title: Cholera toxin, and the related nontoxic adjuvants mmCT and dmLT, promote human Th17 responses via cyclic AMP-protein kinase A and inflammasome-dependent IL-1 signaling.
abstract: We have examined the molecular pathways involved in the adjuvant action of cholera toxin (CT) and two novel nontoxic molecules, multiple-mutated CT (mmCT) and double-mutant heat-labile toxin (dmLT) on human T cell responses. Human PBMCs or isolated monocytes were stimulated in vitro with CT, mmCT, or dmLT plus a polyclonal stimulus (staphylococcal enterotoxin B) or specific bacterial Ags, and effects on expression of cytokines and signaling molecules were determined. CT, mmCT, and dmLT strongly enhanced IL-17A and to a lesser extent IL-13 responses, but had little effect on IFN-γ production or cell proliferation. Intracellular cytokine staining revealed that the enhanced IL-17A production was largely confined to CD4(+) T cells and coculture experiments showed that the IL-17A promotion was effectively induced by adjuvant-treated monocytes. Relative to CT, mmCT and dmLT induced at least 100-fold lower levels of cAMP, yet this cAMP was enough and essential for the promotion of Th17 responses. Thus, inhibition of cAMP-dependent protein kinase A was abolished, and stimulation with a cAMP analog mimicked the adjuvant effect. Furthermore, CT, mmCT, and dmLT induced IL-1β production and caspase-1 activation in monocytes, which was associated with increased expression of key proinflammatory and inflammasome-related genes, including NLRP1, NLRP3, and NLRC4. Inflammasome inhibition with a specific caspase-1 inhibitor, or blocking of IL-1 signaling by IL-1 receptor antagonist, abrogated the Th17-promoting effect. We conclude that CT, mmCT, and dmLT promote human Th17 responses via cAMP-dependent protein kinase A and caspase-1/inflammasome-dependent IL-1 signaling.
authors: University of Gothenburg Vaccine Research Institute (GUVAX), Department of Microbiology and Immunology, University of Gothenburg, 405 30 Sweden.
authors: Maximilian
authors: M
authors: Larena
authors: University of Gothenburg Vaccine Research Institute (GUVAX), Department of Microbiology and Immunology, University of Gothenburg, 405 30 Sweden.
authors: Jan
authors: J
authors: Holmgren
authors: University of Gothenburg Vaccine Research Institute (GUVAX), Department of Microbiology and Immunology, University of Gothenburg, 405 30 Sweden.
authors: Michael
authors: M
authors: Lebens
authors: University of Gothenburg Vaccine Research Institute (GUVAX), Department of Microbiology and Immunology, University of Gothenburg, 405 30 Sweden.
authors: Manuela
authors: M
authors: Terrinoni
authors: University of Gothenburg Vaccine Research Institute (GUVAX), Department of Microbiology and Immunology, University of Gothenburg, 405 30 Sweden anna.lundgren@microbio.gu.se.
authors: Anna
authors: A
authors: Lundgren
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology; D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000328:Adult; D051017:Apoptosis Regulatory Proteins / Q000276:immunology; D053468:CARD Signaling Adaptor Proteins / Q000276:immunology; D002135:Calcium-Binding Proteins / Q000276:immunology; D002352:Carrier Proteins / Q000276:immunology; D020170:Caspase 1 / Q000276:immunology; D002772:Cholera Toxin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000276:immunology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000276:immunology*; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D005260:Female; D006801:Humans; D058847:Inflammasomes / Q000276:immunology*; D053583:Interleukin-1beta / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D000070576:NLR Proteins; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D058504:Th17 Cells / Q000166:cytology / Q000276:immunology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000276:Adjuvants, Immunologic; D051017:Apoptosis Regulatory Proteins; D053468:CARD Signaling Adaptor Proteins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; C508585:IL1B protein, human; D058847:Inflammasomes; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D000070576:NLR Proteins; C435692:NLRC4 protein, human; C427903:NLRP1 protein, human; C453881:NLRP3 protein, human; D002772:Cholera Toxin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D020170:Caspase 1