CAP/CTM assay limit of detection for 8E5 cells. Ten replicates of 100-μl aliquots of 1× PBS containing 8E5 cells with CAH at 1, 10, and 100 copies/ml were lysed with SPEX and tested in the CAP/CTM assay. At 1 cell per ml, 1 of 10 replicates resulted in a value at 38 copies/ml (49 copies per 8E5 cell). All aliquots at 10 and 100 cells/ml were detected and gave a broad range of HIV values of from 55 to 2,149 copies per cell, with a mean of 606 and 1,144 copies/cell, respectively. The CAP/CTM assay is capable of detecting CAH in a single 8E5 cell.