2-LTR CJ PCR assays (CJ primer set C) performed with DNA isolated from CD4+ T cells from FIV-infected cats co-cultured with uninfected feline PBMCs demonstrated appropriately sized amplicons (Figure 6e) consistent with a productive viral infection (mean real-time PCR CT values for lanes 1, 7-10, respectively: 29.9, 36.9, 37.1, 37.2 and 33.9). Here, CD4 is linked to viral infectious disease.