(708) Substance P regulates the immune response to promote coronavirus clearance in the airways

Introduction/Rationale: The sensory neuropeptide Substance P helps to protect against respiratory viral infection by promoting key defense reflexes like cough and bronchoconstriction. It can also promote pathogenic neurogenic inflammation by regulating cytokine production and immune cell activity. We thus asked whether Substance P plays a pro-viral or anti-viral role during coronavirus infection.

Methods: Male C57BL/6 mice 8-12 weeks were infected with the mouse β-coronavirus MHV-A59 (1,000 PFU in 40 µL PBS delivered intranasally) and treated with the Substance P-receptor TacR1 antagonist fosaprepitant (i.p. 20 mg/kg in PBS) or vehicle (meglumine 9.37 mg/kg) twice daily over the course of infection, specifically post-infection days zero through nine. We profiled and quantified pulmonary and splenic immune cells in infected vehicle-treated and fosaprepitant-treated mice using flow cytometry. Serum, BAL fluid, and lung samples were collected at various post-infection timepoints to assess cytokine concentration, antibody titers, and viral load.

Results: Substance P levels were significantly increased in the lungs of MHV-A59 infected mice and were dependent on sensory neuron signaling. Administration of fosaprepitant promoted weight loss, an increase in pulmonary viral titers and significantly decreased survival in infected mice. Immune dysregulation was observed in the lungs and spleen of infected fosaprepitant-treated versus vehicle-treated animals. Overall, blocking Substance P signaling during active infection significantly dysregulated the pulmonary and splenic immune response and increased disease severity.

Conclusion: Substance P receptor signaling plays a key early role in regulating the immune response to significantly improve viral clearance during coronavirus infection. Future experiments will examine the effects of blocking Substance P early vs. late in the infection cycle, and will determine how Substance P signaling affects immune cell function to promote viral clearance in infected animals.