Human Metapneumovirus Infection Research Articles

Novel insights into the host cell glycan binding profile of human metapneumovirus.

Numerous viruses have been found to exploit glycoconjugates expressed on human cells as their initial attachment factor for viral entry and infection. The virus-cell glycointeractome, when characterized, may serve as a template for antiviral drug design. Heparan sulfate proteoglycans extensively decorate the human cell surface and were previously described as a primary receptor for human metapneumovirus (HMPV). After respiratory syncytial virus, HMPV is the second most prevalent respiratory pathogen causing respiratory tract infection in young children. To date, there is neither vaccine nor drug available to prevent or treat HMPV infection. Using a multidisciplinary approach, we report for the first time the glycointeractome of the HMPV fusion (F) protein, a viral surface glycoprotein that is essential for target-cell recognition, attachment, and entry. Our glycan microarray and surface plasmon resonance results suggest that Galβ1-3/4GlcNAc moieties that may be sialylated or fucosylated are readily recognized by HMPV F. The bound motifs are highly similar to the N-linked and O-linked glycans primarily expressed on the human lung epithelium. We demonstrate that the identified glycans have the potential to compete with the cellular receptors used for HMPV entry and consequently block HMPV infection. We found that lacto-N-neotetraose demonstrated the strongest HMPV binding inhibition in a cell infection assay. Our current findings offer an encouraging and novel avenue for the design of anti-HMPV drug candidates using oligosaccharide templates.IMPORTANCEAll cells are decorated with a dense coat of sugars that makes a sugar code. Many respiratory viruses exploit this sugar code by binding to these sugars to cause infection. Human metapneumovirus is a leading cause for acute respiratory tract infections. Despite its medical importance, there is no vaccine or antiviral drug available to prevent or treat human metapneumovirus infection. This study investigates how human metapneumovirus binds to sugars in order to more efficiently infect the human host. We found that human metapneumovirus binds to a diverse range of sugars and demonstrated that these sugars can ultimately block viral infection. Understanding how viruses can take advantage of the sugar code on our cells could identify new intervention and treatment strategies to combat viral disease.

Clinical and epidemiological characteristics of 96 pediatric human metapneumovirus infections in Henan, China after COVID-19 pandemic: a retrospective analysis

BackgroundIn the aftermath of the COVID-19 pandemic, there has been a surge in human metapneumovirus (HMPV) transmission, surpassing pre-epidemic levels. We aim to elucidate the clinical and epidemiological characteristics of HMPV infections in the post-COVID-19 pandemic era.MethodsIn this retrospective single-center study, participants diagnosed with laboratory confirmed HMPV infection through Targeted Next Generation Sequencing were included. The study encompassed individuals admitted to Henan Children's Hospital between April 29 and June 5, 2023. Demographic information, clinical records, and laboratory indicators were analyzed.ResultsBetween April 29 and June 5, 2023, 96 pediatric patients were identified as infected with HMPV with a median age of 33.5 months (interquartile range, 12 ~ 48 months). The majority (87.5%) of infected children were under 5 years old. Notably, severe cases were statistically younger. Predominant symptoms included fever (81.3%) and cough (92.7%), with wheezing more prevalent in the severe group (56% vs 21.1%). Coinfection with other viruses was observed in 43 patients, with Epstein–Barr virus (EBV) (15.6%) or human rhinovirus A (HRV type A) (12.5%) being the most common. Human respiratory syncytial virus (HRSV) coinfection rate was significantly higher in the severe group (20% vs 1.4%). Bacterial coinfection occurred in 74 patients, with Haemophilus influenzae (Hin) and Streptococcus pneumoniae (SNP) being the most prevalent (52.1% and 41.7%, respectively). Severe patients demonstrated evidence of multi-organ damage. Noteworthy alterations included lower concentration of IL-12p70, decreased lymphocytes percentages, and elevated B lymphocyte percentages in severe cases, with statistical significance. Moreover, most laboratory indicators exhibited significant changes approximately 4 to 5 days after onset.ConclusionsOur data systemically elucidated the clinical and epidemiological characteristics of pediatric patients with HMPV infection, which might be instructive to policy development for the prevention and control of HMPV infection and might provide important clues for future HMPV research endeavors.

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.

IFN-λ drives distinct lung immune landscape changes and antiviral responses in human metapneumovirus infection.

