Abstract:
The present invention relates to compositions and methods for enhancing the effect of vaccines in animals, such as domestic, sport, or pet species, and humans. More particularly, the use of Ribavirin as an adjuvant to a vaccine protocol and compositions having Ribavirin and an antigen are described.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 10/719,619 filed on Nov. 20, 2003, which is a continuation of U.S. patent application Ser. No. 10/104,966 filed on Mar. 22, 2002, now U.S. Pat. No. 6,680,059 which is a continuation of U.S. patent application Ser. No. 09/705,547 filed on Nov. 3, 2000, now abandoned both of which claim the benefit of priority of U.S. provisional patent application No. 60/229,175, filed Aug. 29, 2000. The aforementioned applications are hereby expressly incorporated by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to compositions and methods for enhancing the effect of vaccines in animals, such as domestic, sport, or pet species, and humans. More particularly, preferred embodiments concern the use of Ribavirin as an adjuvant and compositions having Ribavirin and an antigen. 
     BACKGROUND OF THE INVENTION 
     The use of vaccines to prevent disease in humans, farm livestock, sports animals, and household pets is a common practice. Frequently, however, the antigen used in a vaccine is not sufficiently immunogenic to raise the antibody titre to levels that are sufficient to provide protection against subsequent challenge or to maintain the potential for mounting these levels over extended time periods. Further, many vaccines are altogether deficient in inducing cell-mediated immunity, which is a primary immune defense against bacterial and viral infection. A considerable amount of research is currently focussed on the development of more potent vaccines and ways to enhance the immunogenicity of antigen-containing preparations. (See e.g., U.S. Pat. Nos. 6,056,961; 6,060,068; 6,063,380; and Li et al.,  Science  288:2219-2222 (2000)). 
     Notorious among such “weak” vaccines are hepatitis B vaccines. For example, recombinant vaccines against hepatitis B virus such as Genhevacb (Pasteur Merieux Serums et Vaccines, 58, Avenue Leclerc 69007 Lyon, France), Engerixb (Smith, Kline and Symbol French), and Recombivaxhb (Merck, Sharp, and Dhome) are effective only after at least three injections at 0, 30, and 60 or 180 days, followed by an obligatory booster after one year. (Chedid et al., U.S. Pat. No. 6,063,380). Additionally, many subjects receiving these vaccines respond poorly, if at all. Because many regions of the world are endemic for HBV infection, the poorly immunogenic character of existing HBV vaccines has become an extremely serious problem. 
     To obtain a stronger, humoral and/or cellular response, it is common to administer a vaccine in a material that enhances the immune response of the patient to the antigen present in the vaccine. The most commonly used adjuvants for vaccine protocols are oil preparations and alum. (Chedid et al., U.S. Pat. No. 6,063,380). A greater repertoire of safe and effective adjuvants is needed. 
     Nucleoside analogs have been widely used in anti-viral therapies due to their capacity to reduce viral replication. (Hosoya et al.,  J. Inf. Dis.,  168:641-646 (1993)). Ribavirin (1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a synthetic guanosine analog that has been used to inhibit RNA and DNA virus replication. (Huffman et al.,  Antimicrob. Agents. Chemother.,  3:235 (1973); Sidwell et al.,  Science,  177:705 (1972)). Ribavirin has been shown to be a competitive inhibitor of inositol mono-phosphate (IMP) dehydrogenase (IMPDH), which converts IMP to IMX (which is then converted to GMP). De Clercq,  Anti viral Agents: characteristic activity spectrum depending on the molecular target with which they interact , Academic press, Inc., New York N.Y., pp. 1-55 (1993). Intracellular pools of GTP become depleted as a result of long term Ribavirin treatment. 
     In addition to antiviral activity, investigators have observed that a few guanosine analogs have an effect on the immune system. (U.S. Pat. Nos. 6,063,772 and 4,950,647). Ribavirin has been shown to inhibit functional humoral immune responses (Peavy et al.,  J. Immunol.,  126:861-864 (1981); Powers et al.,  Antimicrob. Agents. Chemother.,  22:108-114 (1982)) and IgE-mediated modulation of mast cell secretion. (Marquardt et al.,  J. Pharmacol. Exp. Therapeutics,  240:145-149 (1987)). Some investigators report that a daily oral therapy of Ribavirin has an immune modulating effect on humans and mice. (Hultgren et al.,  J. Gen. Virol.,  79:2381-2391 (1998) and Cramp et al.,  Gastron. Enterol.,  118:346-355 (2000)). Nevertheless, the current understanding of the effects of Ribavirin on the immune system is in its infancy. 
