An IgG avidity ELISA to discriminate between recent and chronic Neospora caninum infection

Department of Ruminant Medicine and Veterinary Epidemiology, Swedish University of Agricultural Sciences, Uppsala.

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.

This article has been cited by other articles:

				D. J. L. Williams, C. S. Guy, R. F. Smith, J. Ellis, C. Bjorkman, M. P. Reichel, and A. J. Trees Immunization of Cattle with Live Tachyzoites of Neospora caninum Confers Protection against Fetal Death Infect. Immun., March 1, 2007; 75(3): 1343 - 1348. [Abstract] [Full Text] [PDF]

				T. V. Baszler, S. Adams, J. Vander-Schalie, B. A. Mathison, and M. Kostovic Validation of a Commercially Available Monoclonal Antibody-Based Competitive-Inhibition Enzyme-Linked Immunosorbent Assay for Detection of Serum Antibodies to Neospora caninum in Cattle J. Clin. Microbiol., November 1, 2001; 39(11): 3851 - 3857. [Abstract] [Full Text] [PDF]