A Microengineered Airway Lung Chip Models Key Features of Viral-induced Exacerbation of Asthma.

Viral-induced exacerbation of asthma remains a major cause of hospitalization and mortality. New human-relevant models of the airways are urgently needed to understand how respiratory infections may trigger asthma attacks and to advance treatment development. Here, we describe a new human-relevant model of rhinovirus-induced asthma exacerbation that recapitulates viral infection of asthmatic airway epithelium and neutrophil transepithelial migration, and enables evaluation of immunomodulatory therapy. Specifically, a microengineered model of fully differentiated human mucociliary airway epithelium was stimulated with IL-13 to induce a T-helper cell type 2 asthmatic phenotype and infected with live human rhinovirus 16 (HRV16) to reproduce key features of viral-induced asthma exacerbation. We observed that the infection with HRV16 replicated key hallmarks of the cytopathology and inflammatory responses observed in human airways. Generation of a T-helper cell type 2 microenvironment through exogenous IL-13 stimulation induced features of asthmatic airways, including goblet cell hyperplasia, reduction of cilia beating frequency, and endothelial activation, but did not alter rhinovirus infectivity or replication. High-resolution kinetic analysis of secreted inflammatory markers revealed that IL-13 treatment altered IL-6, IFN-λ1, and CXCL10 secretion in response to HRV16. Neutrophil transepithelial migration was greatest when viral infection was combined with IL-13 treatment, whereas treatment with MK-7123, a CXCR2 antagonist, reduced neutrophil diapedesis in all conditions. In conclusion, our microengineered Airway Lung-Chip provides a novel human-relevant platform for exploring the complex mechanisms underlying viral-induced asthma exacerbation. Our data suggest that IL-13 may impair the hosts' ability to mount an appropriate and coordinated immune response to rhinovirus infection. We also show that the Airway Lung-Chip can be used to assess the efficacy of modulators of the immune response.

HOIL1 mediates MDA5 activation through ubiquitination of LGP2.

The RIG-I-like receptors (RLRs), RIG-I and MDA5, are innate sensors of RNA virus infections that are critical for mounting a robust antiviral immune response. We have shown previously that HOIL1, a component of the Linear Ubiquitin Chain Assembly Complex (LUBAC), is essential for interferon (IFN) induction in response to viruses sensed by MDA5, but not for viruses sensed by RIG-I. LUBAC contains two unusual E3 ubiquitin ligases, HOIL1 and HOIP. HOIP generates methionine-1-linked polyubiquitin chains, whereas HOIL1 has recently been shown to conjugate ubiquitin onto serine and threonine residues. Here, we examined the differential requirement for HOIL1 and HOIP E3 ligase activities in RLR-mediated IFN induction. We determined that HOIL1 E3 ligase activity was critical for MDA5-dependent IFN induction, while HOIP E3 ligase activity played only a modest role in promoting IFN induction. HOIL1 E3 ligase promoted MDA5 oligomerization, its translocation to mitochondrial-associated membranes, and the formation of MAVS aggregates. We identified that HOIL1 can interact with and facilitate the ubiquitination of LGP2, a positive regulator of MDA5 oligomerization. In summary, our work identifies LGP2 ubiquitination by HOIL1 in facilitating the activation of MDA5 and the induction of a robust IFN response.