IMMUNOHISTOLOGICAL STUDIES ON AN ONCHOCERCA-VOLVULUS ANKYRIN (EI)

The distribution of an Onchocerca volvulus ankyrin, designated EI, was studied in different O. volvulus stages and other helminths by immuno histochemistry using rabbit antibodies raised against the recombinant EI protein. In adult O. volvulus thr protein designated EI was localiz ed to the extracellular clefts as well as to the cytoplasm adjacent to the cell membrane in the area of the basal labyrinth in hypodermis, i ntestine and uterus and to a lesser extent in oviduct and vas deferens . Neuronal cell bodies were also labelled. No labelling of the basal l aminae, muscles or epithelia of ovary or testis was observed. Detectio n of the EI protein was associated with embryonic development. Germ ce lls and early morulae showed no reaction; labelling was first seen in late morulae, corresponding to tile stage of gastrulation, and increas ed in the following embryonic stages. In microfilariae the nerve ring and the cephalic space, which represents the anterior nerve-enriched p ortion of the body, were labelled, Tn third-stage larvae of O. volvulu s labelling was associated with the hypodermis, and in those of Anisak is sp. the cytoplasm adjacent to the membrane of the excretory gland c ell and the basal labyrinth of the hypodermis were labelled. Following anthelminthic treatment a disruption of the labelling pattern of the EI protein was observed in adult O. volvulus with leakage of the prote in into neighbouring areas. Damage to the worm was associated with red uction and finally loss of EI protein labelling. No EI protein was det ected in dead adult worms, embryos or microfilariae. Labelling of the same organs was observed in 8 other Onchocerca species and in several other nematodes, but no reaction was seen in trematodes. The results i ndicate that the EI protein is associated with neuronal structures of O. volvulus, that its presence is developmentally regulated and that i t has cross-reactive homologues in other nematodes. The results sugges t that Er is a functional protein. It may be useful for the assessment of parasite damage and death as well as in the characterization of th e filarial nervous system.