Type 2 inflammation reduces SARS-CoV-2 replication in the airway epithelium in allergic asthma through functional alteration of ciliated epithelial cells

BACKGROUND

Despite well-known susceptibilities to other respiratory viral infections, individuals with allergic asthma have shown reduced susceptibility to severe coronavirus disease 2019 (COVID-19).

OBJECTIVE

We sought to identify mechanisms whereby type 2 inflammation in the airway protects against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by using bronchial airway epithelial cells (AECs) from aeroallergen-sensitized children with asthma and healthy nonsensitized children.

METHODS

We measured SARS-CoV-2 replication and ACE2 protein and performed bulk and single-cell RNA sequencing of ex vivo infected AEC samples with SARS-CoV-2 infection and with or without IL-13 treatment.

RESULTS

We observed that viral replication was lower in AECs from children with allergic asthma than those from in healthy nonsensitized children and that IL-13 treatment reduced viral replication only in children with allergic asthma and not in healthy children. Lower viral transcript levels were associated with a downregulation of functional pathways of the ciliated epithelium related to differentiation as well as cilia and axoneme production and function, rather than lower ACE2 expression or increases in goblet cells or mucus secretion pathways. Moreover, single-cell RNA sequencing identified specific subsets of relatively undifferentiated ciliated epithelium (which are common in allergic asthma and highly responsive to IL-13) that directly accounted for impaired viral replication.

CONCLUSION

Our results identify a novel mechanism of innate protection against SARS-CoV-2 in allergic asthma that provides important molecular and clinical insights during the ongoing COVID-19 pandemic.

Temperature synchronisation of circadian rhythms in primary human airway epithelial cells from children

INTRODUCTION

Cellular circadian rhythms regulate immune pathways and inflammatory responses that mediate human disease such as asthma. Circadian rhythms in the lung may also contribute to exacerbations of chronic diseases such as asthma by regulating observed rhythms in mucus production, bronchial reactivity, airway inflammation and airway resistance. Primary human airway epithelial cells (AECs) are commonly used to model human lung diseases, such as asthma, with circadian symptoms, but a method for synchronising circadian rhythms in AECs has not been developed, and the presence of circadian rhythms in human AECs remains uninvestigated.

METHODS

We used temperature cycling to synchronise circadian rhythms in undifferentiated and differentiated primary human AECs. Reverse transcriptase-quantitative PCR was used to measure expression of the core circadian clock genes ARNTL, CLOCK, CRY1, CRY2, NR1D1, NR1D2, PER1 and PER2.

RESULTS

Following temperature synchronisation, the core circadian genes ARNTL, CRY1, CRY2, NR1D1, NR1D2, PER1 and PER2 maintained endogenous 24-hour rhythms under constant conditions. Following serum shock, the core circadian genes ARNTL, NR1D1 and NR1D2 demonstrated rhythmic expression. Following temperature synchronisation, CXCL8 demonstrated rhythmic circadian expression.

CONCLUSIONS

Temperature synchronised circadian rhythms in AECs differentiated at an air-liquid interface can serve as a model to investigate circadian rhythms in pulmonary diseases.

IgM antibodies derived from memory B cells are potent cross-variant neutralizers of SARS-CoV-2

Humoral immunity to SARS-CoV-2 can be supplemented with polyclonal sera from convalescent donors or an engineered monoclonal antibody (mAb) product. While pentameric IgM antibodies are responsible for much of convalescent sera's neutralizing capacity, all available mAbs are based on the monomeric IgG antibody subtype. We now show that IgM mAbs derived from immune memory B cell receptors are potent neutralizers of SARS-CoV-2. IgM mAbs outperformed clonally identical IgG antibodies across a range of affinities and SARS-CoV-2 receptor-binding domain epitopes. Strikingly, efficacy against SARS-CoV-2 viral variants was retained for IgM but not for clonally identical IgG. To investigate the biological role for IgM memory in SARS-CoV-2, we also generated IgM mAbs from antigen-experienced IgM+ memory B cells in convalescent donors, identifying a potent neutralizing antibody. Our results highlight the therapeutic potential of IgM mAbs and inform our understanding of the role for IgM memory against a rapidly mutating pathogen.

