Involvement of Toll-like receptor 4 in the embryogenesis of the rodent filaria Litomosoides sigmodontis.

To examine the role that lipopolysaccharide (LPS)-like molecules from the filarial intracellular endobacteria Wolbachia might play in the development of filarial infections, a natural infection in the LPS-nonresponsive C3H/HeJ mouse strain was compared to that of the LPS-responsive C3H/HeN mouse strain. C3H/HeN mice have been shown to be susceptible to the rodent filarial nematode Litomosoides sigmodontis, with the development of adult worms including females containing mature microfilariae (first stage larvae) in the uterine tubes. However, free microfilariae are not detected. In this study the worm burden and worm length were not significantly different between the C3H/HeN and C3H/HeJ mice. However, the fertility of worms from CeH/HeJ mice was found to be higher than those from C3H/HeN mice. Significantly, mature microfilariae were found at the site of infection only in C3H/HeJ mice. These results indicate a role for TLR4 signaling in the immune response that inhibits worm embryogenesis and prevents the release of microfilariae or directly kills released microfilariae.