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An IgG avidity ELISA to discriminate between recent and chronic Neospora caninum infection
C Björkman1, K Näslund, S Stenlund
1Department of Ruminant Medicine and Veterinary Epidemiology, Swedish University of Agricultural Sciences, Uppsala.
Insights
This study introduces an IgG avidity ELISA to differentiate recent from chronic Neospora caninum infections in cattle. The assay measures antibody avidity, which increases over time post-infection, aiding epidemiological studies.
Area of Science:
- Veterinary Immunology
- Parasitology
- Molecular Diagnostics
Background:
- Neospora caninum is a significant cause of bovine abortion, impacting cattle herds worldwide.
- Accurate diagnosis is crucial for controlling the spread of Neospora caninum infections.
- Distinguishing between recent and chronic infections is vital for herd management and epidemiological surveillance.
Purpose of the Study:
- To develop and validate an IgG avidity enzyme-linked immunosorbent assay (ELISA) for Neospora caninum.
- To assess the utility of IgG avidity in differentiating recent from chronic infections in cattle.
- To evaluate the assay's potential as a complementary tool in Neospora caninum epidemiological studies.
Main Methods:
- An IgG avidity ELISA was developed using N. caninum proteins in immunostimulating complexes.
- Low-affinity antibodies were eluted using a urea incubation step.
- IgG avidity values were calculated by comparing antibody titers with and without urea treatment.
Main Results:
- IgG avidity increased progressively during experimental Neospora caninum infection in calves.
- Avidity ranged from 9-18% at 3 weeks post-infection, rising to 58-76% by 24 weeks.
- Naturally infected cattle ( >6 months) consistently showed avidities >50%.
Conclusions:
- The IgG avidity ELISA effectively discriminates between recent and chronic Neospora caninum infections.
- This assay can serve as a valuable addition to existing IgG assays for Neospora caninum epidemiology.
- The findings support the use of IgG avidity testing for improved surveillance and management of bovine neosporosis.
Abstract:
The avidity of IgG antibodies directed to Neospora caninum was measured using an IgG avidity enzyme-linked immunosorbent assay (ELISA) employing N. caninum proteins incorporated into immunostimulating complexes as antigen. In this ELISA, low-affinity antibodies were eluted by adding an incubation step with urea after the serum incubation. The antibody titers obtained with and without incubation with urea were then used to calculate the IgG avidity values. Analysis of sequential sera collected from experimentally infected calves revealed that the avidity increased during the course of infection. Three weeks after infection, the IgG avidity was 9-18%, and 24 weeks later it had increased to 58-76%. Cattle naturally infected for more than 6 months all had avidities >50%. The results in this study, however preliminary, indicate that the IgG avidity ELISA can be used to discriminate between recent and chronic N. caninum infections and may therefore be a valuable complement to IgG assays in epidemiologic studies of N. caninum infection in cattle.
