Monitoring the T cell response to genital tract infection

Abstract

To date, it has not been possible to study antigen-specific T cell responses during primary infection of the genital tract. The low frequency of pathogen-specific T cells in a naïve mouse makes it difficult to monitor the initial events after antigen encounter. We developed a system to examine the response of pathogen-specific T cells in the genital mucosa after intrauterine infection. We identified the protective CD4 ؉ T cell antigen Cta1 from Chlamydia trachomatis and generated T cell receptor (TCR) transgenic (tg) mice with specificity for this protein. By transferring TCR tg T cells into naïve animals, we determined that Chlamydia-specific T cells were activated and proliferated in the lymph nodes draining the genital tract after primary intrauterine infection. Activated T cells migrated into the genital mucosa and secreted IFN-␥. The development of Chlamydia-specific TCR tg mice provides an approach for dissecting how pathogen-specific T cells function in the genital tract.Chlamydia ͉ adaptive immunity ͉ T cell receptor transgenic M ost pathogens enter a mammalian host by penetrating mucosal surfaces such as the lung, intestine, or genitourinary tract. The prevalence of sexually transmitted diseases has prompted studies to understand how infection is established in the genital tract and how pathogens are cleared from this site. Despite the importance of T cells in controlling a number of genital pathogens, the behavior of pathogen-specific T cells in the genital mucosa is not well characterized. The major obstacle to studying primary T cell responses is the low frequency of antigen-specific T cells in naïve mice. Because it is difficult to identify and track endogenous pathogen-specific T cells before infection, T cell receptor (TCR) transgenic (tg) animals have been developed that express pathogen-specific TCRs. T cells from TCR tg animals can be labeled and transferred into recipient mice, boosting the number of naïve, pathogen-specific T cells so that they can be monitored during infection. Although TCR tg mice have been useful in the study of organisms that infect animals systemically or the tracking of the response of T cells to pathogens that infect the lung or intestine (1-5), they have not been used to examine infection of genital tissues.To develop a system for studying pathogen-specific T cell responses in the genital mucosa, we developed TCR tg mice specific for Chlamydia trachomatis. C. trachomatis is a major cause of sexually transmitted disease and the leading cause of preventable blindness worldwide. In the genital tract, chronic and often undiagnosed infection stimulates a marked inflammatory response that contributes to Chlamydia-associated sequelae such as ectopic pregnancy and infertility (6, 7). Both protective immunity against C. trachomatis and the pathologies associated with Chlamydia infection are mediated by T cells. In humans, T cells respond to C. trachomatis at the site of infection and appear to contribute to pathology (8). In mice, depletion of T cells results in loss of protec...

A Chlamydia-Specific TCR-Transgenic Mouse Demonstrates Th1 Polyfunctionality with Enhanced Effector Function

“…The kinetics reflect the enhanced ability of Tg cells to adopt an activated effector and/or effector memory phenotype in the lymphoid tissues throughout infection compared to the endogenous T cell repertoire, and by day 8 in the infected peripheral tissues. These data collectively support other studies demonstrating Chlamydia -specific CD4 T cell priming and proliferation in the ILN (44, 45) and the presence of activated cells in the genital tract one-week post-infection (46). …”

“…Pathogen-specific TCR Tg mice have been utilized in a variety of infectious disease models (49–56), including NR1 mice that recognize C. trachomatis (46). Adoptive transfer of naïve TCR Tg cells is a superior approach to transfer of in vitro maintained T cell lines, since naïve TCR Tg cells allow analysis of the initial antigen encounter and phenotypic differences between in vivo derived effector and memory populations.…”

Antigen-Specific CD8+ T Cells Respond to Chlamydia trachomatis in the Genital Mucosa

“…It has been demonstrated that following oral infection with Salmonella, Salmonella-specific CD4 ϩ T cells in the Peyer's patches are activated within hours (28). Although the Salmonella study examined the response of CD4 ϩ T cells while our study examined Chlamydia-specific CD8 ϩ T cells, we have also recently demonstrated that activation of Chlamydia-specific CD4 ϩ T cells appears to occur outside of the genital tract (29). Therefore, architectural differences between the genital and intestinal mucosa may result in distinct mechanisms for inducing immunity against pathogens that infect these tissues.…”

Immunization with a Combination of Integral Chlamydial Antigens and a Defined Secreted Protein Induces Robust Immunity against Genital Chlamydial Challenge

“…The reduction in bacterial shedding on day 3 after challenge suggests the efficacy of neutralizing antibodies induced by UV-EB vaccination. Cellular anti-UV-EB responses are unlikely to be responsible for these effects on day 3, since antigen-specific cellular responses were first detected in the genital tract only 5 to 6 days after vaginal chlamydial challenge (15,33). The antibody-mediated neutralizing effects in UV-EB-vaccinated mice does not appear to be efficiently supported by the anti-UV-EB cellular response, as complete clearance fails to occur earlier than that observed in rCPAF-vaccinated mice, wherein only cellular responses, not neutralizing antibodies, help in clearing the infection (15,22).…”