EARLY HUMORAL IMMUNE RESPONSE IN CALVES EXPERIMENTALLY INFECTED WITH DIFFERENT GENOTYPES OF MYCOBACTERIUM AVIUM SUBSP. PARATUBERCULOSIS

FERNÁNDEZ, B.; COLAVECCHIA, SB.; FORTUNY, M. L.; STEMPLER, A; JOLLY, A; GILARDONI, L.R.; PAOLICCHI, F.A.; MUNDO, S. L.

Milan

Seminario; 10th International Veterinary Immunology Symposium; 2013

International Veterinary Immunology Symposium

Johne’s disease, caused by Mycobacterium avium subsp. paratuberculosis (Map), is a chronic granulomatous enteritis affecting ruminants. The aim of this work was to evaluate humoral immune response induced after experimental infection of calves with two different bovine genotypes of Map from Argentina. Holstein calves (6-8 weeks old) were experimentally infected using an oral dose (246 mg of total wet weight) of Map genotypes A (MA, n=2) or C (MC, n=2) and mock infected (MI, n=2). Specific IgG, IgG1 and IgG2 against Map whole bacteria (wMap), protoplasmic antigen (PPA), p34 and Hsp65 were evaluated by ELISA during 180 days. We detected significant increases of wMap-specific IgG and IgG1 in sera from both infected groups from day 80. In addition, MC showed higher levels than MA. Remarkably, wMap-specific IgG2 was the first isotype detected from day 50. Meanwhile, PPA-specific IgG and IgG1 were low during the experiment. PPA-specific IgG2 were positive in MC from day 80. p34 was only recognised by sera of MA group, showing specific IgG from day 15. Moreover p34-specific IgG2 could be detected early (from day 7). On the other hand, only one calf of MC reacted against Hsp65 with high levels of IgG and IgG1 from day 7. Antibody levels in MI remained under cut off values during the whole experiment. Our results demonstrate that humoral immune response is early induced in Map infection. Despite PPA-specific IgG (conventional ELISA) could not detect the infection during all the experiment, the study of IgG2 responses might improve the identification of infected calves. This finding is in agreement with our previous results in subclinical infected cattle. Our data also suggest that differences in early humoral immune responses could be related with the specificity, isotypes and genotypes of Map evaluated.