Carrageenan - a natural inhibitor of ocular chlamydial infection in vitro and in vivo

Abstract

Purpose : Ocular infection with Chlamydia trachomatis (Ct) is the leading cause of infectious blindness. As Ct infects via extracellular elementary bodies (EB), we suggest that carrageenan, a natural extract from red seaweed that binds virus particles, might physically bind EB and thereby prevent their attachment to epithelial cells. We tested the hypothesis that carrageenan inhibits Ct infection in vitro using an experimental ocular infection model and in vivo using our guinea pig model.

Methods : Confluent monolayers of human conjunctival epithelial (HCjE) cells were inoculated with Ct serovar B in the presence or absence of carrageenan. Cells were cultured for 48 hours, then fixed and stained with α-Chlamydia LPS antibody and visualized with fluorescent microscopy. Hartley strain guinea pigs were treated either with placebo or with 0.06 mg per eye of carrageenan for 2h before infecting with 1x10⁴ IFU of Chlamydia caviae (3 animals per group). The palpebral and bulbar conjunctivae were evaluated for erythema, edema, and exudation on days 4, 7, 14, and 21.

Results : HCjE cells treated with 1.2 mg/ml carrageenan showed minimal infection (mean of 326±10.94 IFU), with a 7-fold reduction compared to placebo treated cells (mean of 2403±89.47 IFU, p=0.001). In the guinea pigs the pathology score was significantly reduced in the group pre-treated with carrageenan at all time points (p=0.05).

Conclusions : Carrageenan reduced the absolute number of infected cells in vitro and the pathology in vivo, suggesting it should be investigated further as treatment and/or prophylaxis for Ct infection.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.