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 fowlpoxvirus (FPV) vaccines encoding both HIV-1 gag/pol and interferon-gamma (FPV gag/pol-IFNγ) were hypothesised to enhance HIV-specific cellular immunity and were further evaluated in macaques previously infected with HIV-1. A novel assay to detect IFNγ secretion following HIV antigen stimulation of whole blood was developed to further assess the safety and immunogenicity of the FPV gag/pol-IFNγ vaccine. Immunisation with FPV gag/pol-IFNγ safely enhanced HIV-specific IFNγ secretion following ex vivo stimulation of whole blood, greater than that observed following FPV gag/pol vaccination not co-expressing IFNγ. Both HIV-specific IFNγ-spot-forming cells by ELISPOT and CD69 expression by CD4⁺ lymphocytes were also enhanced following FPV gag/pol-IFNγ vaccination. Hence, the FPV-HIV vaccine co-expressing IFNγ stimulated HIV-specific T cell responses in macaques, and should be further evaluated as a therapeutic or preventive HIV vaccine. (C) Munksgaard, Copenhagen.