Pandemic Influenza Virus Infection Research Articles

Defense mechanisms during respiratory infections in hosts with underlying asthma

Abstract Influenza can often be complicated by superinfections by bacteria such as Streptococcus pneumoniae. While these opportunistic bacterial pathogens do co-infect during seasonal influenza epidemics, the relationship is exaggerated during pandemic influenza virus infections as documented during all four previous influenza pandemics. Approximately 29–55% of hospitalized patients with Swine Flu with severe disease had a bacterial co-infection; however, asthmatics that were hospitalized during this influenza pandemic were less likely to have co-infections. We built a mouse model that recapitulated these intriguing epidemiologic findings that underlying asthma protected the host from severe morbidity and mortality associated with IAV and S. pneumoniae co-infection. These mice had significantly reduced bacterial load in the lungs, increased eosinophils and macrophages in the airways, but reduced tissue inflammation and scarring compared to non-allergic co-infected mice. We hypothesized that TH2-biased programming of eosinophils within the lungs of allergic mice heightened their immune responses to invading respiratory pathogens. We found that allergen sensitization and IAV exposure activated eosinophils marked by upregulation of CD69, ICAM-1, and IL-5Rα, maintained their viability, and enhanced bacterial uptake through receptor-mediated phagocytosis. Activated eosinophils prevented IAV-induced cytopathology on respiratory epithelia and were able to inhibit the growth and kill S. pneumoniae without undergoing cytolysis. Our data suggest a novel pathway by which eosinophils in hosts with asthma may protect the host from severe diseases induced by respiratory pathogens by inhibiting viral-bacterial synergy.

Anti-influenza virus activity of benzo[d]thiazoles that target heat shock protein 90.

Seasonal or pandemic influenza virus infections are a worldwide health problem requiring antiviral therapy. Since virus resistance to the established neuraminidase inhibitors and novel polymerase inhibitors is growing, new drug targets are needed. Heat shock protein 90 (Hsp90) is associated with several aspects of the influenza virus life cycle, and is considered a relevant host cell target. We report here on a series of benzo[d]thiazole and 4,5,6,7-tetrahydrobenzo[d]thiazole derivatives with robust and selective activities against influenza A (H1N1, H3N2) and influenza B viruses. Two compounds, 1 and 4, have low micromolar EC50 values and show high binding affinities for Hsp90, which suggests that inhibition of Hsp90 is the mechanism underlying their antiviral effects. These compounds represent suitable scaffolds for designing novel Hsp90 inhibitors with favourable activities against influenza virus.

Interpretation of an individual functional genomics experiment guided by massive public data.

A key unmet challenge in interpreting omics experiments is inferring biological meaning in the context of public functional genomics data. We developed a computational framework, Your Evidence Tailored Integration (YETI; http://yeti.princeton.edu/ ), which creates specialized functional interaction maps from large public datasets relevant to an individual omics experiment. Using this tailored integration, we predicted and experimentally confirmed an unexpected divergence in viral replication after seasonal or pandemic human influenza virus infection.

Avian influenza A H7N9 virus infects human astrocytes and neuronal cells and induces inflammatory immune responses

Seasonal, pandemic, and avian influenza virus infections may be associated with central nervous system pathology, albeit with varying frequency and different mechanisms. Here, we demonstrate that differentiated human astrocytic (T98G) and neuronal (SH-SY5Y) cells can be infected by avian H7N9 and pandemic H1N1 viruses. However, infectious progeny viruses can only be detected in H7N9 virus infected human neuronal cells. Neither of these viral strains can generate infectious progeny virus in human astrocytes despite replication of viral genome was observed. Furthermore, H7N9 virus triggered high pro-inflammatory cytokine expression, while pandemic H1N1 virus induced only low cytokine expression in either brain cell type. The experimental finding here is the first data to demonstrate that avian H7N9 virus can infect, transcribe, and replicate its viral genome; induce cytokine upregulation; and cause cytopathic effects in human brain cells, which may potentially lead to profound central nervous system injury. Observation for neurological problems due to H7N9 virus infection deserves further attention when managing these patients.

