Synergistic infectivity of highly and minimally infectious clones of human immunodeficiency virus in vitro.

To explore the biologic significance of the presence of a heterogeneous human immunodeficiency virus (HIV) population within infected individuals with regard to ultimate disease progression, the effect of coinfection of more than one variant of HIV on infectivity and cytopathogenicity in CD4-positive cells was examined. Using the lowest and highest infectious clones of HIV obtained by the plaque-cloning method, a clear consistent synergism of infectivity and cytopathic effects was detected when different cell lines were coinfected with a mixture of the two clones. These data suggest that the emergence of a highly infectious variant of HIV due to mutation may modify the infectivity of a minimally infectious latent variant with the final progression of HIV infection to overt AIDS.