Resistance to human immunodeficiency virus type 1 in vitro as a surrogate of vaccine-induced protective immunity

An in vitro assay developed as a correlate of vaccine-induced protection from human immunodeficiency virus (HIV) was validated in populations with relative resistance to HIV-1 as well as in HIV vaccine recipients. Cultures of peripheral blood mononuclear cells (PBMC) were challenged with 10 TCID50 of HIV-1(MN) or HIV-1(BaL), titered in PBMC from normal controls (n = 57), PBMC from HIV-1-infected persons with low viremia (n = 17), exposed uninfected persons (n = 23), and HIV-2-infected Senegalese prostitutes (n = 9) were significantly resistant to HIV-1(BaL) and/or HIV-1(MN) (P < .001). Among 34 HIV vaccine recipients of live canarypox vector expressing multiple HIV-1 gene products with or without rgp120 booster, PBMC from postvaccination samples were significantly resistant to both strains (P < .001), and cytotoxic T lymphocyte precursor-positive samples were significantly more resistant than were precursor-negative samples (P < .03), This is the first evidence of the induction by vaccination of a validated correlate of protection. This assay should serve as a useful criterion for assessing experimental HIV vaccines before phase III efficacy trials.