This procedure is used for establishing cocultures for virus isolation by an endpoint dilution assay in a 96-well tissue culture plate. This is a cell culture assay based on the detection of HIV in patient peripheral blood mononuclear cells (PBMC) by the appearance of p24 gag protein in the culture supernatant. It can be used in a research setting as a measure of viral burden because the number of patient cells required to produce a positive culture is indicative of cellular viral load.