OBJECTIVETo observe the level of anti-adenovirus neutralizing antibodies and Gag specific cellular immune responses in Macaca fascicularis immunized with different dosage of recombinant adenovirus vaccine Ad5-HIVgag by repeated intramuscular injection.

METHODSThe Macaca fascicularis were randomly divided into four groups of 6. Different amount of the purified Ad5-HIVgag (0.99 x 10(11) VP, 4.94 x 10(11) VP, 24.68 x 10(11) VP) or PBS were administered in 3 weeks interval and five times. The level of anti-adenovirus neutralizing antibodies and Gag-specific cellular immune responses at different time points were detected by neutralization assay and Elispot assay respectively.

RESULTSHigh level of anti-adenovirus neutralizing antibodies could be detected in three groups immunized with Ad5-HIVgag at 3 weeks after first immunization. The neutralizing antibodies reached peak at 8 weeks after primary immunization, and declined slightly at late time. Significant HIV-1 Gag-specific cellular immune responses were detected in all Ad5-HIVgag immunized groups at 5 weeks post first immunization. The Gag-specific cellular immune responses declined at 12 weeks and then increased with time.

CONCLUSIONAnti-adenovirus neutralizing antibodies could be induced in Macaca fascicularis immunized with Ad5-HIVgag by repeated intramuscular injection. And the Gag-specific cellular immune responses tended to increase with the injection times. The presence of anti-adenovirus neutralizing antibodies induced by vaccination with adenovirus vectors in Ad5-naive animals did not further reduce Gag-specific cellular immune responses.