Vet. Res. 37 (2006) 607-622
DOI: 10.1051/vetres:2006022

Haemonchus contortus (Nematoda: Trichostrongylidae) infection in lambs elicits an unequivocal Th₂ immune response

Caroline Lacroux^a, Thi Hai Chi Nguyen^b, Olivier Andreoletti^a, Françoise Prevot^a, Christelle Grisez^a, Jean-Paul Bergeaud^a, Lucas Gruner^c, Jean-Claude Brunel^d, Dominique Francois^e, Philippe Dorchies^a and Philippe Jacquiet<sup>a

a</sup>  UMR INRA-ENVT 1225 Interactions Hôtes Agents Pathogènes, École Nationale Vétérinaire de Toulouse, 23 chemin des Capelles, 31076 Toulouse Cedex 03, France
^b  Université d'Agriculture et de Foresterie de Ho Chi Minh Ville, Vietnam
^c  INRA, Écologie et Génétique des Parasites, BioAgresseurs Santé et Environnement, 37880 Nouzilly, France
^d  INRA, Domaine Expérimental de la Sapinière, 18390 Osmoy, France
^e  INRA, Station d'Amélioration Génétique des Animaux, BP 27, 31326 Castanet-Tolosan, France

(Received 28 October 2005; accepted 7 February 2006; published online 16 May 2006)

Abstract - Selection of resistant animals and host immunization have been proposed as alternative methods for the control of gastrointestinal nematode parasites. However, a better knowledge of the mechanisms involved in protective immunity against these parasites is required for the development of optimal strategies. In this study, 3 month old INRA 401 lambs (n = 81) were allocated into three groups: uninfected control, challenged either once (primary-infected animals) or twice (previously-infected animals) with 10 000 Haemonchus contortus L₃. Uninfected control and challenged animals were sequentially sacrificed at 3, 7, 15 and 28 days post challenge. In both challenged groups, a clear Th₂-oriented immune response was observed in the abomasal lymph node and mucosa. IL-4 and IL-13 mRNA over-expression, recruitment of eosinophils, mast cells and globule leukocytes and production of specific systemic IgG and mucosal IgA were observed earlier in previously-infected animals than in primary-infected ones. At 28 days post infection, no differences between intensities of these responses were observed between the challenged groups. Worm establishment rates were similar in previously-infected and primary-infected lambs. However, reductions of worm development, female fecundity and fecal egg output were observed in previously-infected sheep. We conclude that H. contortus infection in young INRA 401 lambs induced an unequivocal Th₂ immune response resulting in the regulation of worm egg production without affecting their establishment.

Key words: Haemonchus contortus / sheep / Th₂ immune response / quantitative PCR / antibody and cellular response

Corresponding author: Philippe Jacquiet p.jacquiet@envt.fr

© INRA, EDP Sciences 2006