In HIV-infected NSG humanized mice, we observed down-regulation of CD27 expression in CD4+ (from 91.25±1.70% positive before infection to 82.00±2.94% at week 6) and CD8+ T cells (from 91.25±1.89% to 77.50±3.11%) (Fig. 5E). The gene discussed is CD8A; the disease is infection.