Project Grant R01AI184568

UNDERSTANDING EARLY MACROPHAGE-T CELL INTERACTIONS, SLAMF1, AND IMMUNITY TO TB - SUMMARY MYCOBACTERIUM TUBERCULOSIS (MTB) CAUSES ONE OF THE WORLD'S MOST DEADLY INFECTIONS. INITIALLY, MTB INFECTS ALVEOLAR MACROPHAGES (AMS), AND OVER TIME, IT DISSEMINATES INTO MONOCYTES, INTERSTITIAL AND RECRUITED MACROPHAGES, AND NEUTROPHILS. ONCE AN ADAPTIVE IMMUNE RESPONSE DEVELOPS, CD4 T CELLS PROMOTE THE ABILITY OF MACROPHAGES TO CONTROL MTB, ALTHOUGH THE MECHANISMS BY WHICH CD4 T CELLS CONFER PROTECTION ARE NOT FULLY UNDERSTOOD. IN ADDITION TO SECRETING DIFFUSIBLE CYTOKINES LIKE IFN-, COGNATE INTERACTIONS BETWEEN CD4 T CELLS AND MTB-INFECTED MACROPHAGES ARE IMPORTANT FOR MTB CONTROL. AT THE SAME TIME, MTB UNDERMINES MACROPHAGE-T CELL INTERACTIONS. THUS, OPTIMIZING MACROPHAGE-T CELL INTERACTIONS MAY BE AN EFFECTIVE STRATEGY TO GENERATE PROTECTION. HOWEVER, UNTIL NOW, THERE HAS NOT BEEN A WAY TO DETERMINE WHICH MACROPHAGES HAVE PRESENTED ANTIGEN TO CD4 T CELLS. WE DISCOVERED THAT MTB-INFECTED MACROPHAGES INDUCE THE CELL SURFACE MOLECULE SLAMF1 (SLAM/CD150) IN RESPONSE TO COGNATE INTERACTIONS WITH CD4 T CELLS. WE SHOW THAT SLAMF1 DISTINGUISHES MACROPHAGES THAT ARE INFECTED AND HAVE INTERACTED WITH T CELLS FROM UNINFECTED, BYSTANDER MACROPHAGES THAT EXPERIENCE THE SAME CYTOKINE MILIEU, BOTH IN VIVO IN MICE AND EX VIVO IN MACROPHAGE-T CELL CO-CULTURES. MOREOVER, WE FOUND THAT SLAMF1-/- MICE HAVE HIGHER MTB BURDEN IN THE LUNGS, ENHANCED INFLAMMATORY CELL RECRUITMENT, ALTERED CYTOKINE RESPONSES, AND DIE EARLIER FROM TB COMPARED TO WT MICE. MACROPHAGE SLAMF1 EXPRESSION ALSO CORRELATES WITH PROTECTION IN NON-HUMAN PRIMATES. SLAMF1 IS A TYPE I TRANSMEMBRANE RECEPTORS THAT IS FOUND EXCLUSIVELY ON HEMATOPOIETIC CELLS. SLAMF1 MEDIATES CELL-CELL SIGNALING THROUGH HOMOTYPIC SLAMF1-SLAMF1 INTERACTIONS, AND IT CAN ALSO DIRECTLY BIND BACTERIA. WE HYPOTHESIZE THAT WHEN MACROPHAGES PRESENT ANTIGEN TO CD4 T CELLS, MACROPHAGES TO UPREGULATE SLAMF1, WHICH PROMOTES CONTROL OF MTB IN THE MACROPHAGES BY ACTIVATING REACTIVE OXYGEN SPECIES (ROS) AND AUTOPHAGY-RELATED PATHWAYS. ACTIVATED T CELLS ALSO EXPRESS SLAMF1, AND WE PROPOSE THAT SLAMF1 SIGNALING FROM MACROPHAGES TO THE T CELLS PROMOTES RESOLUTION OF INFLAMMATION. THUS, ACTIVATING SLAMF1 MAY IMPROVE MTB CONTROL WHILE REDUCING IMMUNOPATHOLOGY. HERE, MAKING USE OF SLAMF1FL/FL CONDITIONAL KNOCK-OUT MICE THAT WE MADE, WE WILL DETERMINE THE CELL TYPE SPECIFIC ROLES OF SLAMF1 DURING TB. USING TRANSWELL ASSAYS TO STUDY MACROPHAGE-T CELL INTERACTIONS, WE WILL ESTABLISH WHETHER MACROPHAGE-CD4 T CELL INTERACTIONS AND SLAMF1 CONTRIBUTE TO MTB CONTROL IN HUMAN AND MURINE MACROPHAGES. WE WILL ESTABLISH WHETHER CD4 T CELLS AND SLAMF1 DRIVE MACROPHAGE ROS PRODUCTION AND AUTOPHAGY, WHETHER THIS PATHWAY IS UNDERMINED BY MTB VIRULENCE FACTORS, AND WHETHER IT CAN BE AUGMENTED BY SMALL MOLECULES AND SLAMF1 AGONISTS. FINALLY, MAKING USE OF SLAMF1 REPORTER MICE THAT WE MADE, WE WILL ELUCIDATE THE DYNAMICS OF EARLY MACROPHAGE-T CELL INTERACTIONS DURING MTB INFECTION, AND HOW THESE INTERACTIONS ARE ALTERED BY VACCINES, TRAINED IMMUNITY, AND CONTAINED INFECTION. THESE STUDIES WILL YIELD MECHANISTIC INSIGHT INTO EARLY EVENTS IN HOST IMMUNITY TO TB AND SUPPORT THE DEVELOPMENT OF NOVEL THERAPIES AND VACCINES TO GENERATE STERILIZING IMMUNITY.