CD4 and AIDS: Third, the prevalence of the genetic factors that we have identified in a U.S.-based cohort of HIV-positive individuals (prevalence of the low, moderate and high GRGs is ∼50, 42 and 8%, respectively) is large enough to be of clinical relevance as these genetic factors can provide dual prognostication: risk of AIDS and disease progression, and recovery of CD4 cell numbers [23] and function [20] during HAART.