Human metapneumovirus (HMPV) is a common respiratory pathogen and often contributes to severe disease, particularly in children, immunocompromised people, and the elderly. There are currently no licensed HMPV antiviral treatments or vaccines. Here, we report novel roles of host factor IFN-λ in HMPV disease that highlight therapeutic potential. We show that IFN-λ promotes lung antiviral responses by restricting lung HMPV replication and spread from upper to lower airways but does so without inducing lung immunopathology. Our data uncover recruitment of lung macrophages, regulation of ciliated epithelial cells, and modulation of inflammatory cytokines and interferon-stimulated genes as likely contributors. Moreover, we found these roles to be distinct and non-redundant, as they are not observed with knockout of, or treatment with, type I IFN. These data elucidate unique antiviral functions of IFN-λ and suggest IFN-λ augmentation as a promising therapeutic for treating HMPV disease and promoting effective vaccine responses.

The burden of HMPV and influenza associated hospitalizations in adults in New Zealand, 2012-2015.

Unlike influenza, information on the burden of human metapneumovirus (HMPV) as a cause of hospitalizations in adults with acute respiratory illness (ARI) is limited. We compared the population-based incidence, seasonality, and clinical characteristics of these two viral infections among adults aged 20 years and over with ARI hospitalisations in Auckland, New Zealand, during 2012-2015 through the Southern Hemisphere Influenza Vaccine Effectiveness Research and Surveillance (SHIVERS) project. Of the 14,139 ARI hospitalisations, 276 (4.3%) of 6484 tested positive for HMPV and 1342 (19.1%) of 7027 tested positive for influenza. Crude rates of 9.8 (95% CI: 8.7-11.0) HMPV and 47.6 (95% CI: 45.1-50.1) influenza-associated ARI hospitalisations were estimated for every 100,000 adult residents annually. The highest rates for both viruses were in those aged 80 years or older, of Māori or Pacific ethnicity, or living in low socioeconomic status (SES) areas. HMPV infections were more common than influenza in those with chronic medical conditions. Although HMPV infections accounted for fewer hospitalisations than influenza in adults aged 20 years and over, HMPV-associated ARI hospitalisation rates were higher than influenza in older adults, Maori and Pacific people and those of low SES. This highlighted a need for vaccine/antiviral development.

Human metapneumovirus respiratory infection affects both innate and adaptive intestinal immunity.

Respiratory infections are one of the leading causes of morbidity and mortality worldwide, mainly in children, immunocompromised people, and the elderly. Several respiratory viruses can induce intestinal inflammation and alterations in intestinal microbiota composition. Human metapneumovirus (HMPV) is one of the major respiratory viruses contributing to infant mortality in children under 5 years of age worldwide, and the effect of this infection at the gut level has not been studied. Here, we evaluated the distal effects of HMPV infection on intestinal microbiota and inflammation in a murine model, analyzing several post-infection times (days 1, 3, and 5). Six to eight-week-old C57BL/6 mice were infected intranasally with HMPV, and mice inoculated with a non-infectious supernatant (Mock) were used as a control group. We did not detect HMPV viral load in the intestine, but we observed significant changes in the transcription of IFN-γ in the colon, analyzed by qPCR, at day 1 post-infection as compared to the control group. Furthermore, we analyzed the frequencies of different innate and adaptive immune cells in the colonic lamina propria, using flow cytometry. The frequency of monocyte populations was altered in the colon of HMPV -infected mice at days 1 and 3, with no significant difference from control mice at day 5 post-infection. Moreover, colonic CD8+ T cells and memory precursor effector CD8+ T cells were significantly increased in HMPV-infected mice at day 5, suggesting that HMPV may also alter intestinal adaptive immunity. Additionally, we did not find alterations in antimicrobial peptide expression, the frequency of colonic IgA+ plasma cells, and levels of fecal IgA. Some minor alterations in the fecal microbiota composition of HMPV -infected mice were detected using 16s rRNA sequencing. However, no significant differences were found in β-diversity and relative abundance at the genus level. To our knowledge, this is the first report describing the alterations in intestinal immunity following respiratory infection with HMPV infection. These effects do not seem to be mediated by direct viral infection in the intestinal tract. Our results indicate that HMPV can affect colonic innate and adaptive immunity but does not significantly alter the microbiota composition, and further research is required to understand the mechanisms inducing these distal effects in the intestine.

Human metapneumovirus infection of organoid-derived human bronchial epithelium represents cell tropism and cytopathology as observed in in vivo models.

