Evaluation of combining the PDX analogue AN-137B with oseltamivir in a mouse model of severe influenza A (H1N1) infection.

BackgroundInfluenza is often not recognized as an important cause of severe or fatal disease in tropical and subtropical countries in Southeast Asia. The extent to which Oseltamivir treatment may protect against a fatal outcome in severe influenza infections is not known. Thailand's National Avian Influenza Surveillance (NAIS) system affords a unique opportunity to describe the epidemiology of laboratory-confirmed severe and fatal human influenza infections.Methodology/Principal FindingsDuring January 2004 through December 2006, 11,641 notifications to the NAIS were investigated in 73 of 76 Thai provinces. Clinical and demographic data and respiratory swab specimens were collected and tested by PCR for influenza. Using the NAIS database, we identified all patients with laboratory confirmed human influenza (A/H3N2, A/H1N1 and Type B) infection. A retrospective medical record review was conducted on all fatal cases with laboratory confirmed influenza and from a sample of hospitalized cases in 28 provinces. The association of underlying risk factors, Oseltamivir treatment and risk of a fatal outcome were examined. Human influenza infections were identified in 2,075 (18%) cases. Twenty-two (1%) deaths occurred including seven deaths in children less than ten years of age. Thirty-five percent of hospitalized human influenza infections had chest X-ray confirmed pneumonia. Current or former smoking; advanced age, hypertension and underlying cardiovascular, pulmonary or endocrine disease were associated with a fatal outcome from human influenza infection. Treatment with Oseltamivir was statistically associated with survival with a crude OR of .11 (95% CI: 0.04–0.30) and .13 (95% CI: 0.04–0.40) after controlling for age.ConclusionsSevere and fatal human influenza infections were commonly identified in the NAIS designed to identify avian A/H5N1 cases. Treatment with Oseltamivir is associated with survival in hospitalized human influenza pneumonia patients.

Infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) or seasonal influenza may lead to respiratory failure requiring intubation and mechanical ventilation. The pathophysiology of this respiratory failure is attributed to local immune dysregulation, but how the immune response to viral infection in the lower airways of the human lung differs between individuals with respiratory failure and those without is not well understood. We used quantitative multiparameter flow cytometry and multiplex cytokine assays to evaluate matched blood and bronchoalveolar lavage (BAL) samples from control human subjects, subjects with symptomatic seasonal influenza who did not have respiratory failure, and subjects with severe seasonal influenza or SARS-CoV-2 infection with respiratory failure. We find that severe cases are associated with an influx of nonclassical monocytes, activated T cells, and plasmablast B cells into the lower airways. Cytokine concentrations were not elevated in the lower airways of moderate influenza patients compared with controls; however, 28 of 35 measured cytokines were significantly elevated in severe influenza, severe SARS-CoV-2 infection, or both. We noted the largest elevations in IL-6, IP-10, MCP-1, and IL-8. IL-1 family cytokines and RANTES were higher in severe influenza infection than severe SARS-CoV-2 infection. Interestingly, only the concentration of IP-10-correlated between blood and BAL during severe infection. Our results demonstrate inflammatory immune dysregulation in the lower airways during severe viral pneumonia that is distinct from lower airway responses seen in human patients with symptomatic, but not severe, illness and suggest that measurement of blood IP-10 concentration may predict this unique dysregulation.

BackgroundInfluenza infections produce a spectrum of disease severity, ranging from a mild respiratory illness to respiratory failure and death. The host-response pathways associated with the progression to severe influenza disease are not well understood.MethodsTo gain insight into the disease mechanisms associated with progression to severe infection, we analyzed the leukocyte transcriptome in severe and moderate influenza patients and healthy control subjects. Pathway analysis on differentially expressed genes was performed using a topology-based pathway analysis tool that takes into account the interaction between multiple cellular pathways. The pathway profiles between moderate and severe influenza were then compared to delineate the biological mechanisms underpinning the progression from moderate to severe influenza.Results107 patients (44 severe and 63 moderate influenza patients) and 52 healthy control subjects were included in the study. Severe influenza was associated with upregulation in several neutrophil-related pathways, including pathways involved in neutrophil differentiation, migration, degranulation and neutrophil extracellular trap (NET) formation. The degree of upregulation in neutrophil-related pathways were significantly higher in severely infected patients compared to moderately infected patients. Severe influenza was also associated with downregulation in immune response pathways, including pathways involved in antigen presentation such as CD4+ T-cell co-stimulation, CD8+ T cell and Natural Killer (NK) cells effector functions. Apoptosis pathways were also downregulated in severe influenza patients compare to moderate and healthy controls.ConclusionsThese findings showed that there are changes in gene expression profile that may highlight distinct pathogenic mechanisms associated with progression from moderate to severe influenza infection.

