hMPV Infection Research Articles

Observational Study on the Clinical Reality of Community-Acquired Respiratory Virus Infections in Adults and Older Individuals

The impact of common respiratory virus infections on adults and older individuals in the community is unclear, excluding seasonal influenza viruses. We examined FilmArray® tests performed on 1828 children aged <10 years and 10,803 adults, including cases with few respiratory symptoms, between January 2021 and June 2024. Approximately 80% of the children tested positive for ≥1 viruses, while 9.5% of the adults tested positive mostly for severe acute respiratory syndrome corona virus-2 (SARS-CoV-2). Besides SARS-CoV-2 infection, 66 out of 97 patients (68.0%) aged >60 years with rhinovirus/enterovirus (RV/EV), respiratory syncytial virus (RSV), parainfluenza virus-3 (PIV-3), or human metapneumovirus (hMPV) infection required hospitalization, of whom seven died; 26 out of 160 patients (16.3%) aged <60 years required hospitalization mostly because of deterioration of bronchial asthma, with no reported deaths. In older patients with RV/EV infection, three with few respiratory symptoms died due to worsened heart failure. Although the frequency of common respiratory virus infections in older adults is low, it may be overlooked because of subclinical respiratory symptoms, and its clinical significance in worsening comorbidities in older adults should not be underestimated.

Demographics, Clinical Presentation and Outcome of Metapneumovirus Infection in Adults: A Case Series Analysis at Scarborough General Hospital, United Kingdom.

Human metapneumovirus (hMPV) was first discovered in 2001 in Netherlands as a leading cause of respiratory infections. hMPV infection is more common in kids, elderly (age ≥ 65) and immuno-compromised adults. Treatment is mainly symptomatic. We collected retrospective data from 31-8-2022 to 01-09-2023 from Microbiology for patients who tested positive for hMPV by polymerase chain reaction (PCR). Only patients aged 18 years and above and admitted to Scarborough General Hospital (SGH) were included in the study. Total patients who tested positive were 38, out of which 73% (n=24) of patients were ≥ 65 years of age. 76.3% (n=29) of these adults were living in their own residence and 53% (n=20) patients never smoked. The most common presentation of these patients was shortness of breath and cough. Fifty-eight percent (n=22) patients had no radiological findings and 74% (n=28) had raised C-reactive protein (CRP). hMPV management was analyzed based on six modalities, we found out that 76% (n=29) patients received antibiotics, 47% (n=18) received nebulizers, 45% (n=17) required oxygen, 37% (n=14) were treated with steroids, 21% (n=8) patients were given inhalers and only one received antivirals. Majority of the patients were discharged and 13% (n=5) of patients died during their inpatient stay. All the deceased patients were aged 65 and above and 80% (n=4) of deceased (n=5) had pre-existing co-morbidities or other acute diagnoses at admission. The patients who tested positive for hMPV were mostly aged ≥ 65 years, 76.3% (n=28) were from personal residence and there was no association of smoking history with hMPV infection. Patients who tested positive for hMPV would mostly present with flu-like symptoms with raised CRP and no radiological manifestation. All these patients were managed conservatively with antibiotics, nebulizers, oxygen, inhalers and antivirals (only one patient). Most of the patients were discharged home and five died during the inpatient stay, all of them were >65 of age and 80% had pre-existing co-morbidities and other acute diagnoses at the time of admission. We could not conclude or hypothesize anything due to small sample size. This data was collected over a one-year period only, and the sample size was very small. Another limitation was that we did not follow up patients after discharge.

Emerging Lineages A2.2.1 and A2.2.2 of Human Metapneumovirus (hMPV) in Paediatric Respiratory Infections: Insights from India"

ObjectiveHuman metapneumovirus (hMPV) is recognized as a significant cause of acute respiratory infections (ARI) among infants under 5 years of age. MethodNasal swabs collected from January 2021 to June 2024 were screened to detect hMPV using RT-qPCR. Further, representative positive samples were sequenced and subjected to phylogenetic analysis. ResultsOut of 4,519 samples tested, 113 were positive for hMPV. Notably, an outbreak occurred between November 2022 and March 2023, where 56 out of 583 patients (9.6%) tested positive. Analysis of the outbreak samples revealed that majority (6.3%) of cases occurred in December and January. hMPV infection was more prevalent in less than 1 year, with clinical manifestations of 29 (67%) patients had a history of wheezing and 3 (6.9%) experienced seizures. On genetic analysis of F protein, 37 samples identified two genotypes as A and B, with sub clusters of 29 (85.29%) samples to A2.1, 1 (2.94%) to A2.2.1and 4 (11.76%) to A2.2.2 within genotype A, and 1 sample clustered with B1 and 2 samples to B2 within genotype B. ConclusionsThe study underscores the significant prevalence and genetic diversity of hMPV among children in Puducherry, India. Notably, the identification of novel A2.2.1 and A2.2.2 lineages highlights the evolving nature of hMPV.

