. virus particles from said cell. 18. Infectious Girdwood S.A. virus particles produced by the method of Claim 17. 19. Infectious Girdwood S.A. virus particles co taining a replicon RNA encoding a promoter, an inserted heterologous RNA, and wherein RNA encoding at least one Girdwood S.A. structural protein is deleted therefrom so that said Girdwood S.A. virus particle is propagation defective. 20. A pharmaceutical formulation comprising infectious Girdwood S.A. virus particles according to claim 18 or 19 in a pharmaceutically acceptable carrier. 21. A helper cell for expressing an infectious, propagation defective, TR339 virus particle, comprising, in a TR339-permissive cell: (a) a first helper RNA encoding (i) at least one TR339 strucmral protein, and (ii) not encoding at least one other TR339 structural protein; and (b) a second helper RNA separate from said first helper RNA, said second helper RNA (i) not encoding said at least one TR339 structural protein encoded by said first helper RNA, and (ii) encoding said at least one other TR339 structural protein not encoded by said first helper RNA, and with all of said TR339 structural proteins encoded by said first and second helper RNAs assembling together into TR339 particles in said cell containing said replicon RNA; and wherein the TR339 packaging segment is deleted from at least said first helper RNA. 22. The helper cell according to claim 21, further containing a replicon RNA; said replicon RNA encoding said TR339 packaging segment and an inserted heterologous RNA; wherein said TR339 packaging segment is deleted from at least one of said helper RNA; and wherein said replicon RNA, said first helper RNA, and said second helper RNA are all separate molecules from one another. 23. The helper cell according to claim 21, further containing a replicon RNA; said replicon RNA encoding said TR339 packaging segment and an inserted heterologous RNA; wherein said replicon RNA and said first helper RNA are separate molecules; and wherein the molecule containing said replicon RNA further contains RNA encoding said at least one TR339 structural protein not encoded by said first helper RNA. 24. The helper cell according to claim 21, wherein said first helper RNA encodes both the TR339 El glycoprotein and the TR339 E2 glycoprotein, and wherein said second helper RNA encodes the TR339 capsid protein. 25. A method of making infectious, propagation defective, TR339 virus particles, comprising: transfecting a TR339-permissive cell according to claim 21 with a propagation defective replicon RNA, said replicon RNA including said TR339 packaging segment and an inserted heterologous RNA; producing said TR339 virus particles in said transfected cell; and then collecting said TR339 virus particles from said cell. 26. Infectious TR339 virus particles produced by the method of Claim 25. 27. Infectious TR339 virus panicles containing a replicon RNA encoding a promoter, an inserted heterologous RNA, and wherein RNA encoding at least one TR339 structural protein is deleted therefrom so that said virus particle is propagation defective. 28. A pharmaceutical formulation comprising infectious TR339 virus particles according to Claim 26 or 27 in a pharmaceutically acceptable carrier. 29. A recombinant DNA comprising a cDNA coding for an infectious Girdwood S.A. virus RNA transcript and a heterologous promoter positioned upstream from said cDNA and operatively associated therewith. 30. An infectious RNA transcript encoded by a cDNA according to claim 29. 31. An infectious RNA according to claim 30, said infectious Girdwood S.A. RNA transcript containing a heterologous RNA segment, said heterologous RNA segment comprising a promoter operably associated with a heterologous RNA. 32. Infectious viral particles containing an RNA transcript according to claim 30. 33. A recombinant DNA comprising a cDNA coding for a Sindbis strain TR339 RNA transcript and a heterologous promoter positioned upstream from said cDNA and operatively associated therewith. 34. An infectious RNA transcript encoded by a cDNA according to claim 33. 35. An infectious RNA according to claim 34, said infectious Girdwood S.A. RNA transcript containing a heterologous RNA segment, said heterologous RNA segment comprising a promoter operably associated with a heterologous RNA. 36. Infectious viral particles containing an RNA transcript according to claim 34.

Inventors: DAVIS NANCY L, JOHNSTON ROBERT E, SIMPSON DENNIS A, DAVIS, NANCY, L., JOHNSTON, ROBERT, E., SIMPSON, DENNIS, A.
Applicants: DAVIS NANCY L, JOHNSTON ROBERT E, SIMPSON DENNIS A, UNIV NORTH CAROLINA, DAVIS, NANCY, L., JOHNSTON, ROBERT, E., SIMPSON, DENNIS, A., UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL
Application year: 1998
Main classification: A61K47
IPC codes: A61K31, A61K35, A61K48, A61P31, C07K14, C12N5, C12N7, C12N15