H1N1pdm09 Virus Research Articles

Physical interventions to interrupt or reduce the spread of respiratory viruses.

Physical interventions to interrupt or reduce the spread of respiratory viruses.

Study on Antiviral Activity and Pharmacological Safety of Double-Stranded Ribonucleic Acid for Intranasal Administration

Interferon inducers are of interest as the first line of defense against viral infections, including influenza. Double-stranded ribonucleic acid (dsRNA) for intranasal administration has been developed, the excipients and drug components were selected at the Institute of Medical Biotechnology, a branch of the State Research Center of Virology and Biotechnology «Vector». This work presents the results of the study on antiviral activity and pharmacological safety of a new form of dsRNA. The antiviral activity of the preparation was studied in BALB/c mice infected with influenza A/Aichi/2/68 (H3N2) or Bishkek/01/2009 (H1N1pdm09) viruses. A safety study was performed with a single administration of intranasal dsRNA into white outbred ICR mice. The study showed that the administration of therapeutic and prophylactic regimen of intranasal dsRNA at a dose of 2.5 mg/kg increases the survival and average life expectancy of mice infected with the mentioned strains of influenza virus. The protective effect of the preparation in mice infected with a lethal dose of Bishkek/01/2009 virus was comparable to the effect of Tamiflu. The absence of toxic effects of intranasal dsRNA at a pharmacological dose in laboratory mice, the functional state of their physiological systems, as well as main types of metabolism, established in the experiments, lead to a conclusion concerning pharmacological safety of the preparation and the prospects for further work to complete pharmaceutical development of a new antiviral drug.

Analysis of non-bacterial respiratory pathogens in children in Ningbo City from 2019 to 2021

Objective: To investigate the distribution characteristics of respiratory non-bacterial pathogens in children in Ningbo from 2019 to 2021. Methods: A retrospective analysis was performed on 23 733 children with respiratory tract infection who visited the department of pediatrics of Ningbo Women and Children's Hospital from July 2019 to December 2021. There were 13 509 males (56.92%) and 10 224 females (43.08%), with an age range of 1 day to 18 years old. There were 981 cases in the neonatal group (younger than 1 month old), 5 880 cases in the infant group (1 month to younger than 1 year old), 6 552 cases in the toddler group (1 to younger than 3 years old), 7 638 cases in the preschool group (3 to younger than 7 years old), and 2 682 cases in the school-age group (7 to 18 years old). Thirteen respiratory pathogens were detected by multiple polymerase chain reaction (PCR) based on capillary electrophoresis, and SPSS 23.0 software was used for statistical analysis of the results, the count data were expressed as percentages, and the χ2 test was used for comparison between groups. Results: Of the 23 733 specimens, 13 330 were positive for respiratory pathogens, with a total positive rate of 56.17%. The positive rates of human rhinovirus (HRV) 24.05% (5 707/23 733), human respiratory syncytial virus (HRSV) 10.45% (2 480/2 3733) and mycoplasma pneumoniae (Mp) 7.03% (1 668/23 733) were in the first three. The positive rates of pathogens in the male and female children were 57.47% (7 763/13 509) and 54.45% (5 567/10 224), respectively, and the difference was statistically significant (χ2=21.488, P<0.001). The positive rates in the neonatal group, infant group, toddler group, preschool group, and school-age group were 31.80% (312/981), 54.71% (3 217/5 880), 63.23% (4 143/6 552), 59.83% (4 570/7 638), 40.57% (1 088/2 682), respectively, and the difference among the groups was statistically significant (χ2=681.225, P<0.001). The single infection rate was 47.43% (11 256/23 733), the mixed infection rate of two or more pathogens was 8.74% (2 074/23 733), most of which were mixed infections of two pathogens. HRV, HADV, HCOV, Ch disseminated in the whole year. HRSV, HMPV, Boca, HPIV occurred mostly in fall and winter. The positive rates of FluA, FluB, Mp were at a low level after the corona virus disease 2019 (COVID-19) epidemic (2020 and 2021). The positive rates of FluA, H1N1, H3N2, FluB, HADV, Mp in 2020 were significantly lower than in 2019 (P<0.05). The positive rates of HPIV, HRV, HCOV, Ch in 2020 were significantly higher than in 2019 (P<0.05). The positive rates of FluA, H1N1, H3N2, HPIV, HCOV, Mp, Ch in 2021 were significantly lower than in 2020 (P<0.05). The positive rates of Boca, HMPV, HRSV in 2021 were significantly higher than in 2020 (P<0.05). Conclusion: From 2019 to 2021, the main non-bacterial respiratory pathogens of children in Ningbo City were Mp and HRV, and the detection rates of respiratory pathogens varied among different ages, seasons and genders.