Human metapneumovirus (HMPV) is one of the leading causative agents of respiratory disease in humans, with no treatment or vaccine available yet. The use of primary epithelial cultures that recapitulate the tissue morphology and biochemistry of the human airways could aid in defining more relevant targets to prevent HMPV infection. For this purpose, this study established the first primary organoid-derived bronchial culture model suitable for a broad range of HMPV isolates. These bronchial cultures were assessed for HMPV replication, cellular tropism, cytopathology, and innate immune responses, where the observations were linked to previous in vivo studies with HMPV. This study exposed an important gap in the HMPV field since extensively cell-passaged prototype HMPV B viruses did not replicate in the bronchial cultures, underpinning the need to use recently isolated viruses with a controlled passage history. These results were reproducible in three different donors, supporting this model to be suitable to study HMPV infection.

Mortality and Morbidity of Human Metapneumovirus Infection in the Pre-COVID-19 Era: The Value of the Charlson Comorbidity Index on Outcome Prediction.

Human metapneumovirus (HMPV) is an important cause of seasonal respiratory tract infections, mainly in children and immunocompromised adults. The use of the Charlson Comorbidity Index (CCI) to predict outcomes in hospitalized patients has been validated in several settings. This study aims to describe the clinical characteristics of adult patients with HMPV infection and evaluate the value of the CCI in predicting outcomes in patients with acute HMPV infections requiring hospitalization. This is a single-center case-series study of hospitalized patients with HMPV infection in 2017. Twenty-two adult patients with a mean age of 65 years were reviewed. The mean CCI was 4.6±2.6. The overall mortality was 22%. An abnormal chest X-ray(CXR) was reported in 15 patients. CCI was not different between survivors and non-survivors. Non-survivors were more likely to have abnormal CXR and a higher fever at the time of diagnosis, required mechanical ventilation, or had other concomitant infections. The average CCI was 4.5, which was not significantly different between survivors and non-survivors. The mortality rate was elevated by 22% and was likely associated with admission to the ICU as well as the presence of another concomitant infection.

Epidemiology and Clinical Characteristics of Human Metapneumovirus Infections in Hospitalized Children in Two Consecutive Postpandemic Years.

We assessed human metapneumovirus infections in children hospitalized between 2011 and 2023 and compared the strongest pre- and postpandemic seasons. After the COVID-19 pandemic, we observed offseason cases and loss of the alternating pattern of the human metapneumovirus season magnitude. Incidence rate ratio of 0- to 11-month-old versus 12- to 23-month-old children was 2.1 (95% CI: 1.0-4.8) before and 1.3 (95% CI: 0.6-2.9) after the pandemic.

Epidemiological trends of respiratory tract pathogens detected via mPCR in Australian adult patients before COVID-19

BackgroundRespiratory tract infections (RTIs) are a major global health burden due to their high morbidity and mortality. This retrospective study described the epidemiology of respiratory pathogens in adults over a 5-year period at an Australian tertiary healthcare network.MethodsAll multiplex reverse transcription polymerase chain reaction respiratory samples taken between the 1st of November 2014 and the 31st of October 2019 were included in this study. Overall prevalence and variations according to seasons, age groups and sex were analysed, as well as factors associated with prolonged hospital and intensive care length of stay.ResultsThere were 12,453 pathogens detected amongst the 12,185 positive samples, with coinfection rates of 3.7%. Picornavirus (Rhinovirus), Influenza A and respiratory syncytial virus were the most commonly detected pathogens. Mycoplasma pneumoniae was the most commonly detected atypical bacteria. Significant differences in the prevalence of Chlamydia pneumoniae and Human metapneumovirus infections were found between sexes. Longest median length of intensive care and hospital stay was for Legionella species. Seasonal variations were evident for certain pathogens.ConclusionsThe high rates of pathogen detection and hospitalisation in this real-world study highlights the significant burden of RTIs, and the urgent need for an improved understanding of the pathogenicity as well as preventative and treatment options of RTIs.