Epidemiology of human metapneumovirus in Taiwan from 2013 to 2023

Human metapneumovirus (HMPV) is a member of the genus Metapneumovirus in the family Pneumoviridae of the order Mononegavirales that can cause upper and lower respiratory tract disease. This retrospective study describes the epidemiology of hMPV based on community viral surveillance results from sentinel sites across Taiwan from 2013 to 2023. A total of 114 hMPV strains were isolated and analyzed to assess viral evolution through sequencing of their fusion protein genes. This study revealed that hMPV cases occur almost year-round in Taiwan, with a peak occurring during spring (March to May). Of the 114 infected patients, 68.4% were children under 4 years old. The geographical distribution of hMPV positivity was highest in Penghu County, followed by Changhua County and Hsinchu County. The clinical symptoms of hMPV infection are nonspecific, with fever (56.1%), cough (44.7%), rhinorrhea (21.1%), and sore throat (14.9%) being the most common. However, a few patients also developed severe central nervous system symptoms (1.8%) or dyspnea (0.9%). Phylogenetic analysis revealed genetic diversity among the 114 isolated hMPV strains, with the A2 lineage (57.9%) being the most frequently observed, followed by the B2 lineage (33.3%), in the Taiwanese community from 2013 to 2023. In conclusion, hMPV causes a serious acute respiratory disease in Taiwan that should not be neglected. Further epidemiological surveillance and investigations of the clinical characteristics of hMPV should be performed continually for prevention and control of this virus.

Exploring Chemical Space to Identify Partial Binders Against hMPV Nucleocapsid Protein.

Human metapneumovirus (hMPV) has gained prominence in recent times as the predominant etiological agent of acute respiratory tract infections. This virus targets children, the elderly, and individuals with compromised immune systems. Given the protracted duration of hMPV transmission, it is probable that the majority of children will have acquired the virus by the age of 5. In individuals with compromised immune systems, recurrence of hMPV infection is possible. As hMPV matures, it remains latent from the time of acquisition. The genome of hMPV encompasses a pivotal protein referred to as the nucleocapsid protein (N). This protein assumes the form of a left-handed helical nucleocapsid, enveloping the viral RNA genome. The primary function of this structure is to protect nucleases, rendering it a potentially promising target for therapeutic advancements. The present study employs a methodology that involves structure-based virtual screening, followed by molecular dynamics simulation at a 250-ns time scale, to identify potential natural molecules or their derivatives from the ZINC Database. These molecules are investigated for their binding properties against the hMPV nucleoprotein. Based on an evaluation of the docking score, binding site interaction, and molecular dynamics studies, it has been found that two naturally occurring molecules, namely M1 (ZINC85629735) and M3 (ZINC85569125), have shown notable docking scores of -9.6and -10.7 kcal/mol, acceptable RMSD, RMSF, Rg, and soon calculated from molecular dynamics trajectory associated with MMGBSA binding energy of -81.94 and -99.63 kcal/mol, respectively. These molecules have shown the highest binding affinity towardnucleocapsid protein and demonstrated promising attributes as potential binders against hMPV.

Changes in the epidemiological patterns of respiratory syncytial virus and human metapneumovirus infection among pediatric patients and their correlation with severe cases: a long-term retrospective study.