Synergy between the classical and alternative pathways of complement is essential for conferring effective protection against the pandemic influenza A(H1N1) 2009 virus infection.

The pandemic influenza A(H1N1) 2009 virus caused significant morbidity and mortality worldwide thus necessitating the need to understand the host factors that influence its control. Previously, the complement system has been shown to provide protection during the seasonal influenza virus infection, however, the role of individual complement pathways is not yet clear. Here, we have dissected the role of intact complement as well as of its individual activation pathways during the pandemic influenza virus infection using mouse strains deficient in various complement components. We show that the virus infection in C3-/- mice results in increased viral load and 100% mortality, which can be reversed by adoptive transfer of naïve wild-type (WT) splenocytes, purified splenic B cells, or passive transfer of immune sera from WT, but not C3-/- mice. Blocking of C3a and/or C5a receptor signaling in WT mice using receptor antagonists and use of C3aR-/- and C5aR-/- mice showed significant mortality after blocking/ablation of C3aR, with little or no effect after blocking/ablation of C5aR. Intriguingly, deficiency of C4 and FB in mice resulted in only partial mortality (24%-32%) suggesting a necessary cross-talk between the classical/lectin and alternative pathways for providing effective protection. In vitro virus neutralization experiments performed to probe the cross-talk between the various pathways indicated that activation of the classical and alternative pathways in concert, owing to coating of viral surface by antibodies, is needed for its efficient neutralization. Examination of the virus-specific complement-binding antibodies in virus positive subjects showed that their levels vary among individuals. Together these results indicate that cooperation between the classical and alternative pathways not only result in efficient direct neutralization of the pandemic influenza virus, but also lead to the optimum generation of C3a, which when sensed by the immune cells along with the antigen culminates in generation of effective protective immune responses.

Impacts of allergic airway inflammation on lung pathology in a mouse model of influenza A virus infection.

Influenza A virus is the respiratory pathogen responsible for influenza. Infection by the 2009 pandemic influenza A (H1N1) virus caused severe lower airway inflammation and pneumonia. Asthma is a chronic inflammatory disorder of the airways that affects the entire brachial tree, and was one of the commonest underlying medical conditions among patients hospitalized with the 2009 pandemic influenza virus infection. Although respiratory virus infections are the major causes of asthma exacerbation, the mechanism by which influenza exacerbates asthma is poorly understood. Animal models of disease comorbidity are crucial to understanding host-pathogen interactions and elucidating complex pathologies. Existing murine models of influenza virus infection in asthmatics show that asthmatic mice are highly resistant to influenza virus infection, which contradicts clinical observations in humans. Here, we developed a murine model of influenza virus/asthma comorbidity using NC/Nga mice, which are highly sensitive to allergic reactions such as atopic dermatitis and allergic airway inflammation. This model was then used to examine the impact of allergic airway inflammation on lung pathology in the 2009 pandemic influenza virus infected mice. The results showed that induction of acute allergic airway inflammation in pre-existing influenza virus infection had additive effects on exacerbation of lung pathology, which mirrors findings in human epidemiological studies. In contrast, pre-existing allergic airway inflammation protected from subsequent influenza virus infection, which was compatible with those of previous murine models of influenza virus infection in asthmatic mice. These variable outcomes of this murine model indicate that the temporal relation between allergic airway inflammation and influenza virus infection might play a critical role in asthma and influenza comorbidity. Thus, this murine model will further our understanding of how influenza virus infection affects an asthmatic host and may aid the development of strategies to improve treatments and outcomes for asthmatics harboring influenza virus infection.

Physician's knowledge, attitudes, and practices regarding seasonal influenza, pandemic influenza, and highly pathogenic avian influenza A (H5N1) virus infections of humans in Indonesia.

