Chlamydia trachomatis genital tract infections have a prevalence of 2-15% in adolescents/young adults in the USA and Europe in spite of public health efforts and effective antibiotic therapy. It is widely accepted that a vaccine is necessary reduce its prevalence. An early C.trachomatis trachoma (eye infection) vaccine delivered poor protection and exacerbated immunopathology. Critical to developing a safe Chlamydia vaccine is a better understanding of immunopathology. Currently there are no practicable biomarkers for Chlamydia immunopathology. In the C. muridarum mouse model others have clearly shown that Chlamydia-specific CD8 T cells are important mediators of immunopathology and infertility. We have recently shown that a subset of Chlamydia-specific CD8 T cell clones derived from mice that self-cleared C. muridarum genital tract infections produce the scar-ogenic cytokines IL-10, TNF?nd IL-13. These CD8 clones are not restricted by MHC class Ia molecules. Similar non-class Ia restricted CD8 T cell clones have been derived from the peripheral blood of humans with C. trachomatis genital tract infections. Using gene expression microarray analysis we have identified a molecular fingerprint for CD8IL-13 T cells. Based on the existing mouse and human Chlamydia literature it clear that the cellular immune response to Chlamydia genital tract infections includes non-class Ia restricted CD8 T cells. The C. muridarum mouse model has unequivocally shown CD8 T cells to be mediators of immunopathology and infertility. We hypothesize that the mechanism underlying CD8 immunopathology is a non-MHC class Ia restricted CD8 T subset secreting IL-10, TNF?and IL-13. To test that hypothesis and investigate the underlying immunobiology we propose the following specific aims:
Specific aim #1 - to investigate the role of CD8IL-13 T cells in immunopathology utilizing adoptive transfer. We have representative conventional Chlamydia-specific CD8 T cell clones, Chlamydia-specific CD8IL-13 T cell clones, and putative cell surface biomarkers for purifying CD8IL-13 T cells from immune splenocytes or bulk T cell populations.
Specific aim #2 - to investigate the activation pathway and other immunobiology specific to Chlamydia-specific CD8IL-13 T cells. Utilizing existing T cell clones and gene expression microarray analysis we will compare activated conventional CD8 with activated CD8IL-13 T cells to identify CD8IL-13 specific immunobiology; potentially identifying additional biomarkers and targets for therapeutic intervention. We will als map the epitope source proteins for the Chlamydia-specific CD8 T cell clone panel.
Specific aim #3 - perform a preliminary investigation of CD8IL-13 T cells in humans. Using putative biomarkers for the CD8IL-13 T cell subset identified in the mouse model we will isolate CD8 T cells from the peripheral blood of healthy individuals and determine whether a similar CD8IL-13 T cell subset exists in humans.
Research outlined in this grant proposal will help future Chlamydia vaccines avoid an undesirable immune response associated with scarring and infertility. Identification of markers for adverse vaccine-generated immune responses will foster development of a safe vaccine to reduce Chlamydia infections and their complications including infertility and potentially fatal tubal pregnancies.
