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Quantitative Detection of Antibodies to Aleutian Disease Virus in Dried Blood Spots as an Estimation of Hypergammaglobulinemia in Mink

Anna-Maria Andersson, Helena Bosaeus Reineck, Ann-Kristin Nyman and Per Wallgren

Infections with Aleutian disease virus (ADV) cause a progressive hypergammaglobulinemia, immune complex formation and plasma cell infiltrations in internal organs which induce a multi-systemic disease with high mortality. Serum ADV antibodies have traditionally been diagnosed with counter immunoelectrophoresis (CIEP) as a gold standard for qualitative assessment separating infected from non-infected animals, but less laborious ELISA methods have been confirmed to be equally sensitive. A way to simplify the diagnostics further could be to demonstrate antibodies in Dried blood spot samples (DBS). However, quantitative analysis of ADV antibodies in DBS and its correlation to the degree of hypergammaglobulinemia have not been scientifically published. The aim of this paper was to describe the adaptation and validation of the VP2 ELISA to ADV antibody detection in DBS and compare the estimated antibody levels in DBS to CIEP results, the estimated antibody levels and albumin: gamma globulin ratio in serum. The VP2 ELISA worked technically well when transferred from serum to DBS with mean intra-assay and mean inter-assay coefficients of variation within ± 20%. The DBS VP2 ELISA had a sensitivity of 97.3% and specificity of 93.2% compared to CIEP. Further, we found a correlation coefficient between the level of antibodies in DBS and the A:γG ratio of -0.81. The correlation between the A:γG ratio and the OD450 value was superior in DBS compared to serum samples from the same mink with the most pronounced difference at low A:γG ratios. Our results confirmed that the VP2 ELISA could detect ADV antibodies in DBS with a high sensitivity and specificity when employing CIEP as gold standard. The antibody titers estimated with DBS VP2 ELISA were well correlated to the antibody titters and A:γG ratios in serum, and the DBS VP2 ELISA could be an applicable and preferable tool for estimating AD progression in mink.