Role of Secreted Conjunctival Mucosal Cytokine and Chemokine Proteins in Different Stages of Trachomatous Disease

Abstract

Background Chlamydia trachomatis is responsible for trachoma, the primary cause of preventable blindness worldwide. Plans to eradicate trachoma using the World Health Organization's SAFE program (Surgery, Antibiotics, Facial Cleanliness and Environment Improvement) have resulted in recurrence of infection and disease following cessation of treatment in many endemic countries, suggesting the need for a vaccine to control infection and trachomatous disease. Vaccine development requires, in part, knowledge of the mucosal host immune responses in both healthy and trachomatous conjuctivae—an area of research that remains insufficiently studied.Methodology/Principal FindingsWe characterized 25 secreted cytokines and chemokines from the conjunctival mucosa of individuals residing in a trachoma endemic region of Nepal using Luminex X100 multiplexing technology. Immunomodulating effects of concurrent C. trachomatis infection were also examined. We found that proinflammatory cytokines IL-1β (r = 0.259, P = 0.001) and TNFα (r = 0.168, P<0.05) were significantly associated with trachomatous disease and concurrent C. trachomatis infection compared with age and sex matched controls from the same region who did not have trachoma. In support of these findings, anti-inflammatory cytokine IL-1 receptor antagonist (IL-1Ra) was negatively associated with chronic scarring trachoma (r = −0.249, P = 0.001). Additional cytokines (Th1, IL-12p40 [r = −0.212, P<0.01], and Th2, IL-4 and IL-13 [r = −0.165 and −0.189, respectively, P<0.05 for both]) were negatively associated with chronic scarring trachoma, suggesting a protective role. Conversely, a pathogenic role for the Th3/Tr1 cytokine IL-10 (r = 0.180, P<0.05) was evident with increased levels for all trachoma grades. New risk factors for chronic scarring trachoma included IL-6 and IL-15 (r = 0.259 and 0.292, respectively, P<0.005 for both) with increased levels for concurrent C. trachomatis infections (r = 0.206, P<0.05, and r = 0.304, P<0.005, respectively). Chemokine protein levels for CCL11 (Eotaxin), CXCL8 (IL-8), CXCL9 (MIG), and CCL2 (MCP-1) were elevated in chronic scarring trachoma compared with age and sex matched controls (P<0.05, for all).Conclusions/SignificanceOur quantitative detection of previously uncharacterized and partially characterized cytokines, a soluble cytokine receptor, and chemokines for each trachoma grade and associations with C. trachomatis infections provide, to date, the most comprehensive immunologic evaluation of trachoma. These findings highlight novel pathologic and protective factors involved in trachomatous disease, which will aid in designing immunomodulating therapeutics and a vaccine.

Conjunctival Transcriptome in Scarring Trachoma

“…In individuals with established conjunctival scarring, nonchlamydial bacterial infection was associated with increased expression of IL1B, suggesting that such infections can promote a proinflammatory response (10). Others have also found in a separate population that tear fluid from people with TTI has increased IL-1␤ compared to (59). There is a growing body of evidence which indicates that C. trachomatis and other nonchlamydial bacterial infections stimulate the production of IL-1␤ through a combination of PRRs, leading to a cascade of proinflammatory products which both help to combat infection but at the same time can damage tissues (50,65).…”

Active Trachoma Is Associated with Increased Conjunctival Expression ofIL17Aand Profibrotic Cytokines

“…IL13 expression, a marked increase in nitric oxide synthase 2A (NOS2A) expression, and only a slight increase in arginase-1 (ARG1) expression, consistent with predominantly classically activated macrophage activity (11,24,62). Similarly, IL-13 has been detected less frequently in tear fluid from individuals with trachomatous scarring than from controls (48). Previous studies of active trachoma in children have examined factors linked to a Th2 response, with inconclusive results.…”

“…Previous studies of active trachoma in children have examined factors linked to a Th2 response, with inconclusive results. IL4 expression has been detected more frequently in children with active trachoma and chlamydial infection than in control children, although a separate study found no difference in the tear IL-4 concentrations (7,48). Conjunctival-transcriptome analysis of children with active chlamydial infection found widespread evidence of IFN-␥ activity but relatively little to suggest Th2 activity (35).…”

“…Immunopathological correlates of active trachoma have been investigated using a number of different approaches, including peripheral blood mononuclear cell (PBMC) responses to chlamydial antigens (4), tear immunoglobulin and cytokine detection (5,19,48), conjunctival gene expression analysis by reverse transcription-PCR (RT-PCR) (6,7), and, more recently, whole-conjunctival-transcriptome analysis (35). From this body of work, some broad conclusions emerge.…”

The effect of topical cyclosporine A treatment on corneal thickness in patients with trachomatous dry eye

“…Cell-mediated immunity plays an important role in the pathogenesis of trachomatous complications, supported by the high number of T-cells in severe disease. 8,9 The International Dry Eye Workshop modified the 1995 definition of dry eye to include the roles of tear film hyperosmolarity and ocular surface inflammation. 10,11 Regardless of the initiating aetiological factor, once dry eye disease develops, inflammation becomes the key mechanism of injury to the ocular surface.…”