Both seasonal and novel avian influenza viruses can result in severe infections requiring hospitalization. Anti-influenza antibodies (Abs) with Fc-mediated effector functions, such as Ab-dependent cellular cytotoxicity (ADCC), are of growing interest in control of influenza but have not previously been studied during severe human infections. As such, the objective of this study was to examine Fc-mediated Ab functions in humans hospitalized with influenza infection. Serum Ab response was studied in subjects hospitalized with either pandemic H7N9 avian influenza virus in China (n = 18) or circulating seasonal influenza viruses in Melbourne, Australia (n = 16). Recombinant soluble Fc receptor dimer ELISAs, natural killer (NK) cell activation assays, and Ab-dependent killing assays with influenza-infected target cells were used to assess the Fc functionality of anti-influenza hemagglutinin (HA) Abs during severe human influenza infection. We found that the peak generation of Fc functional HA Abs preceded that of neutralizing Abs for both severe H7N9 and seasonal influenza infections. Subjects who succumbed to complications of H7N9 infection demonstrated reduced HA-specific Fc receptor-binding Abs (in magnitude and breadth) immediately prior to death compared with those who survived. Subjects who recovered from H7N9 and severe seasonal influenza infections demonstrated increased Fc receptor-binding Abs not only against the homologous infecting strain but against HAs from different influenza A subtypes. Collectively, survivors of severe influenza infection rapidly generate a functional Ab response capable of mediating ADCC against divergent influenza viruses. Broadly binding HA Abs with Fc-mediated functions may be a useful component of protective immunity to severe influenza infection. The National Health and Medical Research Council ([NHMRC] grants 1023294, 1041832, and 1071916), the Australian Department of Health, and the joint University of Melbourne/Fudan University International Research and Research Training Fund provided funding for this study.

Cytokine responses in patients with mild or severe influenza A(H1N1)pdm09

The Role of Viral, Host, and Secondary Bacterial Factors in Influenza Pathogenesis