Zooming in on the molecular characteristics of swine influenza virus circulating in Colombia before and after the H1N1pdm09 virus.

Influenza is one of the most critical viral agents involved in the respiratory disease complex affecting swine production systems worldwide. Despite the absence of vaccination against swine influenza virus in Colombia, the serologic reactivity to classic H1N1 and H3N2 subtypes reported since 1971 indicates the virus has been circulating in the country's swine population for several decades. However, successful isolation and sequencing of field virus from pigs was nonexistent until 2008, when H1N1 classical influenza virus was identified. One year later, due to the emergence of the influenza A (H1N1) pdm09 virus, responsible for the first global flu pandemic of the 21st century, it was introduced in the country. Therefore, to understand the impact of the introduction of the H1N1pdm09 virus in Colombia on the complexity and dynamics of influenza viruses previously present in the swine population, we carried out a study aiming to characterize circulating viruses genetically and establish possible reassortment events that might have happened between endemic influenza viruses before and after the introduction of the pandemic virus. A phylogenetic analysis of ten swine influenza virus isolates from porcine samples obtained between 2008 and 2015 was conducted. As a result, a displacement of the classical swine influenza virus with the pdmH1N1 virus in the swine population was confirmed. Once established, the pandemic subtype exhibited phylogenetic segregation based on a geographic pattern in all the evaluated segments. The evidence presents reassortment events with classic viruses in one of the first H1N1pdm09 isolates. Thus, this study demonstrates complex competition dynamics and variations in Colombian swine viruses through Drift and Shift.

Development of amperometric biosensor based on cloned hemagglutinin gene of H1N1 (swine flu) virus.

The recent emergence of respiratory viruses especially COVID-19 and swine flu has underscored the need for robust and bedside detection methods. Swine flu virus is a very infectious virus of the respiratory system. Timely detection of this virus with high specificity and sensitivity is crucial for reducing morbidity as well as mortality. Cloning of gene segments into a non-infectious agent helps in the development of detection methods, vaccine development, and other studies. In this study, cloning was used to develop a biosensor for H1N1 pdm09 detection. A segment of the hemaglutinin gene was cloned in a vector and characterized with the help of colony touch PCR and blue–white screening. The recombinant plasmid was extracted, and the gene segment was confirmed with the help of HA-specific primers. A 5′ amine group-attached hemagglutinin (HA) gene-specific DNA probe was immobilized on the working gold electrode surface to make a quick, specific, reliable, and sensitive detection method for H1N1pdm09 virus in human nasal swab samples. The HA probe was immobilized on the cysteine applied gold electrode of the screen-printed electrode through 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Differential pulse voltammetry was performed with the help of methylene blue, which is a redox indicator for the detection of single-stranded cloned HA gene segment. The developed sensor depicted high sensitivity for the H1N1 influenza virus with a detection limit of 0.6 ng ssDNA/6 µl of the cloned HA sample. Specificity was also checked using H3N2 virus, N. meningitides, influenza A and positive H1N1pdm09 samples.

Influenza A Virus Infection in Domestic Ferrets.

Ferrets are animals that are known to be susceptible to influenza A virus (IAV) infection. To evaluate the risk of IAV transmission from diseased ferrets to humans, a survey was performed to detect specific antibodies against the H1, H3, H5, and H7 subtypes of IAV. Using enzyme-linked immunosorbent assay for hemagglutinin proteins, we found a high positive rate for the H1 (24.1%) and H3 (5.2%) subtypes. The results were confirmed by a virus neutralization test for representative antibody-positive serum samples. We also detected hemagglutinin and neuraminidase genes in two ferrets showing acute respiratory disease and whose owner was diagnosed with IAV infection; a human H1N1pdm virus was isolated from one of these ferrets. Our findings suggest that attention should be paid to IAV infection from humans to ferrets and vice versa.

