CD4, CCR5, and CXCR4 expression and HIV replication in untransformed CD4⁺ T-cell lines from ADA-SCID children. (A) CD4⁺ T-cell lines of 3 children affected by ADA-SCID that were established before and after GT were stained with anti-CD4–FITC, anti-CCR5–PE, and anti-CXCR4–PE mAb at the time of viral infection, and the percentage of positive cells was detected by cytofluorimetric analysis. (Left panels) The results from a single experiment on pediatric cell lines representative of the pattern observed with cells from 3 independent patients isolated before (top panel) and after (bottom panel) GT. (Right panels) Mean ± SEM values. No significant differences in terms of percentage of CD4⁺ T cells expressing the HIV-1 entry CoR was noted. (B) ADA-SCID CD4⁺ T-cell lines were infected with R5 and X4 HIV-1. Only R5 HIV-1 efficiently replicated in these cell lines before and after GT (which, however, significantly boosted the levels of virus replication). The results obtained with the cell lines established from a single child before and after GT are shown and are representative of those collected with the cell lines derived from 2 additional patients. (Bottom panels) Mean ± SEM of the peaks of virus replication in cell lines established before and after GT from the 3 patients.