Immunogenicity Of Multiple Vector Vaccines Expressing HIV-1 Gag And Env Genes In Mice And Rhesus Macaques

The global HIV epidemic continues to expand,exceeding previous predictions and causing tremendous suffering.At the same time,a rapid increase of HIV infection was also found in China in recent years.The cumulative reported cases living with HIV/AIDS were 223,501 by the end of Oct 2007.Therefore,developing HIV vaccines targeting the prevalent strains in China is one of the most important tasks of Chinese HIV/AIDS therapy and prevention.Subtype B is found to be prevalent in several epidemic regions where paid blood donors are mainly affected population.HIV-1 Subtype B isolates in these epidemic regions are relatively conserved,so the prevalent strains isolated from these regions were used as vaccine strain.The purpose of this study is developing therapeutic vaccines using multiple vectors in combination with HAART treatment for enhancing the host specific immunity.The study in untreated HIV-1 infected cohort and HIV-2 long-term non-progressors indicated that only Gag-specific responses were associated with lowering viremia and may play an important role in controlling viral load during chronic infection.Therefore,we made DNA,adenovirus type 5(rAd5), adenoassociated virus type 1(rAAV2/1) and Sendai virus(rSeV) vectors expressing gag gene of the prevalent Subtype B strains in China as candidate vaccine strategies.Firstly,we examined the potency of vaccine regimens of DNA,rAd5-gag, rAAV2/1-gag and rSeV-gag for inducing specific immune responses.The Gag-specific cellular immune responses were detected by intracellular cytokine staining(ICS), ELISPOT and in vivo CTL,and humoral immune resposes were detected by ELISA.In Balb/C mice,the immunogenecity of candidate vaccines were rAd5>rSeV>DNA and stronger cellular immune reponses companied with stronger humoral responses.However, it's different from the immunogenecity of rAAV2/1 vacccine,rAAV2/1 vaccine induced potent and long lasting Gag-specific antibody responses but very moderate cellular immune responses.Moreover,rAAV2/1-gag impaired the Gag-specific immune responses induced by follwing rAd vaccines(rAd5-gag and rAd5/F35-gag) boosting.The same results were observed in rAAV2/1 and rAd5 vaccines expressing HIV-1 gp120 gene.It indicates that the different immunogenicity is vector dependent and independent of the nature of antigen.Then the potency of DNA,rAd5-gag and rSeV-gag to induce HIV-1 cellular responses were tested in combined modality.The results showed that combination of these vectors induced higher Gag-specific cellular immune response than any regimen using single vector alone.Commonly,vaccination protocols require multiple immunizations to achieve robust,protective and sustained immune responses.However, the immunity against viral vectors has limited the repeated use of same candidate vaccine. Most researches have focused on vaccination protocols based on one or two candidates.In this study we addressed the magnitude,sustain and breadth of HIV-1 Gag-specific immune responses induced by prime-boost-boost scheme with combination of triple heterologous vectors.The prime-boost-boost regimen consisting of the triple heterologous vectors(i.e. DNA,adenovirus and SeV) induced Gag-specific T-cell responses the most efficiently as well as humoral response.In rhesus macaques,the prime-boost-boost regimen induced potent Gag-specific cellular immune responses as well as long lasting humoral immune response,and each boosting resulted in rapid and efficient expansion of Gag-specific T cells.These results indicate that this prime-boost-boost regimen using triple heterologous vectors is a promising AIDS vaccine candidate for efficiently inducing HIV-1-specific cellular and humoral immune responses.Its further studies as a promising scheme for prophylactic and/or therapeutic HIV-1 vaccines should be grounded.Based on the results of strong and long lasting humoral responses induced by rAAV2/1-gp120 in Balb/C mice,the potency of rAAV2/1-gpl20 to induce Env-specific humoral responses was also tested in rhesus macaques.However,only moderate Env-specific IgG were induced.Gene optimization may be necessary to induce high level of Env-specific humoral responses and neutralizing antibody.