P41.17
Background: HIV-1 protease mediates the cleavage of Gag, Gag-Pol and Nef precursor polyproteins in a highly specific and temporally regulated manner. Because a total of 12 cleavage reactions are required to generate a mature virion, generating focused immune response targeting the sequences surrounding the protease cleavage sites (PCS) could drive viral mutations to its disadvantage. We have conducted a proof of concept study with Cynomolgus macaques and pathogenic SIVmac239 as a model and used a modified recombinant vesicular stomatitis vector and nanocarriers to deliver 12 20-amino acid antigens. We showed that a vaccine targeting the sequences surrounding the 12 protease cleavage sites is promising at prevention of HIV-1 infection and disease progression. In this study we systematically analyzed breakthrough viruses of vaccinated and control macaques.
Methods: The sequences surrounding the 12 protease cleavage sites were amplified from plasma RNA of all SIVmac239 positive samples. The amplified PCR products were sequenced with 454 pyrosequencing technology. The amino acid and frame shift mutations were analyzed and correlated with viral load and CD4 counts. Regression analysis was conducted to correlate the viral mutations with viral load and CD4 counts. WebLogo was used to plot the amino acid mutations.
Results: Extensive mutations were detected around PCS and both conserved and non-conserved mutations are correlated with lower viral load (p<0.0001). The breakthrough viruses from the vaccinated macaques carry significantly higher mutations than the controls. Longitudinal analysis revealed that the high rate of non-conserved and conserved amino acid mutations along the sequences surrounding the PCS lead to the reduction and diminishing of viral load.
Conclusions: The pathogenic SIVmac239 is extremely vulnerable to any amino acid alternations around PCS and focusing immune response to sequences surrounding the PCS of HIV-1 can drive amino acid mutations and lead to complete viral control.