Infection of a naïve sow herd with Mycoplasma hyopneumoniae

A 2500-sow herd previously free of, and unvaccinated for, Mycoplasma hyopneumoniae became infected. Both M hyopneumoniae and influenza A H1N1pdm09 virus were identified in sows showing clinical signs. Coughing lasting 2 to 4 days was observed in approximately 10% of sows and 26 sows died over the course of the outbreak. There was no apparent impact on performance indicators. Polymerase chain reaction and serological results showed that M hyopneumoniae progression within the herd was fast and that infection may have occurred within a few weeks. An elimination program was quickly implemented so that sale of negative animals could resume.

The Epidemiological Pattern and Co-infection of Influenza A and B by Surveillance Network From 2009 to 2014 in Anhui Province, China.

Influenza-like illness (ILI) is one of the most important public health problems globally, causing an enormous disease burden. Influenza infections are the most common cause of ILI. Bacterial and virus co-infection is common yet the data of co-infection with influenza A and B viruses are scarce. To identify the epidemiological patterns of and co-infection of influenza A and B in Anhui province, China, we analyzed the surveillance data of 5 years from 2009 to 2014 collected by the Chinese National influenzas network. The results showed that the weekly ratio of ILI was 3.96 ± 1.9% (95% CI 3.73–4.2%) in outpatients and the highest affected population was children under 5 years old. The epidemic of influenza viruses was highest during 2009–2010. For the other 4 surveillance years, school-aged people (5–14 years) were the most highly affected population. Influenza B and H3N2 viruses were more prevalent than H1N1pdm09 virus after 2010. In addition, a significant co-circulation of influenza A (H1N1pdm09 and H3N2) and influenza B virus was detected with 0.057% PCR positive rate during 2009–2014 in Eastern China, yet isolated only in pediatric patients. Our data reveals school-aged population would be the main vulnerable population and a distinct seasonality for influenza. In addition, the co-infection of influenza A and B were found in Anhui Province, China. Ongoing surveillance is critical to understand the seasonality variation and make evidence-based vaccination recommendations. Information on the epidemiological patterns and co-infections of influenza A and B can help us to implement different strategies for selecting vaccine formulations and monitoring new emerging influenza strains. In addition, the identification of the susceptible population can help us to develop more precise protection measures.

Whole-genome analysis to determine the rate and patterns of intra-subtype reassortment among influenza type-A viruses in Africa.

