The activities of DDD2-T20, h734-(T20)4, and the unconjugated T20 to inhibit the infection of HIV-16920, a primary, nonsyncytium-inducing (NSI), CCR5-tropic, clade B isolate [13], to human peripheral blood mononuclear cells (PBMCs) were determined by HIV p24 ELISA [14] and compared in Fig. 2A–C. The gene discussed is CCR5; the disease is infection.