Effects of syphilis infection among HIV-1-positive individuals on suppressive antiretroviral therapy

Abstract

IntroductionIncident syphilis leads to changes in plasma HIV-1 RNA and CD4 + T-cell level in people with HIV (PWH) with viraemia. Its effect in PWH on suppressive antiretroviral therapy (ART) is less clear.MethodsPWH on suppressive ART (plasma HIV-1 RNA < 50copies/mL) followed at the Queen Elizabeth Hospital, Hong Kong, China were regularly screened for syphilis. Their plasma HIV-1 RNA, CD4 + and CD8 + T-cell, and total lymphocyte levels before syphilis, during syphilis, and after successful treatment were compared.ResultsBetween 2005 and 2020, 288 syphilis episodes from 180 individuals wereidentified; 287 episodes were related to male, with a median age of 41 atdiagnosis; 221 (77%) were syphilis re-infection. The rates of plasma HIV-1suppression were statistically unchanged across the time-points (97% pre-syphilis,98% during syphilis, and 99% post-treatment).Total lymphocyte, CD4+ and CD8+ T-cell levels decreased duringincident syphilis (p<0.01), and rebounded post-treatment (p<0.01). VDRLtitre was associated with declines in CD4+ T-cell (p=0.045), CD8+ T-cell(p=0.004), and total lymphocyte levels (p=0.021). Pre-syphilis CD4/CD8 ratiowas associated with increases in CD8+ T-cell (p=0.001) and total lymphocytelevels (p=0.046) during syphilis. Syphilis re-infection was associated with anincrease in total lymphocyte level (p=0.037). In the multivariable analysis,only pre-syphilis CD4/CD8 ratio was independently associated with increases in CD8+T-cell (p=0.014) and total lymphocyte levels (p=0.039) during syphilis.ConclusionsAmong virally-suppressed PWH, total lymphocyte, CD4+, and CD8+ T-celllevels declined duringincident syphilis but rebounded post-treatment. The status of plasma HIV suppressionwas unaffectedby syphilis.