PD-1 signaling in neonates restrains CD8+ T cell function and protects against respiratory viral immunopathology

Respiratory viral infections, including human metapneumovirus (HMPV), remain a leading cause of morbidity and mortality in neonates and infants. However, the mechanisms behind the increased sensitivity to those respiratory viral infections in neonates are poorly understood. Neonates, unlike adults, have several anti-inflammatory mechanisms in the lung, including elevated baseline expression of programmed death ligand 1 (PD-L1), a ligand for the inhibitory receptor programmed cell death protein 1 (PD-1). We thus hypothesized that neonates would rely on PD-1:PD-L1 signaling to restrain antiviral CD8 responses. To test this, we developed a neonatal primary HMPV infection model using wild-type C57BL/6 (B6) and Pdcd1-/- (lacking PD-1) mice. HMPV-infected neonatal mice had increased PD-L1/PD-L2 co-expression on innate immune cells but a similar number of antigen-specific CD8+ T cells and upregulation of PD-1 to that of adult B6 mice. Neonatal CD8+ T cells had reduced interferon-gamma (IFN-γ), granzyme B, and interleukin-2 production compared with B6 adults. Pdcd1-/- neonatal CD8+ T cells had markedly increased production of IFN-γ and granzyme B compared with B6 neonates. Pdcd1-/- neonates had increased acute pathology with HMPV or influenza. Pdcd1-/- neonates infected with HMPV had long-term changes in pulmonary physiology with evidence of immunopathology and a persistent CD8+ T-cell response with increased granzyme B production. Using single-cell ribonucleic acid sequencing from a child lacking PD-1 signaling, a similar activated CD8+ T-cell signature with increased granzyme B expression was observed. These data indicate that PD-1 signaling critically limits CD8+ T-cell effector functions and prevents immunopathology in response to neonatal respiratory viral infections.

Suppressed pediatric asthma hospitalizations during the COVID-19 pandemic in Japan, from a national survey.

Acute asthma exacerbation in children is often caused by respiratory infections. In this study, a coordinated national surveillance system for acute asthma hospitalizations and causative respiratory infections was established. We herein report recent trends in pediatric acute asthma hospitalizations since the COVID-19 pandemic in Japan. Thirty-three sentinel hospitals in Japan registered all of their hospitalized pediatric asthma patients and their causal pathogens. The changes in acute asthma hospitalization in children before and after the onset of the COVID-19 pandemic and whether or not COVID-19 caused acute asthma exacerbation were investigated. From fiscal years 2010-2019, the median number of acute asthma hospitalizations per year was 3524 (2462-4570), but in fiscal years 2020, 2021, and 2022, the numbers were 820, 1,001, and 1,026, respectively (the fiscal year in Japan is April to March). This decrease was observed in all age groups with the exception of the 3- to 6-year group. SARS-CoV-2 was evaluated in 2094 patients from fiscal years 2020-2022, but the first positive case was not detected until February 2022. Since then, only 36 of them have been identified with SARS-CoV-2, none of which required mechanical ventilation. Influenza, RS virus, and human metapneumovirus infections also decreased in FY 2020. In contrast, 24% of patients had not been receiving long-term control medications before admission despite the severity of bronchial asthma. SARS-CoV-2 was hardly detected in children with acute asthma hospitalization during the COVID-19 pandemic. This result indicated that SARS-CoV-2 did not induce acute asthma exacerbation in children. Rather, infection control measures implemented against the pandemic may have consequently reduced other respiratory virus infections and thus acute asthma hospitalizations during this period. However, the fact that many hospitalized patients have not been receiving appropriate long-term control medications is a major problem that should be addressed.

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.

Development of a novel multi-epitope mRNA vaccine candidate to combat HMPV virus

ABSTRACT Human metapneumovirus (HMPV) is one of the main pathogens causing severe respiratory infections in children, as a common cause of immunodeficiency-related deaths in children and elderly individuals, the prevalence of HMPV has been showing an increasing trend during the last years. However, no vaccines or effective treatment plans are available currently. In this present, based on candidate proteins highly associated with viral virulence and has promising protective potential, we screened for immunodominant cytotoxic T cells, helper T cells, and Linear B-cell epitopes from the most promising candidate Fusion protein, together with G, SH, M, and M2. All epitopes were predicted to have strong antigenicity by Vaxijen and pose no potential toxicity, allergenicity, or hormonology to human proteins by Toxinpred, Allerpred, and Blast analysis, meanwhile, high conservancy is demanded to cover different subtypes. adjuvants β-defensin II and Pam2Cys was attached with EAAAK linkers to improve vaccine’s efficiency. Then, calculation of physicochemical properties proved the protein vaccine as a product can stably exist in the human body. Besides, we assessed the docking between the vaccine and immune receptors to evaluate its ability to stimulate immune responses, and the dynamic simulation further confirmed that the vaccine can tightly bind with immune receptors, which approved that the construction has the potential to induce strong humoral and cellular immune response. Finally, the vaccine was constructed into a multi-epitope mRNA vaccine, the immune simulations suggest that this is a vaccine candidate for controlling HMPV infection.

