Variation and immunity to intestinal worms

• Published in: Parasitology Vol. 125; no. 7; pp. S39 - S50
• Main Authors: WAKELIN, D., FARIAS, S. E., BRADLEY, J. E.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.10.2002
• Subjects: Animals; Ascaris; Biological and medical sciences; Drug Resistance - genetics; Environmental conditions; Fundamental and applied biological sciences. Psychology; Genetic engineering; Genetic Variation; Genetics of eukaryotes. Biological and molecular evolution; Genotype; host immunity; Host-Parasite Interactions - genetics; Host-Parasite Interactions - immunology; Humans; Immunity, Cellular; Immunization; Influence; Intestinal Diseases, Parasitic - immunology; Intestinal Diseases, Parasitic - parasitology; Invertebrata; Mice; Nematodes; Parasite variation; Phenotype; Population; Population genetics, reproduction patterns; selection; Selection, Genetic; Trichinella; Trichinella - genetics; Trichinella - immunology; Trichinella - pathogenicity; Trichinellosis - immunology; Trichinellosis - parasitology; Trichuriasis - immunology; Trichuriasis - parasitology; Trichuris - genetics; Trichuris - immunology; Trichuris muris; Worms; Parasite variation; Trichuris muris; selection; host immunity; Trichinella; Host parasite relation; Genetic selection; Immune response; Genetic variability; Digestive system; Gut; Parasite; Host; Review; Parasitosis; Population genetics; Helminthiasis; Immunity; Infection; Sensitivity resistance; Antigenic variation; Nematode disease; Helmintha; Selection pressure; Nemathelminthia; Invertebrata; Nematoda
• ISSN: 0031-1820; 1469-8161
• DOI: 10.1017/S0031182002001440

Genetically determined variation in host capacity to express resistance to a given parasite plays a major role in determining the outcome of infection. It can be assumed that the same is true of variation in parasites, but very much less is known of its influence on the host–parasite relationship. Phenotypic and genotypic variation within species of intestinal worms is now well documented, detailed studies having been made of parasites such as Ascaris in humans and trichostrongyles in domestic animals. However, the extent to which this variation affects the course of infection or the host immune response in these hosts is limited. Of the nematodes used as experimental models in laboratory rodents, detailed data on phenotypic or genotypic variation are limited to Strongyloides and Trichinella. Parasite variation is known to be subject to host-mediated selection, the emergence of anthelmintic resistance being a good example. Repeated passage has been used to select lines of parasite that survive in abnormal hosts or which show adaptation to host immunity. Experimental studies with Trichinella genotypes in mice have demonstrated the extent to which parasite variation influences the nature and degree of the host's immune and inflammatory responses, the complex interplay between immunogenicity and pathogenicity influencing both partners in the relationship. Recent studies with isolates of Trichuris muris have shown how parasite variation influences the capacity of mice to express the T helper cell responses necessary for resistance. Molecular differences between T. muris isolates have been shown in their excreted/secreted products as well as at the level of their DNA. Knowledge of the functional consequences of parasite variation will add to our understanding of host-parasite evolution as well as providing a rational basis for predicting the outcome of controls strategies that rest on the improvement of host resistance through vaccination or selective breeding.