Therapeutic Vaccination Expands and Improves the Function of the HIV-Specific Memory T-Cell Repertoire

Background. The licensing of herpes zoster vaccine has demonstrated that therapeutic vaccination can help control chronic viral infection. Unfortunately, human trials of immunodeficiency virus (HIV) vaccine have shown only marginal efficacy. Methods. In this double-blind study, 17 HIV-infected individuals with viral loads of <50 copies/mL and CD4+ T-cell counts of>350 cells/µL were randomly assigned to the vaccine or placebo arm. Vaccine recipients received 3 intramuscular injections of HIV DNA (4 mg) coding for clade B Gag, Pol, and Nef and clade A, B, and C Env, fol-lowed by a replication-deficient adenovirus type 5 boost (1010 particle units) encoding all DNA vaccine antigens except Nef. Humoral, total T-cell, and CD8+ cytotoxic T-lymphocyte (CTL) responses were studied before and after vaccination. Single-copy viral loads and frequencies of latently infected CD4+ T cells were determined. Results. Vaccination was safe and well tolerated. Significantly stronger HIV-specific T-cell responses against Gag, Pol, and Env, with increased polyfunctionality and a broadened epitope-specific CTL repertoire, were observed after vaccination. No changes in single-copy viral load or the frequency of latent infection were observed. Conclusions. Vaccination of individuals with existing HIV-specific immunity improved the magnitude