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.

Granulocyte Transfusion Therapy as a Bridge to Hematopoietic Stem Cell Transplant in a Child with Aplastic Anemia and Refractory Perirectal Abscess

Abstract Background Idiopathic aplastic anemia is a rare form of bone marrow failure characterized by multilineage cytopenias and hypocellular bone marrow [A]. Persistent neutropenia is an important risk factor for the development of life-threatening infections [B]. Perirectal cellulitis and perianal abscess are associated with high rates of morbidity, and eradication of such infections in the absence of neutrophil recovery is challenging. Here we report the use of adjuvant granulocyte transfusion therapy to treat antibiotic refractory proctitis with perirectal abscess, in a child with severe aplastic anemia. Method A 7-year-old previously healthy female presented with pancytopenia in the setting of Human Meta-pneumovirus and Parainfluenza infection. Initial bone marrow evaluation revealed mildly hypocellular bone marrow (60-70%) with granulocytic and megakaryocytic hypoplasia. Flow cytometry did not reveal malignancy, and her pancytopenia progressed to transfusion dependence. Two months following initial presentation, she presented with rectal pain and febrile neutropenia (ANC< 200/mm) requiring admission for IV antibiotics. She defervesced on piperacillin-tazobactam, and was discharged to home with negative blood culture, but one week later, re-presented with recurrence of fever and worsening perirectal pain, and evidence of proctitis without abscess on abdominal CT scan. A repeat bone marrow evaluation showed progression to bone marrow aplasia. She was discharged on oral levofloxacin prophylaxis but Three days later, developed hematochezia and fevers, with evidence of proctitis with perirectal abscess on MRI. She was started on vancomycin and meropenem and discharged home on outpatient piperacillin-tazobactam to complete at least a14-day course. The patient was subsequently readmitted on day 15 of therapy with new fevers and persistent proctitis on CT scan. Given her persistent proctitis despite 2 weeks of antibiotic therapy, a trial of granulocyte infusion therapy was administered from days 22-26 and 31-32 Abdominal CT on day 33 showed improvement in anorectal inflammatory changes and decreased size of perianal fluid collection. She was subsequently discharged home on IV piperacillin-tazobactam with a plan to continue parenteral antibiotic therapy until evidence of radiographic cure. One week later, she was noted to have rising inflammatory markers, with evolving proctitis on interval CT, leading to readmission on day 46 for fever and worsening pain despite IV antibiotics. HSCT was deferred until resolution of her infection. Combination therapy consisting of granulocyte infusions with continued antimicrobials was initiated, and she received an additional 10-day course of granulocytes with piperacillin-tazobactam Results Patient subsequently demonstrated resolution of fevers, declining CRP, and radiographic resolution of perirectal abscess and proctitis. She was cleared for transplant and underwent Haplo-identical related BMT without recurrence of infection. Conclusion We report the successful use of granulocyte transfusion with antimicrobials to treat antibiotic refractory proctitis, in a child with profound neutropenia. In our case, infection persisted despite prolonged antimicrobial therapy with resolution only after an extended course of granulocyte transfusion. In the setting of stable but refractory bacterial perianal infection, granulocyte transfusion therapy in conjunction with antibiotics should be considered in profoundly neutropenic patients without anticipated count recovery. Discussion Perirectal cellulitis and perianal abscess are a frequent complication of hematologic malignancies and are associated with significant morbidity and mortality in the neutropenic patient. Management is particularly challenging in the absence of neutrophil count recovery, with high rates of recurrence, morbidity and mortality associated with surgical incision and drainage [C] and significant failure rates with medical therapy alone. High-dose granulocyte transfusion therapy has been proposed as an adjunct to antibiotic therapy in such