Chicken egg yolk immunoglobulin ( I g Y ) developed against fusion protein LTB – ST a– ST b neutralizes the toxicity of E scherichia coli heat‐stable enterotoxins

Aim To obtain a recombinant enterotoxigenic E scherichia coli ( ETEC ) fusion enterotoxin protein LTB – ST a– ST b ( B ab) that can express the immunogenicity of the haptens ST a and ST b and induce their corresponding neutralizing antibodies. Methods and Results The three important ETEC enterotoxin genes coding LTB , ST a and ST b were PCR ‐amplified, and the amplified products were fused to construct the trivalent enterotoxin expression vector p ET 30‐ B ab. SDS ‐ PAGE and Western blot were used to verify the expression of the fusion protein B ab by E . coli BL 21 carrying plasmid p ET 30‐ B ab. Laying hens immunized with B ab developed high egg yolk immunoglobulin ( I g Y ) titres specific to LTB , ST a and ST b, and all were significantly higher than those in the control group ( P  <   0·01). A suckling mouse assay showed that anti‐ B ab I g Y can neutralize the natural toxicity of ST a and ST b with the highest dilution of 1/2 and 1/32, respectively. Conclusions Genetically constructed B ab induced significant antibody responses against ST a and ST b in chickens, and the resulting I g Y had the capacity to neutralize the toxicity of ST . Significance and Impact of the Study The recombinant B ab protein containing three important ETEC enterotoxins may serve as an effective and convenient polyvalent toxoid that can be used to produce multiple antitoxin I g Y s to prevent colibacillosis caused by ETEC with various fimbriae in young animals.