     SUMMARY OF THE INVENTION 
     It has been discovered that Ribavirin can be used as an adjuvant to enhance an immune response to an antigen. Embodiments described herein include “strong” vaccine preparations that comprise an antigen and Ribavirin. Generally, these preparations have an amount of Ribavirin that is sufficient to enhance an immune response to the antigen. Other aspects of the invention include methods of enhancing the immune response of an animal, including a human, to an antigen. By one approach, for example, an animal in need of a potent immune response to an antigen is identified and then is provided an amount of Ribavirin together with the antigen that is effective to enhance an immune response in the animal. In some methods, the Ribavirin and the antigen are provided in combination and in others, the Ribavirin and the antigen are provided separately. Thus, several embodiments concern the manufacture and use of vaccine preparations having Ribavirin and an antigen. 
     Preferred vaccine compositions comprise Ribavirin and a hepatitis viral antigen. The antigen can be a peptide or nucleic acid-based (e.g., a RNA encoding a peptide antigen or a construct that expresses a peptide antigen when introduced to a subject). HBV antigens that are suitable include, for example, hepatitis B surface antigen (HBsAg), hepatitis core antigen (HBcAg), hepatitis e antigen (HBeAg), and nucleic acids encoding these molecules. Compositions having Ribavirin and an antigen from the hepatitis A virus (HAV) or Ribavirin and a nucleic acid encoding an antigen from HAV are also embodiments. Still further, compositions having Ribavirin and an antigen from the hepatitis C virus (HCV) or Ribavirin and a nucleic acid encoding an antigen from HCV are embodiments. 
     Furthermore, compositions having a mixture of the antigens above are embodiments of the present invention. For example, some compositions comprise a HBV antigen, a HAV antigen, and Ribavirin or a HBV antigen, a HCV antigen, and Ribavirin or a HAV antigen, a HCV antigen, and Ribavirin or a HBV antigen, a HAV antigen, a HCV antigen, and Ribavirin. Other embodiments comprise Ribavirin and a nucleic acid encoding a mixture of the antigens described above. Some embodiments also include other adjuvants, binders, emulsifiers, carriers, and fillers, as known in the art, including, but not limited to, alum, oil, and other compounds that enhance an immune response. 
     Preferred methods involve providing an animal in need with a sufficient amount of Ribavirin and a hepatitis viral antigen (e.g., HBV antigen, HAV antigen, HCV antigen a nucleic acid encoding one of these antigens or any combination thereof). Accordingly, one embodiment includes identifying an animal in need of an enhanced immune response to a hepatitis viral antigen (e.g., an animal at risk or already infected with a hepatitis infection) and providing to said animal an amount of Ribavirin that is effective to enhance an immune response to the hepatitis viral antigen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a graph showing the humoral response to 10 and 100 μg recombinant Hepatitis C virus (HCV) non structural 3 protein (NS3), as determined by mean end point titres, when a single dose of 1 mg of Ribavirin was co-administered. 
         FIG. 2  is a graph showing the humoral response to 20 μg recombinant Hepatitis C virus (HCV) non structural 3 protein (NS3), as determined by mean end point titres, when a single dose of 0.1, 1.0, or 10 mg of Ribavirin was co-administered. 
         FIG. 3  is a graph showing the effects of a single dose of 1 mg Ribavirin on NS3-specific lymph node proliferative responses, as determined by in vitro recall responses. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It has been discovered that compositions comprising Ribavirin and an antigen can boost an animal&#39;s immune response to the antigen. That is. Ribavirin can be used as an “adjuvant,” which for the purposes of this disclosure, refers to a compound that has the ability to enhance the immune response to a particular antigen. Such adjuvant activity is manifested by a significant increase in immune-mediated protection against the antigen, and was demonstrated by an increase in the titer of antibody raised to the antigen and an increase in proliferative T cell responses. 
     Several vaccine preparations that comprise Ribavirin and an antigen are described herein. Vaccine formulations containing Ribavirin can vary according to the amount of Ribavirin, the form of Ribavirin, and the type of antigen. The antigen can be a peptide or a nucleic acid (e.g., a RNA encoding a peptide antigen or a construct that expresses a peptide antigen when introduced into a subject). Preferred vaccine formulations comprise Ribavirin and a hepatitis viral antigen (e.g., HBV antigen, HAV antigen, HCV antigen, a nucleic acid encoding these molecules, or any combination thereof). 