Indonesia has reported highest number of fatal human cases of highly pathogenic avian influenza (HPAI) A (H5N1) virus infection worldwide since 2005. There are limited data available on seasonal and pandemic influenza in Indonesia. During 2012, we conducted a survey of clinicians in two districts in western Java, Indonesia, to assess knowledge, attitudes, and practices (KAP) of clinical diagnosis, testing, and treatment of patients with seasonal influenza, pandemic influenza, or HPAI H5N1 virus infections. Overall, a very low percentage of physician participants reported ever diagnosing hospitalized patients with seasonal, pandemic, or HPAI H5N1 influenza. Use of influenza testing was low in outpatients and hospitalized patients, and use of antiviral treatment was very low for clinically diagnosed influenza patients. Further research is needed to explore health system barriers for influenza diagnostic testing and availability of antivirals for treatment of influenza in Indonesia.

Resistance to Mutant Group 2 Influenza Virus Neuraminidases of an Oseltamivir-Zanamivir Hybrid Inhibitor.

Oseltamivir and zanamivir are the two major antiviral drugs available for the treatment of influenza virus infections. However, multidrug-resistant viruses have emerged in clinical cases, which pose a challenge for the development of new drugs. N1 and N2 subtypes exist in the viruses which cause seasonal epidemics and past pandemics. Although N1 drug resistance is well characterized, the molecular mechanisms underlying N2 drug resistance are unknown. A previous report showed that an N2 E119V/I222L dual mutant conferred drug resistance to seasonal influenza virus. Here, we confirm that these substitutions result in multidrug resistance and dramatically reduced sensitivity to NAI. We further elucidate the molecular mechanism underlying N2 drug resistance by solving crystal structures of the N2 E119V and I222L mutants and the dual mutant. Most importantly, we found that a novel oseltamivir-zanamivir hybrid inhibitor, MS-257, remains more effective against drug-resistant N2 and is a promising candidate as a next-generation anti-influenza virus drug.

Twin Peaks: A/H1N1 Pandemic Influenza Virus Infection and Vaccination in Norway, 2009-2010.

BackgroundVaccination campaigns against A/H1N1 2009 pandemic influenza virus (A/H1N1p) began in autumn 2009 in Europe, after the declaration of the pandemic at a global level. This study aimed to estimate the proportion of individuals vaccinated against A/H1N1p in Norway who were already infected (asymptomatically or symptomatically) by A/H1N1p before vaccination, using a mathematical model.MethodsA dynamic, mechanistic, mathematical model of A/H1N1p transmission was developed for the Norwegian population. The model parameters were estimated by calibrating the model-projected number of symptomatic A/H1N1p cases to the number of laboratory-confirmed A/H1N1p cases reported to the surveillance system, accounting for potential under-reporting. It was assumed in the base case that the likelihood of vaccination was independent of infection/disease state. A sensitivity analysis explored the effects of four scenarios in which current or previous symptomatic A/H1N1p infection would influence the likelihood of being vaccinated.ResultsThe number of model-projected symptomatic A/H1N1p cases by week during the epidemic, accounting for under-reporting and timing, closely matched that of the laboratory-confirmed A/H1N1p cases reported to the surveillance system. The model-projected incidence of symptomatic A/H1N1p infection was 27% overall, 55% in people <10 years old and 41% in people 10–20 years old. The model-projected percentage of individuals vaccinated against A/H1N1p who were already infected with A/H1N1p before being vaccinated was 56% overall, 62% in people <10 years old and 66% in people 10–20 years old. The results were sensitive to assumptions about the independence of vaccination and infection; however, even when current or previous symptomatic A/H1N1p infection was assumed to reduce the likelihood of vaccination, the estimated percentage of individuals who were infected before vaccination remained at least 32% in all age groups.ConclusionThis analysis suggests that over half the people vaccinated against A/H1N1p in Norway during the 2009 pandemic may already have been infected by A/H1N1p before being vaccinated.

