Protein G Binding to Enriched Serum Immunoglobulin from Nondomestic Hoofstock Species

Abstract

Quick and cost-effective serologic assays, such as those based on enzyme-linked immunosorbent assay (ELISA) technology, are useful for screening animal populations for infectious diseases. Recombinant protein G is described as an almost universal ELISA conjugate for the detection of antibodies from a wide range of animal species. However, there is limited data documenting the ability of protein G to bind immunoglobulin (Ig) from many captive and free-ranging nondomestic hoofstock (Order Artiodactyla, e.g., elk, antelope, bison). Protein G binding to Ig from 11 species within this taxonomic order (addax, antelope, bison, bontebok, elk, impala, kudu/nyala, muntjac, oryx, sheep, and white-tailed deer) and 2 control species (bovine and chicken) was assessed. A serum Ig enrichment protocol, using high-performance liquid chromatography (HPLC), was optimized in bovids ( Bos taurus) and then applied to the other study species. Binding assays were performed by adding protein G to microtiter wells coated with titrated dilutions of enriched artiodactyl Ig. Optical densities were measured and binding curves generated. Differences in protein G binding were observed, both within and among species, as well as within taxonomic families. Significant intraspecies binding variation was observed for 7 species tested (antelope, oryx, sheep, muntjac, impala, bontebok, and addax). No statistically significant intraspecies differences in protein G binding were found for Ig from bison, elk, kudu/nyala, white-tailed deer, plus control species (cattle and chicken). Binding of protein G to Ig from impala, muntjac, and elk was statistically different from the positive control (cattle), with muntjac binding curves statistically comparable with the negative control (chicken). For the other 7 species tested, binding curves illustrated the ability of protein G to bind Ig as well as, or better than, the positive control. These findings expand the list of animal species whose Ig is capable of being detected using recombinant protein G, with the caveat that protein G does not bind Ig uniformly in closely related species. It is concluded that recombinant protein G conjugates may serve as useful reagents for serodiagnosis by ELISA in nondomestic hoofstock, although different assay interpretation algorithms and assay protocols may need to be developed on a per species basis for maximum diagnostic effectiveness.