The median CD4 + T-cell levels (cells/mm3) decreased from 559 (IQR 405–699) before syphilis at T1 to 519 (IQR 390–687) at the time of syphilis diagnosis at T2 (p < 0.001) and rebounded to 562 (IQR 430–725) after successful syphilis treatment at T3 (p < 0.001). This evidence concerns the gene CD4 and syphilis.