Parasitology
Intestinal cell membrane proteins from non blood-feeding
parasitic nematodes as protective antigens for ruminants
Smith, D
In the UK Teladorsagia circumcincta and Ostertagia ostertagi are the most important nematode parasites of sheep and cattle, respectively. Alternative methods for their control are required because of the threat posed by resistance to anthelmintic drugs.
One possibility is control by vaccination, especially as previous work at Moredun has identified digestive enzymes from the intestinal cells of closely related Haemonchus contortus as strong vaccine candidates. However, the equivalent proteins from Teladorsagia or Ostertagia were only modestly protective, probably because, unlike Haemonchus, adult Teladorsagia and Ostertagia do not feed on blood and so in vaccinated animals do not ingest enough host antibody to seriously affect nutrient uptake. In contrast, their fourth stage larvae may be much more vulnerable. By inhabiting and thereby damaging the gastric glands they are exposed to and ingest higher concentrations of antibody, moreover, because they grow very rapidly, they should be highly sensitive to digestive interference.
Fourth stage Ostertagia probably contain membrane proteins additional to or different from those found in the adult stage, representing new targets for the gut antigen approach to vaccination. This project aims to identify these membrane proteins, to determine whether Teladorsagia contains the same proteins and to test such proteins in immunisation trials. If, however, additional larval proteins are not discovered or are not found to be protective, effort will be directed at stimulating higher concentrations of mucosal antibodies to adult worm gut antigens in the hope that this will improve the partially protective effects obtained previously.