Purpose. We previously reported allergic conjunctivitis was associated with a local pattern of cytokines and identified respiratory syncytial virus (RSV) in the conjunctival epithelium, in patients with allergic conjunctivitis. We hypothesized that RSV infected the normal conjunctival epithelium and produced interleukin-4 (IL-4), causing an allergic reaction. To determine this event, we studied production of IL-4 by human conjunctival epithelial cells, after infection with RSV. Methods. Conjunctival samples were collected with a special brush and were challenged with 5 x 106 pfu/ml of live RSV. RSV infection was detected by immunocytochemical study and RT-PCR. HLA-DR antigen was expressed by flow cytometry. IL-4 was assayed by a sandwich ELISA. Results. Immunocytochemical study and RT-PCR showed that RSV infected the conjunctival epithelial cells. HLA-DR was demonstrated in the RSV-infected conjunctival epithelial cells. Average concentrations of IL-4 in culture supernatants in infected cells were 3.8 ± 1.8, 3.6 ± 1.1, and 5.4 ± 1.8 pg/ml at 24, 48, and 72 h, respectively. Levels in non-infected cells were 0.33 ± 0.0, 0.59 ± 0.69, and 0.4 ± 0.22 pg/ml, respectively (p > 0.001). Conclusion. Findings suggest that the expression of IL-4 is associated with intracellular infection by RSV in conjunctiva. With our former reports, RSV infection in conjunctival epithelial cells can be suggested as one of the possible environmental pathogens of allergic conjunctivitis.
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