We aim to investigate the prevalence of respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) among pediatric patients with acute respiratory tract illness (ARTI) in southern China both pre- and post-COVID-19 pandemic, as well as identify associated risk factors for severe infections. The study conducted a real-time PCR analysis on hospitalized children with ARTI from 2012 to 2023, specifically targeting RSV, hMPV, and other respiratory pathogens. Additionally, demographic data was collected during this analysis. The prevalence of RSV occurs triennially, and likewise, the temporal pattern of hMPV outbreaks mirrors that of RSV. The peak infection rates of RSV and hMPV occurred during and following the implementation of COVID-19 epidemic prevention and control measures. The incidence of RSV infection exhibited bimodal peaks in 2022, while hMPV demonstrated seasonal peaks during the spring, fall, and winter periods post-COVID-19 pandemic. After the COVID-19 outbreak, there has been an upward trend in the proportion of female patients and patients aged one year and older presenting with ARTI, RSV infections, and hMPV infections. Infant (OR = 4.767, 95%CI: [3.888-5.846], p < 0.0001), presence of co-infection (OR = 0.540, 95%CI: [0.404-0.722], p < 0.0001), and existence of comorbidities (OR = 1.582, 95%CI: [1.285-1.949], p < 0.0001) was the risk ratio for the severity of RSV infection. Children infected with hMPV under the age of 1 year (OR = 0.322, 95%CI: [0.180 - 0.575], p < 0.0001), as well as those with comorbidities (OR = 8.809, 95%CI: [4.493 - 17.272], p < 0.0001), have a higher risk of developing severe illness. The changing epidemiological patterns have the potential to lead to widespread severe outbreaks among children, particularly those with underlying medical conditions who may experience more severe symptoms. Conducting surveillance for pneumoviridae viruses in children is an imperative measure to establish a robust foundation for future epidemic prevention and treatment strategies.

Epidemiological characteristics of human metapneumovirus among children in Nanjing, China.

The objective of this study was to examine the molecular epidemiology and clinical characteristics of HMPV infection among children with ARIs in Nanjing. The respiratory samples were collected from 2078 children (≤ 14 years) with acute respiratory infections and were tested for HMPV using real-time RT-PCR. Amplification and sequencing of the HMPV G gene were followed by phylogenetic analysis using MEGA 7.0. The detection rate of HMPV among children was 4.7% (97/2078), with a concentration in those under 5 years of age. Notably, the peak season for HMPV prevalence was observed in winter. Among the 97 HMPV-positive samples, 51.5% (50/97) were available for characterization of the HMPV G protein gene. Phylogenetic analysis indicated that the sequenced HMPV strains were classified into three sublineages: A2c111nt - dup (84.0%), B1 (2.0%), and B2 (14.0%). There was an incidence of HMPV among hospitalized children during 2021-2022 in Nanjing with A2c111nt - dup being the dominant strain. This study demonstrated the molecular epidemiological characteristics of HMPV among children with respiratory infections in Nanjing, China.

Epidemiological and clinical characteristics of hospitalized human metapneumovirus patients in Israel, 2015-2021: A retrospective cohort study.

This study evaluated the epidemiological and clinical characteristics of human metapneumovirus (hMPV) infection among hospitalized patients with acute respiratory infections during 2015-2021 and assessed the impact of the coronavirus disease 2019 pandemic on hMPV infection. A single-center, retrospective cohort study was performed, including pediatric and adult patients with laboratory-confirmed hMPV. Of a total of 990 patients, 253 (25.6%), 105 (10.6%), 121 (12.2%), and 511 (51.6%) belonged to age groups 0-2, 3-17, 18-59, and ≥60 years, respectively. The highest percentage (23.0%) of patients were hospitalized during 2019 and the lowest (4.7%) during 2020. Patients < 18 years experienced high rates of comorbidities (immunodeficiencies: 14.4% and malignancies: 29.9%). Here, 37/39 (94.9%) of all bronchiolitis cases were diagnosed in patients < 2 years, whereas more patients in older age groups were diagnosed with pneumonia. A greater proportion of hMPV patients diagnosed with viral coinfection (mostly respiratory syncytial virus and adenovirus) were <18 years. The highest percentages of intensive care unit admissions were recorded among patients < 18 years. Our findings demonstrate that hMPV is an important cause of morbidity in young children and a possibly underestimated cause of morbidity among older adults.

