Authors

A Correia¹;  ¹ University of Porto - ICBAS, Portugal

Discussion

The apicomplexan parasite Neospora caninum is a major causative agent of abortions and stillbirths in cattle, representing a global economic burden surpassing one billion dollars per year. Vaccination is considered the most cost-effective approach to manage neosporosis; however, no commercial vaccine is currently available to prevent this disease. We previously determined that mucosal immunisation with N. caninum membrane proteins plus CpG ODN adjuvant successfully protected mice challenged with this parasite by inducing a strong Th1-type response. Here, we aimed at improving the immunogenicity of the antigenic preparation for use in cattle. In this sense, we included additional adjuvants to the preparation and promoted the host’s systemic immune response by combining intranasal and subcutaneous dose administrations. Parasite-specific cellular and humoral responses were evaluated in immunised and sham-immunised Holstein-Friesian female calves. Immunisation raised N. caninum-specific serum and saliva IgG and IgA antibodies. Moreover, it induced the generation of memory CD4+, CD8+, and TCRγδ T cells that responded with extensive proliferation and elevated production of IFN-gamma to the antigenic restimulation. Protection conferred by the refined immunisation procedure was assessed in sham-immunised and immunised calves experimentally infected with N. caninum. Preliminary results, using nested PCR and multiple amplification replicas, indicated that 8/8 control animals presented detectable brain parasitic DNA, while consistent parasitic DNA amplification occurred only in 3/8 brain samples from immunised calves. Taken together, these results show that our immunisation strategy was effective in inducing parasite-specific humoral and cellular immunity in the bovine host and encourage testing this strategy on a larger scale and in bovine pregnancy models. Funded by FCT - PTDC/CVT-CVT/3045/2021.