Influenza type-A viruses (IAVs) present a global burden of human respiratory infections and mortality. Genome reassortment is an important mechanism through which epidemiologically novel influenza viruses emerge and a core step in the safe reassortment-incompetent live-attenuated influenza vaccine development. Currently, there are no data on the rate, spatial and temporal distribution, and role of reassortment in the evolution and diversification of IAVs circulating in Africa. We aimed to detect intra-subtype reassortment among Africa pandemic H1N1pdm09 (2009–10), seasonal H1N1pdm09 (2011–20), and seasonal H3N2 viruses and characterize the genomic architecture and temporal and spatial distribution patterns of the resulting reassortants. Our study was nested within the Uganda National Influenza Surveillance Programme. Next-generation sequencing was used to generate whole genomes (WGs) from 234 H1N1pdm09 (n = 116) and H3N2 (n = 118) viruses sampled between 2010 and 2018 from seven districts in Uganda. We combined our newly generated WGs with 658 H1N1pdm09 and 1131 H3N2 WGs sampled between 1994 and 2020 across Africa and identified reassortants using an automated Graph Incompatibility Based Reassortment Finder software. Viral reassortment rates were estimated using a coalescent reassortant constant population model. Phylogenetic analysis was used to assess the effect of reassortment on viral genetic evolution. We observed a high frequency of intra-subtype reassortment events, 12 · 4 per cent (94/758) and 20 · 9 per cent (256/1,224), and reassortants, 13 · 3 per cent (101/758) and 38 · 6 per cent (472/1,224), among Africa H1N1pdm09 and H3N2 viruses, respectively. H1N1pdm09 reassorted at higher rates (0.1237–0.4255) than H3N2 viruses (0 · 00912–0.0355 events/lineage/year), a case unique to Uganda. Viral reassortants were sampled in 2009 through 2020, except in 2012. 78 · 2 per cent (79/101) of H1N1pdm09 reassortants acquired new non-structural, while 57 · 8 per cent (273/472) of the H3N2 reassortants had new hemagglutinin (H3) genes. Africa H3N2 viruses underwent more reassortment events involving larger reassortant sets than H1N1pdm09 viruses. Viruses with a specific reassortment architecture circulated for up to five consecutive years in specific countries and regions. The Eastern (Uganda and Kenya) and Western Africa harboured 84 · 2 per cent (85/101) and 55 · 9 per cent (264/472) of the continent’s H1N1pdm09 and H3N2 reassortants, respectively. The frequent reassortment involving multi-genes observed among Africa IAVs showed the intracontinental viral evolution and diversification possibly sustained by viral importation from outside Africa and/or local viral genomic mixing and transmission. Novel reassortant viruses emerged every year, and some persisted in different countries and regions, thereby presenting a risk of influenza outbreaks in Africa. Our findings highlight Africa as part of the global influenza ecology and the advantage of implementing routine whole-over partial genome sequencing and analyses to monitor circulating and detect emerging viruses. Furthermore, this study provides evidence and heightens our knowledge on IAV evolution, which is integral in directing vaccine strain selection and the update of master donor viruses used in recombinant vaccine development.

Comparison of the pediatric hospitalizations due to COVID-19 and H1N1pdm09 virus infections during the pandemic period.

There are two major pandemics in the new millennium, including the pandemic of swine influenza and the COVID‐19 pandemic. These two pandemics affected children as well as the adult population. In this case‐control study, we compared children with COVID‐19 infection and those with H1N1pdm09 virus infection. We also compared the demographic factors, underlying disease, and the requirement for intensive care admission between the hospitalized children with COVID‐19 infection and children with H1N1pdm09 virus infection who were hospitalized during the 2009 H1N1 pandemic. In this study, we evaluated 103 patients with H1N1pdm09 virus infection and 392 patients with COVID‐19 infection. The age was significantly higher in the COVID‐19 patients' group compared to the pandemic influenza group (p < 0.001). The ratio of the children ≥12 years was 10.7% (n = 11) in the H1N1pdm09 virus infection and 36.2% (n = 142) in the COVID‐19 group. The rate of underlying disease was significantly higher in the patients with H1N1pdm09 virus infections (p = 0.02). The prevalence of underlying disease in patients requiring PICU hospitalization was 69.2% (n = 9/13) compared to 25.7% (n = 124/482) in patients who did not require PICU hospitalization. The rate of underlying disease was significantly higher in the PICU group regardless of COVID‐19 or H1N1pdm09 virus (p = 0.002). Our results suggest that older children were more hospitalized for COVID‐19 infections compared to pandemic influenza. In addition, regardless of the type of pandemic infection, the underlying disease is an important factor for pediatric intensive care unit admission. This finding is important for developing strategies for the protection of children with the underlying disease in the upcoming pandemics.

CD33 is downregulated by influenza virus H1N1pdm09 and induces ROS and the TNF-α, IL-1β, and IL-6 cytokines in human mononuclear cells.

