IgA binding characteristics of golden hamster and ferret Fcα receptors

Golden hamster (Mesocricetus auratus) and ferret (Mustela putorius furo) are important animal models in studies of human infectious disease. They are used widely to investigate pathogen-spreading mechanisms and host immunology to evaluate the safety and efficacy of small molecules, biologic drugs and vaccines. To this end, immunoglobulin A (IgA) and its Fcα receptor (FcαR) play critical roles in humans but are not well characterized in these 2 species. Golden hamster and ferret IgA and FcαR were recombinantly expressed, purified, and characterized for N-linked glycosylation site occupancy and binding affinity. Based on sequence and structural alignments, hamster IgA showed greater similarity to human IgA than did ferret, and hinge domains in both small animal models suggested greater structural homology to human IgA2 than IgA1. Despite considerable sequence divergence in both immunoglobulins and receptors, and the lack of binding between ferret FcαR and ferret IgA, human IgA bound to both hamster and ferret FcαR with high affinity. Further, differences in dissociation rates were dependent on test format, suggesting that the 2:1 stoichiometry of human FcαR: IgA is recapitulated in these animals. Overall, this work suggests the suitability of these animals to model protection or pathology driven by interactions between human IgA and host FcαR and will aid in critical and confident interpretation of infection and immunization studies in each species.