Potent cross-reactive immune response against the wild-type and drug-resistant forms of HIV reverse transcriptase after the chimeric gene immunization.

HIV reverse transcriptase (RT) can be considered as a target and an instrument of immunotherapy aimed at limiting the emergence and spread of drug-resistant HIV. The chimeric genes coding for the wild-type and multi-drug-resistant RT (RT1.14) fused to lysosome-associated membrane protein 1 (LAMP-1) were injected intramuscularly into BALB/c mice. The immune response was assessed by ELISpot, cytokine ELISA intracellular IFN-gamma staining, and antibody ELISA. The genes for RT- and RT1.14-LAMP fusions (RT-LAMP and RT1.14-LAMP) were immunogenic generating a mixed Th1/Th2-profile of immune response, while the wild-type RT gene induced only weak immune response. Specific secretion of Th1-cytokines increased with increasing level of RT modification: RT<RT1.14 approximately RT-LAMP<RT1.14-LAMP. LAMP gene fusions generated a cross-reactive T-cell response against epitopes harboring drug-resistance mutations and their wild-type variants. Gene immunization induced specific IgG (10(3)), and transient serum IgA (10(2)). Low immunogenicity of the parental RT may be explained by tolerance to the enzyme that is a common endogenous retroviral antigen. Potent immune recognition of RT after immunization with chimeric RT genes indicates that this tolerance could be overcome. Immunization with mutant HIV genes may represent an immunotherapeutical supplement to antiretroviral treatment preventing the emergence of drug resistance.