The nematode parasite Onchocerca volvulus generates the transforming growth factor-beta (TGF-beta)

Transforming growth factor-beta (TGF-beta) is a highly conserved cytokine that has a well-known regulatory role in immunity, but also in organ development of most animal species including helminths. Homologous tgf-b genes and mRNA have been detected in the filaria Brugia malayi. The in situ protein expression is unknown for filariae. Therefore, we examined several filariae for the expression and localization of latent (stable) TGF-beta in adult and larval stages. A specific goat anti-human latency associated protein (LAP, TGF-beta 1) antibody, purified by affinity chromatography, was used for light and electron microscopic immunohistochemistry. Adult Onchocerca volvulus, Onchocerca gibsoni, Onchocerca ochengi, Onchocerca armillata, Onchocerca fasciata, Onchocerca flexuosa, Wuchereria bancrofti, Dirofilaria sp., B. malayi, and infective larvae of W. bancrofti reacted with the antibody. Labeling of worm tissues varied between negative and all degrees of positive reactions. Latent TGF-beta was strongly expressed adjacent to the cell membranes of the hypodermis, epithelia, and muscles and adjacent to many nuclei in all organs. TGF-beta was well expressed in worms without Wolbachia endobacteria eliminated by doxycycline treatment. Pleomorphic neoplasms in O. volvulus were also labeled. We conclude that latent TGF-beta protein is expressed by filariae independently of Wolbachia, possibly regulating worm tissue homeostasis.