Systemic coordination of pro-inflammatory immune reactions through dendritic cell-restricted sIL6R biogenesis

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Project Summary / Abstract This is an application by Dr. Daniel Lingwood (PI), and Dr. Alejandro Balazs (Co-I), Assistant Professors at Harvard Medical School and faculty members of the Ragon Institute of MGH, MIT and Harvard. Their laboratories specialize in defining the immunology of antibody responses to vaccines (Lingwood) and in the engineering of immunity through AAV-mediated gene delivery (Balazs). Dr. Lingwood has discovered that antibody responses to vaccination, and pro-inflammatory immune reactions generally, are centrally regulated by novel control axis supplied by conventional dendritic cells (cDC), a single lymphoid lineage defined in mice by expression of the transcription factor Zbtbt46. Dr. Lingwood has found that cDCs are responsible for the in vivo biogenesis of the soluble, circulating form of the IL-6 receptor (sIL6R), which normally captures IL-6 from solution to systemically coordinate its signaling activity. IL-6 is a potent pro-inflammatory cytokine released following immune challenge or tissue injury, and dysregulation of its capture by sIL6R leads to hyperphysiologic IL-6 levels and inflammatory disease. This proposal will test the central hypothesis that biogenesis of sIL6R by cDC forms a centralized control axis that can be modulated to enhance immune defense and restore IL-6 homoeostasis in disease states. In Aim 1, Dr. Lingwood will define the contribution of the metalloproteases ADAM10 and ADAM17 to systemic sIL6R release from the cDC cell surface. These proteases cleave surface IL6R to shed sIL6R from tissue culture cells lines, potentiating a drugable target to modulate IL-6 immune effects. However, ADAM10/17 knockouts are embryonic lethal, preventing mechanistic evaluation of their activity in vivo. Dr. Lingwood has now selectively directed ADAM10 and/or ADAM17 knockouts to the cDC lineage and will use these transgenic animals to define ADAM activity within two cDC- dependent parameters: circulating sIL6R set-point and induction of sIL6R biogenesis after immune challenge. Dr. Lingwood has also discovered that cDC-derived sIL6R, and subsequent trans IL-6 signaling through the sIL6R:IL-6 complex, is necessary for B cell differentiation to antibody secreting plasma cells, and tunes antibody output following immunization with a variety of protein vaccine antigens. In Aim 2, Dr. Lingwood will define how cDC-derived sIL6R links innate and adaptive immunity through this pathway (outside the traditional T cell priming activity of cDC), and more specifically how this can be harnessed as a natural adjuvant principle to improve the efficacy of influenza vaccines. In Aim 3, Dr. Lingwood and Dr. Balazs have developed a AAV- gene delivery platform that rescues sIL6R levels and its IL-6 capture activity in vivo. They will use this system to experimentally define how disease-causing polymorphisms within sIL6R dysregulate IL-6 capture and inflammatory activity in vivo, and then in parallel, the therapeutic sIL6R expression level needed to correct IL-6 homeostasis and restore function therein. Collectively, this proposal will define and exploit newly discovered biology of sIL6R immune-defense to treat human disease, consistent with the goals and mission of the NIH.