Chlamydia trachomatis (Ct) is the most prevalent sexually transmitted bacterial infection in the world. In ~50% of cisgender women, Ct ascends from the cervix to infect the upper genital tract and increased ascension is linked to hormonal therapies. Oviduct infection induces inflammation which can lead to tubal scarring and sequelae of infertility and ectopic pregnancy. Fortunately, these complications occur in a minority of infected women, suggesting that intrinsic factors may protect the fallopian tubes from infection or tissue damage. In vitro inoculation of primary fallopian tube epithelial (FTE) cells with Ct serovar E resulted in a 10-fold reduction in infected cells compared to transformed endocervical HeLa cells. Indoleamine 2,3-dioxygenase (IDO) in the cytoplasm of epithelial cells acts as a key mediator of chlamydial host defense by metabolizing tryptophan, an essential Ct nutrient. We determined that uninfected primary FTE cells expressed on average 9 times higher levels of ido1 transcripts by qPCR compared to HeLa cells, and that in vitro infectivity of FTE cells was rescued by addition of an IDO-inhibitor (9-fold), tryptophan (21-fold), or indole (a metabolite that bypasses tryptophan starvation; 16-fold). Induction of IDO has mostly been attributed to IFNγ, but it can also be induced by Type I IFNs. Detection of high constitutive ido1 transcription in primary FTE cells indicates their ability to produce IDO independently of IFNγ. Ongoing studies are examining the role of Type I IFNs, including IFNɛ, which is constitutively expressed by reproductive tract epithelium and regulated by hormones. This work has implications for defining factors that contribute to protection of women from Ct-induced disease. The study was funded through a Translational Team Science Award (UNC School of Medicine and NC TRaCS) and also funded by NIAID NIH R01 AI067678 to U.M.N., NIAID NIH R01 AI119164 to T.D., and NIH grant DK065988 and Cystic Fibrosis Foundation grant BOUCHE15R0 to S.H.R.

Genital infections with Chlamydia trachomatis can lead to uterine and oviduct tissue damage in the female reproductive tract. Neutrophils are strongly associated with tissue damage during chlamydial infection, while an adaptive CD4 T cell response is necessary to combat infection. Activation of triggering receptor expressed on myeloid cells-1 (TREM-1) on neutrophils has previously been shown to induce and/or enhance degranulation synergistically with Toll-like receptor (TLR) signaling. Additionally, TREM-1 can promote neutrophil transepithelial migration. In this study, we sought to determine the contribution of TREM-1,3 to immunopathology in the female mouse genital tract during Chlamydia muridarum infection. Relative to control mice, trem1,3-/- mice had no difference in chlamydial burden or duration of lower-genital-tract infection. We also observed a similar incidence of hydrosalpinx 45 days postinfection in trem1,3-/- compared to wild-type (WT) mice. However, compared to WT mice, trem1,3-/- mice developed significantly fewer hydrometra in uterine horns. Early in infection, trem1,3-/- mice displayed a notable decrease in the number of uterine glands containing polymorphonuclear cells and uterine horn lumens had fewer neutrophils, with increased granulocyte colony-stimulating factor (G-CSF). trem1,3-/- mice also had reduced erosion of the luminal epithelium. These data indicate that TREM-1,3 contributes to transepithelial neutrophil migration in the uterus and uterine glands, promoting the occurrence of hydrometra in infected mice.

Chlamydia trachomatis (Ct) causes the most prevalent bacterial sexually transmitted disease leading to ectopic pregnancy and infertility. Swine not only have many similarities to humans, but they are also susceptible to Ct. Despite these benefits and the ease of access to primary tissue from this food animal, in vitro research in swine has been underutilized. This study will provide basic understanding of the Ct host–pathogen interactions in porcine oviduct epithelial cells (pOECs)—the counterparts of human Fallopian tube epithelial cells. Using NanoString technology, flow cytometry, and confocal and transmission-electron microscopy, we studied the Ct developmental cycle in pOECs, the cellular immune response, and the expression and location of the tight junction protein claudin-4. We show that Ct productively completes its developmental cycle in pOECs and induces an immune response to Ct similar to human cells: Ct mainly induced the upregulation of interferon regulated genes and T-cell attracting chemokines. Furthermore, Ct infection induced an accumulation of claudin-4 in the Ct inclusion with a coinciding reduction of membrane-bound claudin-4. Downstream effects of the reduced membrane-bound claudin-4 expression could potentially include a reduction in tight-junction expression, impaired epithelial barrier function as well as increased susceptibility to co-infections. Thereby, this study justifies the investigation of the effect of Ct on tight junctions and the mucosal epithelial barrier function. Taken together, this study demonstrates that primary pOECs represent an excellent in vitro model for research into Ct pathogenesis, cell biology and immunity.

Chlamydia trachomatis infection of the human fallopian tubes can lead to damaging inflammation and scarring, ultimately resulting in infertility. To study the human cellular responses to chlamydial infection, researchers have frequently used transformed cell lines that can have limited translational relevance. We developed a primary human fallopian tube epithelial cell model based on a method previously established for culture of primary human bronchial epithelial cells. After protease digestion and physical dissociation of excised fallopian tubes, epithelial cell precursors were expanded in growth factor-containing medium. Expanded cells were cryopreserved to generate a biobank of cells from multiple donors and cultured at an air-liquid interface. Culture conditions stimulated cellular differentiation into polarized mucin-secreting and multiciliated cells, recapitulating the architecture of human fallopian tube epithelium. The polarized and differentiated cells were infected with a clinical isolate of C. trachomatis, and inclusions containing chlamydial developmental forms were visualized by fluorescence and electron microscopy. Apical secretions from infected cells contained increased amounts of proteins associated with chlamydial growth and replication, including transferrin receptor protein 1, the amino acid transporters SLC3A2 and SLC1A5, and the T-cell chemoattractants CXCL10, CXCL11, and RANTES. Flow cytometry revealed that chlamydial infection induced cell surface expression of T-cell homing and activation proteins, including ICAM-1, VCAM-1, HLA class I and II, and interferon gamma receptor. This human fallopian tube epithelial cell culture model is an important tool with translational potential for studying cellular responses to Chlamydia and other sexually transmitted pathogens.