The response of red deer to oral administration of heat-inactivated Mycobacterium bovis and challenge with a field strain

Deer species (family Cervidae) are often part of the Mycobacterium tuberculosis complex maintenance host community, and tuberculosis (TB) control in deer, including vaccination, is consequently an area of ongoing research. However, most research into deer vaccination against TB is focused on using the live bacillus Calmette Guerin (BCG). Oral inactivated vaccines represent an interesting alternative to either oral or parenteral BCG, since neither diagnostic cross-reactions nor vaccine strain survival are likely to occur. In order to describe the red deer response to heat-inactivated M. bovis (IV) as compared to BCG and to unvaccinated controls (n = 5/group), we ran an experiment with five month-old vaccinated red deer, which were challenged with a virulent M. bovis strain 70 days later and necropsied at 60 days post-challenge. A reduction in the IV group infection burden was discovered. There were significant differences between the IV group and the control group (53% lesion reduction) as regards to the TB lesion scores, but not between other pairs. Complement component 3 plasma levels increased after challenge, and there were no differences between groups. The plasma cytokines (IL-1β, TNFα, IFNγ, IL-10 and IL-12) levels did not change after vaccination, but IL-1β, TNFα and IL-10 did so following the challenge. The IL-1β level increased in all the groups while TNFα levels had a distinct response pattern in the IV group and IL-10 had a distinct response pattern in control group. The results showed that oral vaccination with IV reduces the TB lesion score in red deer challenged with a M. bovis field strain without interfering with the in vivo diagnosis of infection in this species.Research funding was provided by ‘Plan Nacional’ grant AGL2014-56305 (MINECO, Spain and FEDER). M.A. Risalde holds a ‘Juan de la Cierva program’ contract and F. Ruiz-Fons is funded by the ‘Ramón y Cajal’ program (Ministry of Economy and Competitiveness, Spain). J. Thomas was supported by a grant from the Indian Council of Agricultural Research-International Fellowship 2014–15 (ICAR-IF 2014–15). M. Serrano holds a pre-doctoral fellowship from the Department of Education of the Basque Government (PRE_2016_2_0155).Peer Reviewe