Improving the Immunogenicity of Pneumococcal Conjugate Vaccine in HIV-Infected Adults with a Toll-Like Receptor 9 Agonist Adjuvant: A Randomized, Controlled Trial

Background. Persons infected with human immunodeficiency virus (HIV) are often hyporesponsive to immunization, including pneumococcal vaccines. We hypothesized that adding CPG 7909, a toll-like receptor 9 (TLR9) agonist and vaccine adjuvant, to 7-valent pneumococcal conjugate vaccine (7vPnC) would increase its immunogenicity in HIV-infected adults. Methods. We performed a double-blind, placebo-controlled, phase 1b/2a trial randomizing HIV-positive patients to receive double doses of 7vPnC (Prevnar) at 0 and 3 months and 1 dose of 23-valent pneumococcal polysaccharide vaccine (PPV-23; Pneumo Novum) at 9 months, with experimental patients receiving 1 mg of CPG 7909 added to each of their 3 vaccine doses; control patients had phosphate-buffered saline added instead. Immunogenicity and safety were evaluated for up to 10 months. The primary end point was the proportion of vaccine high responders at 9 months, defined as a 2-fold increase in IgG levels to >= 1 mu g/mL for at least 5 of 7 of the 7vPnC serotypes. Results. Ninety-seven participants were included in the study. The proportion of vaccine high responders was higher in the experimental group (n = 48) than among controls (n = 49; 48.8% vs 25.0%; P = .02) at 9 months. Greater proportions of high responders were also observed at 3 (51.1% vs 39.6%; P = .26), 4 (77.3% vs 56.3%; P = .03), and 10 months (87.8% vs 51.1%; P < .001). Mild systemic and injection site reactions to 7vPnC were more common in the experimental group than the control group (100% vs 81.3%; P = .002). CPG 7909 did not increase non-7vPnC IgG levels after PPV-23 immunization. No adverse effects on CD4(+) cell count or organ functions occurred in either group. Conclusions. The addition of a TLR9 agonist to 7vPnC significantly enhanced the proportion of vaccine high responders.