Daily Respiratory Research Analysis
Three studies stand out today: a meta-analysis quantifying the global hospitalization burden of human metapneumovirus in older adults, a shark-derived broadly neutralizing nanobody targeting a conserved S2 HR1 epitope across sarbecoviruses with intranasal protection in vivo, and a diagnostic study showing metagenomic sequencing of BALF greatly improves detection of smear-negative pulmonary tuberculosis. Together they span prevention, therapeutics, and diagnostics in respiratory medicine.
Summary
Three studies stand out today: a meta-analysis quantifying the global hospitalization burden of human metapneumovirus in older adults, a shark-derived broadly neutralizing nanobody targeting a conserved S2 HR1 epitope across sarbecoviruses with intranasal protection in vivo, and a diagnostic study showing metagenomic sequencing of BALF greatly improves detection of smear-negative pulmonary tuberculosis. Together they span prevention, therapeutics, and diagnostics in respiratory medicine.
Research Themes
- Global burden and surveillance of respiratory viral infections in older adults
- Broadly neutralizing biologics targeting conserved coronavirus epitopes
- Next-generation sequencing to close diagnostic gaps in pulmonary tuberculosis
Selected Articles
1. The global burden of human metapneumovirus-associated acute respiratory infections in older adults: a systematic review and meta-analysis.
This PROSPERO-registered meta-analysis estimated that hMPV accounts for approximately 473,000 hospitalisations in adults ≥65 years globally in 2019, with a pooled US rate of 231 per 100,000. Data scarcity outside hospitals highlights the need for expanded surveillance and improved diagnostics.
Impact: Quantifying hMPV burden in older adults fills a key evidence gap and informs vaccine prioritization, surveillance, and resource allocation for respiratory illness seasons.
Clinical Implications: Clinicians should consider hMPV in differential diagnoses of severe ARIs in older adults and advocate for expanded testing and surveillance; policymakers can use these estimates to guide vaccine development and preparedness planning.
Key Findings
- Estimated 473,000 hMPV-associated hospitalisations globally in adults ≥65 years in 2019
- Pooled US hospitalisation rate: 231 per 100,000 older adults (≈122,000 admissions)
- Higher absolute burden in LMICs (≈288,000) than HICs (≈185,000)
- Substantial data gaps in outpatient/community settings limit incidence estimation
Methodological Strengths
- Comprehensive multi-database search with PROSPERO-registered protocol
- Random-effects meta-analysis and Monte Carlo simulation for burden estimation
- Critical appraisal using Joanna Briggs Institute tools
Limitations
- Heterogeneity across studies and limited outpatient/community data
- Burden estimates rely on proportion positive and extrapolation, which may bias absolute numbers
Future Directions: Establish large-scale, year-round surveillance including outpatient settings; improve diagnostics; and evaluate candidate hMPV vaccines in older adults.
BACKGROUND: The human metapneumovirus (hMPV)-associated disease burden in older adults remains under-researched. We aimed to systematically estimate the global burden of hMPV-associated disease in older adults. METHODS: We searched MEDLINE, Embase, Global Health, CINAHL, Web of Science, and Global Index Medicus in February, 2023, November, 2023, and October, 2024; and CNKI, Wanfang, and CQVip, in April, 2024, and October, 2024. We included studies conducted over at least 12 consecutive months, reporting on adults aged 60 years or older, and with laboratory-confirmed hMPV infections. Critical appraisal of included studies was conducted using the Joanna Briggs Institute critical appraisal tools. To estimate the hMPV pooled proportions positive in acute respiratory infections (ARIs), random effects meta-analyses were conducted. Using Monte Carlo simulation, we estimated the hMPV-associated hospitalisations globally and separately in high-income countries, low-income and middle-income countries, and the USA in individuals aged 65 years or older in 2019, as most studies reported on this age group. The hMPV-associated ARI incidence in countries other than the USA and in outpatient or community settings in the USA was summarised narratively due to scarcity of data. The review protocol was registered on PROSPERO (CRD42023422325). FINDINGS: 46 studies conducted between 2005 and 2023, and reporting on hMPV proportion positive estimates (n=36, with 29 866 laboratory tests), hospitalisation rates in the USA (n=4), and hMPV incidence (n=6) were included. We estimated 473 000 (95% CI 396 000-777 000) hMPV-associated hospitalisations globally, of which 185 000 (105 000-340 000) were in high-income countries (n=6 studies), and 288 000 (193 000-436 000) in low-income and middle-income countries (n=10 studies) in people aged 65 years or older in 2019. In the USA, the pooled hMPV-associated hospitalisation rate was 231 (95% CI 41-421) per 100 000 people in adults aged 65 years or older, representing approximately 122 000 (41 000-398 000) hospital admissions in this population in 2019. INTERPRETATION: hMPV-associated ARIs contribute to a substantial disease and hospitalisation burden in older adults. However, more large-scale surveillance studies and greater investment in research and diagnostic methods are required to develop reliable estimates. FUNDING: Icosavax, a member of the AstraZeneca group.
2. A shark-derived broadly neutralizing nanobody targeting a highly conserved epitope on the S2 domain of sarbecoviruses.
The shark-derived nanobody 79C11 neutralized all tested Omicron subvariants and related sarbecoviruses, protected against XBB infection via intranasal administration in vivo, and targets a conserved S2 HR1 epitope. Multivalent engineering further enhanced potency, supporting prospects for universal vaccine design and intranasal prophylaxis.
Impact: Demonstrates a conserved S2 HR1 targetable epitope and a single-domain biologic with cross-sarbecovirus breadth and in vivo protection, addressing antigenic drift that undermines RBD-directed antibodies.
