Interclade neutralization and enhancement of human immunodeficiency virus type 1 identified by an assay using HeLa cells expressing both CD4 receptor and CXCR4/CCR5 coreceptors.

We report on the development and evaluation of a human immunodeficiency virus (HIV) neutralization assay that uses P4P cells, which are CD4+CXCR4+CCR5+ HeLa cells that carry the lacZ gene under the control of the HIV-1 long terminal repeat. The results of the present study suggest that the P4P assay can be used for the extensive study of both neutralizing and enhancing activity in serum samples from HIV-1-infected patients and from vaccinated individuals.