THE IMMUNOGENICITY OF THE ACETYLCHOLINESTERASES OF THE CATTLE LUNGWORM DICTYOCAULUS-VIVIPARUS

Somatic extracts and excretory/secretory (ES) products of the adult st age of the cattle nematode, Dictyocaulus viviparus, were examined for acetylcholinesterase (AChE) activity. Both were found to contain activ ity which had an optimum pH of 9.5, however, the adult ES products con tained over 200 times more AChE activity per unit protein. Gel electro phoresis and specific enzyme staining revealed 5 migratory isoforms of AChE which were common to adult ES products and adult homogenates. Co mparison of L3 with L4 and adult extracts indicated that the AChE were only produced by later developmental stages of this parasite. The ant igenicity of D. viviparus AChE was demonstrated by binding to serum Ig G from naturally and experimentally infected calves but the enzymes we re not recognized by calves vaccinated twice with 400 Gy-irradiated la rvae. This is the first report of helminth AChE release by a parasitic nematode in a pulmonary location. The presence of these enzymes in su ch high amounts in the ES products, along with their immunogenicity, s uggests that they might have an important role to play in the immunobi ology of D. viviparus in the lungs.