Title: Antigen-specific T cell responses to Chlamydia trachomatis
Description: Although both CD4 + and CD8 + T cells contribute to controlling Chlamydia trachomatis infection, the details of how Chlamydia -specific T cells respond to the initial encounter with antigen remain unclear. This is because it has been difficult to identify and detect the small population of naive Chlamydia -specific T cells within the pool of T cells with other specificities. In order to increase the frequency of Chlamydia -specific T cells for analysis, we generated Chlamydia -specific T cell receptor (TCR) transgenic and retrogenic mice. In order to generate the TCR transgenic and retrogenic mice, we first needed to identify Chlamydia -specific TCRs, which we obtained from Chlamydia -specific T cell clones. We generated a CD4 + T cell clone, which we designated NR9.2, and a CD8 + T cell clone, which we designated NR23.4. NR9.2 recognized a previously undescribed C. trachomatis protein which we have designated C hlamydia -specific T cell a ntigen- 1 , or Cta1. In contrast, NR23.4 recognized the C. trachomatis inclusion membrane protein CrpA which had previously been described as a CD8 + T cell antigen. In addition to recognizing C. trachomatis antigens, both T cell clones protected mice against C. trachomatis challenge. Having characterized NR9.2 and NR23.4, we then generated TCR transgenic and retrogenic mice expressing the TCRs from these clones. These Chlamydia -specific TCR transgenic and retrogenic mice provided an abundant source of antigen-inexperienced T cells against defined C. trachomatis antigens. By transferring cells from these mice into wild type recipients, we increased the frequency of Chlamydia -specific T cells to a level where they could be monitored and characterized over the course of infection.

In mice that received the Chlamydia -specific T cells, we demonstrated that genital infection with C. trachomatis resulted in preferential activation and proliferation of the transferred cells in the iliac lymph nodes (ILNs), which drain antigen from the genital mucosa. In addition, activated T cells produced the inflammatory cytokine IFNγ and migrated to the infected genital mucosa. We observed that the proliferation of the Chlamydia -specific CD4 + T cells occurred earlier than the proliferation of the Chlamydia -specific CD8 + T cells, possibly as a result of differential expression of the antigens recognized by these cells. The TCR transgenic and retrogenic mice described in this dissertation have proven useful for examining T cell responses to genital infection with C. trachomatis. These mice were generated against only two C. trachomatis antigens. As more Chlamydia antigens are identified, we will be able to compare T cell responses to proteins expressed at different times during C. trachomatis development. In addition to describing the development of TCR transgenic and retrogenic tools, this dissertation also describes a variety of approaches we used to identify new Chlamydia -specific CD4 + and CD8 + T cell antigens. Since retrogenic mice require less time and fewer resources to generate than conventional TCR transgenic mice, we envision that retrogenic mice expressing TCRs specific for these new antigens can be readily generated and used to monitor Chlamydia -specific T cell responses in vivo. By comparing T cell responses to multiple antigens, we will obtain a better understanding of the T cell response to C. trachomatis infection.