Daily Respiratory Research Analysis
Three impactful respiratory studies span mechanism to implementation: (1) genome-wide CRISPR screens identify glycosylphosphatidylinositol (GPI) biosynthesis as a conserved host defense against coronaviruses via regulation of LY6E; (2) dual inhibition of TMPRSS2 and cathepsin B/L (camostat + K11777) synergistically blocks SARS-CoV-2 entry in vitro and in vivo by targeting S2' cleavage; (3) adopting anti-inflammatory reliever (AIR)–based regional asthma guidelines in England accelerates reduction
Summary
Three impactful respiratory studies span mechanism to implementation: (1) genome-wide CRISPR screens identify glycosylphosphatidylinositol (GPI) biosynthesis as a conserved host defense against coronaviruses via regulation of LY6E; (2) dual inhibition of TMPRSS2 and cathepsin B/L (camostat + K11777) synergistically blocks SARS-CoV-2 entry in vitro and in vivo by targeting S2' cleavage; (3) adopting anti-inflammatory reliever (AIR)–based regional asthma guidelines in England accelerates reductions in SABA prescribing in interrupted time series analyses.
Research Themes
- Host-virus interactions and intrinsic antiviral restriction factors
- Host-targeted antiviral therapeutics and entry inhibition
- Implementation science: asthma guideline adoption and prescribing behavior
Selected Articles
1. Glycosylphosphatidylinositol biosynthesis functions as a conserved host defense pathway against coronaviruses via regulation of LY6E.
Genome-wide CRISPR knockout screens across three coronaviruses revealed that GPI biosynthesis acts as a conserved host restriction pathway by impeding spike-mediated membrane fusion at endosomal and plasma membranes. A focused screen of GPI-anchored proteins pinpointed LY6E as the key downstream effector mediating this antiviral effect.
Impact: Identifying a conserved host defense pathway and its effector (LY6E) across diverse coronaviruses provides a mechanistic foundation for host-targeted antivirals with potential pan-coronavirus activity.
Clinical Implications: While preclinical, these findings nominate GPI biosynthesis/LY6E as tractable targets to modulate coronavirus entry; pharmacologic enhancement of LY6E activity or mimicking GPI-AP effects could complement vaccine and direct-acting antiviral strategies.
Key Findings
- Genome-wide CRISPR screens identified GPI biosynthesis as a pan-coronavirus host restriction pathway.
- GPI biosynthesis restricts viral entry by disrupting spike-mediated membrane fusion at endosomal and plasma membranes.
- Focused CRISPR knockout of 193 GPI-anchored proteins identified LY6E as the key downstream effector mediating antiviral activity.
Methodological Strengths
- Genome-wide CRISPR knockout screens across multiple coronaviruses enable unbiased discovery of conserved host restriction factors.
- Orthogonal focused screens of GPI-anchored proteins provide mechanistic resolution and identify a specific effector (LY6E).
Limitations
- Findings are primarily from cell-based systems; in vivo validation in animal models or human tissues is needed.
- Potential pleiotropic effects of modulating GPI biosynthesis and GPI-APs could limit therapeutic windows.
Future Directions: Validate LY6E/GPI-AP–mediated restriction in primary human airway epithelium and in vivo; explore small-molecule or biologic strategies to enhance LY6E function or mimic GPI-AP-mediated entry restriction.
Coronaviruses, including SARS-CoV-2, rely on host factors for their replication and pathogenesis, while hosts deploy defense mechanisms to counteract viral infections. Although numerous host proviral factors have been identified, the landscape of host restriction factors and their underlying mechanisms remain less explored. Here, we conducted genome-wide CRISPR knockout screens using three distinct coronaviruses-SARS-CoV-2, HCoV-OC43 (a common cold human virus from the genus Betacoronavirus) and porcine epidemic diarrhea virus (Alphacoronavirus) to identify conserved host restriction factors. We identified glycosylphosphatidylinositol (GPI) biosynthesis as the pan-coronavirus host factor that restrict viral entry by disrupting spike protein-mediated membrane fusion at both endosomal and plasma membranes. GPI biosynthesis generates GPI moieties that covalently anchor proteins (GPI-anchored proteins [GPI-APs]) to the cell membrane, playing essential roles in various cellular processes. Through focused CRISPR knockout screens targeting 193 GPI-APs, we identified LY6E, a known pan-coronavirus restriction factor for viral entry, as the key downstream effector mediating the antiviral activity of the GPI biosynthesis pathway. These findings reveal the role for GPI biosynthesis as a conserved host defense mechanism against coronaviruses via regulation of downstream effectors.
2. Synergistic antiviral activity of a cathepsin B/L inhibitor and a TMPRSS2 inhibitor against SARS-CoV-2 in vitro and in vivo.
Camostat (TMPRSS2 inhibitor) and K11777 (cathepsin B/L inhibitor) exhibit complementary activity against SARS-CoV-2 variants differing at the furin cleavage site, with escape mapping implicating S2' cathepsin L-mediated cleavage. Combined inhibition potently suppresses infection in vitro and in vivo, supporting host-targeted combination entry therapy.
Impact: Defines S2' cleavage as a critical node for SARS-CoV-2 entry and demonstrates preclinical efficacy of dual host protease inhibition, informing rational combination strategies resilient to spike processing variation.
