Mutants of type II heat-labile enterotoxin LT-IIa with altered ganglioside-binding activities and diminished toxicity are potent mucosal adjuvants

Infect Immun. 2007 Feb;75(2):621-33. doi: 10.1128/IAI.01009-06. Epub 2006 Nov 21.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / immunology
  • Adjuvants, Immunologic*
  • Administration, Intranasal
  • Animals
  • Antibodies, Bacterial / blood
  • Antigens, Bacterial / immunology
  • B7-1 Antigen / biosynthesis
  • B7-2 Antigen / biosynthesis
  • Bacterial Toxins / genetics*
  • Bacterial Toxins / immunology*
  • Bacterial Toxins / metabolism
  • Bacterial Toxins / toxicity
  • CD40 Antigens / biosynthesis
  • Cell Line
  • Dendritic Cells / immunology
  • Enterotoxins / genetics*
  • Enterotoxins / immunology*
  • Enterotoxins / metabolism
  • Enterotoxins / toxicity
  • Escherichia coli / immunology
  • Escherichia coli Proteins / administration & dosage
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / immunology
  • Escherichia coli Proteins / metabolism
  • Escherichia coli Proteins / pharmacology*
  • Escherichia coli Proteins / toxicity
  • Female
  • Gangliosides / metabolism*
  • Histocompatibility Antigens Class II / biosynthesis
  • Immunity, Mucosal
  • Immunoglobulin G / blood
  • Mice
  • Mice, Inbred BALB C
  • Models, Animal
  • Protein Binding
  • Streptococcal Vaccines / immunology
  • Streptococcus mutans / immunology
  • Vaccines, Subunit / immunology

Substances

  • Adhesins, Bacterial
  • Adjuvants, Immunologic
  • Antibodies, Bacterial
  • Antigens, Bacterial
  • B7-1 Antigen
  • B7-2 Antigen
  • Bacterial Toxins
  • CD40 Antigens
  • Enterotoxins
  • Escherichia coli Proteins
  • Gangliosides
  • Histocompatibility Antigens Class II
  • Immunoglobulin G
  • Streptococcal Vaccines
  • Vaccines, Subunit
  • heat-labile enterotoxin, E coli