     Methods of enhancing the immune response of an animal, including humans, to an antigen are also described herein. One method, for example, involves identifying an animal in need of an enhanced immune response to an antigen and providing the animal the antigen and an amount of Ribavirin that is effective to enhance an immune response to the antigen. Preferred methods involve providing the animal in need with Ribavirin and a hepatitis antigen (e.g., HBV antigen, HAV antigen, HCV antigen, a nucleic acid encoding these molecules, or any combination thereof). The section below describes the manufacture of vaccines having Ribavirin and an antigen in greater detail. 
     Vaccines Containing Ribavirin 
     The vaccines comprise Ribavirin and an antigen and may contain other ingredients including, but not limited to, adjuvants, binding agents, excipients such as stabilizers (to promote long term storage), emulsifiers, thickening agents, salts, preservatives, solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. These vaccine preparations are suitable for treatment of animals either as a preventive measure to avoid a disease or condition or as a therapeutic to treat animals already afflicted with a disease or condition. 
     The vaccine compositions can be manufactured in accordance with conventional methods of galenic pharmacy to produce medicinal agents for administration to animals, e.g., mammals including humans. Ribavirin can be obtained from commercial suppliers (e.g., Sigma and ICN). Ribavirin and/or the antigen can be formulated into the vaccine with and without modification. For example, the Ribavirin and/or antigen can be modified or derivatized to make a more stable molecule and/or a more potent adjuvant. By one approach, the stability of Ribavirin and/or an antigen can be enhanced by coupling the molecules to a support such as a hydrophilic polymer (e.g., polyethylene glycol). 
     Many more ribavirin derivatives can be generated using conventional techniques in rational drug design and combinatorial chemistry. For example, Molecular Simulations Inc. (MSI), as well as many other suppliers, provide software that allows one of skill to build a combinatorial library of organic molecules. The C2.Analog Builder program, for example, can be integrated with MSI&#39;s suite of Cerius2 molecular diversity software to develop a library of ribavirin derivatives that can be used with the embodiments described herein. 
     By one approach, the chemical structure of Ribavirin is recorded on a computer readable media and is accessed by one or more modeling software application programs. The C2.Analog Builder program in conjunction with C2Diversity program allows the user to generate a very large virtual library based on the diversity of R-groups for each substituent position, for example. Compounds having the same structure as the modeled Ribavirin derivatives created in the virtual library are then made using conventional chemistry or can be obtained from a commercial source. 
     The newly manufactured Ribavirin derivatives are then screened in characterization assays, which determine the extent of adjuvant activity of the molecule and/or the extent of its ability to modulate of an immune response. Some characterization assays may involve virtual drug screening software, such as C2.Ludi. C2.Ludi is a software program that allows a user to explore databases of molecules (e.g., Ribavirin derivatives) for their ability to interact with the active site of a protein of interest (e.g., RAC2 or another GTP binding protein). Based upon predicted interactions discovered with the virtual drug screening software, the Ribavirin derivatives can be prioritized for further characterization in conventional assays that determine adjuvant activity and/or the extent of a molecule to modulate an immune response. 
     Example 1 describes a characterization assay that was used to evaluate the adjuvant activity of Ribavirin. 
     EXAMPLE 1 
     This characterization assay can be used with any Ribavirin derivative or combinations of Ribavirin derivatives to determine the extent of adjuvant activity of the particular vaccine formulation. Accordingly, groups of three to five Balb/c mice (BK Universal, Uppsala, Sweden) were immunized i.p or s.c. (e.g., at the base of the tail) with 10 μg or 100 μg of recombinant hepatitis C virus non-structural 3 (NS3) protein. The rNS3 was dissolved in phosphate buffered saline (PBS) alone or PBS containing 1 mg Ribavirin (obtained from ICN, Costa Mesa, Calif.). Mice were injected with a total volume of 100 μl per injection. 
