Canarypox vaccines induce antigen-specific human gammadelta T cells capable of interferon-gamma production

Induction of human gammadelta T cells was investigated in subjects who were vaccinated with live recombinant canarypox virus expressing human immunodeficiency virus (HIV) proteins or soluble MN rgp120. Both canarypox and rgp120 induced antigen-specific lymphoproliferative and interferon (IFN)-gamma responses. However, only canarypox vaccination induced increased gammadelta T cell responses detectable after secondary in vitro expansion (P<.02). These enhanced gammadelta T cell responses were specific for canarypox but not HIV antigens. Canarypox-specific gammadelta T cells were predominantly Vgamma9(+) and produced intracellular and secreted IFN-gamma. gammadelta T cell lines generated from canarypox vaccinees responded to canarypox antigens but not to mycobacterial antigens shown previously to induce bacille Calmette-Guérin-specific gammadelta T cells. Furthermore, canarypox vaccinations were associated with significantly higher NK cell expansions (P=.02). Increased IFN-gamma production by gammadelta T and NK cells could enhance the induction of protective type 1 memory immunity. Thus, stimulation of gammadelta T cells might be an important feature of live vaccines.