settings, but evidence for clinical efficacy remains limited [D]. A systemic review [E] in 2015 was unable to clarify standard use of granulocytes nor clearly shown a survival benefit to their use. In the same year, the RING randomized controlled trial was also published [D]. Unfortunately, RING was underpowered due to low enrollment and there was no (P>0.99 intention to treat, P=0.64 with treatment) mortality difference at 42 days. Post hoc analysis showed patients receiving a high dose (>0.6 x 109 per kg) did significantly better than low dose patients (but not controls). More recent single center studies/series [F] in pediatrics have shown safety and efficacy locally in retrospective analysis. Granulocyte transfusion is currently considered when patients have neutropenia (<500/uL), bacterial or fungal infection not responding to antimicrobials, and a reasonable expectation of neutrophil recovery [H]. As was required by our transfusion medicine service, we chose to attempt a proscribed (10-day) rather than open-ended treatment course (ten daily doses) of granulocyte transfusion in this patient with a known response to allow for entry into HSCT for treatment of her underlying disease. Here we report the successful use of granulocyte transfusion in conjunction with antimicrobials to treat antibiotic refractory proctitis, in a child with profound neutropenia. In our case, infection persisted despite prolonged antimicrobial therapy with evidence of radiographic and clinical resolution only after an extended course of granulocyte transfusion. As our patient was awaiting HSCT for definitive treatment of her very severe idiopathic aplastic anemia, there was no expectation of imminent bone marrow recovery, with clearance of her infection following granulocyte transfusion allowing her to proceed to transplant. In the setting of stable but refractory bacterial perianal infection, the use of granulocyte transfusion therapy in conjunction with antibiotics should be considered among profoundly neutropenic patients without anticipated count recovery. References A.Wilson DB, Link DC, Mason PJ, Bessler M. Inherited bone marrow failure syndromes in adolescents and young adults. Ann Med. 2014 Sep;46(6):353-63. doi: 10.3109/07853890.2014.915579. Epub 2014 Jun 3. PMID: 24888387; PMCID: PMC4426964. B.Valdez JM, Scheinberg P, Young NS, Walsh TJ. Infections in patients with aplastic anemia. Semin Hematol. 2009 Jul;46(3):269-76. doi: 10.1053/j.seminhematol.2009.03.008. PMID: 19549579. C.Baker B, Al-Salman M, Daoud F. Management of acute perianal sepsis in neutropenic patients with hematological malignancy. Tech Coloproctol. 2014 Apr;18(4):327-33. doi: 10.1007/s10151-013-1082-z. Epub 2013 Nov 26. PMID: 24276114. D.Price TH, Boeckh M, Harrison RW, McCullough J, Ness PM, Strauss RG, Nichols WG, Hamza TH, Cushing MM, King KE, Young JA, Williams E, McFarland J, Holter Chakrabarty J, Sloan SR, Friedman D, Parekh S, Sachais BS, Kiss JE, Assmann SF. Efficacy of transfusion with granulocytes from G-CSF/dexamethasone-treated donors in neutropenic patients with infection. Blood. 2015 Oct 29;126(18):2153-61. doi: 10.1182/blood-2015-05-645986. Epub 2015 Sep 2. PMID: 26333778; PMCID: PMC4626256. E.Estcourt LJ, Stanworth SJ, Hopewell S, Doree C, Trivella M, Massey E. Granulocyte transfusions for treating infections in people with neutropenia or neutrophil dysfunction. Cochrane Database Syst Rev. 2016 Apr 29;4(4):CD005339. doi: 10.1002/14651858.CD005339.pub2. PMID: 27128488; PMCID: PMC4930145. F.Kagızmanlı GA, Guzelkucuk Z, Işık P, Kara A, Ozbek NY, Yarali N. Efficacy and safety of granulocyte transfusion in children: A single-center experience. J Clin Apher. 2020 Sep;35(5):420-426. doi: 10.1002/jca.21818. Epub 2020 Jul 28. PMID: 32722895. G.Cushing MM, Poisson JL. Blood transfusion therapy: a handbook. Bethesda: AABB, 2020 Figure 1. Figure 2 A.Initial CT scan pf pelvis showing proctitis B.First follow up CT scan with improvement after initial granulocyte trial C.Second follow up CT scan with evolving proctitis after 6-week course of antibiotics alone D.Third follow up CT scan after second granulocyte course showing complete resolution of proctitis

Human Metapneumovirus-Induced Host microRNA Expression Impairs the Interferon Response in Macrophages and Epithelial Cells.

