Stromal Fibroblasts Drive Host Inflammatory Responses That Are Dependent on Chlamydia trachomatis Strain Type and Likely Influence Disease Outcomes

Abstract

Chlamydia trachomatisocular strains cause a blinding disease known as trachoma. These strains rarely cause urogenital infections and are not found in the upper genital tract or rectum. Urogenital strains are responsible for a self-limited conjunctivitis and the sequelae of infertility, ectopic pregnancy, and hemorrhagic proctitis. However, the differential cellular responses that drive these clinically observed disease outcomes are not completely understood. Primary conjunctival, endocervical, and endometrial epithelial and stromal fibroblast cells, HeLa229 cells, and immortalized conjunctival epithelial (HCjE) cells were infected with the ocular A/Har-13 (A) and Ba/Apache-2 (Ba) strains and urogenital D/UW-3 (D) and E/Bour (E) strains. Infection rates, progeny production, and cytokine/chemokine secretion levels were evaluated in comparison with those in uninfected cells. All strain types infected all cell types with similar levels of efficacy and development. However, progeny production levels differed among primary cells: Ba produced significantly more progeny than E in endocervical and endometrial fibroblasts, while A progeny were less abundant than E progeny.C.trachomatisinfection of primary epithelial cells elicited an increase in pro- and anti-inflammatory mediators compared to levels in uninfected cells, but there were no significant differences by strain type. In contrast, for primary fibroblasts, ocular strains elicited significant increases in the pro- and anti-inflammatory mediators macrophage inflammatory protein (MIP)-1β, thymus- and activation-regulated chemokine (TARC), interleukin (IL)-2, IL-12p70, and interferon gamma-induced protein 10 (IP-10) compared to levels in urogenital strains, while urogenital strains elicited a distinct and significant increase in the proinflammatory mediators IL-1α, IL-1β, IL-8, gamma interferon (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Our data indicate that primary fibroblasts, not epithelial cells, drive host inflammatory responses that are dependent on strain type and likely influence disease outcomes, establishing their importance as a novel model for studies ofC. trachomatisdisease pathogenesis.IMPORTANCEChlamydia trachomatisis a human pathogen and the leading cause of preventable blindness and sexually transmitted diseases in the world. CertainC. trachomatisstrains cause ocular disease, while others cause upper genital tract pathology. However, little is known about the cellular or immunologic basis for these differences. Here, we compared the abilities of the strain types to infect, replicate, and initiate an immune response in primary human ocular and urogenital epithelial cells, as well as in fibroblasts from the underlying stroma. While there were no significant differences in infection rates or intracellular growth for any strain in any cell type, proinflammatory responses were driven not by the epithelial cells but by fibroblasts and were distinct between ocular and urogenital strains. Our findings suggest that primary fibroblasts are a novel and more appropriate model for studies of immune responses that will expand our understanding of the differential pathological disease outcomes caused by variousC. trachomatisstrain types.

Chlamydia trachomatis Serovars Drive Differential Production of Proinflammatory Cytokines and Chemokines Depending on the Type of Cell Infected

“…Infection with C. trachomatis involves a complex interplay between many cell-types that orchestrate cytokine and chemokine production to stimulate leukocyte, granulocyte, and monocyte production and homing to the infection site. Our study and recent published work (Jolly et al, 2019) suggest that stromal fibroblasts and genitourinary epithelial cells play an important role in the initial response to C. trachomatis. Importantly, we and others (Jolly et al, 2019) have shown that the innate immune response to C. trachomatis is mounted in a cell-type and serovar-specific manner.…”

“…Our study and recent published work (Jolly et al, 2019) suggest that stromal fibroblasts and genitourinary epithelial cells play an important role in the initial response to C. trachomatis. Importantly, we and others (Jolly et al, 2019) have shown that the innate immune response to C. trachomatis is mounted in a cell-type and serovar-specific manner. We show for the first time that human foreskin keratinocytes can be infected by C. trachomatis and that serovars D and L2 form normal inclusions and robustly replicate in these cells suggesting that the human foreskin may be infected during early stages of colonization.…”

“…Uniquely, we show here that L2 represses IP-10 in HVEC and HCjE cells whereas serovar A induces IP-10 expression in these cells. Recent work has also demonstrated an increase in IP-10 production in endometrial stromal fibroblast infected with ocular isolates (A or Ba) compared to genital isolates (D or E) (Jolly et al, 2019). Collectively, these results suggest that IP-10 induction occurs in a cell-type and serovar-specific manner and infection of macrophages during human infection may be important for inducing T cell chemotaxis during C. trachomatis infection, which may promote tissue pathology.…”

“…Most studies have used human cervical carcinoma epithelioid (HeLa), human laryngeal carcinoma (Hep2), or murine fibroblast cells to model Chlamydia infection (Rasmussen et al, 1997;Dessus-Babus et al, 2002;Cunningham et al, 2013) while others have focused on epithelial cells of the endocervix (Ibana et al, 2012;Buckner et al, 2013). While Chlamydia can infect and replicate in a plethora of cell types, recent studies have shown that cells derived from different anatomical sites support different levels of Chlamydia replication and inclusion development (Miyairi et al, 2006;Jolly et al, 2019). Furthermore, HeLa cells, the most common model for studying chlamydial infection, are known to have many abnormalities and the immune signaling pathways of these cells have been altered over the years through high passage in vitro growth (Masters, 2002;Landry et al, 2013).…”

Unveiling Interindividual Variability of Human Fibroblast Innate Immune Response Using Robust Cell-Based Protocols

“…Moreover, dominant producers of interleukin-6 (IL-6) at sites of peripheral inflammation, fibroblasts are now recognized for their major contribution to inflammatory regulation ( 9 , 10 ). Fibroblasts are emerging with a key role in local innate immunity evoked during response to pathogens as well as vaccines ( 11 – 14 ).…”