Antibodies from healthy or paratuberculosis infected cows have different effects on Mycobacterium avium subspecies paratuberculosis invasion in a calf ileal loop model.

In this work, we used a calf ileal loop model to evaluate whether the preincubation of Mycobacterium avium subspecies paratuberculosis (MAP) with antibodies from healthy, MAP-positive or Lipoarabinomannan (LAM) immunized cows could affect the results of infection after 3.5 h. Bacterial load in tissue was assessed by Ziehl-Neelsen and by culture for each loop. MAP was detectable in all infected loops after 3.5 h.p.i.; although the presence of antibodies from MAP-positive cows significantly reduced bacterial load in loops as compared with antibodies from healthy donors (by Ziehl-Neelsen and culture, p-value < 0.003 and 0.0203, respectively). A possible direct effect of antibodies on MAP viability was shown to be not significant. Severity of histopathologic changes induced by MAP infection also varied according to the pretreatment: MAP induced less changes when inoculated in the presence of antibodies from MAP-positive cows as compared with antibodies from healthy donors. Overall, our results show that the presence of antibodies from MAP-positive cows reduced MAP invasion and consequent early histological changes in this ileal short-term loop model. These results may suggest a protective role of antibodies in the response against MAP at the portal of entry in cattle.

Induction of apoptosis in the bursa of Fabricius by vaccination against Gumboro disease.

Infectious bursal disease is a severe acute viral disease of young chickens, affecting mainly the B-lymphocytes in the bursa of Fabricius, leading to severe immunosuppression as a result of the death of lymphoid cells. In the bursa infected with infectious bursal disease virus, viral replication is associated with apoptosis of lymphoid cells, inflammatory change and atrophy. Vaccination has appeared to be a crucial factor for control, with live attenuated vaccines being the most used. However, the apoptotic effect of these vaccines on the bursa has not been tested. We determined the apoptotic effect caused by the most used vaccines in local production on the bursa of Fabricius cells and the correlation with histological changes. In this study, it was demonstrated that apoptosis levels in the vaccinated groups were higher than those observed in the non-vaccinated birds leading to the conclusion that the action of the live virus vaccine strains modifies the boundary of the bursa and shapes processes of cell death by apoptosis. In contrast to other studies, the vaccine strains used did not show the phenomenon of bursal atrophy during the experimental period.