Deciphering mechanisms of hydrogen sulfide-induced susceptibility to influenza A virus infection - Project Summary Respiratory tract infections and air pollution separately are each major causes of morbidity and mortality worldwide. The COVID-19 pandemic revealed that the environment strongly contributed to the severity of infectious respiratory tract diseases as communities with higher air pollution were most affected. However, currently, there is a critical knowledge gap at the nexus of respiratory tract disease infections and environmental stressors, including air pollutants. This is partly because toxicologists and experts in respiratory tract viral infections work in silos. Hydrogen sulfide (H2S) and Influenza A (IAV) virus are common and relevant public health hazards affecting the respiratory tract globally. To our knowledge, no studies have examined the interaction between exposure to environmentally relevant H2S concentrations and IAV infection, a zoonotic pathogen, on the respiratory system. The potential for exposure to H2S and IAV exists daily in the workplace, homes, and communities. There are > 80 occupational settings in which H2S is a human health hazard. The current Occupational Safety and Health Administration’s (OSHA) H2S guideline for a 40 h work week is 10 ppm to protect workers from toxic effects of H2S. We have obtained striking preliminary data showing that pre- exposing mice to 5 or 10 ppm H2S for 2 h/day, 5 days/week, for 25 days caused acute mortality in mice challenged with IAV. No mortality was recorded in control mice breathing room air challenged with an equal dose of the virus. The goal of this proof of principle study is to generate sufficient pilot data and to identify underlying toxic mechanisms for future development of target-specific therapeutic drugs to reduce morbidity and mortality of IAV infection. Our overarching hypothesis is that environmental H2S exposure predisposes mice to respond to respiratory tract viral infections in an overly robust manner with high mortality. The study will consist of 2 Specific Aims (SA). SA #1: to test the hypothesis that repeated exposure to H2S causes lung immunotoxicity. An equal number (6) of M/F C57BL/6j mice will be exposed to room air (RA) or H2S at 0.5 or 5 ppm 2 h/day, 5 days/week for 25 days and euthanized to assess lung injury by histopathology, flow cytometry, RNA-Seq, and cytokine analysis using multiplex technology. In SA #2 we shall investigate the mechanisms by which pre-exposure to 0.5 or 5 ppm H2S significantly aggravates the outcome of IAV infection in mice. An equal number (6) of M/F C57BL/6j mice will be exposed to RA or H2S as in SA1 followed by a single challenge with 10 plaque forming units IAV PR/8. Cohorts of mice will be sacrificed at 72 h and on DPI 7. In addition to the lung assays as in SA1, oxygen saturation, immunoblotting, flow cytometry and viral load will be performed to determine mechanisms and severity of lung injury. Successful completion of this interdisciplinary study will open a novel line of inquiry on environment/host interaction and susceptibility to IAV, a major zoonotic pathogen globally. We shall use strengthened preliminary data from this work to apply for NIH grants to map out underlying toxic mechanisms in order to effectively treat patients and to protect public health better.