Burden of respiratory syncytial virus, human metapneumovirus and influenza virus infections in Japanese adults in the Hospitalized Acute Respiratory Tract Infection study

BackgroundRespiratory syncytial virus (RSV), human metapneumovirus (hMPV), and influenza virus are responsible for acute respiratory tract infections (ARTIs) in adults. We assessed the clinical burden of RSV, hMPV and influenza virus infection among Japanese adults hospitalized with ARTIs. MethodsThe Hospitalized Acute Respiratory Tract Infection (HARTI) study was a multinational, prospective cohort study in adults with ARTIs across the 2017–2019 epidemic seasons. Enrolment in Japan began in Sept 2018 and ran until Oct 2019. The clinical diagnosis of ARTI and the decision to hospitalize the patient were made according to local standard of care practices. Viral testing was performed by reverse transcription polymerase chain reaction. ResultsOf the 173 adults hospitalized with ARTI during this period at the Japan sites, 7 (4.0%), 9 (5.2%), and 11 (6.4%) were positive for influenza virus, RSV, and hMPV, respectively. RSV season was observed from Oct 2018 to Jan 2019, followed by influenza from Dec 2018 to Apr 2019. hMPV was detected across both the RSV and influenza seasons. Two patients with RSV and 1 patient with hMPV required ICU admission whereas none with influenza. Use of antibiotics, bronchodilators and inhaled corticosteroids was high amongst patients with RSV and hMPV at 1, 2, and 3 months’ post-discharge compared with patients with influenza, with few exceptions. ConclusionThese findings highlight the need for a high degree of clinical suspicion for RSV and hMPV infection in adults hospitalized with ARTIs.

A Case of Metapneumovirus Pneumonia-Related Acute Respiratory Distress Syndrome in a Young Adult Patient

Human metapneumovirus (hMPV) infections commonly present as mild upper respiratory tract infections in healthy adults, although severe respiratory complications have been observed, particularly in elderly and immunocompromised patients. We report a case in whom pneumonia caused by hMPV progressed to acute respiratory distress syndrome (ARDS) in a healthy adult without underlying diseases. A 31-year-old female presented with fever and dyspnea, prompting transfer to our hospital for mechanical ventilation 3 days after symptom onset. Auscultation revealed coarse breath sounds and crackles in both lung fields, and chest X-ray showed non-specific infiltrative nodules with poorly defined borders throughout both lungs. ARDS caused by community-acquired pneumonia was diagnosed. hMPV was identified via rapid testing of respiratory samples for genes that encode pneumonia pathogens and drug resistance markers; we employed reverse transcription polymerase chain reactions to these ends. Six days later, the patient was weaned off the mechanical ventilator, and discharged from the hospital in good clinical condition.

Exploring Clinical Predictors of Severe Human Metapneumovirus Respiratory Tract Infections in Children: Insights from a Recent Outbreak.

Human metapneumovirus (hMPV) is an important pathogen that causes both upper (URTIs) and lower respiratory tract infections (LRTIs) in children. The virus can be implicated in severe bronchiolitis and pneumonia, necessitating hospitalization, with certain cases requiring intensive care unit intervention. As part of a retrospective observational study, we aimed to identify indicators of severe hMPV respiratory tract infections in children referred to the University Children's Hospital Ljubljana and the Department of Infectious Diseases Ljubljana, Slovenia, during a recent outbreak. We analyzed clinical data from November 2022 to January 2023 and compared the characteristics of children presenting with URTIs and LRTIs. We also examined the characteristics of children with hMPV LRTIs, distinguishing between children with and without LRTI-associated hypoxemia. Of 78 hMPV-PCR-positive pediatric patients (mean age 3.1 years; 60.3% boys), 36% had a URTI, and 64% had an LRTI. Hospitalization was required in 64% (50/78), with 42% (21/50) requiring oxygen therapy. LRTI-associated hypoxemia was more common in patients with atopy who showed dyspnea, tachypnea, crackles, and wheezing on lung auscultation. In a multivariable logistic regression analysis, wheezing detected on lung auscultation was a significant predictive factor for hypoxemic hMPV-LRTI. Specifically, children presenting with wheezing were found to be ten times more likely to experience hypoxemia. Prematurity and chronic conditions did not influence the presentation or severity of hMPV infection. This study highlights wheezing and atopy as crucial indicators of severe hMPV LRTI in children, emphasizing the importance of early recognition and intervention.

