Mechanisms of Pathogenesis in Staphylococcal Enterotoxin B-Induced Acute Respiratory Distress Syndrome

PROJECT SUMMARY Acute Respiratory Distress Syndrome (ARDS) is a severe condition characterized by non-compliant lung, hypoxemia, protein-rich pulmonary edema, and cytokine storm. The COVID-19 pandemic highlighted ARDS as a significant public health burden that annually affects approximately 200,000 patients in the US with a 35-45% mortality rate. ARDS develops via a myriad of etiologies, though the most common underlying conditions in the US include pneumonia (44.9% of all cases) and nonpulmonary sepsis (46.8% of all cases). The gram-positive bacterial pathogen Staphylococcus aureus is one of the most commonly isolated pathogens in sepsis patients. S. aureus produces superantigens (SAgs), including Staphylococcal Enterotoxin B (SEB). SEB exposure can induce ARDS by activating up to 30% of the naïve T cell pool through the formation of non-specific cross-linkages between antigen-presenting cells (APCs) and T cells. The receptors involved in this interaction are classically believed to include Vβ TCRs, CD28, CD80/CD86, and MHC class II, though some studies suggest that MHC class II may be dispensable for inflammatory response. Interestingly, recent studies have demonstrated that the SARS-CoV-2 Spike protein contains a superantigen-like motif similar to SEB; additionally, the CDC has classified SEB as a Category B Biological Agent due to its ease of dissemination and inhalation toxicity. Therefore, murine models of SEB-induced ARDS can provide valuable insights into S. aureus and SARS-CoV-2 infection treatment, ARDS pathogenesis and prevention, and biological weapon response. My preliminary data demonstrates that the H2k C3H/HeJ mouse strain, but not the H2b C57BL/6J strain, are susceptible to SEB-induced ARDS, which suggests that H2 haplotype may play a role in superantigen response. Therefore, the central hypothesis of the proposed project is that C3H/HeJ mice are susceptible to SEB-induced ARDS due to alterations in MHC Class II, Vβ TCRs, CD28, or CD80/CD86, which allow SEB to more effectively form cross-linkages between APCs and T cells, thereby increasing SAg-mediated T cell activation and subsequent myeloid infiltration to the alveoli. To test this hypothesis, I propose the following specific aims: 1) Establish the cellular and molecular mechanisms of SEB-induced ARDS pathogenesis in C3H/HeJ and C57BL/6J mouse strains; 2) Determine whether strain-specific differences in MHC Class II, Vβ TCRs, CD28, or CD80/CD86 drives differential response to SEB in C3H/HeJ and C57BL/6J strains. The proposed experiments align with my goals for fellowship training and will allow me the opportunity to gain expertise in high-throughput immune cell profiling, transcriptome analysis, and in vivo approaches to elucidate immune response at the respiratory site. Furthermore, the proposed professional development plan will propel my career goals by enhancing my research independence.