Show simple item record

dc.contributor.authorNawar, Hesham Fawzi
dc.date.accessioned2016-04-05T16:18:53Z
dc.date.available2016-04-05T16:18:53Z
dc.date.issued2006
dc.identifier.isbn0542631326
dc.identifier.isbn9780542631320
dc.identifier.other304939914
dc.identifier.urihttp://hdl.handle.net/10477/49563
dc.description.abstractThe respiratory, gastrointestinal, and genitourinary tracts represent natural sites for entry of many human pathogens. Thus, it is desirable to develop vaccines that are capable of establishing strong protective immune responses at those mucosal sites. LT-IIa and LT-IIb, two type II heat-labile enterotoxins of Escherichia coli , are potent mucosal adjuvants that augment immune responses to weak antigens. These enterotoxins exert their immunomodulatory effects using molecular and cellular pathways that are different from those employed by other mucosal adjuvants such as cholera toxin and E. coli LT-1. LT-IIa and LT-IIb are closely related in structure and in function to cholera toxin and LT-I, the type I heat-labile enterotoxins (HLT) of Vibrio cholerae and E. coli , respectively. Each of these enterotoxins has been shown to exert an immunomodulatory effect. Recent studies from our group demonstrated that LT-IIa and LT-IIb are potent systemic and mucosal adjuvants. The mechanisms by which the type II HLT modulate the immune response and act as adjuvants have been shown to differ from those used by type I HLT. To determine whether binding of LT-IIa and LT-IIb to their specific ganglioside receptors is essential for adjuvant activity, the immunomodulatory properties of LT-IIa and LT-IIb were compared to those of their respective single-point substitution mutants [e.g., LT-IIa(T34I) and LT-IIb(T13I)] which have no detectable binding activity for their major ganglioside receptors (Chapter 2). Unlike their wildtype (wt) parental enterotoxins, both mutant enterotoxins exhibited an extremely low capacity for intoxicating mouse Y1 adrenal cells and for inducing production of adenosine 3',5' cyclic monophosphate (cAMP) in a macrophage cell line. To determine whether other mutant enterotoxins of LT-IIa that have altered ganglioside-binding activities exhibit adjuvant activity, BALB/c female mice were also immunized by the intranasal route with the surface adhesin protein AgI/II of S. mutans alone or in combination with LT-IIa, LT-IIa(T14S), LT-IIa(T14I), or LT-IIa(T14D) (Chapter 3). All these mutant enterotoxins potentiated strong mucosal immune responses that were equivalent to the response elicited by wt LT-IIa. I also examined the nature of the unidentified receptor(s) of LT-IIb and LT-IIb(T13I) using different chemical and enzymatic treatments of RAW264.7 macrophage cells (Chapter 4). My results indicate that the unidentified functional receptor(s) is/are one or more glycosphingolipid(s). Thin layer chromatography (TLC) experiments using total gangliosides purified from RAW264.7 cells and from thioglycolate-activated peritoneal macrophages in combination with immunoblotting technology indicated that LT-IIb and LT-IIb(T13I) bind to a broad range of gangliosides other than GD1a, GM2 and GM3. (Abstract shortened by UMI.)
dc.languageEnglish
dc.sourceDissertations & Theses @ SUNY Buffalo,ProQuest Dissertations & Theses Global
dc.subjectHealth and environmental sciences
dc.subjectMucosal adjuvant
dc.subjectLT-IIa
dc.subjectEnterotoxins
dc.subjectGangliosides
dc.titleMucosal adjuvant properties of mutant LT-IIa and LT-IIb enterotoxins that exhibit altered ganglioside-binding activities
dc.typeDissertation/Thesis


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record