Therapeutic immunization in HIV infected Ugandans receiving stable antiretroviral treatment: A Phase I safety study

Therapeutic immunizations in HIV infection may boost immunity during antiretroviral treatment. We report on the first therapeutic vaccine trial in Uganda, Africa. This open label Phase I trial was designed to assess the safety, tolerability and immunogenicity of a therapeutic HIV-1 vaccine candidate. Thirty HIV positive volunteers receiving a stable regimen of antiretroviral therapy with CD4 counts >400 were recruited for the safety evaluation of LFn-p24C, a detoxified anthrax-derived polypeptide fused to the subtype C HIV gag protein p24. The vaccine was well tolerated and HIV RNA levels remained undetectable following three immunizations. CD4 counts in vaccine recipients were significantly higher compared to the control individuals after 12 months. HIV-specific responses were associated with higher gain in CD4 counts following LFn-p24C immunizations. Volunteers were subsequently asked to undergo a 30-day period of observed treatment interruption. 8/24 (30%) individuals showed no evidence of viral rebound during treatment interruption. All demonstrated prompt suppression of viral load following resumption of ART. Our data demonstrate the safety of LFn-p24C and suggest that adjunct therapeutic immunization may benefit select individuals in further boosting an immune response.