Contrasting the microbiomes from healthy volunteers and patients with chronic rhinosinusitis.

IMPORTANCE: Chronic rhinosinusitis (CRS) is the persistent inflammation of the sinus and nasal passages lasting over 3 months. The etiology of CRS is not well understood. OBJECTIVE: To obtain insights into the disease process, we contrasted the microbiome and immune response from patients with CRS and healthy controls. DESIGN, SETTING, AND PARTICIPANTS: A case vs control design was used. Samples were collected in the operating room in an institutional hospital or clinic. Thirty patients with CRS and 12 healthy controls undergoing surgery were recruited. MAIN OUTCOMES AND MEASURES: The microbiome was analyzed by deep sequencing of the bacterial 16S and fungal 18S ribosomal RNA genes. Immune response was measured by quantification of 30 different cytokines by multiplexed enzyme-linked immunosorbent assay, and immune cells in the lavage were identified by flow cytometry. The immune response of peripheral blood leukocytes to the lavage microbiota was assessed by interleukin (IL)-5 enzyme-linked immunospot assay. RESULTS: While quantitative increase in most bacterial and fungal species was observed in patients with CRS relative to controls, the microbiomes of patients with CRS were qualitatively similar to the controls. Because these results indicated that bacteria and fungi are not triggering CRS, we undertook a more detailed characterization of the immune response. Patients with CRS had increased levels of the following cytokines: IL-4, IL-5, IL-8, and IL-13, along with increased levels of eosinophils and basophils in the lavage. Importantly, peripheral blood leukocytes isolated from patients with CRS responded to control lavage samples (ie, to commensals) to produce IL-5. In contrast, the same lavage sample evoked no IL-5 production in leukocytes from healthy controls. CONCLUSIONS AND RELEVANCE: These findings support the theory that in some cases CRS results from an immune hyperresponsiveness to commensal organisms.

Matrix metalloprotease 9 mediates neutrophil migration into the airways in response to influenza virus-induced toll-like receptor signaling.

The early inflammatory response to influenza virus infection contributes to severe lung disease and continues to pose a serious threat to human health. The mechanisms by which neutrophils gain entry to the respiratory tract and their role during pathogenesis remain unclear. Here, we report that neutrophils significantly contributed to morbidity in a pathological mouse model of influenza virus infection. Using extensive immunohistochemistry, bone marrow transfers, and depletion studies, we identified neutrophils as the predominant pulmonary cellular source of the gelatinase matrix metalloprotease (MMP) 9, which is capable of digesting the extracellular matrix. Furthermore, infection of MMP9-deficient mice showed that MMP9 was functionally required for neutrophil migration and control of viral replication in the respiratory tract. Although MMP9 release was toll-like receptor (TLR) signaling-dependent, MyD88-mediated signals in non-hematopoietic cells, rather than neutrophil TLRs themselves, were important for neutrophil migration. These results were extended using multiplex analyses of inflammatory mediators to show that neutrophil chemotactic factor, CCL3, and TNFα were reduced in the Myd88⁻/⁻ airways. Furthermore, TNFα induced MMP9 secretion by neutrophils and blocking TNFα in vivo reduced neutrophil recruitment after infection. Innate recognition of influenza virus therefore provides the mechanisms to induce recruitment of neutrophils through chemokines and to enable their motility within the tissue via MMP9-mediated cleavage of the basement membrane. Our results demonstrate a previously unknown contribution of MMP9 to influenza virus pathogenesis by mediating excessive neutrophil migration into the respiratory tract in response to viral replication that could be exploited for therapeutic purposes.