Project Grant R01AI184867

EXTRAFOLLICULAR B CELL RESPONSE REGULATION DURING INFLUENZA INFECTION - PROJECT SUMMARY INFECTION-INDUCED B CELL ACTIVATION OCCURS IN THE CONTEXT OF COMPLEX INNATE IMMUNE RESPONSES, INCLUDING THE ELABORATION OF CYTOKINES, AND THE REMODELING OF SECONDARY LYMPH TISSUES DRAINING SITES OF INFECTION. OUR LONG-TERM OBJECTIVE IS TO DETERMINE HOW OPTIMAL PROTECTIVE HUMORAL IMMUNITY TO INFECTIONS IS INDUCED AND MAINTAINED. EXPLORING INFECTION-INDUCED INNATE STIMULI THAT MODULATE ADAPTIVE IMMUNITY, WE SHOWED THAT INFECTION-INDUCED AND TLR-AGONIST ADJUVANTED S.C. IMMUNIZATION PROVIDE REQUIRED B CELL INTRINSIC TLR SIGNALING VIA BOTH ADAPTORS (MYD88 AND TRIF) FOR EXTRAFOLLICULAR RESPONSES, AS DELETION OF BOTH ADAPTORS ABROGATED EF RESPONSES. WHILE B CELL INTRINSIC MYD88 STIMULATION DRIVES B CELL PROLIFERATION, TRIF SIGNALING DOES NOT, INDICATING DISTINCT YET UNKNOWN MECHANISMS OF TRIF-MEDIATED SUPPORT FOR EF FORMATION. WHEN AND WHERE, DURING B CELL ACTIVATION, THESE INNATE SIGNALS REGULATE B CELL FATE IS UNKNOWN. RECENTLY WE IDENTIFIED AN EARLY INDUCED, POST PROLIFERATIVE, INFLUENZA SPECIFIC B CELL POPULATION WITH A UNIQUE PHENOTYPE AND TRANSCRIPT PROFILE THAT MIGHT REPRESENT AN ACTIVATION INTERMEDIATE OF EF. THE OBJECTIVES FOR THIS PROJECT ARE TO TEST THE HYPOTHESIS THAT EARLY IN INFLUENZA INFECTION B CELL INTRINSIC TRIF/TLR3 AND MYD88-MEDIATED SIGNALS SUPPORT EF DIFFERENTIATION VIA TWO DISTINCT DIFFERENTIATION PATHS, EACH DIFFERENTLY AFFECTING EXTRAFOLLICULAR ANTIBODY QUALITY, ACTING ON ANTIGEN-STIMULATED, POST-PROLIFERATIVE B CELLS. TO ACHIEVE OUR OBJECTIVES, WE WILL TEST IN SPECIFIC AIM 1 THE HYPOTHESIS THAT B CELL INTRINSIC TLR3-SIGNALS SUPPORT EFFECTIVE PLASMABLAST DIFFERENTIATION BY ENHANCING B CELL RESPONSIVENESS TO IL2, WHILE MYD88 PRINCIPALLY DRIVES PROLIFERATION FOLLOWED BY TERMINAL DIFFERENTIATION, DIFFERENTIALLY AFFECTING ANTIBODY QUALITY. IN SPECIFIC AIM 2 WE WILL DETERMINE THE EXTENT TO WHICH THE POPULATION OF TRANSCRIPTIONALLY DISTINCT, ANTIGEN-EXPERIENCED, MOSTLY NON-SWITCHED AND POST-PROLIFERATIVE B CELLS THAT APPEAR IN THE DRAINING LN AT 5 DPI WITH INFLUENZA VIRUS, REPRESENT AN INTERMEDIARY, QUIESCENT STAGE IN B CELL ACTIVATION TO EF, EXTRAFOLLICULAR MEMORY B CELLS AND/OR GC DEVELOPMENT AND DETERMINE THE IMPACT OF TLR SIGNALING ON THEIR DEVELOPMENT AND FATE. SUCCESSFUL COMPLETION OF THE WORK WOULD PROVIDE SIGNIFICANT CONCEPTUAL ADVANCES TO UNDERSTANDING EARLY B CELL ACTIVATION AND EXTRAFOLLICULAR MEMORY B AND PLASMA CELL RESPONSE INDUCTION. IT WOULD ALSO IDENTIFY A NOVEL ROLE FOR TLR3 IN SUPPORT OF EF DEVELOPMENT AND CLARIFY THE FUNCTION OF TLRS ON B CELL RESPONSES. COLLECTIVELY THESE ADVANCES WOULD IDENTIFY NEW, CRITICAL JUNCTURES IN B CELL ACTIVATION, REGULATED BY INNATE IMMUNE SIGNALS FOR POTENTIAL EXPLOITATION IN VACCINE DESIGN.