The influenza A virus (IAV) H1N1pdm09 induces exacerbated inflammation, contributing to disease complications. Inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), favor an inflammatory response that aids viral replication and survival. A pathway by which spontaneous TNF-α production occurs involves either the reduction of Siglec-3 (CD33) levels or the absence of its ligand, sialic acid. Influenza virus uses sialic acid to enter cells by reducing their expression; however, the role of CD33 in IAV H1N1pdm09 stimulation and its relationship with inflammation have not yet been studied. To evaluate the role of CD33 in proinflammatory cytokine production in IAV H1N1pdm09 stimulation, peripheral blood mononuclear cells from healthy subjects were incubated with IAV H1N1pdm09. We observed that the infection caused an increase in the mRNA expression of proinflammatory cytokines such as TNF-α, interleukin (IL)-1β, and IL-6 and a significant reduction in CD33 expression by monocytes at an early stage of infection. Additionally, suppressor of cytokine signaling 3 (SOCS-3) mRNA expression was upregulated at 6h, and reactive oxygen species (ROS) production increased at 1.5h. Moreover, a significant reduction in CD33 expression on the cell surface of monocytes from influenza patients or of IAV H1N1pdm09-stimulated monocytes incubated in vitro was observed by flow cytometry. The results suggest that the decrease in CD33 and increase of SOCS-3 expression induced by IAV H1N1pdm09 triggered TNF-α secretion and ROS production, suggesting an additional way to exacerbate inflammation during viral infection.

Severe influenza: is there a role for antiviral combinations?

Neuraminidase inhibitors have been approved for over 20 years and are currently the standard of care for the treatment of influenza. However, meta-analyses have shown only modest benefit of neuraminidase inhibitors for influenza. 1 Dobson J Whitley RJ Pocock S Monto AS Oseltamivir treatment for influenza in adults: a meta-analysis of randomised controlled trials. Lancet. 2015; 385: 1729-1737 Summary Full Text Full Text PDF PubMed Scopus (361) Google Scholar , 2 Muthuri SG Venkatesan S Myles PR et al. Effectiveness of neuraminidase inhibitors in reducing mortality in patients admitted to hospital with influenza A H1N1pdm09 virus infection: a meta-analysis of individual participant data. Lancet Respir Med. 2014; 2: 395-404 Summary Full Text Full Text PDF PubMed Scopus (457) Google Scholar New treatment strategies for severe influenza are urgently required. A novel antiviral, baloxavir marboxil (baloxavir hereafter), was first approved in Japan in 2018, and subsequently in other countries. Baloxavir belongs to a new class of antivirals that inhibit the endonuclease function of the polymerase acidic protein. 3 O'Hanlon R Shaw ML Baloxavir marboxil: the new influenza drug on the market. Curr Opin Virol. 2019; 35: 14-18 Crossref PubMed Scopus (69) Google Scholar In a 2018 clinical trial, 4 Hayden FG Sugaya N Hirotsu N et al. Baloxavir marboxil for uncomplicated influenza in adults and adolescents. N Engl J Med. 2018; 379: 913-923 Crossref PubMed Scopus (407) Google Scholar a single dose of baloxavir produced greater reductions in influenza viral load than did oseltamivir, with equivalent time to symptom alleviation. Combining baloxavir marboxil with standard-of-care neuraminidase inhibitor in patients hospitalised with severe influenza (FLAGSTONE): a randomised, parallel-group, double-blind, placebo-controlled, superiority trialCombining baloxavir with NAIs did not result in superior clinical outcomes compared with NAIs alone. The combination of baloxavir plus NAI was well tolerated. The findings suggest that combination antivirals would not be routinely indicated in clinical practice for hospitalised patients with severe influenza. Full-Text PDF

Plasma Levels of Mid-Regional Proadrenomedullin Accurately Identify H1N1pdm09 Influenza Virus Patients with Risk of Intensive Care Admission and Mortality in the Emergency Department.