     At two and four weeks following i.p. immunization, all mice were bled by retro-orbital sampling. Serum samples were collected and analyzed for the presence of antibodies to rNS3. To determine the antibody titer, an enzyme immunoassay (EIA) was performed. (See e.g., Hultgren et al.,  J Gen Virol.  79:2381-91 (1998) and Hultgren et al.,  Clin. Diagn. Lab. Immunol.  4:630-632 (1997), both of which are herein expressly incorporated by reference in their entireties). The antibody levels were recorded as the highest serum dilution giving an optical density at 405 nm more than twice that of non-immunized mice. 
     Mice that received 10 μg or 100 μg rNS3 mixed with 1 mg Ribavirin in PBS displayed consistently higher levels of NS3 antibodies. The antibody titer that was detected by EIA at two weeks post-immunization is shown in  FIG. 1 . The vaccine formulations having 1 mg of Ribavirin and either 10 μg or 100 μg of rNS3 induced a significantly greater antibody titer than the vaccine formulations composed of only rNS3. This data provides evidence that Ribavirin has an adjuvant effect on the humoral immune response of an animal and thus, enhances the immune response to the antigen. 
     The example below describes experiments that were performed to determine the amount of Ribavirin that was needed to elicit an adjuvant effect. 
     EXAMPLE 2 
     To determine the dose of Ribavirin that is required to provide an adjuvant effect, the following experiments were performed. Groups of mice (three per group) were immunized with a 20 μg rNS3 alone or a mixture of 20 μg rNS3 and 0.1 mg, 1 mg, or 10 mg Ribavirin. The levels of antibody to the antigen were then determined by EIA. The mean endpoint titers at weeks 1 and 3 were plotted and are shown in  FIG. 2 . It was discovered that the adjuvant effect provided by Ribavirin had different kinetics depending on the dose of Ribavirin provided. For example, low doses (&lt;1 mg) of Ribavirin were found to enhance antibody levels at week one but not at week three, whereas, higher doses (1-10 mg) were found to enhance antibody levels at week three. These data further verify that Ribavirin can be administered as an adjuvant and establish that the dose of Ribavirin can modulate the kinetics of the adjuvant effect. 
     The example below describes another characterization assay that was performed to evaluate the ability of Ribavirin to modulate a cellular immune response. 
     EXAMPLE 3 
     This characterization assay can be used with any Ribavirin derivative or combinations of Ribavirin derivatives to determine the extent that a particular vaccine formulation modulates a cellular immune response. To determine CD4 +  T cell responses to Ribavirin-containing vaccine, groups of mice were immunized s.c. with either 100 μg rNS3 in PBS or 100 μg rNS3 and 1 mg Ribavirin in PBS. The mice were sacrificed ten days post-immunization and their lymph nodes were harvested and drained. In vitro recall assays were then performed. (See e.g., Hultgren et al.,  J Gen Virol.  79:2381-91 (1998) and Hultgren et al.,  Clin. Diagn. Lab. Immunol.  4:630-632 (1997), both of which are herein expressly incorporated by reference in their entireties). The amount of CD4 +  T cell proliferation was determined at 96 h of culture by the incorporation of [ 3 H] thymidine. 
     As shown in  FIG. 2 , mice that were immunized with 100 μg rNS3 mixed with 1 mg Ribavirin had a much greater T cell proliferative response than mice that were immunized with 100 μg rNS3 in PBS. This data provides evidence that Ribavirin can enhance a cellular immune response (e.g., by promoting the effective priming of T cells). 
     The example below describes the use of Ribavirin in conjunction with a commercial vaccine preparation. 
     EXAMPLE 4 
     The adjuvant effect of Ribavirin was also tested when mixed with two doses of a commercially available vaccine containing HBsAg and alum. (Engerix, SKB). Approximately 0.2 μg or 2 μg of Engerix vaccine was mixed with either PBS or 1 mg Ribavirin in PBS and the mixtures were injected intra peritoneally into groups of mice (three per group). A booster containing the same mixture was given on week four and all mice were bled on week six. The serum samples were diluted from 1:60 to 1:37500 and the dilutions were tested by EIA, as described above, except that purified human HBsAg (kindly provided by Professor DL Peterson, Commonwealth University, VA) was used as the solid phase antigen. As shown in TABLE 1, vaccine formulations having Ribavirin enhanced the response to 2 μg of an existing vaccine despite the fact that the vaccine already contained alum. That is, by adding Ribavirin to a suboptimal vaccine dose (i.e., one that does not induce detectable antibodies alone) antibodies became detectable, providing evidence that the addition of Ribavirin allows for the use of lower antigen amounts in a vaccine formulation without compromising the immune response. 
     
