Immunogenicity of a vaccine formulated with the Chlamydia trachomatis serovar F, native major outer membrane protein in a nonhuman primate model

To determine the ability of a vaccine formulated with the genital Chlamydia trachomatis, serovar F, native major outer membrane protein (Ct-F-nMOMP), to induce systemic and mucosal immune responses, rhesus macaques (Macaca mulatta) were immunized three times by the intramuscular (i.m.) and subcutaneous (s.c.) routes using CpG-2395 and Montanide ISA 720 VG, as adjuvants. As controls, another group of M. mulatta was immunized with ovalbumin instead of Ct-F-nMOMP using the same formulation and routes. High levels of Chlamydia-specific IgG and IgA antibodies were detected in plasma, vaginal washes, tears, saliva, and stools from the Ct-F-nMOMP immunized animals. Also, high neutralizing antibody titers were detected in the plasma from these animals. Monkeys immunized with ovalbumin had no detectable Chlamydia-specific antibodies. Furthermore, as measured by a lymphoproliferative assay, significant Chlamydia-specific cell-mediated immune responses were detected in the peripheral blood mononuclear cells (PBMC) from the rhesus macaques vaccinated with Ct-F-nMOMP when compared with the animals immunized with ovalbumin. In addition, the levels of two Th1 cytokines, IFN-γ and TNF-α, were significantly higher in the animals immunized with Ct-F-nMOMP when compared with those from the monkeys immunized with ovalbumin. To our knowledge, this is the first time that mucosal and systemic immune responses have been investigated in a nonhuman primate model using a subunit vaccine from a human genital C. trachomatis serovar.