Clinical Implications: Combination host protease inhibition could broaden antiviral coverage across variants and reduce resistance; translational studies should assess safety, PK/PD, and efficacy in humans.
Key Findings
- Camostat potently inhibits WT SARS-CoV-2 but not a furin cleavage site-deleted mutant (del2), whereas K11777 is potent against del2.
- K11777-escape mutants facilitate S2' site cleavage by cathepsin L, underscoring the functional importance of S2' processing.
- Combined K11777 + camostat treatment strongly inhibits WT SARS-CoV-2 infection in vitro and in vivo.
Methodological Strengths
- Use of both WT and furin site-deleted mutant viruses across multiple cell systems enables pathway dissection.
- Integration of escape mutant mapping and in vivo validation strengthens causal inference and translational relevance.
Limitations
- Host protease inhibition may entail off-target and safety liabilities not addressed here.
- Animal model details and human translational data are limited; dosing and therapeutic windows require definition.
Future Directions: Advance to translational studies evaluating safety/PK of camostat + K11777, explore inhaled delivery to the airway, and test breadth against emergent variants and clinical isolates.
The spike (S) protein of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) binds to a host cell receptor which dictates the viral entry pathway. SARS-CoV-2 utilizes two different pathways for cellular entry mediated by both a host type II transmembrane serine protease (TMPRSS2) and cathepsin proteases. These host proteases cleave the viral S protein and initiate membrane fusion allowing viral infection. We previously isolated a SARS-CoV-2 mutant with deletion in the furin cleavage site of the S gene (del2) and revealed differences in cell tropism between wild-type (WT) and del2 viruses. Here, we evaluated the antiviral activities of cellular protease inhibitors against SARS-CoV-2 WT and del2 viruses using several different cell lines. The TMPRSS2 inhibitor, camostat, exhibited strong antiviral activity against WT virus but not del2, while the cathepsin B/L inhibitor, K11777, exhibited potent antiviral activity against the del2 virus. We isolated K11777-escape mutants of SARS-CoV-2 and SARS-CoV and demonstrated that these mutations facilitated S protein cleavage at the S2' site mediated by cathepsin L. Finally, we demonstrated that combination treatment of K11777 and camostat potently inhibited SARS-CoV-2 WT infection in vitro and in vivo, suggesting the usefulness of combination therapeutics targeting host TMPRSS2 and cathepsin proteases against coronavirus infection. In summary, our study characterized K11777 as an inhibitor of S2' cleavage by cathepsins, highlighting the critical role of the S2' site in SARS-CoV-2 cellular entry. This research sheds light on the infection process and has implications for potential therapeutic interventions for SARS-CoV-2 infection.
3. Impact of regional asthma guidelines on SABA prescribing patterns across England: an interrupted time series analysis.
Reviewing 34 English regional asthma guidelines and applying interrupted time series analyses, AIR-based guidance was associated with the steepest monthly declines in SABA prescribing compared with SABA-first or ICS+SABA strategies. Findings support aligning regional policies with national AIR recommendations to curb SABA overuse.
Impact: Demonstrates at scale that guideline content influences prescribing behavior; provides policy-relevant evidence to accelerate adoption of AIR-based management and reduce SABA overuse.
Clinical Implications: Health systems should prioritize AIR-based initial management in regional guidance, monitor SABA-to-ICS prescribing ratios, and couple implementation with education and audit to improve outcomes.
Key Findings
- Regional guidelines were categorized into SABA-first, ICS+SABA, and AIR based on initial treatment recommendations.
- AIR guideline publication was associated with the largest monthly decline in SABA prescribing proportion (−0.26% per month), exceeding SABA-first (−0.10% per month) and ICS+SABA (−0.16% per month).
- Interrupted time series analyses using public data indicate guideline content measurably shifts prescribing patterns.
Methodological Strengths
- Interrupted time series design strengthens causal inference for policy impact using longitudinal population-level data.
- Systematic classification of 34 regional guidelines allows comparative policy evaluation.
Limitations
- Ecological design lacks patient-level outcomes; unmeasured co-interventions or secular trends may confound estimates.
- Heterogeneity in regional implementation fidelity and timing may influence effect sizes.
Future Directions: Link prescribing shifts to patient outcomes (exacerbations, ED visits, hospitalizations), assess equity and acceptability, and evaluate implementation strategies to scale AIR adoption.
The 2024 British Thoracic Society/ National Institute for Health and Care Excellence/ Scottish Intercollegiate Guidelines Network asthma guidelines recommend anti-inflammatory reliever (AIR)-based management, providing opportunity to reduce short-acting beta agonist (SABA) over-use. Many English regions also publish local guidelines. Analysis of 34 regional guidelines enabled grouping into three categories: SABA-first, inhaled corticosteroid (ICS) plus SABA and AIR (as-needed AIR), based on recommended initial treatment. Interrupted time series analysis using publicly available data demonstrated that AIR guideline publication resulted in the greatest decline in SABA prescribing, expressed as the proportion of all ICS-containing and SABA inhaler prescriptions (AIR: -0.26% (SD 0.09%) per month; SABA-first: -0.1% (SD 0.03%) per month, p=0.001 vs AIR; and ICS plus SABA: -0.16% (SD 0.06%) per month, p=0.004, vs AIR). Therefore, regional guidelines do affect local prescribing practice and alignment with the latest national recommendations could improve asthma prescribing and resulting patient outcomes.