The development of an effective
vaccine against Neospora caninum
infection in cattle is an important issue due to the significant economic impact of this
parasitic disease worldwide. In this work, the immune response, safety and efficacy of different
vaccine formulations using the N. caninum
recombinant proteins rNcSAG4 (the first bradyzoite-specific
protein assayed as a
vaccine) and rNcGRA7 were evaluated in mouse models. The survival curves of pups from all vaccinated groups showed a slight delay in time to death compared to control groups; this difference was statistically significant for rNcSAG4+adjuvant group. Immune response of mice vaccinated with rNcSAG4 was characterized by reduced specific
IgG and
cytokine levels with an equilibrated IFN-gamma/IL-10 balance. Regarding mice vaccinated with rNcGRA7, a very strong humoral and cellular immune response was generated characterized by a hyper-production of IFN-gamma. This response was not accompanied by significant protection. Vaccination with a mixture of both
recombinant proteins reduced
infection in lung and brain during acute and
chronic infection, respectively, although it was not statistically significant. In summary, no significant protection was obtained with these
vaccine formulations in the present mouse models. However, the study reveals some positive results on immune response and efficacy for both
recombinant proteins; these results are being discussed in order to suggest new approaches with new
chronic infection mouse models and adjuvants.