The Dynamic Relationship Between Clinical Symptomatology and Viral Shedding in Naturally Acquired Seasonal and Pandemic Influenza Virus Infections.

Although the pattern of viral shedding over time has been documented in volunteer challenge studies, understanding of the relationship between clinical symptomatology and viral shedding in naturally acquired influenza infections in humans remains limited. In a community-based study in Hong Kong from 2008 to 2014, we followed up initially healthy individuals and identified 224 secondary cases of natural influenza virus infection in the household setting. We examined the dynamic relationship between patterns of clinical symptomatology and viral shedding as quantified using reverse transcription polymerase chain reaction and viral culture in 127 cases with a clinical picture of acute respiratory infection. Viral shedding in influenza A virus infections peaked on the first 1-2 days of clinical illness, and decreased gradually to undetectable levels by day 6-7, matching closely with the dynamics of clinical illness. Viral shedding in influenza B virus infections rose up to 2 days prior to symptom onset and persisted for 6-7 days after onset with a bimodal pattern. Our results suggest that while clinical illness profiles may serve as a proxy for clinical infectiousness in influenza A virus infections, patients may potentially be infectious even before symptom onset or after clinical improvement in influenza B virus infections.

Mortality Associated With Seasonal and Pandemic Influenza Among Pregnant and Nonpregnant Women of Childbearing Age in a High-HIV-Prevalence Setting—South Africa, 1999–2009

Information on the mortality burden associated with seasonal and pandemic influenza virus infection among pregnant women is scarce in most settings, particularly in sub-Saharan Africa where pregnancy and maternal mortality rates as well as human immunodeficiency virus (HIV) prevalence are elevated. We used an ecological study design to estimate the seasonal and A(H1N1)pdm09 influenza-associated mortality among pregnant and nonpregnant women of childbearing age (15-49 years) by HIV serostatus during 1999-2009 in South Africa. Mortality rates were expressed per 100 000 person-years. During 1999-2009, the estimated mean annual seasonal influenza-associated mortality rates were 12.6 (123 deaths) and 7.3 (914 deaths) among pregnant and nonpregnant women, respectively. Among pregnant women, the estimated mean annual seasonal influenza-associated mortality rates were 74.9 (109 deaths) among HIV-infected and 1.5 (14 deaths) among HIV-uninfected individuals. Among nonpregnant women, the estimated mean annual seasonal influenza-associated mortality rate was 41.2 (824 deaths) among HIV-infected and 0.9 (90 deaths) among HIV-uninfected individuals. Pregnant women experienced an increased risk of seasonal influenza-associated mortality compared with nonpregnant women (relative risk [RR], 2.8; 95% confidence interval [CI], 1.7-3.9). In 2009, the estimated influenza A(H1N1)pdm09-associated mortality rates were 19.3 (181 deaths) and 9.4 (1189 deaths) among pregnant and nonpregnant women, respectively (RR, 3.2; 95% CI, 2.3-4.1). Among women of childbearing age, the majority of estimated seasonal influenza-associated deaths occurred in HIV-infected individuals. Pregnant women experienced an increased risk of death associated with seasonal and A(H1N1)pdm09 influenza infection compared with nonpregnant women.

The draft genome sequence of the ferret (Mustela putorius furo) facilitates study of human respiratory disease.

The domestic ferret (Mustela putorius furo) is an important animal model for multiple human respiratory diseases. It is considered the ‘gold standard’ for modeling human influenza virus infection and transmission1–4. Here we describe the 2.41 Gb draft genome assembly of the domestic ferret, constituting 2.28 Gb of sequence plus gaps. We annotate 19,910 protein-coding genes on this assembly using RNA-seq data from 21 ferret tissues. We characterize the ferret host response to two influenza virus infections by RNA-seq analysis of 42 ferret samples from influenza time courses, and show distinct signatures in ferret trachea and lung tissues specific to 1918 or 2009 human pandemic influenza virus infections. Using microarray data from 16 ferret samples reflecting cystic fibrosis (CF) disease progression, we show that transcriptional changes in the CFTR-knockout ferret lung reflect pathways of early disease that cannot be readily studied in human infants with CF disease.