To the editor: In Okinawa, Japan, we have experienced two epidemics of influenza caused by the pandemic H1N1 2009 virus. Given this epidemic history, we compared the characteristics of critically ill (intubated) patients observed during the first epidemics (2009–2010) and during the first post-pandemic seasonal activity (2010–2011) caused by pandemic H1N1 2009 in Okinawa, Japan. Upon initial analysis, it was observed that the durations of these two influenza epidemics were significantly different. For the first epidemics, the outbreak of influenza started in August 2009 and ended in February 2010 (7 months’ duration). In contrast, in the first post-pandemic seasonal activity, the outbreak started in December 2010 and ended in February 2011 (3 months’ duration). The duration of the first epidemics was much longer despite the peak level being lower. In contrast, the pattern of the epidemic for the first post-pandemic seasonal activity closely resembled that for seasonal influenza. There have been several previous reports that compared differences between the first and second waves of epidemics during the same 2009–2010 season.1–5 However, there is only one report that compared the clinical features observed between the two influenza seasons.6 It was reported that the second year of pandemic H1N1 2009 in New Zealand produced an epidemic curve similar in shape to the first wave, of about half to two-thirds the size, and starting 1 month later in the winter. In contrast to this report, our experience in Okinawa has shown the incidence of influenza mainly caused by pandemic H1N1 2009 virus increased markedly in August 2009, peaked in mid-September, and then declined thereafter. In addition, the incidence of influenza increased again and peaked in December 2009, and, overall, the influenza epidemics lasted 26 weeks. We also compared the clinical features of patients that required intubation during the first epidemics with those that were intubated during the first post-pandemic seasonal activity, namely patients with severe influenza infection. The most striking difference observed in patients with severe influenza during the first epidemics and the first post-pandemic seasonal activity was the difference in the age of the patients. As shown in Figure 1, patients with severe influenza seen during the first epidemics were significantly younger compared with patients with severe influenza observed during the first post-pandemic seasonal activity. As demonstrated in Figure 1, in the first epidemics, younger children were more likely to deteriorate and require intubation mainly because of influenza encephalopathy as reported previously.7,8 In addition, three of 21 intubated patients died during the first epidemics. The age distribution of severe influenza observed during the first epidemics had the highest rates in children under the age of 10 years, and intubation rates declined significantly for most age groups (Figure 1). Among the 21 patients with severe influenza, only eight patients had underlying diseases (two had only bronchial asthma). In addition, four children had complications with bronchial asthma during the first epidemics. Distribution of the age of patients with severe influenza during the first epidemics and during the first post-pandemic seasonal activity caused by pandemic H1N1 2009. In contrast, during the first post-pandemic seasonal activity, the status of patients with increased age deteriorated, and seven of 16 intubated patients died. The age distribution of severe influenza infection during the first post-pandemic seasonal activity was highest in adult patients aged 50–59 years, as well as adult patients aged 70–79 (Figure 1). In addition, among the 16 patients with severe influenza infections, 15 patients had underlying diseases (one had only bronchial asthma and another had only obesity). In conclusion, there were significant differences observed in the clinical features of critically ill patients observed in Okinawa, Japan, during the first epidemics and the first post-pandemic seasonal activity. Further study will be required to clarify the pathogenesis of severe influenza. The authors have no conflicts of interest to declare.

Hepatitis C virus entry: Role of host and viral factors

BackgroundThe pandemic influenza A (H1N1) pdm09 virus, avian influenza A (H5N1) virus, and influenza A (H7N9) virus induced severe morbidity and mortality throughout the world. Previous studies suggested a close association between the interferon-induced transmembrane protein-3 (IFITM3) genetic variant rs12252 and influenza. Here, we explored the correlation between the rs12252 and influenza susceptibility and severity using meta-analysis.MethodsRelevant studies published before May 22, 2014 were retrieved from PubMed, ISI web of knowledge, EBSCO, and Cochrane central register of controlled trials databases. Association between rs12252 and influenza susceptibility and severity were determined using statistical analysis of odds ratios (ORs).ResultsA total of four studies consisting of 445 cases and 4180 controls were included in our analysis. Generally, there is increased risk of influenza in subjects carrying rs12252 in the recessive model (CC vs. CT+TT: OR = 2.35, 95% CI: 1.49-3.70, P<0.001), the dominant model (CC+CT vs. TT: OR=1.60, 95% CI: 1.18–2.22, P=0.003), the homozygote comparison (CC vs. TT: OR=4.11, 95% CI: 2.15–7.84, P<0.001), and the allele contrast (C vs. T: OR=1.67, 95% CI: 1.32–2.13, P<0.001). Stratification analysis of ethnicity and severity revealed a significant increase in influenza susceptibility by IFITM3-SNP rs12252 among both Asian and Caucasian population. SNP rs12252 shows significant impact on severe infections (P<0.05), but not on mild influenza. Besides, our result also associated rs12252 with influenza severity (severe vs. mild: OR=2.37, 95% CI: 1.32–4.25, P=0.004), (severe vs. control: OR=2.70, 95% CI: 1.85–3.94, P<0.001).ConclusionOur meta-analysis suggests a significant association between a minor IFITM3 allele (SNP rs12252-C) with severe influenza susceptibility, but not in mild influenza subjects, in both UK Caucasians and Han Chinese population. The rs12252-C allele causes a 23.7% higher chance of infection and also constitutes a risk factor for more severe influenza.

