High-throughput proteomic screening identifies Chlamydia trachomatis antigens that are capable of eliciting T cell and antibody responses that provide protection against vaginal challenge.

A comprehensive proteomic screening technology was previously used to characterize T cell responses to Chlamydia trachomatis infection. In this study, we demonstrated that T cells specific for protein antigens identified through this comprehensive technology home to the site of infection after mucosal challenge with C. trachomatis. In addition, T cell responses to these proteins were elicited in multiple genetic backgrounds. Two protein antigens, CT823 and CT144, were evaluated as vaccine candidates. When administered with AbISCO-100 adjuvant, these antigens stimulated potent CD8(+) T cell responses, polyfunctional T(H)1-polarized CD4(+) T cell responses, and high titer protein-specific T(H)1-skewed antibody responses. Vaccination with either antigen with AbISCO-100 provided long-lived protection against intravaginal challenge with C. trachomatis. Adoptive transfer of immune T cells also conferred protection in the challenge model whereas passive transfer of immune serum did not, indicating the critical role for T cell responses in control of this infection. The ability of these antigens to induce potent immune responses and provide long-lived protection in response to challenge provides a basis for the rational design of a C. trachomatis subunit vaccine.

High-affinity interactions between peptides and heat shock protein 70 augment CD8+ T lymphocyte immune responses.

Exogenously delivered antigenic peptides complexed to heat shock proteins (HSPs) are able to enter the endogenous Ag-processing pathway and prime CD8+ CTL. It was determined previously that a hybrid peptide containing a MHC class I-binding epitope and HSP70-binding sequence Javelin (J0) in complex with HSP70 could induce cytotoxic T cell responses in vivo that were more robust than those induced by the minimal epitope complexed with HSP70. The present study introduces a novel, higher-affinity HSP70-binding sequence (J1) that significantly enhances binding of various antigenic peptides to HSP70. A competition binding assay revealed a dissociation constant that was 15-fold lower for the H2-K(b) OVA epitope SIINFEKL-J1 compared with SIINFEKL-J0, indicating a substantially higher affinity for HSP70. Further, modifying the orientation of the hybrid epitope and introducing a cleavable linker sequence between the Javelin and the epitope results in even greater immunogenicity, presumably by greater efficiency of epitope processing. The enhanced immunogenicity associated with Javelin J1 and the cleavable linker is consistently observed with multiple mouse and human epitopes. Thus, by creating a series of epitopes with uniform, high-affinity binding to HSP70, successful multiple epitope immunizations are possible, with equal delivery of each antigenic epitope to the immune system via HSP70. These modified epitopes have the potential for creating successful multivalent vaccines for immunotherapy of both infectious disease and cancer.