       
         
               
               
             
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 End point antibody titer to HBsAg in EIA 
               
             
          
           
               
                   
                 0.02 μg Engerix 
                 0.2 μg Engerix 
               
             
          
           
               
                   
                 No Ribavirin 
                 1 mg Ribavirin 
                 No Ribavirin 
                 1 mg Ribavirin 
               
             
          
           
               
                 Week 
                 #1 
                 #2 
                 #3 
                 #1 
                 #2 
                 #3 
                 #1 
                 #2 
                 #3 
                 #1 
                 #2 
                 #3 
               
               
                   
               
               
                 6 
                 &lt;60 
                 &lt;60 
                 &lt;60 
                 &lt;60 
                 &lt;60 
                 &lt;60 
                 &lt;60 
                 &lt;60 
                 &lt;60 
                 300 
                 60 
                 &lt;60 
               
               
                   
               
             
          
         
       
     
     Any antigen that can be used to generate an immune response in an animal can be combined with Ribavirin so as to prepare the vaccines described herein. That is, antigens that can be incorporated into such a vaccine comprise bacterial antigens, fungal antigens, plant antigens, mold antigens, viral antigens, cancer cell antigens, toxin antigens, chemical antigens, and self-antigens. Although many of these antigens are molecules that induce a significant immune response without an adjuvant, Ribavirin can be administered in conjunction with or combined with “strong” or “weak” antigens to enhance the immune response. In addition, the use of Ribavirin as an adjuvant may allow for the use of lower amounts of vaccine antigens while retaining immunogenicity. 
     Preferred embodiments comprise Ribavirin and a viral antigen. Preferred viral antigens are hepatitis viral antigens. Vaccines can comprise, for example, Ribavirin and an HBV antigen, HAV antigen, HCV antigen or any combination of these antigens. Preferred viral antigens include hepatitis B surface antigen (HBsAg), hepatitis core antigen (HBcAg), and hepatitis E antigen (HBeAg). 
     For example, HCV vaccine embodiments comprise Ribavirin and a HCV peptide of at least 3 consecutive amino acids of SEQ. ID. No.: 1. That is, a vaccine embodiment can have Ribavirin and a HCV peptide with a length of at least 3-10 consecutive amino acids, 10-50 consecutive amino acids, 50-100 consecutive amino acids, 100-200 consecutive amino acids, 200-400 consecutive amino acids, 400-800 consecutive amino acids, 800-1200 consecutive amino acids, 1200-1600 consecutive amino acids, 1600-2000 consecutive amino acids, 2000-2500 consecutive amino acids, and 2500-3011 consecutive amino acids of SEQ ID. No. 1. Preferred HCV vaccines comprise Ribavirin and a peptide of at least 3 consecutive amino acids of HCV core protein (SEQ. ID. No. 2), HCV E1 protein (SEQ. ID. No. 3), HCV E2 protein (SEQ. ID. No. 4), HCV NS2 (SEQ. ID. No. 5), HCV NS3 (SEQ. ID. No. 6), HCV NS4A (SEQ. ID. No. 7), HCV NS4B (SEQ. ID. No. 8), or HCV NS5A/B (SEQ. ID. No. 9). That is, preferred HCV vaccines can comprise Ribavirin and a peptide with a length of at least 3-10 consecutive amino acids, 10-50 consecutive amino acids, 50-100 consecutive amino acids, 100-200 consecutive amino acids, 200-400 consecutive amino acids, 400-800 consecutive amino acids, and 800-1040 consecutive amino acids of any one of (SEQ. ID. Nos. 2-9). 
     Similarly, preferred HBV vaccine embodiments comprise Ribavirin and a HBV peptide of at least 3 consecutive amino acids of HBsAg (SEQ. ID. No.: 10) or HBcAg and HBeAg (SEQ. ID. No. 11). That is, a vaccine embodiment can have Ribavirin and a HBV peptide with a length of at least 3-10 consecutive amino acids, 10-50 consecutive amino acids, 50-100 consecutive amino acids, 100-150 consecutive amino acids, 150-200 consecutive amino acids, and 200-226 consecutive amino acids of either SEQ. ID. No. 10 or SEQ. ID. No. 11. Further, preferred HAV embodiments comprise Ribavirin and a HAV peptide with a length of at least 3-10 consecutive amino acids, 10-50 consecutive amino acids, 50-100 consecutive amino acids, 100-200 consecutive amino acids, 200-400 consecutive amino acids, 400-800 consecutive amino acids, 800-1200 consecutive amino acids, 1200-1600 consecutive amino acids, 1600-2000 consecutive amino acids, and 2000-2227 consecutive amino acids of SEQ ID. No. 12. 
     In addition to peptide antigens, nucleic acid-based antigens can be used in the vaccine compositions described herein. Various nucleic acid-based vaccines are known and it is contemplated that these compositions and approaches to immunotherapy can be augmented by introducing Ribavirin (See e.g., U.S. Pat. No. 5,589,466, herein expressly incorporated by reference in its entirety). 
