A Chlamydia trachomatis Strain Expressing Ovalbumin Stimulates an Antigen-Specific CD4+ T Cell Response in Mice

T cell responses to Chlamydia

Chlamydia trachomatis is the most commonly reported sexually transmitted infection in the United States. The high prevalence of infection and lack of a vaccine indicate a critical knowledge gap surrounding the host's response to infection and how to effectively generate protective immunity. The immune response to C. trachomatis is complex, with cells of the adaptive immune system playing a crucial role in bacterial clearance. Here, we discuss the CD4+ and CD8+ T cell response to Chlamydia, the importance of antigen specificity and the role of memory T cells during the recall response. Ultimately, a deeper understanding of protective immune responses is necessary to develop a vaccine that prevents the inflammatory diseases associated with Chlamydia infection.

Antigen-specific memory and naïve CD4+ T cells following secondary Chlamydia trachomatis infection

Memory antigen-specific CD4+ T cells against Chlamydia trachomatis are necessary for protection against secondary genital tract infection. While it is known that naïve antigen-specific CD4+ T cells can traffic to the genital tract in an antigen-specific manner, these T cells are not protective during primary infection. Here, we sought to compare the differences between memory and naïve antigen-specific CD4+ T cells in the same mouse following secondary infection using transgenic CD4+ T cells (NR1 T cells). Using RNA sequencing, we found that there were subtle but distinct differences between these two T cell populations. Naïve NR1 T cells significantly upregulated cell cycle genes and were more proliferative than memory NR1 T cells in the draining lymph node. In contrast, memory NR1 T cells were more activated than naïve NR1 T cells and were enriched in the genital tract. Together, our data provide insight into the differences between memory and naïve antigen-specific CD4+ T cells during C. trachomatis infection.