CD4 and HIV-1 infection: There was no evidence of an interaction between age and HIV-1 infection in either naïve subset (interaction p = 0.9564 for CD31+ and p = 0.5492 for CD31- CD4+ naïve T-cell subsets) indicating that, although age and HIV-1 serostatus each contribute to telomere shortening, these effects appear to be additive.