Early identification of severe viral pneumonia in influenza virus A (H1N1pdm09) patients is extremely important for prompt admission to the ICU. The objective is to evaluate the usefulness of MR-proadrenomedullin (MR-proADM) compared to C reactive protein (CRP), procalcitonin (PCT), and ferritin in the prognosis of influenza A pneumonia. This prospective, observational, multicenter study included one hundred thirteen patients with confirmed influenza virus A (H1N1pdm09) admitted to an Emergency Department and ICUs of six hospitals in Spain. Measurements and Main Results: one-hundred thirteen patients with confirmed influenza virus A (H1N1pdm09) were enrolled. Seventy-five subjects (mortality 29.3%) with severe pneumonia caused by influenza A H1N1pdm09 virus (H1N1vIPN) were compared with 38 controls (CG).The median MR-proADM levels at hospital admission were 1.2 nmol/L (IQR (0.8–2.6) vs. 0.5 nmol/L (IQR 0.2–0.9) in the CG (p = 0.01), and PCT levels were 0.43 μg/L (IQR 0.2–1.2) in the H1N1vIPN group and 0.1 μg/L (IQR 0.1–0.2) in the CG (p < 0.01). CRP levels at admission were 15.5 mg/dL(IQR 9.2–24.9) in H1N1vIPN and 8.6 mg/dL(IQR 3–17.3) in the CG (p < 0.01). Ferritin levels at admission were 558.1 ng/mL(IQR 180–1880) in H1N1vIPN and 167.7 ng/mL(IQR 34.8–292.9) in the CG (p < 0.01). A breakpoint for hospital admission of MR-proADM of 1.1 nmol/L showed a sensitivity of 55% and a specificity of 90% (AUC-ROC0.822). Non-survivors showed higher MR-proADM levels: median of 2.5 nmol/L vs. 0.9 nmol/L among survivors (p < 0.01). PCT, CRP, and ferritin levels also showed significant differences in predicting mortality. The MR-proADM AUC-ROC for mortality was 0.853 (p < 0.01). In a Cox proportional hazards model, MR-proADM levels > 1.2 nmol/L at hospital admission were significant predictive factors for ICU and 90-day mortality (HR: 1.3). Conclusions: the initial MR-proADM, ferritin, CRP, and PCT levels effectively determine adverse outcomes and risk of ICU admission and mortality in patients with influenza virus pneumonia. MR-proADM has the highest potency for survival prediction.

Serologic evidence of pandemic (H1N1) 2009 virus infection in camel and Eld's deer, Thailand.

Background and Aim:The pandemic (H1N1) 2009 influenza (H1N1pdm09) virus has affected both human and animal populations worldwide. The transmission of the H1N1pdm09 virus from humans to animals is increasingly more evident. Captive animals, particularly zoo animals, are at risk of H1N1pdm09 virus infection through close contact with humans. Evidence of exposure to the H1N1pdm09 virus has been reported in several species of animals in captivity. However, there is limited information on the H1N1pdm09 virus infection and circulation in captive animals. To extend the body of knowledge on exposure to the H1N1pdm09 virus among captive animals in Thailand, our study investigated the presence of antibodies against the H1N1pdm09 virus in two captive animals: Camelids and Eld’s deer.Materials and Methods:We investigated H1N1pdm09 virus infection among four domestic camelid species and wild Eld’s deer that were kept in different zoos in Thailand. In total, 72 archival serum samples from camelid species and Eld’s deer collected between 2013 and 2014 in seven provinces in Thailand were analyzed for influenza antibodies using hemagglutination inhibition (HI), microneutralization, and western blotting (WB) assays.Results:The presence of antibodies against the H1N1pdm09 virus was detected in 2.4% (1/42) of dromedary camel serum samples and 15.4% (2/13) of Eld’s deer serum samples. No antibodies were detected in the rest of the serum samples derived from other investigated camelids, including Bactrian camels (0/3), alpacas (0/5), and llamas (0/9). The three positive serum samples showed HI antibody titers of 80, whereas the neutralization titers were in the range of 320-640. Antibodies specific to HA and NP proteins in the H1N1pdm09 virus were detected in positive camel serum samples using WB. Conversely, the presence of the specific antibodies in the positive Eld’s deer serum samples could not be determined using WB due to the lack of commercially labeled secondary antibodies.Conclusion:The present study provided evidence of H1N1pdm09 virus infection in the captive dromedary camel and Eld’s deer in Thailand. Our findings highlight the need for continuous surveillance for influenza A virus in the population of dromedary camels and Eld’s deer. The susceptible animal populations in close contact with humans should be closely monitored. Further study is warranted to determine whether Eld’s deer are indeed a competent reservoir for human influenza virus.

