Simple methods for measurement of bovine mucosal antibody responses in vivo

The mucosal immune response serves as the first line of defence against many bacterial and viral diseases. Therefore, measurement of mucosal immune responses is important in evaluating mucosal immunisation protocols and understanding initial host/pathogen interactions. In this study we compare two methods for repeated sampling of bovine rectal mucosal secretions, namely rectal swabbing and rectal biopsies, and evaluate a simple swabbing method for sampling bovine nasal secretions. Both rectal swabs and rectal biopsies yielded similar quantities of total IgA (TIgA)/ml. However, rectal biopsies yielded five times more total IgG (TIgG)/ml than rectal swabs. Blood contamination was estimated to contribute approximately 7% of TIgG and <0.05% TIgA in rectal swab samples compared to 40% of TIgG and 4.5% of TIgA in rectal biopsy samples, indicating that rectal swabbing was more effective at sampling rectal mucosal secretions. Nasal swabs were effective at obtaining nasal secretion samples with only 1% of TIgG and <0.05% TIgA estimated to be blood derived. Furthermore, H7 flagellin-specific antibodies were detected in both nasal and rectal swab samples following either rectal immunisation with purified H7 flagellin or oral challenge with live E. coli O157:H7, indicating that both techniques are effective methods for monitoring mucosal antibody responses in cattle.