Clinical Implications: If translated to humans, intranasal nanobody prophylaxis could provide pre- or post-exposure protection against current and future SARS-CoV-2 variants and zoonotic sarbecoviruses; however, pharmacokinetics, immunogenicity, dosing, and safety require rigorous clinical evaluation.
Key Findings
- Nanobody 79C11 neutralized Omicron subvariants from BA.1 to JN.1 and KP.2, and also SARS-CoV-1 and pangolin coronavirus
- Intranasal 79C11 prevented infection with Omicron XBB in vivo
- Multivalent formats enhanced binding and neutralization potency
- Epitope mapping identified a highly conserved HR1 region in the S2 domain as the target
Methodological Strengths
- Combines epitope mapping and structural simulation with in vitro neutralization
- Demonstrates in vivo protection via intranasal delivery
- Explores multivalent engineering to enhance potency
Limitations
- Preclinical study; no human pharmacokinetic or safety data
- Potential for viral escape and durability of protection not fully assessed
Future Directions: Humanization and developability assessment, intranasal PK/PD and safety studies, and early-phase clinical trials; evaluate combinations with other broadly neutralizing agents.
The continuously evolving Omicron subvariants has diminished the effectiveness of almost all RBD-targeted antibodies in neutralizing these subvariants. The development of broad-spectrum neutralizing antibodies is desired for addressing both current and future variants. Here, we identified a shark-derived nanobody, 79C11, that can neutralize all Omicron subvariants tested so far, including BA.1 to JN.1 and KP.2, and exhibits comparable neutralizing potency against SARS-CoV-1 and pangolin coronavirus. Intranasal instillation of 79C11 can effectively prevent the infection of Omicron subvariant XBB in vivo. The designs of multivalent forms of 79C11 further enhance binding and neutralizing activity. Epitope mapping and structure simulation reveal that this nanobody binds to a highly conserved HR1 region in S2 domain of the spikes from all sarbecoviruses, suggesting that a universal vaccine may be designed to target this region for eliciting broadly neutralizing antibody response. This nanobody can also be developed as an intranasally administered prophylactic agent for preventing the infection of current and likely future SARS-CoV-2 variants, as well as other animal derived sarbecoviruses that may infect humans.
3. Metagenomic next-generation sequencing of bronchoalveolar lavage fluid samples offers diagnostic utility in bacteriologically negative pulmonary tuberculosis.
In 300 hospitalized, bacteriologically negative suspected PTB cases, BALF mNGS achieved 94.6% sensitivity and 98.9% specificity against clinical diagnosis and outperformed AFS, culture, and Xpert. Findings support integrating mNGS into diagnostic pathways for smear-negative PTB.
Impact: Addresses a critical diagnostic gap in smear-negative PTB and demonstrates clear superiority over existing methods, enabling earlier, accurate treatment.
Clinical Implications: Consider BALF mNGS for high-suspicion, bacteriologically negative PTB to expedite diagnosis; implementation should weigh invasiveness, turnaround time, and costs within local workflows.
Key Findings
- BALF mNGS sensitivity 94.64% (106/112) and specificity 98.94% (186/188) versus clinical diagnosis
- Outperformed AFS, Roche culture, and Xpert in sensitivity, specificity, PPV, and NPV (p < 0.05)
- Study included 300 bacteriologically negative suspected PTB patients (112 PTB, 188 non-PTB)
- High diagnostic accuracy supports use in smear-negative PTB pathways
Methodological Strengths
- Head-to-head comparison with standard methods using a clinical gold standard
- Relatively large sample with predefined inclusion period
- Reporting of full diagnostic metrics including AUC
Limitations
- Single-center hospitalized cohort and use of BALF (invasive sampling) may limit generalizability
- Cost, turnaround time, and access to mNGS were not evaluated
Future Directions: Multicenter cost-effectiveness studies, evaluation on less invasive specimens, and integration into tiered diagnostic algorithms with clinical decision support.
Rapid diagnosing Mycobacterium tuberculosis (M. tb) in patients with pulmonary tuberculosis (PTB) cases is critical, particularly in cases without bacteriologically confirmed disease, as it enables timely treatment initiation and can thus interrupt further disease transmission. In this study, the utility of metagenomic next-generation sequencing (mNGS) as a diagnostic tool was evaluated using samples of bronchoalveolar lavage fluid (BALF) samples from 300 bacteriologically negative PTB (BN-PTB) patients hospitalized from January 2020 through December 2023. The diagnostic performance of mNGS was compared to that of acid-fast staining (AFS), conventional Roche culture, and the Xpert method among these BN-PTB patients, using clinical diagnosis as the gold standard. The final analyses enrolled 112 PTB patients and 188 non-PTB cases. These analyses revealed that mNGS-based M. tb detection yields a sensitivity of 94.64 % (106/112), a specificity of 98.94 % (186/188), a positive predictive value (PPV) of 98.15 % (106/108), and a negative predictive value (NPV) of 96.88 % (186/192). This mNGS approach outperformed the AFS, Roche culture, and Xpert methods in terms of sensitivity, specificity, PPV, and NPV (p < 0.05). The superior diagnostic performance of this approach was further supported by its area under the curve and corresponding confidence intervals. Together, these data demonstrate that mNGS can improve the detection of M. tb in BALF samples from BN-PTB patients with high levels of speed, sensitivity, and specificity. This mNGS approach may thus be a valuable diagnostic tool for the rapid detection of M. tb in BN-PTB, providing a foundation for the precision diagnosis and treatment of PTB in the future.