In view of the worldwide importance of Toxoplasma gondii and Neospora caninum and the limited data on the seroprevalence of these parasites in Egypt, this study aimed to estimate the prevalence of anti-T. gondii and anti-N. caninum antibodies in rabbits, cattle, and humans. We used ELISA methods based on surface antigen 2 of T. gondii (TgSAG2t) and surface antigen 1 of N. caninum (NcSAG1t). High seroprevalence of T. gondii (51.49%) was detected in pregnant women, and antibodies to N. caninum were also detected in human samples (7.92%). Anti-T. gondii or N. caninum antibodies were detected in cattle (TgSAG2t: 10.75%; NcSAG1t: 20.43%). In rabbits, only one sample was N. caninum positive (1.85%). The high prevalence of toxoplasmosis and neosporosis in cattle affects the development of the livestock industry and is also an important infective source for human infection in Egypt.
To investigate whether the production of an antigen-specific antibody is associated with Neospora caninum-induced bovine abortion, 62 serum samples were tested with an enzyme-linked immunosorbent assay using the recombinant antigens NcSAG1, NcSRS2, and NcGRA7. Our study suggested that NcGRA7 would be a new marker for the serodiagnosis of N. caninum infection resulting in abortion.
The characterization of the cross-reactive and species-specific antigens of Neospora caninum and Toxoplasma gondii is important in the exploration to determine the common mechanisms of parasite-host interaction and to improve the serological diagnosis; it is also useful for the selection of the cross-reactive antigens that could be used in the development of vaccines or drugs for controlling the diseases caused by these two parasites. In this study, cross-reactive and species-specific antigens between N. caninum and T. gondii tachyzoites were comprehensively investigated using a proteomics approach with the application of two-dimensional gel electrophoresis, immunoblot analysis, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS), and MALDI-TOF/TOF-MS analysis. Immunoblotting and mass spectrometry analysis revealed that at least 42 individual protein spots of N. caninum were reacted with the anti-N. caninum serum, among which at least 18 protein spots were cross-reacted with the anti-T. gondii serum. Moreover, at least 31 protein spots of T. gondii were reacted with the anti-T. gondii serum, among which at least 19 protein spots were cross-reacted with the anti-N. caninum serum. Furthermore, some new specific proteins were also identified in the N. caninum protein profile by searching Toxoplasma sequences or sequences from other organisms. This study substantiates the usefulness of proteomics in the immunoscreening of the cross-reactive or species-specific antigens of both parasites. In addition, the present study showed that there was significant homology in the antigenic proteome profiles between the two parasites. These observations have implications for the design of multicomponent common vaccines against both parasite infections.
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