AUTHOR=Zhang Xinyu , Yu Shupei , Cheng Darong , Feng Yu , Yang Yuefei , Sun Huaichang , Ding Jiabo , Wang Fang 

TITLE=An Attenuated Escherichia coli K88ac LT(S63K)ΔSTb Efficiently Provides Protection Against Enterotoxigenic Escherichia coli in the Mouse Model

JOURNAL=Frontiers in Veterinary Science

VOLUME=7

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2020.620255

DOI=10.3389/fvets.2020.620255

ISSN=2297-1769

ABSTRACT=<p>To develop an attenuated vaccine candidate against K88ac enterotoxigenic <italic>Escherichia coli</italic> (ETEC), a novel <italic>Escherichia coli</italic> (<italic>E. coli</italic>) K88ac <italic>LT(S63K)</italic>Δ<italic>STb</italic> with <italic>LT(S63K)</italic> mutation and <italic>ST1</italic> deletion was generated using site mutagenesis and λ-Red homologous recombination based on wild paternal ETEC strain C83902. <italic>E. coli</italic> K88ac <italic>LT(S63K)</italic>Δ<italic>STb</italic> showed very similar fimbriae expression and growth kinetics to the wild strain C83902, but it was significantly attenuated according to the results of a rabbit ligated ileal loop assay and mouse infection study. Oral inoculation with <italic>E. coli</italic> K88ac <italic>LT(S63K)</italic>Δ<italic>STb</italic> stimulated the mucosa immune response and induced the secretion of IgA to K88ac in the intestines in mice. A challenge experiment revealed that the attenuated strain provided efficient protection against C83902 in the following 7 days and at the 24th day post-inoculation, suggesting that the attenuated isolate could act as an ecological protectant and vaccine in preventing K88ac ETEC.</p>