Functional Affinity of Eleven Commercial Conjugates for Use in Serologic Assays for Wild Rodents and Shrews

Serologic assays are important tools for detecting the presence of antibodies that are indicative of past and ongoing infections. For wildlife, species-specific conjugates, which are used as detection antibodies in primary binding assays, are not available for most species. In these cases, conjugates for closely related species or immunoglobulin-binding proteins are frequently used. These are often not validated and their low functional affinity may result in false-negative results. We tested 11 commercial conjugates, including protein G and species- or family-specific secondary conjugated antibodies, on eight rodent and two insectivore species (shrews). Using direct ELISAs, between-species and within-species differences in the functional affinity of the conjugates were assessed. Large differences in antibody binding of the conjugates were observed. Some conjugates were species-specific, binding only to antibodies from one species, whereas others were able to bind across a broad range of species. The strength of the antibody-conjugate interaction varied between species and sometimes within species. In general, stronger antibody-conjugate interactions were observed for rodent species than for shrews. Our study underlines the importance of confirming species-specific functional affinity of a conjugate, even if the conjugate is known to bind to antibodies of a closely related species.