The aim of this study is to investigate the effectiveness of prolonged versus standard course oseltamivir treatment among critically ill patients with severe influenza. Aretrospective study of a prospectively collected database including adults with influenza infection admitted to 184 intensive care units (ICUs) in Spain from 2009 to 2018. Prolonged oseltamivir was defined if patients received the treatment beyond 5 days, whereas the standard-course group received oseltamivir for 5 days. The primary outcome was all-cause ICU mortality. Propensity score matching (PSM) was constructed, and the outcome was investigated through Cox regression and RCSs. Two thousand three hundred and ninety-sevensubjects were included, of whom 1943 (81.1%) received prolonged oseltamivirand 454 (18.9%) received standard treatment. An optimal full matching algorithm was performed by matching 2171 patients, 1750 treated in the prolonged oseltamivir group and 421 controls in the standard oseltamivir group. After PSM, 387 (22.1%) patients in the prolonged oseltamivir and 119 (28.3%) patients in the standard group died (p = 0.009). After adjusting confounding factors, prolonged oseltamivir significantly reduced ICU mortality (odds ratio [OR]: 0.53, 95% confidence interval [CI]: 0.40-0.69). Prolonged oseltamivir may have protective effects on survival at Day 10 compared with a standard treatment course. Sensitivity analysis confirmed these findings. Compared with standard treatment, prolonged oseltamivir was associated with reduced ICU mortality in critically ill patients with severe influenza. Clinicians should consider extending the oseltamivir treatment duration to 10 days, particularly in higher-risk groups of prolonged viral shedding. Further randomized controlled trials are warranted to confirm these findings.

Please cite this paper as: Howard et al. (2011) Report of the ‘Mechanisms of lung injury and immunomodulator interventions in influenza’ workshop, 21 March 2010, Ventura, California, USA*. Influenza and Other Respiratory Viruses 5(6), 453–e475.The clinical course of influenza and the extent of lung injury are determined by both viral and host factors, as well as sometimes secondary bacterial infections and exacerbations of underlying conditions. The balance between viral replication and the host immune responses is central to disease pathogenesis, and the extent of lung injury in severe influenza infections may be due in part to overly exuberant or dysregulated innate inflammatory responses or sometimes deficient responses. Acute respiratory distress syndrome (ARDS) is the principal cause of respiratory failure associated with severe influenza. ARDS can be triggered by both direct lung insults (e.g. respiratory pathogens) and systemic insults (e.g. sepsis), and the lung damage is exacerbated by the inflammatory response associated with either infectious or non‐infectious insults. This workshop aimed to review the current understanding of lung injury in acute influenza and describe cellular and molecular mechanisms of lung injury that are common to influenza and infections by other respiratory pathogens. In addition, therapeutic agents that target host response proteins and pathways were identified and investigational agents in development reviewed. A logical strategy would be to combine antiviral treatment with drugs that modify excessive host responses or supplement deficient ones. However, a better understanding of common cell signalling pathways associated with acute lung injury caused by influenza and other pathogens is necessary to understand immunopathologic causes of lung injury. This will help determine which immunomodulatory interventions might be useful, and to predict the appropriate timing and consequences of their use.

The effectiveness of repeated vaccination for influenza to prevent severe cases remains unclear. We evaluated the effectiveness of influenza vaccination on preventing admissions to hospital for influenza and reducing disease severity. We conducted a case-control study in 20 hospitals in Spain during the 2013/14 and 2014/15 influenza seasons. Community-dwelling adults aged 65 years or older who were admitted to hospital for laboratory-confirmed influenza were matched with inpatient controls by sex, age, hospital and admission date. The effectiveness of vaccination in the current and 3 previous seasons in preventing influenza was estimated for inpatients with nonsevere influenza and for those with severe influenza who were admitted to intensive care units (ICUs) or who died. We enrolled 130 inpatients with severe and 598 with nonsevere influenza who were matched to 333 and 1493 controls, respectively. Compared with patients who were unvaccinated in the current and 3 previous seasons, adjusted effectiveness of influenza vaccination in the current and any previous season was 31% (95% confidence interval [CI] 13%-46%) in preventing admission to hospital for nonsevere influenza, 74% (95% CI 42%-88%) in preventing admissions to ICU and 70% (95% CI 34%-87%) in preventing death. Vaccination in the current season only had no significant effect on cases of severe influenza. Among inpatients with influenza, vaccination in the current and any previous season reduced the risk of severe outcomes (adjusted odds ratio 0.45, 95% CI 0.26-0.76). Among older adults, repeated vaccination for influenza was twice as effective in preventing severe influenza compared with nonsevere influenza in patients who were admitted to hospital, which is attributable to the combination of the number of admissions to hospital for influenza that were prevented and reduced disease severity. These results reinforce recommendations for annual vaccination for influenza in older adults.

