In a longitudinal mixed effects regression model, we observed that persons with HIV-1/HSV-2 co-infection sustained higher CD4+ T cell counts over time (average of 69 cells/μl greater (SD = 33.7, p = 0.04)) than those with HIV-1 infection alone (Fig. 1), after adjustment for HIV-1 RNA levels (−57 cells per 1 log10 higher HIV-1 RNA, p<0.0001). The gene discussed is CD4; the disease is HIV-1 infection.