Abstract
Abstract: :
Purpose: The clinical symptoms of river blindness occur as a result of the host inflammatory response to dead and degenerating worms in the cornea. The parasitic nematode that causes river blindness, Onchocerca volvulus, harbors Rickettsia-like endosymbiotic Wolbachia bacteria, which have an essential role in mediating the inflammatory response in the cornea [Science 2002; 295:1892]. The purpose of this study was to determine if there is any direct association between Wolbachia endobacteria and neutrophils in the cornea after degeneration of the parasitic worms. Methods: Parasite larvae containing Wolbachia were injected into the corneal stroma, mice were sacrificed at various times thereafter, and Wolbachia were detected by immuno-histochemistry and immuno-gold labeling electron microscopy using antibodies specific for the major Wolbachia surface protein. Results: Wolbachia were detected in intact worms 4h and 8h after injection. However, by 18h and 24h after injection, there was a pronounced neutrophil infiltrate into the corneal stroma, and Wolbachia were detected not only in degenerating worms, but also within neutrophil vacuoles. Furthermore, neutrophils appeared to be in direct contact with the nematode cuticle, suggesting that they may have a role in either killing or degradation of these parasitic worms. Conclusions: This study demonstrates that Wolbachia endobacteria are ingested by neutrophils in the corneal stroma. As neutrophils and neutrophil granule products are known to cause stromal destruction, this finding suggests that ingestion of Wolbachia by these cells is a critical step in the pathogenesis of ocular onchocerciasis.
Keywords: keratitis • inflammation • microbial pathogenesis: experimental studies