Determinants of radiological patterns and severity in immunocompromised adults with Metapneumovirus infection

BackgroundHuman Metapneumovirus (HMPV) belongs to the Pneumoviridae family and is responsible for respiratory infections. Mild infections are well-recognized in children, while its precise impact in various categories of immunocompromised adults has not been well addressed. Research questionWe retrospectively studied HMPV infections in immunocompromised adults followed in two large French university medical centers. Study design and methodsWe identified immunocompromised adults with positive HMPV Polymerase Chain Reaction (PCR) for 36 months and reviewed their medical charts. For lung transplant recipients (LTR), FEV1 was collected at baseline, during and after infection. Imaging was centralized and chest involvement was categorized by dominant CT patterns. We compared severe patients (requiring oxygen or ventilation) and non hypoxemic patients. ResultsSeventy-two patients were included, 27 were LTR, 25 had a hematological malignancy or were hematopoietic stem cell recipients, 20 had another immunocompromised status. Twenty patients (28%) presented a hypoxemic infection, requiring hospitalization and intensive care units transfers in 50/72 (69.4%) and 9/72 (12.5%) respectively, with only one death. Hypoxemia was less pronounced in LTRs (p = 0.014). Finally, age and dyspnea remained independent factors associated with hypoxemia (p < 0.005). The most frequent radiological patterns were bronchopneumonia (34.2%) and bronchiolitis (39.5% and 64.3% in the overall population and in LTRs respectively, p = 0.045). FEV1 improved in LTRs at one month and 85% had recovered their baseline FEV1 within 6 months. InterpretationsIn immunocompromised adults, HMPV infections required frequent hospitalizations and ICU transfers, while mortality is low. In LTRs, bronchiolitis pattern was predominant with short and long-term favorable outcome.

Comparative analysis of mortality in patients admitted with an infection with influenza A/B virus, respiratory syncytial virus, rhinovirus, metapneumovirus or SARS-CoV-2.

While influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are recognised as a cause of severe illness and mortality, clinical interest for respiratory syncytial virus (RSV), rhinovirus and human metapneumovirus (hMPV) infections is still limited. We conducted a retrospective database study comparing baseline characteristics and 30-day mortality in a large cohort of adult patients admitted for an overnight stay or longer with an influenza virus (A/B), rhinovirus, hMPV, RSV or SARS-CoV-2 infection. For non-SARS-CoV-2 viruses, data were included for the period July 2017-February 2020. For SARS-CoV-2, data between March 2020 and March 2022 were included. Covariate-adjusted 30-day mortality following RSV, hMPV or rhinovirus infections was substantial (crude mortality 8-10%) and comparable with mortality following hospitalisation with an influenza A virus infection. Mortality following a SARS-CoV-2 infection was consistently higher than for any other respiratory virus, at any point in time (crude mortality 14-25%). Odds of mortality for SARS-CoV-2 compared with influenza A declined from 4.9 to 1.7 over the course of the pandemic. Patients with SARS-CoV-2 infection had less comorbidity than patients with other respiratory virus infections and were more often male. In this cohort, age was related to mortality following hospitalisation, while an association with comorbidity was not apparent. With the exception of SARS-CoV-2 infections, we find the clinical outcome of common respiratory virus infections requiring hospitalisation more similar than often assumed. The observed mortality from SARS-CoV-2 was significantly higher, but the difference with other respiratory viruses became less distinct over time.

Resurgence of human metapneumovirus infection and influenza after three seasons of inactivity in the post-COVID-19 era in Hokkaido, Japan, 2022-2023.

Following the coronavirus disease 2019 (COVID-19) outbreak in February 2020, incidences of various infectious diseases decreased notably in Hokkaido Prefecture, Japan. However, Japan began gradually easing COVID-19 infection control measures in 2022. Here, we conducted a survey of children hospitalized with human metapneumovirus (hMPV), influenza A and B, and respiratory syncytial virus infections in 18 hospitals across Hokkaido Prefecture, Japan, spanning from July 2019 to June 2023. From March 2020 to June 2022 (28 months), only 13 patients were hospitalized with hMPV, and twopatients had influenza A. However, in October to November 2022, there was a re-emergence of hMPV infections, with a maximum of 27 hospitalizations per week. From July 2022 to June 2023 (12 months), the number of hMPV-related hospitalizations dramatically increased to 317 patients, with the majority aged 3-6 years (38.2%, [121/317]). Influenza A also showed an increase from December 2022, with a peak of 13 hospitalizations per week in March 2023, considerably fewer than the pre-COVID-19 outbreak in December 2019, when rates reached 45 hospitalizations per week. These findings suggest the possibility of observing more resurgences in infectious diseases in Japan after 2023 if infection control measures continue to be relaxed. Caution is needed in managing potential outbreaks.

