Increased Regulatory T Cell Counts in HIV-Infected Nonresponders to Hepatitis B Virus Vaccine

Hepatitis B virus (HBV) coinfection is a main cause of liver-related mortality in human immunodeficiency virus (HIV)-infected subjects. Unfortunately, HIV-infected subjects show a low rate of response to standard HBV vaccination (23%-56%), in contrast to rates 190% found in the general population, and the underlying causes (particularly cellular and molecular causes) are still unknown. We hypothesized that an increased frequency of regulatory T (T-reg) cells could be involved in the low rate of seroconversion in HIV-infected subjects. Forty HIV-infected subjects were enrolled in the Assistance Vaccination Program against HBV of the Infectious Diseases Service from the Virgen del Rocio University Hospital, Seville, Spain. Freshly isolated peripheral blood mononuclear cells from baseline were immunophenotyped for T-reg cells, CD4, and CD8 T cells in both naive and memory subpopulations and activation degree, as well as recent thymic emigrants. Baseline T-reg cell frequency was found independently associated with the final nonresponse to HBV vaccine in HIV-infected subjects. Furthermore, a negative correlation between baseline frequency of T-reg cells and antibody titers in the final response was found. These findings suggest an active role played by T-reg cells on the immunization antigen-specific T and/or B cell responses with the final consequence of a B cell anti-HBs lower production.