The Role of Intracellular Pattern Recognition Receptors (prrs) in Recognition and Immunomodulation of Dendritic Cells (DC) in Response to Daptomycin (dap) Resistant MRSA

Abstract Methicillin resistant Staphylococcus aureus (MRSA) infection is one of the leading causes of hospital-acquired infections and is more difficult to treat than other bacterial infections. In recent years, resistance to last line anti-staphylococcal antibiotic daptomycin has been observed during treatment of MRSA bacteremia. Protection against MRSA infection is challenging and requires both innate and adaptive immune effector mechanisms. Being at the interface between innate and adaptive immune responses, DCs are thus central to the immune protection against S. aureus. We have previously shown that distinct and paired clinical isolates of MRSA have differential capacity to induce DC activation, with MRSA strains resistant to the last_line antibiotic daptomycin inducing a compromised response to MRSA. However, this study explores the molecular mechanism by which MRSA strains impede DC activation. We explored the role of intracellular PRRs in the recognition and immunomodulation of these clinical isolates. We found that the cytosolic sensors cGAS and STING are implicated in the sensing of clinical isolates of MRSA, but their use is more prominent in response to DapS strains. We also determined that the TLR3 ligand poly(I:C) induced a highly synergistic increase in the activation of DC in response to both Daptomycin sensitive (DapS) and Daptomycin resistant (DapR) MRSA. Our work, thus provides important insights for the mechanism of differential recognition of clinical isolates of MRSA and immunomodulation through engagement of PRR pathways which are critical to achieve effective and comprehensive immune defense against this pathogen.