The Impact of Bacterial Co-Infection on Hospitalized Children with Human Rhinovirus and Human Metapneumovirus Infections: A Retrospective Analytical Cross-Sectional Study

Background: Human rhinovirus (HRV) and human metapneumovirus (hMPV) are common viral causes of pediatric respiratory tract infections. Bacterial co-infections frequently complicate HRV and hMPV illnesses in children, but the interactions between viral and bacterial pathogens and their impacts on disease severity are not well understood. Objectives: The present research aimed to analyze and compare the clinical features of HRV and hMPV mono-infections in hospitalized children and to assess the impact of bacterial co-infection on the disease severity of HRV and hMPV infections. Methods: The present retrospective analytical cross-sectional study was conducted to compare the clinical features between HRV and hMPV mono-infections and HRV and hMPV with bacterial co-infections in hospitalized children aged 14 years or younger. Results: Between January and December 2022, we investigated 1,978 children hospitalized with HRV infection, of which 1,529 had HRV mono-infection and 1,117 hospitalized with hMPV infection, among whom 910 had hMPV mono-infection. Compared to HRV, hMPV mono-infection exhibited more pronounced symptoms of fever, cough, and rales in most age groups, while HRV showed more wheezing. Except in patients ≥ 6 years old, hMPV was more associated with pneumonia and longer hospitalizations. In contrast to HRV mono-infections, children with bacterial co-infections had a higher proportion of coughs (P &lt; 0.001), pneumonia (P &lt; 0.001), pediatric intensive care unit (PICU) admissions (P &lt; 0.001), and longer hospitalizations (P = 0.003). Demographic characteristics, clinical presentation, diagnosis, and treatments showed no significant differences between patients with hMPV mono-infection and co-infection. Conclusions: Among hospitalized children, hMPV mono-infection resulted in more severe respiratory illnesses compared to HRV mono-infection. Bacterial co-infections exacerbated disease severity in HRV infections.

Clinical factors associated with extended hospitalization in pediatric patients ≥3 years of age with respiratory syncytial virus or human metapneumovirus infection: A Japanese single-center, retrospective study.

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) infections are common in children worldwide. However, the clinical factors related to extended hospitalization in Japanese patients aged ≥3 years remain elusive. We aimed to elucidate the clinical risk factors contributing to hospital stays ≥7 days in patients with RSV and hMPV infections. Patients ≥3 years of age who were hospitalized due to RSV or hMPV infection between 2014 to 2020 were included. Twenty-one RSV- and 27 hMPV-infected patients were enrolled. Patients were divided into 2 groups: hospitalization for ≥ and <7 days. Univariate and multivariate analyses determined the clinical risk factors contributing to hospital stay ≥7 days. The RSV- and hMPV-infected patients had similar clinical characteristics. The clinical risk factors contributing to extended hospitalization were analyzed in the 48 infected patients of the 2 groups. The presence of prophylactic antibiotics usage, co-bacterial colonization, and underlying diseases were extracted by univariate analysis (P < .05). In multivariate analysis, underlying diseases were determined as an independent clinical risk factor (odds ratio 8.09, P = .005). Underlying diseases contributed to extended hospitalization in RSV- or hMPV-infected patients ≥3 years of age.

Identification of γ-Fagarine as a novel antiviral agent against respiratory virus (hMPV) infection

