Abstract
The apicomplexan parasite Neospora caninum causes neosporosis, an illness that leads to abortion or stillbirth in cattle, causing massive economic losses to the livestock industry. Rapid and viable diagnosis is the premise of prevention and control for neosporosis. In this study, we screened a new microneme protein 26 (NcMIC26) through western blot and mass spectrometry identification from the excretory secretion antigen (ESA) of N. caninum tachyzoites. NcMIC26 is subcellularly localized to the microneme of parasites. NcMIC26 is a specific antigen of N. caninum and has no cross-reaction with Toxoplasma gondii. Therefore, NcMIC26 has the potential to be a candidate diagnostic antigen for neosporosis. To test this hypothesis, recombinant NcMIC26 (rNcMIC26) was expressed in Escherichia coli (E. coli), and an indirect ELISA for detecting anti-N. caninum antibodies in cattle was established. Compared with that of the indirect immunofluorescent antibody test (IFAT), the positive coincidence rate of the ELISA based on rNcMIC26 was 76.53% (75/98), which was higher than that of an ELISA based on rSRS2 (66.33%), and the negative coincidence rate was 84.62% (33/39). It is noteworthy that 30 positive samples confirmed by IFAT were consistent with the rNcMIC26 ELISA but were negative by the rNcSRS2 ELISA. Our research illustrated that NcMIC26 is a dependable diagnostic marker for the serodiagnosis of N. caninum infection in cattle and could be utilized as a supplementary antigen for missed detection by NcSRS2.
Highlights
Neospora caninum is an obligate intracellular apicomplexan parasite that is the etiologic agent of neosporosis for a variety of animals, for which canids are the definitive hosts [1]
We mainly screened for proteins related to the three major secretory organelles and, eventually, determined NcMIC26 to be a candidate antigen of N. caninum, which was present in the tachyzoite-secreted fraction excretory secretion antigen (ESA) (50–70 kDa from Figure 1A)
In addition to the affirmation that the bovine antiserum recognized rNcMIC26, the results of the current study suggest that the bovine antisera against the whole parasite recognized NcMIC26 as an immunodominant antigen
Summary
Neospora caninum is an obligate intracellular apicomplexan parasite that is the etiologic agent of neosporosis for a variety of animals, for which canids are the definitive hosts [1]. The disease tends to be globally distributed and is most serious in cattle [2]. Abortion is the main clinical symptom of infection, and neosporosis is one of the main causes of cattle abortion worldwide [3]. Reproductive loss is the main clinical outcome of neosporosis in cattle and a major reason for the economic impact on the dairy and beef cattle trade [2]. In the absence of an effective treatment or vaccine against bovine neosporosis, control of the disease depends on an accurate diagnosis of neosporosis-infected cattle for timely treatment or early elimination of livestock and other farm management measures
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