DNA immunization with HIV-1 tat mutated in the trans activation domain induces humoral and cellular immune responses against wild-type tat

Intramuscular immunization of mice with plasmids encoding two transdominant negative mutants of the HIV-1 Tat protein (Tat(22) and Tat(22/37)) elicite d a humoral response to wild-type Tat that is comparable to that induced by inoculation of wild-type fat DNA or Tat protein. The percentage of the res ponders and the Ab titers continued to increase after three additional DNA boosts and pretreatment with bupivacaine at the site of inoculation, withou t a significant difference (p > 0.05) among the three groups of mice immuni zed with mutant and wild-type tat genes. By utilizing synthetic peptides re presenting the amino acid sequence of Tat, one major B cell epitope was def ined within the cysteine-rich domain of Tat,;Anti-Tat IgG Abs directed agai nst this epitope,were found in mice immunized with all far DNA constructs, whereas different Tat epitopes were detected in mice immunized with the Tat protein. Similarly, IgG2a was the predominant isotype in DNA-immunized mic e, with both mutants and wild-type tat genes, as compared with protein immu nization, which induced mostly IgG1 and IgG3, Sera from most immunized mice neutralized the effect of extracellular Tat in activating HIV-1 replicatio n. A cellular response was also elicited as indicated by the proliferation of splenocytes when stimulated with wild-type Tat, These results indicate t hat the wild-type Tat Ag is recognized by Abs and T cells induced by DNA im munization with mutated rat genes, suggesting the possible use of these Tat transdominant mutants, lacking viral trans activation activity and capable of blocking wild-type Tat activity, in the development of an anti-HIV-1 va ccine.