Two antigenically distinct subtypes of human immunodeficiency virus type 1: viral genotype predicts neutralization serotype.

At least five distinct genetic subtypes (genotypes) of human immunodeficiency virus type 1 (HIV-1) have been identified by DNA sequencing. Current vaccine candidates are based on virus strains from North America and Europe that represent only one subtype. The extent to which distinct genotypes of HIV-1 correspond to antigenically distinguishable serotypes is largely unknown and may be critically important to vaccine design. Cross-neuralization studies were done with viruses and plasma from two different genotypes. Based on neutralization susceptibility, 10 primary HIV-1 isolates from Thailand and the United States were classified into one of two antigenic subtypes that correlated with viral genotype. The existence of serotypes of HIV-1 suggests that a broadly effective vaccine may have to include strains from multiple subtypes. Neutralization of these primary HIV-1 isolates differed substantially from results with laboratory strains. Future neutralization studies using primary isolates and multiple genotypes may be important for assessment of HIV-1 antigenic diversity.