Bone marrow transplantation alters lung antigen-presenting cells to promote TH17 response and the development of pneumonitis and fibrosis following gammaherpesvirus infection

Abstract

Hematopoietic stem cell transplantation (HSCT) efficacy is limited by numerous pulmonary complications. We developed a model of syngeneic bone marrow transplant (BMT) followed by infection with murine gamma herpesvirus (γHV-68) that results in pneumonitis and fibrosis and mimics human “non-infectious” HSCT complications. BMT mice experience increased early lytic replication, but establish viral latency by 21 days post infection (dpi). CD4 T cells in BMT mice are skewed towards IL-17A rather than IFN-γ production. Transplantation of bone marrow from Il-17a−/− donors or treatment with anti-IL-17A neutralization antibodies at late stages attenuates pneumonitis and fibrosis in infected BMT mice, suggesting that hematopoietic-derived IL-17A is essential for development of pathology. IL-17A directly influences activation and extracellular matrix production by lung mesenchymal cells. Lung CD11c+ cells of BMT mice secrete more TGF-β1, and pro-TH17 mRNAs for IL-23 and IL-6, and less TH1-promoting cytokine mRNA for IFN-γ but slightly more IL-12 mRNA in response to viral infection. Adoptive transfer of non-BMT lung CD11c-enriched cells restores robust TH1 response and suppresses aberrant TH17 response in BMT mice to improve lung pathology. Our data suggest “non-infectious” HSCT lung complications may reflect preceding viral infections and demonstrate that IL-17A neutralization may offer therapeutic advantage even after disease onset.

The Lung Microbiome, Immunity, and the Pathogenesis of Chronic Lung Disease

“…It is possible that IL-17 responses arising in the gut may further impact lung disease (114). IL-17 is involved in the elimination of certain pathogens (115) and is implicated in the pathogenesis of several pulmonary pathologies including asthma, Sarcoidosis, Obliterative Bronchiolitis, CF and bone marrow transplant related pneumonitis(116–120). …”

“…The neutralization of IL-17 in mice harboring microbiota led to dampened inflammation and reduced disease burden (121). Several studies have implicated IL-17 in hepatic fibrosis, and certain experimental models of pulmonary fibrosis are IL-17A dependent (120, 122, 123). Furthermore, studies examining the development of intestinal fibrosis have reported an association with alterations in the microbiota and Th17 responses (124).…”

Adoptive Transfer of Lung Antigen Presenting Cells

“…Single cell suspension was prepared from the lungs of C57BL/6 mice three days post infection of murine gamma herpesvirus 68 (MHV-68) intranasal at a dose of 5 × 10 4 pfu/mouse (Zhou, et al 2016). CD11c + cells were then enriched by using anti-mouse CD11c microbeads.…”

“…We developed a protocol of isolating lung APCs from normal mice and then adoptively transferring them to syngeneic bone marrow transplanted mice. We used this protocol to determine whether normal lung APCs are sufficient to restore T helper cell polarization in response to herpesvirus infection post-transplant (Zhou et al ., 2016). …”

Lung Section Staining and Microscopy

“…To study lung development or lung diseases in mouse models, the lungs can be removed from mice and either frozen and embedded in optimal cutting temperature (OCT) compound or chemically preserved and embedded in paraffin. To preserve lung tissue architecture, we filled the lung with 1 ml of OCT compound for preparing frozen sections, or 10% buffered formalin for paraffin sections (Zhou et al , 2016). Lung sections are then sliced from frozen or paraffin-embedded lungs and mounted onto slides for preparation of staining.…”