Background: Although sex hormones are recognized to induce immune variations, the effect of hormonal therapy use on immunity is only poorly understood. Here, we quantified how hormonal therapy use affects HIV-1 immune markers in cis women (CW) and trans women and non-binary people (TNBP) with HIV.

Methods: We considered CD4, CD8 and lymphocyte measurements from cis men (CM), CW and TNBP in the Swiss HIV Cohort Study. We modelled HIV-1 markers using linear mixed-effects models with an interaction between 'gender' (CW, TNBP) and 'hormonal therapy use' (yes/no). Models were adjusted on age, ethnicity, education level, time since start of antiretroviral therapy and use of intravenous drugs. We assessed the inflammatory effect of hormonal therapy use in 31 TNBP using serum proteomics measurements of 92 inflammation markers.

Results: We included 54 083 measurements from 3092 CW and 83 TNBP, and 147 230 measurements from 8611 CM. Hormonal therapy use increased CD4 count and CD4:CD8 ratio in TNBP more than in CW (p_interaction  = 0.02 and 0.007, respectively). TNBP with hormonal therapy use had significantly higher CD4 counts [median = 772 cells/μL, interquartile range (IQR): 520-1006] than without (617 cells/μL, 426-892). This was similar to the effect of CW versus CM on CD4 T cells. Hormonal therapy use did not affect serum protein concentrations in TNBP.

Conclusion: This study highlights the potential role of hormonal therapy use in modulating the immune system among other biological and social factors, especially in TNBP with HIV.