Human metapneumovirus (hMPV) causes significant upper and lower respiratory disease in all age groups worldwide. However, there is no licensed drugs or vaccine available against hMPV. γ-Fagarine, an alkaloid isolated from the root of zanthoxylum, has been reported to be effective in the treatment of cancer, inflammatory diseases and antivirals. However, little is known about the inhibitory effect of γ-Fagarine against respiratory virus infection and the mechanism. In this study, we aim to investigate the effect of γ-Fagarine on hMPV infection and explore its underlying molecular mechanisms. Vero-E6 and 16HBE cells were used as cell models. Virus replication and microcosm character were explored in Vero-E6 cells. Then, the antiviral activities were investigated by quantitative real-time PCR (RT-qPCR), western blotting (WB), and indirect immunofluorescence assays (IFAs) in Vero-E6 and 16HBE. Potential mechanisms of γ-Fagarine related to HSPG and lysosome pH were assessed in 16HBE cells. Lastly, a virus-infected mouse model was established and antiviral assay in vivo was conducted. γ-Fagarine showed no toxicity toward Vero-E6 cells and 16HBE cells but demonstrated anti-hMPV activity. Virus titers of γ-Fagarine group were reduced to 33% and 45% of the hMPV groups, respectively. Besides, mechanistic studies revealed that γ-Fagarine could inhibit hMPV by dual mechanisms of direct restraining virus binding with HSPG and influencing lysosome pH. Furthermore, oral delivery of γ-Fagarine to hMPV-infected mice at a dosage of 25 mg/kg reduced the hMPV load in lung tissues. After γ-Fagarine treatment, pathological damage caused by viral infection was also ameliorated. These findings suggest that γ-Fagarine has antiviral effects in vitro and in vivo, which are associated with its ability to restrain virus binding with HSPG and influence lysosome pH, thus indicating that γ-Fagarine has the potential to serve as a candidate to fight against hMPV infection and other respiratory viruses such as influenza viruses and SARS-CoV-2.

Development of a duplex real-time RT-PCR assay for the detection and identification of two subgroups of human metapneumovirus in a single tube

Human metapneumovirus (hMPV) is a common cause of respiratory infections in children. Many genetic diagnostic assays have been developed, but most detect hMPV regardless of the subgroup. In this study, we developed a real-time RT-PCR assay that can detect and identify the two major subgroups of hMPV (A and B) in one tube. Primers and probes were designed based on the sequences of recent clinical isolates in Japan. The assay showed comparable analytical sensitivity to a previously reported real-time RT-PCR assay and specific reactions to hMPV subgroups. The assay also showed no cross-reactivity to clinical isolates of 19 species of other respiratory viruses. In a validation assay using post-diagnosed clinical specimens, 98% (167/170) positivity was confirmed for the duplex assay, and the three specimens not detected were of low copy number. The duplex assay also successfully distinguished the two major subgroups for all 12 clinical specimens, for which the subgroup had already been determined by genomic sequencing analysis. The duplex assay described here will contribute to the rapid and accurate identification and surveillance of hMPV infections.

Potent cross-neutralization of respiratory syncytial virus and human metapneumovirus through a structurally conserved antibody recognition mode

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) infections pose a significant health burden. Using pre-fusion conformation fusion (F)proteins, we isolated a panel of anti-F antibodies from a human donor. One antibody (RSV-199) potently cross-neutralized 8 RSV and hMPV strains by recognizing antigenic site III, which is partially conserved in RSV and hMPV F. Next, we determined the cryoelectron microscopy (cryo-EM) structures of RSV-199 bound to RSV F trimers, hMPV F monomers, and an unexpected dimeric form of hMPV F. These structures revealed how RSV-199 engages both RSV and hMPV F proteins through conserved interactions of the antibody heavy-chain variable region and how variability within heavy-chain complementarity-determining region 3 (HCDR3) can be accommodated at the F protein interface in site-III-directed antibodies. Furthermore, RSV-199 offered enhanced protection against RSV A and B strains and hMPV in cotton rats. These findings highlight the mechanisms of broad neutralization and therapeutic potential of RSV-199.

Interleukin-4 Promotes Human Metapneumovirus Replication Through the JAK/STAT6 Pathway.

Respiratory virus infections are the main causes of pediatric diseases. Human metapneumovirus (hMPV) is an enveloped RNA virus similar to severe acute respiratory syndrome coronavirus type 2, both of which have emerged as important new respiratory viruses. Recent studies have found that interleukin-4 (IL-4) is involved in the replication of a variety of viruses, and its role differs in different viruses. The purpose of this study was to investigate the effect of IL-4 on hMPV and to elucidate its mechanism of action. We found that hMPV infection promoted the expression of IL-4 in human bronchial epithelial cells. The replication of the virus was reduced using small interfering RNA knockdown of IL-4 expression, while the addition of exogenous recombinant human IL-4 to IL-4 knockdown cells restored viral replication ability. These results demonstrate that the expression of IL-4 is closely related to the replication of hMPV; moreover, further experiments revealed that IL-4 promotes the replication of hMPV through a mechanism dependent on the Janus kinase/signal transductor and transcription activator 6 signaling pathway. Therefore, anti-IL-4 strategies may be a promising avenue for the treatment of hMPV infection, representing an important breakthrough for children at risk from hMPV infection.