CD4 and HIV-1 infection: An HLA association analysis with human immunodeficiency virus type 1 (HIV-1) susceptibility identified HLA-DRB1*01:01 to be protective (P-value = 0·0003 [log rank test], incidence response ratio (IRR)= 0·22, 95% CI = 0·06-0·60) supporting the well-established role of class II CD4 effector cells in response to HIV-1 infection [39].