Investigating the sequence variation in the influenza A matrix genes during the 2017-2018 and 2018-2019 seasons in samples from a local population in London

Recent publications have highlighted the emergence of mutations in the M1 gene of both influenza A H1N1pdm09 and H3N2 subtypes affecting the performance of commercial RT-PCR assays. Respiratory samples from the 2018/2019 season positive by our in-house RT-PCR for influenza A were analysed for the prevalence and impact of any M1 gene mutations. Sequence information was used to re-design primers for our routine assay and their performance assessed. Forty-five samples, consisting of 11 H1N1pdm09 and 34 H3N2 subtypes, together with the NIBSC H1N1 control were sequenced. All samples displayed the core mutations for H1N1 M1(C154T; G174A and G238A) and for H3N2 M1(C153T; C163T and G189T); three of the H1N1pdm09 viruses also showed a small number of point mutations. None of the mutations appeared to affect either the sensitivity or efficiency of the RT-PCR when compared to the re-designed primers. Although the mutations we found agreed with those in the publications cited we did not encounter any problems with our routine diagnostic assay and no improvements were found when the primers were modified to suit those mutations. However, it is likely that the influenza A virus M1 gene will accumulate further mutations that could impact RT-PCR assays and, therefore, it would be prudent to implement routine sequencing of samples during the influenza seasons to ensure no loss in assay performance.

Interferon Lambda Delays the Emergence of Influenza Virus Resistance to Oseltamivir.

Influenza viruses are a leading cause of morbidity and mortality worldwide. These air-borne pathogens are able to cross the species barrier, leading to regular seasonal epidemics and sporadic pandemics. Influenza viruses also possess a high genetic variability, which allows for the acquisition of resistance mutations to antivirals. Combination therapies with two or more drugs targeting different mechanisms of viral replication have been considered an advantageous option to not only enhance the effectiveness of the individual treatments, but also reduce the likelihood of resistance emergence. Using an in vitro infection model, we assessed the barrier to viral resistance of a combination therapy with the neuraminidase inhibitor oseltamivir and human interferon lambda against the pandemic H1N1 A/Netherlands/602/2009 (H1N1pdm09) virus. We serially passaged the virus in a cell line derived from human bronchial epithelial cells in the presence or absence of increasing concentrations of oseltamivir alone or oseltamivir plus interferon lambda. While the treatment with oseltamivir alone quickly induced the emergence of antiviral resistance through a single mutation in the neuraminidase gene, the co-administration of interferon lambda delayed the emergence of drug-resistant influenza virus variants. Our results suggest a possible clinical application of interferon lambda in combination with oseltamivir to treat influenza.

Pre-existing heterosubtypic immunity provides a barrier to airborne transmission of influenza viruses.

Human-to-human transmission of influenza viruses is a serious public health threat, yet the precise role of immunity from previous infections on the susceptibility to airborne infection is still unknown. Using the ferret model, we examined the roles of exposure duration and heterosubtypic immunity on influenza transmission. We demonstrate that a 48 hour exposure is sufficient for efficient transmission of H1N1 and H3N2 viruses. To test pre-existing immunity, a gap of 8-12 weeks between primary and secondary infections was imposed to reduce innate responses and ensure robust infection of donor animals with heterosubtypic viruses. We found that pre-existing H3N2 immunity did not significantly block transmission of the 2009 H1N1pandemic (H1N1pdm09) virus to immune animals. Surprisingly, airborne transmission of seasonal H3N2 influenza strains was abrogated in recipient animals with H1N1pdm09 pre-existing immunity. This protection from natural infection with H3N2 virus was independent of neutralizing antibodies. Pre-existing immunity with influenza B virus did not block H3N2 virus transmission, indicating that the protection was likely driven by the adaptive immune response. We demonstrate that pre-existing immunity can impact susceptibility to heterologous influenza virus strains, and implicate a novel correlate of protection that can limit the spread of respiratory pathogens through the air.

Simultaneous Aerosol and Intramuscular Immunization with Influenza Vaccine Induces Powerful Protective Local T Cell and Systemic Antibody Immune Responses in Pigs.

