Date of Award

9-16-2010

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

First Advisor

Paula B. Kavathas

Second Advisor

Vikki Abrahams

Abstract

MECHANISMS OF INTERLEUKIN-1â PRODUCTION IN CHLAMYDIA TRACHOMATIS INFECTED TROPHOBLASTS. Crina M. Boeras, Vikki Abrahams, and Paula B. Kavathas. Department of Laboratory Medicine, Yale University, School of Medicine, New Haven, CT. In a normal pregnancy the immune system plays the critical task of protecting the fetus from the constant threat posed by pathogens while limiting the effects of the mothers immune response on the fetus itself. Viral and bacterial infections can cause preterm labor and intrauterine growth restriction, and the placental trophoblasts express pattern recognition receptors (PRRs) to help detect invading pathogens and initiate an effective immune response. Chlamydia trachomatis (Ct) is the most common sexually transmitted bacterial infection in the United States and can infect the decidua and placenta. Chlamydia infection of first trimester placental trophoblasts induces a change in the cytokines and chemokines present at the maternal-fetal interface and results in production of the pro-inflammatory cytokine interlukin-1β (IL-1β). We hypothesize that the IL-1β response is mediated through toll-like receptor 2 (TLR-2) for transcription, and inflammasome forming Nod-like receptors (NLRP-3 or IPAF) for its processing and secretion. Our work in the trophoblast cell lines H8 and Sw.71 demonstrated that Ct induces the transcription of IL-1β mRNA and translation of intracellular pro-IL-1β as early as 12h, and the secretion of active-IL-1β starting at 24h post infection. The induction of IL-1β is independent of MyD88, as there was no change in IL-1β production when we blocked MyD88 by using dominant-negative (DN) MyD88 cells. The production of IL-8 and IL-6 by trophoblasts after Ct infection is mediated through MyD88 and TLRs as described in other cell types, which confirms that our DN-MyD88 system is functional. Further we demonstrated that preventing NALP-3 inflammasome activation by blocking potassium (K+) efflux from cells partially inhibited IL-1β secretion in both H8 and Sw.71 cells. This suggests a role for NLRP-3 inflammasome in mediating the processing and secretion of IL-1β. In summary we have shown that Chlamydia is able to act through different pathways to affect its host. It can induce IL-1β transcription through PRRs in a MyD88 independent manner, it can potentially induce the processing of pro-IL-1β through the NALP-3 inflammasome, and it can stimulate the secretion of active-IL-1β from the cells. The presence of Chlamydia trachomatis in the placenta, and the many mechanisms it uses to modulate the immune system, like IL-1β secretion, can result in negative pregnancy outcomes, miscarriages and preterm labor.

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