     By one approach, for example, a gene encoding a polypeptide antigen of interest is cloned into an expression vector capable of expressing the polypeptide when introduced into a subject. The expression construct is introduced into the subject in a mixture of Ribavirin or in conjunction with Ribavirin (e.g., Ribavirin is administered shortly after the expression construct at the same site). Alternatively, RNA encoding a polypeptide antigen of interest is provided to the subject in a mixture with Ribavirin or in conjunction with Ribavirin. Where the polynucleotide is to be DNA, promoters suitable for use in various vertebrate systems are well known. For example, for use in murine systems, suitable strong promoters include RSV LTR, MPSV LTR, SV40 IEP, and metallothionein promoter. In humans, on the other hand, promoters such as CMV IEP can be used. All forms of DNA, whether replicating or non-replicating, which do not become integrated into the genome, and which are expressible, can be used. 
     Preferred nucleic acid-based antigens include a nucleotide sequence of at least 9 consecutive nucleotides of HCV (SEQ. ID. No. 13), HBV (SEQ. ID. No.: 14), or HAV (SEQ. ID. No. 15). That is, a nucleic acid based antigen can comprise at least 9-25 consecutive nucleotides, 25-50 consecutive nucleotides, 50-100 consecutive nucleotides, 100-200 consecutive nucleotides, 200-500 consecutive nucleotides, 500-1000 consecutive nucleotides, 1000-2000 consecutive nucleotides, 2000-4000 consecutive nucleotides, 4000-8000 consecutive nucleotides, and 8000-9416 consecutive nucleotides of any one of SEQ. ID. Nos.: 13-15 or an RNA that corresponds to these sequences. 
     The example below describes one approach for using a nucleic acid-based antigen in conjunction with Ribavirin. 
     EXAMPLE 5 
     The following describes an approach to immunize an animal with a vaccine comprising a nucleic acid-based antigen and Ribavirin. Five to six week old female and male Balb/C mice are anesthetized by intraperitoneal injection with 0.3 ml of 2.5% Avertin. A 1.5 cm incision is made on the anterior thigh, and the quadriceps muscle is directly visualized. One group of mice are injected with approximately 20 μg of an expression construct having the gp-120 gene, driven by a cytomegalovirus (CMV) promotor and second group of mice are injected with approximately 5 μg of capped in vitro transcribed RNA (e.g., SP6, T7, or T3 (Ambion)) encoding gp-120. These two groups are controls. A third group of mice is injected with approximately 20 μg of the expression vector having the gp-120 gene and the CMV promoter mixed with 1 mg of Ribavirin and a fourth group of mice is injected with approximately 5 μg of capped in vitro transcribed RNA mixed with 1 mg Rbavirin. The vaccines are injected in 0.1 ml of solution (PBS) in a 1 cc syringe through a 27 gauge needle over one minute, approximately 0.5 cm from the distal insertion site of the muscle into the knee and about 0.2 cm deep. A suture is placed over the injection site for future localization, and the skin is then closed with stainless steel clips. 
     Blood samples are obtained prior to the injection (Day 0) and up to more than 40 days post injection. The serum from each sample is serially diluted and assayed in a standard ELISA technique assay for the detection of antibody, using recombinant gp-120 protein made in yeast as the antigen. Both IgG and IgM antibodies specific for gp-120 will be detected in all samples, however, groups three and four, which contained the Ribavirin, will exhibit a greater immune response to the gp-120 as measured by the amount and/or titer of antibody detected in the sera. 
     Many other ingredients can be present in the vaccine. For example, the Ribavirin and antigen can be employed in admixture with conventional excipients (e.g., pharmaceutically acceptable organic or inorganic carrier substances suitable for parenteral, enteral (e.g., oral) or topical application that do not deleteriously react with the Ribavirin and/or antigen). Suitable pharmaceutically acceptable carriers include, but are not limited to, water, salt solutions, alcohols, gum arabic, vegetable oils, benzyl alcohols, polyetylene glycols, gelatine, carbohydrates such as lactose, amylose or starch, magnesium stearate, talc, silicic acid, viscous paraffin, perfume oil, fatty acid monoglycerides and diglycerides, pentaerythritol fatty acid esters, hydroxy methylcellulose, polyvinyl pyrrolidone, etc. Many more suitable carriers are described in  Remmington&#39;s  Pharmaceutical Sciences, 15th Edition, Easton:Mack Publishing Company, pages 1405-1412 and 1461-1487(1975) and The National  Formulary  XIV, 14th Edition, Washington, American Pharmaceutical Association (1975), herein expressly incorporated by reference in their entireties. Vaccines can be sterilized and if desired mixed with auxiliary agents, e.g., lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, coloring, flavoring and/or aromatic substances and the like that do not deleteriously react with Ribavirin or the antigen. 