Human metapneumovirus (HMPV) is a nonsegmented, single-stranded negative RNA virus and a member of the Pneumoviridae family. During HMPV infection, macrophages play a critical role in defending the respiratory epithelium by secreting large amounts of type I interferon (IFN). MicroRNAs (miRNAs) are small, noncoding, single-stranded RNAs that play an essential role in regulating gene expression during normal cellular homeostasis and disease by binding to specific mRNAs, thereby regulating at the transcriptional and post-transcriptional levels with a direct impact on the immune response and other cellular processes. However, the role of miRNAs in macrophages and respiratory viral infections remains largely unknown. Here, we characterized the susceptibility of THP-1-derived macrophages to HMPV infection and the effect of hsa-miR-4634 on these cells. Transfection of an miRNA mimic and inhibitor demonstrated that hsa-miR-4634 regulates the IFN response in HMPV-infected macrophages, suggesting that HMPV induces the expression of the miRNA as a subversion mechanism of the antiviral response. This effect was not limited to macrophages, as a similar effect was also observed in epithelial cells. Overall, our results demonstrate that hsa-miR-4634 is an important factor in regulating the IFN response in macrophages and epithelial cells during HMPV infection.

Protective efficacy of a novel recombinant influenza virus carrying partial human metapneumovirus F protein epitopes

ABSTRACT Human metapneumovirus (HMPV) is a leading cause of acute respiratory tract infections in infants and children. Currently, no approved HMPV vaccine is available. We developed a novel recombinant influenza virus, which carried partial HMPV F protein (HMPV-F) epitopes, utilizing reverse genetics. The novel single-stranded RNA virus, termed rFLU-HMPV/F-NA, was synthesized in the neuraminidase (NA) fragment of influenza virus A/PuertoRico/8/34 (PR8). The morphological characteristics of rFLU-HMPV/F-NA were consistent with the wild-type flu virus. The virus could passage in specific pathogen-free (SPF) chicken embryos for at least five consecutive generations with haemagglutinin (HA) titres of 28–9 or 8–9LogTCID50/mL. BALB/c mice were intranasally immunized at 21-day intervals with 104 TCID50 (low-dose group) or 106 TCID50 (high-dose group) rFLU-HMPV/F-NA, and PBS or PR8 vaccine was used for the control group. rFLU-HMPV/F-NA induced robust humoral, mucosal, and cellular immune responses in vivo in a dose-dependent manner. More importantly, wt clinical HMPV isolate challenge studies showed that rFLU-HMPV/F-NA provided significant immune protection against HMPV infection compared to the PBS or PR8 vaccine control group, as shown by improved histopathological changes and reduced viral titres in the lungs of immunized mice post-challenge. These findings demonstrate that rFLU-HMPV/F-NA has potential as a promising HMPV candidate vaccine and warrants further investigation into its control of HMPV infection.

PD-1 Impairs CD8+ T Cell Granzyme B Production in Aged Mice during Acute Viral Respiratory Infection.

CD8+ T cell dysfunction contributes to severe respiratory viral infection outcomes in older adults. CD8+ T cells are the primary cell type responsible for viral clearance. With increasing age, CD8+ T cell function declines in conjunction with an accumulation of cytotoxic tissue-resident memory (TRM) CD8+ T cells. We sought to elucidate the role of PD-1 signaling on aged CD8+ T cell function and accumulation of CD8+ TRM cells during acute viral respiratory tract infection, given the importance of PD-1 regulating CD8+ T cells during acute and chronic infections. PD-1 blockade or genetic ablation in aged mice yielded improved CD8+ T cell granzyme B production comparable to that in young mice during human metapneumovirus and influenza viral infections. Syngeneic transplant and adoptive transfer strategies revealed that improved granzyme B production in aged Pdcd1-/- CD8+ T cells was primarily cell intrinsic because aged wild-type CD8+ T cells did not have increased granzyme B production when transplanted into a young host. PD-1 signaling promoted accumulation of cytotoxic CD8+ TRM cells in aged mice. PD-1 blockade of aged mice during rechallenge infection resulted in improved clinical outcomes that paralleled reduced accumulation of CD8+ TRM cells. These findings suggest that PD-1 signaling impaired CD8+ T cell granzyme B production and contributed to CD8+ TRM cell accumulation in the aged lung. These findings have implications for future research investigating PD-1 checkpoint inhibitors as a potential therapeutic option for elderly patients with severe respiratory viral infections.

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 < 0.001), pneumonia (P < 0.001), pediatric intensive care unit (PICU) admissions (P < 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.