Evaluation of prime-boost immunizations with a heat-killed Mycobacterium avium subsp. paratuberculosis vaccine, and modified Vaccinia Ankara virus expressing antigen 85A in a mouse model.

COLOMBATTI OLIVIERI, M. A.; MOYANO, R. D.; MONTENEGRO, V.; MON, M. L.; VIALE, M.; ALONSO, N.; DEL MEDICO ZAJAC, M. P., CALAMANTE, G; DELGADO, F.; SANTANGELO, M., ROMANO, M. I

Nantes

Otro; 13th International Colloquium on Paratuberculosis; 2016

INTRODUCTION: Paratuberculosis is a chronic disease caused by Mycobacterium avium subsp. paratuberculosis (Map). Considering the economic losses, it is necessary to control the disease and to develop an effective vaccine. To evaluate the protection conferred by a heat-killed local Map strain, we chose BALB/c mice as the experimental model, and use a prime-boost strategy with a MVA85A and challenge with a virulent local strain. MATERIALS AND METHODS: 5 groups of 15 female BALB/c mice 7 weeks of age were used. The groups were: A) unvaccinated control, B) 2 doses of the commercial vaccine Silirum® (CZ Veterinaria S.A.), C) 2 doses of the inactivated local strain, D) 2 doses of inactivated local strain with a boost of MVA85A and E) single dose of the inactivated local strain and the boost of MVA85A. The local strain evaluated as a vaccine candidate was prepared by removing bacterial clumps with 25G needle passages, heat inactivated and suspended in PBS at a concentration of 2.5 mg dry pellet /ml with incomplete Freund_adjuvant. 0.2 ml of the Silirum® vaccine or the local strain was injected subcutaneously, and MVA85A was inoculated intraperitoneally at a concentration of 5.6x105 PFU/ml. The different doses were administered 15 days apart. One month post vaccination, the animals were challenged with a virulent strain at a concentration of 1x108 CFU/mouse intraperitoneal. A pre-challenge blood sample was taken for the measurement of serum total IgG and isotypes (IgG1, IgG2a) by ELISA. 6 and 12 weeks post-challenge the animals were sacrificed and spleen was processed for CFU counting and cytokines quantitation. RESULTS: The groups D and E which received the prime-boost scheme resulted in CFU counts significantly lower than the unvaccinated control group, and also lower than the vaccinated groups without MVA85A boost. Groups receiving 2 doses of vaccine (with or without MVA85A boost) had significantly higher levels of total IgG compared to a single dose group and the RATIO IgG2a / IgG1 was < 1 for all groups.CONCLUSION: The vaccination scheme with the local strain and the MVA85A boost resulted in better protection than the commercial vaccine in the murine model.