     The effective dose and method of administration of a particular vaccine formulation can vary based on the individual patient and the type and stage of the disease, as well as other factors known to those of skill in the art. Therapeutic efficacy and toxicity of the vaccines can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., ED50 (the dose therapeutically effective in 50% of the population). The data obtained from cell culture assays and animal studies can be used to formulate a range of dosage for human use. The dosage of the vaccines lies preferably within a range of circulating concentrations that include the ED50 with no toxicity. The dosage varies within this range depending upon the type of Ribavirin derivative and antigen, the dosage form employed, the sensitivity of the patient, and the route of administration. 
     Since Ribavirin has been on the market for several years, many dosage forms and routes of administration are known. All known dosage forms and routes of administration can be provided within the context of the embodiments described herein. Preferably, an amount of Ribavirin that is effective to enhance an immune response to an antigen in an animal can be considered to be an amount that is sufficient to achieve a blood serum level of antigen approximately 0.25-12.5 μg/ml in the animal, preferably, about 2.5 μg/ml. In some embodiments, the amount of Ribavirin is determined according to the body weight of the animal to be given the vaccine. Accordingly, the amount of Ribavirin in a vaccine formulation can be from about 0.1-6.0 mg/kg body weight. That is, some embodiments have an amount of Ribavirin that corresponds to approximately 0.1-1.0 mg/kg, 1.1-2.0 mg/kg, 2.1-3.0 mg/kg, 3.1-4.0 mg/kg, 4.1-5.0 mg/kg, 5.1, and 6.0 mg/kg body weight of an animal. More conventionally, the vaccines contain approximately 0.25 mg-2000 mg of Ribavirin. That is, some embodiments have approximately 250 μg, 500 μg, 1 mg, 25 mg, 50 mg, 100 mg, 150 mg, 200 mg, 250 mg, 300 mg, 350 mg, 400 mg, 450 mg, 500 mg, 550 mg, 600 mg, 650 mg, 700 mg, 750 mg, 800 mg, 850 mg, 900 mg, 1 g, 1.1 g, 1.2 g, 1.3 g, 1.4 g, 1.5 g, 1.6 g, 1.7 g, 1.8 g, 1.9 g, and 2 g of Ribavirin. 
     Vaccines comprising various antigens and amounts of these antigens have been provided to animals for many years. Thus, conventional vaccine preparations can be modified by adding an amount of Ribavirin that is sufficient to enhance an immune response to the antigen. That is, existing conventional vaccine formulations can be modified by simply adding Ribavirin to the preparation or by administering the conventional vaccine in conjunction with Ribavirin (e.g., shortly before or after providing the antigen). As one of skill in the art will appreciate, the amount of antigens in a vaccine can vary depending on the type of antigen and its immunogenicity. The amount of antigens in the vaccines can vary accordingly. Nevertheless, as a general guide, the vaccines can have approximately 0.25 mg-2000 mg of an antigen (e.g., a hepatitis viral antigen). 
     In some approaches described herein, the exact amount of Ribavirin and/or antigen is chosen by the individual physician in view of the patient to be treated. Further, the amounts of Ribavirin can be added in combination to or separately from the same or equivalent amount of antigen and these amounts can be adjusted during a particular vaccination protocol so as to provide sufficient levels in light of patient-specific or antigen-specific considerations. In this vein, patient-specific and antigen-specific factors that can be taken into account include, but are not limited to, the severity of the disease state of the patient, age, and weight of the patient, diet, time and frequency of administration, drug combination(s), reaction sensitivities, and tolerance/response to therapy. 
     Routes of administration of the vaccines described herein include, but are not limited to, transdermal, parenteral, gastrointestinal, transbronchial, and transalveolar. Transdermal administration can be accomplished by application of a cream, rinse, gel, etc. capable of allowing Ribavirin and antigen to penetrate the skin. Parenteral routes of administration include, but are not limited to, electrical or direct injection such as direct injection into a central venous line, intravenous, intramuscular, intraperitoneal, intradermal, or subcutaneous injection. Gastrointestinal routes of administration include, but are not limited to, ingestion and rectal. Transbronchial and transalveolar routes of administration include, but are not limited to, inhalation, either via the mouth or intranasally. 
     Compositions having Ribavirin and an antigen that are suitable for transdermal administration include, but are not limited to, pharmaceutically acceptable suspensions, oils, creams, and ointments applied directly to the skin or incorporated into a protective carrier such as a transdermal device (“transdermal patch”). Examples of suitable creams, ointments, etc. can be found, for instance, in the Physician&#39;s Desk Reference. Examples of suitable transdermal devices are described, for instance, in U.S. Pat. No. 4,818,540 issued Apr. 4, 1989 to Chinen, et al., herein expressly incorporated by reference in its entirety. 
     Compositions having Ribavirin and an antigen that are suitable for parenteral administration include, but are not limited to, pharmaceutically acceptable sterile isotonic solutions. Such solutions include, but are not limited to, saline, phosphate buffered saline and oil preparations for injection into a central venous line, intravenous, intramuscular, intraperitoneal, intradermal, or subcutaneous injection. 