Highly synergistic combinations of nanobodies that target SARS-CoV-2 and are resistant to escape

The emergence of SARS-CoV-2 variants threatens current vaccines and therapeutic antibodies and urgently demands powerful new therapeutics that can resist viral escape. We therefore generated a large nanobody repertoire to saturate the distinct and highly conserved available epitope space of SARS-CoV-2 spike, including the S1 receptor binding domain, N-terminal domain, and the S2 subunit, to identify new nanobody binding sites that may reflect novel mechanisms of viral neutralization. Structural mapping and functional assays show that indeed these highly stable monovalent nanobodies potently inhibit SARS-CoV-2 infection, display numerous neutralization mechanisms, are effective against emerging variants of concern, and are resistant to mutational escape. Rational combinations of these nanobodies that bind to distinct sites within and between spike subunits exhibit extraordinary synergy and suggest multiple tailored therapeutic and prophylactic strategies.

Airway epithelial interferon response to SARS-CoV-2 is inferior to rhinovirus and heterologous rhinovirus infection suppresses SARS-CoV-2 replication

INTRODUCTION

Common alphacoronaviruses and human rhinoviruses (HRV) induce type I and III interferon (IFN) responses important to limiting viral replication in the airway epithelium. In contrast, highly pathogenic betacoronaviruses including SARS-CoV-2 may evade or antagonize RNA-induced IFN I/III responses.

METHODS

In airway epithelial cells (AECs) from children and older adults we compared IFN I/III responses to SARS-CoV-2 and HRV-16, and assessed whether pre-infection with HRV-16, or pretreatment with recombinant IFN-β or IFN-λ, modified SARS-CoV-2 replication. Bronchial AECs from children (ages 6-18 yrs.) and older adults (ages 60-75 yrs.) were differentiated ex vivo to generate organotypic cultures. In a biosafety level 3 (BSL-3) facility, cultures were infected with SARS-CoV-2 or HRV-16, and RNA and protein was harvested from cell lysates 96 hrs. following infection and supernatant was collected 48 and 96 hrs. following infection. In additional experiments cultures were pre-infected with HRV-16, or pre-treated with recombinant IFN-β1 or IFN-λ2 before SARS-CoV-2 infection.

RESULTS

Despite significant between-donor heterogeneity SARS-CoV-2 replicated 100 times more efficiently than HRV-16. IFNB1, INFL2, and CXCL10 gene expression and protein production following HRV-16 infection was significantly greater than following SARS-CoV-2. IFN gene expression and protein production were inversely correlated with SARS-CoV-2 replication. Treatment of cultures with recombinant IFNβ1 or IFNλ2, or pre-infection of cultures with HRV-16, markedly reduced SARS-CoV-2 replication.

DISCUSSION

In addition to marked between-donor heterogeneity in IFN responses and viral replication, SARS-CoV-2 elicits a less robust IFN response in primary AEC cultures than does rhinovirus, and heterologous rhinovirus infection, or treatment with recombinant IFN-β1 or IFN-λ2, markedly reduces SARS-CoV-2 replication.

Effect of Angiotensin-Converting-Enzyme Inhibitor and Angiotensin II Receptor Antagonist Treatment on ACE2 Expression and SARS-CoV-2 Replication in Primary Airway Epithelial Cells