Hypercoagulability in ICU Patients With Coronavirus Disease 2019 With Respiratory Failure Results in Increased Prevalence of Venous Thromboembolic Disease

BackgroundInfluenza virus is a contagious respiratory pathogen that can cause severe acute infections with long-term adverse outcomes. For paediatric patients at high risk of severe influenza, the readmission and the associated risk factors remain unclear.MethodsChildren discharged with a diagnosis of severe or critical influenza from October 2021 to March 2022 were included. The disease severity was categorized according to the “2020 edition of the Chinese expert consensus on the diagnosis and treatment of influenza in children”. Demographic data, clinical characteristics, underlying medical conditions, microbiology, treatment outcomes, and 90-day readmissions were retrieved and retrospectively analyzed. Those who tested positive for COVID-19 were excluded. Risk factors independently associated with readmission were identified using multiple logistic regression models.ResultsDuring the study period, 225 children with severe influenza were hospitalized and 14.7% (33/225) of them were readmitted within 90 days. The median length of readmission was 62 (IQR, 31–76) days, and the most common cause of readmission was pneumonia. M. pneumoniae and influenza virus are the most common infections for readmission The children who were readmitted were more likely to have critical influenza and neurological comorbidities compared to patients without readmission. The readmitted children had a significantly higher proportion of natural killer cells and a shorter febrile duration and length of stay on their first admission, compared with those who were not readmitted. Rhinosinusitis (OR = 30.085, p = .008) and high level of natural killer cells (OR = 1.107, p = .012) were independent risk factors and febrile duration (OR, 0.748, p = .018) was a protective factor for 90-day readmission.ConclusionsOur findings suggest that, to reduce the potential readmission of children with severe influenza, a sustained focus on the risk factors including rhinosinusitis and over-activated host immune response during the index hospitalization is needed.

The amino acid substitution of aspartic acid to glycine in hemagglutinin (HA) in position 222 (HA-D222G) as well as HA-222D/G polymorphism of pandemic (H1N1) 2009 influenza viruses (A(H1N1)pdm09) were frequently reported in severe influenza in humans and mice. Their impact on viral pathogenicity and the course of influenza has been discussed controversially and the underlying mechanism remained unclarified. In the present study, BALB/c mice, infected with the once mouse lung- and cell-passaged A(H1N1)pdm09 isolate A/Jena/5258/09 (mpJena/5258), developed severe pneumonia. From day 2 to 3 or 4 post infection (p.i.) symptoms (body weight loss and clinical score) continuously worsened. After a short disease stagnation or even recovery phase in most mice, severity of disease further increased on days 6 and 7 p.i. Thereafter, surviving mice recovered. A 45 times higher virus titer maximum in the lung than in the trachea on day 2 p.i. and significantly higher tracheal virus titers compared to lung on day 6 p.i. indicated changes in the organ tropism during infection. Sequence analysis revealed an HA-222D/G polymorphism. HA-D222 and HA-G222 variants co-circulated in lung and trachea. Whereas, HA-D222 variant predominated in the lung, HA-G222 became the major variant in the trachea after day 4 p.i. This was accompanied by lower neutralizing antibody titers and broader receptor recognition including terminal sialic acid α-2,3-linked galactose, which is abundant on mouse trachea epithelial cells. Plaque-purified HA-G222-mpJena/5258 virus induced severe influenza with maximum symptom on day 6 p.i. These results demonstrated for the first time that HA-222D/G quasispecies of A(H1N1)pdm09 caused severe biphasic influenza because of fast viral intra-host evolution, which enabled partial antibody escape and minor changes in receptor binding.