Toxin-Based Mucosal Adjuvants

Adjuvants: Engineering Protective Immune Responses in Human and Veterinary Vaccines

“…LTs can be classified into types I and II subfamilies, according to biochemical properties and antigenic capacity [276,277]. Type I LTs consist of E. coli heat-labile enterotoxin (LT-I) and cholera toxin (CT), which typically promote a mixed Th1/Th2/Th17 response, and IgG1 and IgG2a antibody responses when administered with antigen to mice [278][279][280]. In contrast, type II LTs such as LT-IIa, LT-IIb and LT-IIc predominantly induce Th1 and IgG2a responses [278,281].…”

“…Type I LTs consist of E. coli heat-labile enterotoxin (LT-I) and cholera toxin (CT), which typically promote a mixed Th1/Th2/Th17 response, and IgG1 and IgG2a antibody responses when administered with antigen to mice [278][279][280]. In contrast, type II LTs such as LT-IIa, LT-IIb and LT-IIc predominantly induce Th1 and IgG2a responses [278,281]. Both LT types share a similar AB5 oligomeric structure but differ in B subunit amino acid sequences, leading to distinct target specificities [281].…”

“…Both LT types share a similar AB5 oligomeric structure but differ in B subunit amino acid sequences, leading to distinct target specificities [281]. Despite exhibiting potent immunostimulatory properties, LT-based adjuvants have not been approved from human use due to inherent toxicity linked to their ADP-ribosylating enzymatic activity [278]. Oral and intranasal administration of LT-based formulations have also been linked to adverse effects such as diarrhea and Bell's palsy (temporary facial paralysis or weakness), respectively [282,283].…”