Cord factor and peptidoglycan recapitulate the Th17-promoting adjuvant activity of mycobacteria through mincle/CARD9 signaling and the inflammasome

K Shenderov, DL Barber, KD Mayer-Barber… - The Journal of …, 2013 - journals.aai.org
K Shenderov, DL Barber, KD Mayer-Barber, SS Gurcha, D Jankovic, CG Feng, S Oland…
The Journal of Immunology, 2013journals.aai.org
Although adjuvants are critical vaccine components, their modes of action are poorly
understood. In this study, we investigated the mechanisms by which the heat-killed
mycobacteria in CFA promote Th17 CD4+ T cell responses. We found that IL-17 secretion by
CD4+ T cells following CFA immunization requires MyD88 and IL-1β/IL-1R signaling.
Through measurement of Ag-specific responses after adoptive transfer of OTII cells, we
confirmed that MyD88-dependent signaling controls Th17 differentiation rather than simply …
Abstract
Although adjuvants are critical vaccine components, their modes of action are poorly understood. In this study, we investigated the mechanisms by which the heat-killed mycobacteria in CFA promote Th17 CD4+ T cell responses. We found that IL-17 secretion by CD4+ T cells following CFA immunization requires MyD88 and IL-1β/IL-1R signaling. Through measurement of Ag-specific responses after adoptive transfer of OTII cells, we confirmed that MyD88-dependent signaling controls Th17 differentiation rather than simply production of IL-17. Additional experiments showed that CFA-induced Th17 differentiation involves IL-1β processing by the inflammasome, as mice lacking caspase-1, ASC, or NLRP3 exhibit partially defective responses after immunization. Biochemical fractionation studies further revealed that peptidoglycan is the major component of heat-killed mycobacteria responsible for inflammasome activation. By assaying Il1b transcripts in the injection site skin of CFA-immunized mice, we found that signaling through the adaptor molecule caspase activation and recruitment domain 9 (CARD9) plays a major role in triggering pro–IL-1β expression. Moreover, we demonstrated that recognition of the mycobacterial glycolipid trehalose dimycolate (cord factor) by the C-type lectin receptor mincle partially explains this CARD9 requirement. Importantly, purified peptidoglycan and cord factor administered in mineral oil synergized to recapitulate the Th17-promoting activity of CFA, and, as expected, this response was diminished in caspase-1–and CARD9-deficient mice. Taken together, these findings suggest a general strategy for the rational design of Th17-skewing adjuvants by combining agonists of the CARD9 pathway with inflammasome activators.
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