Measurement of specific IgA in faecal extracts and intestinal lavage fluidfor monitoring of mucosal immune responses

Currently available methods for the evaluation of antigen-specific immune r esponses in the intestine, i.e. measurement of IgA in intestinal lavage and antibody secreting cells (ASC) in peripheral blood, are not applicable to large-scale immunogenicity studies or to kinetic studies where repeated sam pling is required. Simple and reliable methods need to be developed. Intest inal lavage and faecal samples were collected from 12 mice on days 0, 14, 2 1, 28 and 35 following initial immunization with four doses of cholera toxi n (CT) by the gastric or rectal routes. The concentrations of anti-CT IgA i n the faecal extracts showed a high level of correlation with those in the lavage samples (Spearman's correlation coefficient=0.85, P<0.0001) regardle ss of the route of CT administration. Moreover, the kinetics of the immune response as reflected in the faecal extracts mirrored those in the lavage s amples regardless of immunization route. As compared to gastric immunizatio n, rectal administration of CT yielded higher levels of anti-CT IgA in both intestinal lavage fluids and in faecal extracts. The use of rectal immuniz ation and the measurement of IgA in faecal extracts for monitoring mucosal immune responses may be relevant for the development of effective enteric v accines. (C) 2000 Elsevier Science B.V. All rights reserved.