A vaccine providing both powerful Ab and cross-reactive T cell immune responses against influenza viruses would be beneficial for both humans and pigs. In this study, we evaluated i.m., aerosol (Aer), and simultaneous systemic and respiratory immunization (SIM) by both routes in Babraham pigs, using the single cycle candidate influenza vaccine S-FLU. After prime and boost immunization, pigs were challenged with H1N1pdm09 virus. i.m.-immunized pigs generated a high titer of neutralizing Abs but poor T cell responses, whereas Aer induced powerful respiratory tract T cell responses but a low titer of Abs. SIM pigs combined high Ab titers and strong local T cell responses. SIM showed the most complete suppression of virus shedding and the greatest improvement in pathology. We conclude that SIM regimes for immunization against respiratory pathogens warrant further study.

Safety, Immunogenicity, and Protective Efficacy of a Chimeric A/B Live Attenuated Influenza Vaccine in a Mouse Model.

Influenza A and B viruses cause significant morbidity and mortality worldwide. Current influenza vaccines are composed of three or four strains: A/H1N1, A/H3N2, and B (Victoria and Yamagata lineages). It is of great interest if immunization against both type A and B influenza viruses can be combined in a single vaccine strain, thus reducing the cost of vaccine production and the possibility of strain interference within the multicomponent vaccine. In the current study, we developed an experimental live cold-adapted influenza intertype reassortant (influenza A and B) vaccine on the live attenuated influenza vaccine (LAIV) A/Leningrad/134/17/57 backbone. Hemagglutinin (HA) and neuraminidase (NA) functional domains were inherited from the influenza B/Brisbane/60/2008 strain, whereas their packaging signals were substituted with appropriate fragments of influenza A virus genes. The recombinant A/B virus efficiently replicated in eggs and Madin–Darby Canine Kidney (MDCK) cells under optimal conditions, temperature-sensitive phenotype was maintained, and its antigenic properties matched the influenza B parental virus. The chimeric vaccine was attenuated in mice: after intranasal immunization, viral replication was seen only in nasal turbinates but not in the lungs. Immunological studies demonstrated the induction of IgG antibody responses against the influenza A and B virus, whereas hemagglutination inhibition (HAI) and neutralizing antibodies were detected only against the influenza B virus, resulting in significant protection of immunized animals against influenza B virus challenge. IFNγ-secreting CD8 effector memory T cells (CD44+CD62L−) were detected in mouse splenocytes after stimulation with the specific influenza A peptide (NP366); however, the T-cell response was not sufficient to protect animals against infection with a high-dose mouse-adapted A/California/07/2009 (H1N1pdm09) virus, most probably due to the mismatch of key T-cell epitopes of the H1N1 virus and the LAIV backbone. Overall, generation of the chimeric A/B LAIV virus on a licensed LAIV backbone demonstrated prospects for the development of safe and efficacious vaccine candidates that afford combined protection against both type A and type B influenza viruses; however, further optimization of the T-cell epitope content within the LAIV backbone may be required.

Differential disease severity and whole-genome sequence analysis for human influenza A/H1N1pdm virus in 2015-2016 influenza season.

During the 2015–16 winter, the US experienced a relatively mild influenza season compared to Taiwan, which had a higher number of total and severe cases. While H1N1pdm viruses dominated global surveillance efforts that season, the global distribution of genetic variants and their contributions to disease severity have not been investigated. Samples collected from influenza A-positive patients by the Johns Hopkins Center of Excellence for Influenza Research and Surveillance active surveillance in the emergency rooms in Baltimore, Maryland, USA, and northern Taiwan between November 2015 and April 2016, were processed for influenza A virus whole-genome sequencing. In Baltimore, the majority of the viruses were the H1N1pdm clade 6B.1 and no H1N1pdm clade 6B.2 viruses were detected. In northern Taiwan, more than half of the H1N1pdm viruses were clade 6B.1 and 38% were clade 6B.2, consistent with the global observation that most 6B.2 viruses circulated in Asia and not North America. Whole virus genome sequence analysis identified two genetic subgroups present in each of the 6B.1 and 6B.2 clades and one 6B.1 interclade reassortant virus. Clinical data showed 6B.2 patients had more disease symptoms including higher crude and inverse probability weighted odds of pneumonia than 6B.1 patients, suggesting 6B.2 circulation may be one of the reasons for the severe flu season in Taiwan. Local surveillance efforts linking H1N1pdm virus sequences to patient clinical and demographic data improve our understanding of influenza circulation and disease potential.