     Compositions having Ribavirin and an antigen that are suitable for transbronchial and transalveolar administration include, but not limited to, various types of aerosols for inhalation. Devices suitable for transbronchial and transalveolar administration of these are also embodiments. Such devices include, but are not limited to, atomizers and vaporizers. Many forms of currently available atomizers and vaporizers can be readily adapted to deliver vaccines having Ribavirin and an antigen. 
     Compositions having Ribavirin and an antigen that are suitable for gastrointestinal administration include, but not limited to, pharmaceutically acceptable powders, pills or liquids for ingestion and suppositories for rectal administration. 
     Once the vaccine comprising Ribavirin and an antigen has been obtained, it can be administered to a subject in need to treat or prevent diseases. The next section describes methods that employ the vaccines described above. 
     Methods of Use of Vaccines that Contain Ribavirin 
     The vaccines containing Ribavirin and an antigen can be used to treat and prevent a vast spectrum of diseases and can enhance the immune response of an animal to an antigen. As one of skill in the art will appreciate conventional vaccines have been administered to subjects in need of treatment or prevention of bacterial diseases, viral diseases, fungal diseases, and cancer. Because the vaccines described herein include conventional vaccines, which have been modified by the addition of Ribavirin, the methods described herein include the treatment and prevention of a disease using a vaccine that comprises an antigen and Ribavirin. 
     Preferred embodiments concern methods of treating or preventing hepatitis infection. In these embodiments, an animal in need is provided a hepatitis antigen (e.g., a peptide antigen or nucleic acid-based antigen) and an amount of Ribavirin sufficient to exhibit an adjuvant activity in said animal. Accordingly, an animal can be identified as one in need by using currently available diagnostic testing or clinical evaluation. The range of hepatitis viral antigens that can be used with these embodiments is diverse. Preferred hepatitis viral antigens include an HBV antigen, an HAV antigen, an HCV antigen, nucleic acids encoding these antigens, or any combination thereof. Highly preferred embodiments include an HBV antigen selected from the group consisting of hepatitis B surface antigen (HBsAg), hepatitis core antigen (HBcAg), and hepatitis E antigen (HBeAg), in particular, the peptide and nucleic acid-based antigens describes supra. The Ribavirin and antigen can be provided separately or in combination, and other adjuvants (e.g., oil, alum, or other agents that enhance an immune response) can also be provided to the animal in need. Thus, preferred embodiments include methods of treating or preventing hepatitis in an animal (e.g., HBV) by identifying an infected animal or an animal at risk of infection and providing said animal a hepatitis antigen (e.g., HBsAg, HBcAg, and HBeAg) and an amount of Ribavirin sufficient to exhibit adjuvant activity. 
     Other embodiments include methods of enhancing an immune response to an antigen by providing an animal in need with an amount of Ribavirin that is effective to enhance said immune response. In these embodiments, an animal in need of an enhanced immune response to an antigen is identified by using currently available diagnostic testing or clinical evaluation. Oftentimes these individuals will be suffering from a disease (e.g., bacterial, fungal, mold, viral, or cancer) or are at risk from contracting the disease. However, an animal in need of an enhanced immune response can be an animal that has been poisoned (e.g., bit by a poisonous insect or animal) or that has been exposed to a toxin or other toxic compound. Once identified, these animals are provided an appropriate antigen and an amount of Ribavirin effective to enhance an immune response in the animal. 
     As above, the hepatitis viral antigens that can be used with these embodiments include, but are not limited to, an HBV antigen, an HAV antigen, an HCV antigen, a nucleic acid encoding these molecules, or any combination thereof. Highly preferred embodiments include an HBV antigen selected from the group consisting of hepatitis B surface antigen (HBsAg), hepatitis core antigen (HBcAg), and hepatitis E antigen (HBeAg), in particular, the peptide and nucleic acid-based antigens described supra. The Ribavirin and antigen can be provided separately or in combination, and other adjuvants (e.g., oil, alum, or other agents that enhance an immune response) can also be provided to the animal in need. Thus, preferred embodiments include methods of enhancing an immune response to a hepatitis antigen (e.g., HBV) by identifying an animal in need and providing the animal a hepatitis antigen (e.g., HBsAg, HBcAg, and HBeAg) and an amount of Ribavirin that is effective to enhance an immune response in the animal. 
     Although the invention has been described with reference to embodiments and examples, it should be understood that various modifications can be made without departing from the spirit of the invention. Accordingly, the invention is limited only by the following claims. All references cited herein are hereby expressly incorporated by reference.