The parasite Neospora caninum is an important abortifacient agent in cattle worldwide. At present, the development of an effective and safe vaccine against bovine neosporosis is of great relevance. Recently, a new isolate of N. caninum (Nc-Spain 1H) which was obtained from the brain of an asymptomatic congenitally infected calf, exhibited non-virulent behaviour in mouse and bovine infection models. The aim of this study was to determine the safety and efficacy of Nc-Spain 1H when used as a vaccinal isolate in well-established BALB/c models of congenital and cerebral neosporosis. Mice were subcutaneously immunised twice at 3-week intervals and were challenged with 2×10 6 tachyzoites of the virulent Nc-Liv isolate. After immunisation with live Nc-Spain 1H tachyzoites, no parasitic DNA was detected in the dams brains before challenge and microsatellite analysis performed in PCR-positive mice showed that the profiles corresponded to the challenge isolate Nc-Liv, indicating the Nc-Spain 1H isolate to be a safe vaccine candidate. The efficacy of the live vaccine was evaluated in the first experiment after the immunisation of mice with 5×10 5 live Nc-Spain 1H tachyzoites. This immunisation protocol significantly reduced the neonatal mortality to 2.4%, reduced the vertical transmission from 89.1% to 2.3% and completely limited the cerebral infection. These results were associated with a Th1-type immune response. In the second experiment, the effect of various immunising doses was established using ten-fold dilutions of the tachyzoites (from 5×10 5 to 5×10). In all the cases, congenital protection rates above 60% were observed, and the mice that were immunised with the lowest dose (5×10) presented the highest protection rate (86%). Moreover, low immunising doses of Nc-Spain 1H induced an IgG2a response, and high parasitic doses induced an IgG1 response. These results evidence the safety and the efficient protection that was conferred by Nc-Spain 1H against congenital neosporosis, even when the mice were immunised with low parasitic doses. © 2012 Rojo-Montejo et al.; licensee BioMed Central Ltd.
CITATION STYLE
Rojo-Montejo, S., Collantes-Fernández, E., Lápez-Pérez, I., Risco-Castillo, V., Prenafeta, A., & Ortega-Mora, L. M. (2012). Evaluation of the protection conferred by a naturally attenuated Neospora caninum isolate against congenital and cerebral neosporosis in mice. Veterinary Research, 43(1). https://doi.org/10.1186/1297-9716-43-62
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