Significance of Enterotoxigenic Escherichia coli (ETEC) Heat-Labile Toxin (LT) Enzymatic Subunit Epitopes in LT Enterotoxicity and Immunogenicity

No vaccine is licensed for enterotoxigenicEscherichia coli (ETEC) strains, which remain a leading cause of diarrhea in children from developing countries and international travelers. GM1 -binding heat-labile toxin (LT) which is a key virulence factor of ETEC diarrhea is a strong vaccine antigen and a self-adjuvant. LT can also serve a backbone or platform for MEFA (multiepitope fusion antigen), a newly developed structural vaccinology technology, to present heterogeneous epitopes (by replacing LT epitopes) and to mimic epitope antigenicity for development of broadly protective vaccines. Data from this study identified neutralizing LT epitopes and demonstrated that substitution of LT epitopes eliminated LT enterotoxicity without altering GM1 -binding activity, suggesting LT is potentially a versatile MEFA platform to present heterogeneous epitopes for multivalent vaccines against ETEC and other pathogens.