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

J Immunol. 2013 Jun 1;190(11):5722-30. doi: 10.4049/jimmunol.1203343. Epub 2013 Apr 29.


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.

Publication types

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

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Adjuvants, Immunologic
  • Animals
  • CARD Signaling Adaptor Proteins
  • Cell Differentiation / immunology
  • Cord Factors / immunology*
  • Inflammasomes / metabolism
  • Interleukin-1beta / metabolism
  • Lectins, C-Type / metabolism*
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Knockout
  • Mycobacterium / chemistry
  • Mycobacterium / immunology*
  • Myeloid Differentiation Factor 88 / metabolism
  • Peptidoglycan / immunology*
  • Receptors, Interleukin-1 / metabolism
  • Receptors, Interleukin-18 / metabolism
  • Signal Transduction
  • Th17 Cells / cytology
  • Th17 Cells / immunology*
  • Th17 Cells / metabolism*
  • Toll-Like Receptors / metabolism


  • Adaptor Proteins, Signal Transducing
  • Adjuvants, Immunologic
  • CARD Signaling Adaptor Proteins
  • Card9 protein, mouse
  • Clecsf8 protein, mouse
  • Cord Factors
  • Inflammasomes
  • Interleukin-1beta
  • Lectins, C-Type
  • Membrane Proteins
  • Myeloid Differentiation Factor 88
  • Peptidoglycan
  • Receptors, Interleukin-1
  • Receptors, Interleukin-18
  • Toll-Like Receptors