title: Mutants of type II heat-labile enterotoxin LT-IIa with altered ganglioside-binding activities and diminished toxicity are potent mucosal adjuvants.
abstract: The structure and function LT-IIa, a type II heat-labile enterotoxin of Escherichia coli, are closely related to the structures and functions of cholera toxin and LT-I, the type I heat-labile enterotoxins of Vibrio cholerae and enterotoxigenic Escherichia coli, respectively. While LT-IIa is a potent systemic and mucosal adjuvant, recent studies demonstrated that mutant LT-IIa(T34I), which exhibits no detectable binding activity as determined by an enzyme-linked immunosorbent assay, with gangliosides GD1b, GD1a, and GM1 is a very poor adjuvant. To evaluate whether other mutant LT-IIa enterotoxins that also exhibit diminished ganglioside-binding activities have greater adjuvant activities, BALB/c mice were immunized by the intranasal route with the surface adhesin protein AgI/II of Streptococcus mutans alone or in combination with LT-IIa, LT-IIa(T14S), LT-IIa(T14I), or LT-IIa(T14D). All three mutant enterotoxins potentiated strong mucosal immune responses that were equivalent to the response promulgated by wt LT-IIa. All three mutant enterotoxins augmented the systemic immune responses that correlated with their ganglioside-binding activities. Only LT-IIa and LT-IIa(T14S), however, enhanced expression of major histocompatibility complex class II and the costimulatory molecules CD40, CD80, and CD86 on splenic dendritic cells. LT-IIa(T14I) and LT-IIa(T14D) had extremely diminished toxicities in a mouse Y1 adrenal cell bioassay and reduced abilities to induce the accumulation of intracellular cyclic AMP in a macrophage cell line.
authors.affiliation: The Witebsky Center for Microbial Pathogenesis and Immunology, The Department of Microbiology and Immunology, University at Buffalo, Buffalo, New York 14214, USA.
authors.forename: Hesham F
authors.initials: HF
authors.lastname: Nawar
authors.forename: Sergio
authors.initials: S
authors.lastname: Arce
authors.forename: Michael W
authors.initials: MW
authors.lastname: Russell
authors.forename: Terry D
authors.initials: TD
authors.lastname: Connell
mesh_terms: D018829:Adhesins, Bacterial / Q000276:immunology; D000276:Adjuvants, Immunologic; D000281:Administration, Intranasal; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000276:immunology; D018122:B7-1 Antigen / Q000096:biosynthesis; D051940:B7-2 Antigen / Q000096:biosynthesis; D001427:Bacterial Toxins / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism / Q000633:toxicity; D019013:CD40 Antigens / Q000096:biosynthesis; D002460:Cell Line; D003713:Dendritic Cells / Q000276:immunology; D004768:Enterotoxins / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism / Q000633:toxicity; D004926:Escherichia coli / Q000276:immunology; D029968:Escherichia coli Proteins / Q000008:administration & dosage / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D005260:Female; D005732:Gangliosides / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D018928:Immunity, Mucosal; D007074:Immunoglobulin G / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D023421:Models, Animal; D011485:Protein Binding; D022541:Streptococcal Vaccines / Q000276:immunology; D013295:Streptococcus mutans / Q000276:immunology; D022223:Vaccines, Subunit / Q000276:immunology
chemical_list: D018829:Adhesins, Bacterial; D000276:Adjuvants, Immunologic; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D001427:Bacterial Toxins; D019013:CD40 Antigens; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D005732:Gangliosides; D000949:Histocompatibility Antigens Class II; D007074:Immunoglobulin G; D022541:Streptococcal Vaccines; D022223:Vaccines, Subunit; C027538:heat-labile enterotoxin, E coli