Immunoproteomic Discovery of Novel T Cell Antigens from the Obligate Intracellular PathogenChlamydia

Abstract

*Chlamydia infections cause substantial morbidity worldwide and effective prevention will depend on a vaccine. Since Chlamydia immunity is T cell-mediated, a major impediment to developing a molecular vaccine has been the difficulty in identifying relevant T cell Ags. In this study, we used a combination of affinity chromatography and tandem mass spectrometry to identify 13 Chlamydia peptides among 331 self-peptides presented by MHC class II (I-A b ) molecules from bone marrow-derived murine dendritic cells infected with Chlamydia muridarum. These MHC class II-bound peptides were recognized by Chlamydia-specific CD4 T cells harvested from immune mice and adoptive transfer of dendritic cells pulsed ex vivo with the peptides partially protected mice against intranasal and genital tract Chlamydia infection. The results provide evidence for lead vaccine candidates for a T cell-based subunit molecular vaccine against Chlamydia infection suitable for human study. The Journal of Immunology, 2008, 180: 2459 -2465. W orld-wide Chlamydia trachomatis is annually responsible for Ͼ92 million sexually transmitted infections and 85 million ocular infections (1). Public health programs have targeted C. trachomatis as a major problem because the organism causes long-term sequelae such as infertility, ectopic pregnancy, and blindness. Sexually transmitted C. trachomatis is also a potent cofactor facilitating the transmission of HIV (2) and interacts with oncogenic human papilloma virus in the pathogenesis of cervical neoplasia (3). In developed countries, public health measures to control Chlamydia are failing as case rates continue to rise, perhaps due to early antibiotic treatment interfering with the acquisition of immunity (4); these approaches to control Chlamydia are not feasible for much of the developing world. Thus, a new approach, such as an effective vaccine, is needed if Chlamydia control is to be achieved in the developing and developed world.Previous vaccine research using inactivated Chlamydia bacterial cells demonstrated partial short-term protection which may have been complicated by immunopathology during breakthrough infection (5). These vaccine trials yielded important lessons for the modern era of Chlamydia vaccinology, namely, that an effective Chlamydia vaccine will need to be molecularly defined and engender long-lived protective immune responses. Immunity to C. trachomatis is now known to depend on cell-mediated immune (CMI) 3 responses, especially Th1-polarized cytokine responses (6). Abs appear to play a secondary role (7). Experience has shown that developing vaccines for intracellular pathogens that require protective CMI is more difficult than for pathogens that simply require protective Ab (8). Part of the problem has been the identification of Ags that induce CMI responses because such Ags need to be presented to T cells by MHC molecules, and identifying MHC-bound microbial epitopes has been notoriously difficult (6). Since T cell responses mainly recognize protein Ags, protective vaccine candida...

Interleukin-17 Contributes to Generation of Th1 Immunity and Neutrophil Recruitment duringChlamydia muridarumGenital Tract Infection but Is Not Required for Macrophage Influx or Normal Resolution of Infection

“…Immunostimulatory peptides GNEVFVSPAAHIIDRPG (RplF 51-59 ), SPIYVDPAAAGGQPPA (PmpG 1303-311 ), and AFHLFASPAANYIHTG (PmpE/F 2351-359 ) were synthesized and purified by Synthetic Biomolecules (San Diego, CA). These chlamydial peptides correspond to major histocompatibility complex (MHC) class II epitopes that were discovered by Karunakaran et al using immunoproteomics (18). Pooled peptides were solubilized in dimethyl sulfoxide (DMSO) (4 mg/ml) and used at a concentration of 2 g/ml each in medium as stimulatory antigens for enzyme-linked immunospot (ELISPOT) assays.…”

Outer and Inner Membrane Proteins Compose an Arginine-Agmatine Exchange System inChlamydophila pneumoniae

“…The CPn1033 protein belongs to the OprB family of outer membrane porins, but it was originally annotated as a hypothetical protein due to its low sequence similarity to any characterized member of that porin family (1). A peptide from the Chlamydia muridarum homolog of CPn1031 was presented by major histocompatibility complex class I molecules from murine dendritic cells (24). The CPn1031 protein belongs to the basic amino acid/polyamine antiporter family of transporters (APA; TC 2.A.3.2) (21), and it was originally annotated as an arginine/ornithine antiporter based on its similarity to the Pseudomonas aeruginosa ArcD transporter (51).…”

CPAF selectively degrades chlamydial T cell antigens for inhibiting antigen presentation

“…Therefore, the T cell antigens processed by CPAF and identified in the current study should be further validated during in vivo infection in the future. In addition, identifying specific T cell antigens through the dendritic cell-based immunopretomic approach is considered a promising way to research a chlamydia vaccine [39,58], and several promising T cell antigens were identified to be likely candidates for vaccine but require further validation. In this study, we took advantage of this system to identify several T cells antigens and we further investigated whether CPAF blocks the presentation of these T cells antigens.…”

“…The dendritic cells (DC) used for the antigen presentation experiment were generated from bone marrow-derived dendritic cells (BMDCs) according to a method previously described [39]. Briefly, mice were sacrificed and bone marrow cells were isolated from mouse femurs and tibiae by flushing with RPMI 1640 medium.…”