Rationale: SARS-CoV-2 gains entrance to airway epithelial cells (AECs) through binding of the viral spike protein to the angiotensin-converting enzyme 2 (ACE2) on the cell surface. However, ACE2 also converts angiotensin II into angiotensin-(1-7) and counterbalances the renin-angiotensin-aldosterone system, with resultant protective effects in the cardiovascular system. Some data suggest that two common antihypertension medications (angiotensin II receptor antagonists, ARBs; and angiotensin-converting-enzyme inhibitors, ACEIs) may increase ACE2 expression in heart and kidney cells, fueling debate about how these widely used medications may modulate SARS-CoV-2 infectivity and risk of COVID-19. Aim: Determine whether exposure of bronchial AECs to the ARB losartan or the ACEI captopril modulate expression of ACE2 by AECs, SARS CoV2 replication, or expression of proinflammatory cytokines and type I and III interferon (IFN) responses. Methods: Primary bronchial AECs from children and adults (n = 19; Ages 8-75 yrs) were differentiated ex vivo at an air-liquid interface to generate organotypic cultures. Cultures were treated with captopril (1 μM) or losartan (2 μM) with culture media changes starting 72 h before infection with SARS-CoV-2. In a biosafety level 3 (BSL-3) facility, cultures were infected with SARS-CoV-2 isolate USA-WA1/2020 at a multiplicity of infection (MOI) of 0.5. At 96 h following infection, RNA and protein were isolated. SARS-CoV-2 replication in cultures was assessed with quantitative PCR (qPCR). ACE2, IL-6, IL-1B, IFNB1, and IFNL2 expression were assessed by qPCR. Results: Neither captopril nor losartan treatment significantly changed ACE2, IL-6, IL-1B, IFNB1, or IFNL2 expression by AECs as compared to SARS-CoV-2 infected AEC cultures without captopril or losartan treatment. At 96 h following infection, SARS-CoV-2 copy number/ng RNA was not significantly different between untreated AEC cultures, cultures treated with captopril, or cultures treated with losartan. Conclusion: These findings suggest that at the level of the airway epithelium neither the ACEI captopril or ARB losartan significantly modify expression of the SARS-CoV-2 entry factor ACE2, nor does either medication increase replication SARS-CoV-2 replication. This ex vivo data is reassuring and is consistent with evolving clinical data suggesting ACEIs and ARBs do not increase the risk for poor prognosis with COVID-19 and may actually reduce the risk of COVID-19 disease.

Nanobody Repertoires for Exposing Vulnerabilities of SARS-CoV-2

Despite the great promise of vaccines, the COVID-19 pandemic is ongoing and future serious outbreaks are highly likely, so that multi-pronged containment strategies will be required for many years. Nanobodies are the smallest naturally occurring single domain antigen binding proteins identified to date, possessing numerous properties advantageous to their production and use. We present a large repertoire of high affinity nanobodies against SARS-CoV-2 Spike protein with excellent kinetic and viral neutralization properties, which can be strongly enhanced with oligomerization. This repertoire samples the epitope landscape of the Spike ectodomain inside and outside the receptor binding domain, recognizing a multitude of distinct epitopes and revealing multiple neutralization targets of pseudoviruses and authentic SARS-CoV-2, including in primary human airway epithelial cells. Combinatorial nanobody mixtures show highly synergistic activities, and are resistant to mutational escape and emerging viral variants of concern. These nanobodies establish an exceptional resource for superior COVID-19 prophylactics and therapeutics.

Inactivation of Material from SARS-CoV-2-Infected Primary Airway Epithelial Cell Cultures

Given that the airway epithelium is the initial site of infection, study of primary human airway epithelial cells (AEC) infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) will be crucial to improved understanding of viral entry factors and innate immune responses to the virus. Centers for Disease Control and Prevention (CDC) guidance recommends work with live SARS-CoV-2 in cell culture be conducted in a Biosafety Level 3 (BSL-3) laboratory. To facilitate downstream assays of materials from experiments there is a need for validated protocols for SARS-CoV-2 inactivation to facilitate safe transfer of material out of a BSL-3 laboratory. We propagated stocks of SARS-CoV-2, then evaluated the effectiveness of heat (65 °C) or ultraviolet (UV) light inactivation. We infected differentiated human primary AECs with SARS-CoV-2, then tested protocols designed to inactivate SARS-CoV-2 in supernatant, protein isolate, RNA, and cells fixed for immunohistochemistry by exposing Vero E6 cells to materials isolated/treated using these protocols. Heating to 65 °C for 10 min or exposing to UV light fully inactivated SARS-CoV-2. Furthermore, we found in SARS-CoV-2-infected primary AEC cultures that treatment of supernatant with UV light, isolation of RNA with Trizol^®, isolation of protein using a protocol including sodium dodecyl sulfate (SDS) 0.1% and Triton X100 1%, and fixation of AECs using 10% formalin and Triton X100 1%, each fully inactivated SARS-CoV-2.