Neospora caninum is the causal agent of bovine neosporosis which results in high levels of
abortion. The present study determined the protective
efficacy of two Neospora antigens—Neospora
cyclophilin (NcCyP) and NcSRS2. The ability of native NcCyP to upregulate mouse IFNγ was also confirmed in this study. Recombinant NcCyP or NcSRS2 were tested either alone or in combination and formulated with
adjuvant ImmuMax-SR and CpG. Female BALB / c mice (n=15) of 10-12 weeks of age were immunized s.c. twice in a 2-week interval with vaccines containing either NcCyP alone, NcSRS2 alone, NcCyP plus NcSRS2, or non-recombinant
bacterial antigen (NR) in 2 separate trials. All mice were challenge-infected 3 weeks following the booster immunization and necropsied 3 weeks after the challenge infection. Brain and serum were collected and Nc-specific
DNA sequence in
brain tissue and antibodies in serum were analyzed by PCR or ELISA / Western blotting. Results showed that mice vaccinated with rNcCyP, rNcSRS2, or both rNcCyP and rNcSRS2 responded with high levels of NcCyP or NcSRS2 specific antibodies. Overall, mice received vaccines formulated with either rNcCyP or rNcCyP and rNcSRS2 had a higher (p<0.01) percent protection when compared to the mock- or non-vaccinated mice. The groups immunized with rNcSRS2 alone exhibited slightly lower levels of protection, which was higher (p<0.05) than that of the non-vaccinated group but did not differ (p=0.06) from that of the mock-vaccinated group. The results of the present study indicate that NcCyP is a highly efficacious vaccine candidate which may be useful in protection against Neospora infection.