Trimethoprim-Sulfamethoxazole Effects on the Nasal Microbiome in Granulomatosis With Polyangiitis

Granulomatosis with polyangiitis (GPA; Wegener's) is a multi-organ autoimmune disease characterized by necrotizing granulomatous inflammation and vasculitis. Upper respiratory involvement occurs in up to 90% of patients with GPA and is often the first manifestation of the disease. Patients with upper respiratory tract disease are more at risk of local and systemic relapse. Microbial organisms may be involved in inducing disease activity in GPA. Previous culture-dependent studies found that patients with GPA were more likely to be chronic nasal carriers of Staphylococcus aureus compared to non-GPA chronic rhinosinusitis and healthy controls; additionally, GPA patients with S. aureus colonization are more likely to experience a future relapse. This led to a randomized placebo-controlled trial of trimethoprim-sulfamethoxazole (TMP-SMX) which showed this antibiotic/antifungal was effective in preventing relapse in GPA. Whether the benefits of TMP-SMX are related to its antimicrobial properties versus anti-inflammatory effects is still unknown. The objective of this study is to prospectively evaluate the changes in the nasal microbiome, mycobiome, and host immunity in patients with GPA before, during, and after receipt of TMP-SMX for 4 weeks. The target enrollment number is 30 participants, and the investigators will include patients seen at the Penn Vasculitis Center with GPA (diagnosed according to the American College of Rheumatology Classification Criteria or based on investigator's judgment). To analyze nasal microbiome and host immunity, participants will be swabbed with nasal swab and cytobrush for DNA sequencing and other studies. An optional research blood draw is also included. The investigators and coordinators will follow each patient longitudinally over a 6-month period.