Serological report of pandemic and seasonal human influenza virus infection in dogs in southern China.

From January to July 2012, we looked for evidence of subclinical A (H1N1) pdm09 and seasonal human influenza viruses infections in healthy dogs in China. Sera from a total of 1920 dogs were collected from Guangdong, Guangxi, Fujian and Jiangxi provinces. We also examined archived sera from 66 dogs and cats that were collected during 2008 from these provinces. Using hemagglutination inhibition (HI) and microneutralization (MN) assays, we found that only the dogs sampled in 2012 had elevated antibodies (≥ 1:32) against A(H1N1)pdm09 virus and seasonal human influenza viruses: Of the 1920 dog sera, 20.5 % (n = 393) had elevated antibodies against influenza A(H1N1) pdm09 by the HI assay, 1.1 % (n = 22), and 4.7 % (n = 91) of the 1920 dogs sera had elevated antibodies against human seasonal H1N1 influenza virus and human seasonal H3N2 influenza virus by the HI assay. Compared with dogs that were raised on farms, dogs that were raised as pets were more likely to have elevated antibodies against A(H1N1)pdm09 and seasonal human influenza viruses. Seropositivity was highest among pet dogs, which likely had more diverse and frequent exposures to humans than farm dogs. These findings will help us better understand which influenza A viruses are present in dogs and will contribute to the prevention and control of influenza A virus. Moreover, further in-depth study is necessary for us to understand what roles dogs play in the ecology of influenza A.

Asthma and the flu: a tricky two‐step

Seasonal and pandemic influenza virus infections cause substantial mortality and morbidity. At least 18 500 confirmed deaths occurred in the first year of the 2009 H1N1 influenza A pandemic, but modeling estimates suggest that over 200 000 respiratory deaths and an additional 85 000 cardiovascular deaths occurred worldwide, with the majority in Africa and Southeast Asia.1 Like most infectious diseases, influenza virus morbidity and mortality are skewed toward the very young ( 65 years) and pregnant women, conditions in which key elements of the immune system necessary to curtail influenza are compromised.

Determinants of individuals’ risks to 2009 pandemic influenza virus infection at household level amongst Djibouti city residents - A CoPanFlu cross-sectional study

BackgroundFollowing the 2009 swine flu pandemic, a cohort for pandemic influenza (CoPanFlu) study was established in Djibouti, the Horn of Africa, to investigate its case prevalence and risk predictors’ at household level.MethodsFrom the four city administrative districts, 1,045 subjects from 324 households were included during a face-to-face encounter between 11th November 2010 and 15th February 2011. Socio-demographic details were collected and blood samples were analysed in haemagglutination inhibition (HI) assays. Risk assessments were performed in a generalised estimating equation model.ResultsIn this study, the indicator of positive infection status was set at an HI titre of ≥ 80, which was a relevant surrogate to the seroconversion criterion. All positive cases were considered to be either recent infections or past contact with an antigenically closely related virus in humans older than 65 years. An overall sero-prevalence of 29.1% and a geometrical mean titre (GMT) of 39.5% among the residents was observed. Youths, ≤ 25 years and the elderly, ≥65 years had the highest titres, with values of 35.9% and 29.5%, respectively. Significantly, risk was high amongst youths ≤ 25 years, (OR 1.5-2.2), residents of District 4(OR 2.9), students (OR 1.4) and individuals living near to river banks (OR 2.5). Belonging to a large household (OR 0.6), being employed (OR 0.5) and working in open space-outdoor (OR 0.4) were significantly protective. Only 1.4% of the cohort had vaccination against the pandemic virus and none were immunised against seasonal influenza.ConclusionDespite the limited number of incident cases detected by the surveillance system, A(H1N1)pdm09 virus circulated broadly in Djibouti in 2010 and 2011. Age-group distribution of cases was similar to what has been reported elsewhere, with youths at the greatest risk of infection. Future respiratory infection control should therefore be tailored to reach specific and vulnerable individuals such as students and those working in groups indoors. It is concluded that the lack of robust data provided by surveillance systems in southern countries could be responsible for the underestimation of the epidemiological burden, although the main characteristics are essentially similar to what has been observed in developed countries.

