Induction of HIV-1-specific T-helper responses and type 1 cytokine secretion following therapeutic vaccination of macaques with a recombinant fowlpoxvirus co-expressing interferon-gamma

Preventive and/or therapeutic vaccines against Human Immunodeficiency Virus (HIV-1) are urgently required. Induction of cellular immunity is favoured since these responses correlate with control of HIV-1. Recombinant fowlpoxv irus (FPV) vaccines encoding both HIV-1 gag/pol and interferon-gamma (FPV g ag/pol-IFN gamma) were hypothesised to enhance HIV-specific cellular immuni ty and were further evaluated in macaques previously infected with HIV-1. A novel assay to detect IFN gamma secretion following HIV antigen stimulatio n of whole blood was developed to further assess the safety and immunogenic ity of the FPV gag/pol-IFN gamma vaccine. Immunisation with FPV gag/pol-IFN gamma safely enhanced HIV-specific IFN gamma secretion following ex vivo s timulation of whole blood, greater than that observed following FPV gag/pol vaccination not co-expressing IFN gamma. Both HIV-specific IFN gamma-spot- forming cells by ELISPOT and CD69 expression by CD4(+) lymphocytes were als o enhanced following FPV gag/pol-IFN gamma vaccination. Hence, the FPV-HIV vaccine co-expressing IFN gamma stimulated HIV-specific T cell responses in macaques, and should be further evaluated as a therapeutic or preventive H IV vaccine.