Pandemic influenza A (H1N1) infection in pregnant and nonpregnant women in Spain (2009-2010).

The present study aimed to compare the main features of infection with pandemic influenza A virus in pregnant and nonpregnant women admitted to hospitals in Spain during the first waves of the 2009-2010 influenza pandemic. This was a prospective (November 2009 to June 2010), multicenter observational study. All cases were women of reproductive age who had not been vaccinated against seasonal or pandemic influenza A. Influenza infection was confirmed by reverse transcription-polymerase chain reaction (RT-PCR). The sociodemographic and clinical data of all cases were reviewed. A total of 219 inpatients, including 49 pregnant women and 170 nonpregnant women, were enrolled in the study upon admission to participating hospitals. The most substantially different symptoms between the groups were respiratory distress and unilobar consolidation, both of which were more frequent among nonpregnant women. Antibiotics and systemic corticosteroids were more frequently used in nonpregnant women; however, there were no differences in the rates of treatment with antivirals. Our findings indicated that the compared with nonpregnant women, pregnant women in this study did not have significantly different symptoms and were not at increased risk of complications from pandemic influenza virus infection.

Innate immune sensing and response to influenza.

Influenza viruses pose a substantial threat to human and animal health worldwide. Recent studies in mouse models have revealed an indispensable role for the innate immune system in defense against influenza virus. Recognition of the virus by innate immune receptors in a multitude of cell types activates intricate signaling networks, functioning to restrict viral replication. Downstream effector mechanisms include activation of innate immune cells and, induction and regulation of adaptive immunity. However, uncontrolled innate responses are associated with exaggerated disease, especially in pandemic influenza virus infection. Despite advances in the understanding of innate response to influenza in the mouse model, there is a large knowledge gap in humans, particularly in immunocompromised groups such as infants and the elderly. We propose here, the need for further studies in humans to decipher the role of innate immunity to influenza virus, particularly at the site of infection. These studies will complement the existing work in mice and facilitate the quest to design improved vaccines and therapeutic strategies against influenza.

Pandemic influenza H1N1 outbreak in the military school

The first cases of the pandemic pH1N1 influenza virus infection was observed in the Unated States and Mexico in April 2009 and the first laboratory confirmed case in Serbia was registered in June 2009. The aim of this paper was to report on the investigation of the first confirmed outbreak of the 2009 pandemic H1N1 influenza in Serbia and to describe the clinical and epidemiologic findings from this investigation. Descriptive and analytical epidemiological methods were used. Data were collected from medical records of the Military School students and epidemiological questionnaire. Pandemic H1N1 infection was initially confirmed by the RT-PCR assay in nasopharyngeal and oropharyngeal swabs and subsequently by the complement fixation test in serum samples. The attack rate of acute respiratory illness was 70.8% (204/288). Pandemic H1N1 virus infection was confirmed in 44 of 82 tested cases of acute respiratory illness (53.7%) The most common clinical manifestations of pandemic influenza H1N1 were fever (88.6%/), cough (61.4%/o), malaise (38.6%/), runny nose (36.4%), headache (29.60/%), sore throat (20.50/%) and muscle pain (15.9%). The findings from this investigation suggest that pandemic H1N1 influenza in a high military school was widespread but did not cause severe illness.

877 Prevalence of Pandemic (H1N1) and Seasonal Influenza Virus Infection in Pediatric Age Group in Southern Iran

BackgroundA novel strain of H1N1 Influenza (A/California/7/2009) has been prevalent since April 2009. Epidemiological and clinical studies showed that children at high risk for severe infection. Influenza virus infections are...

Poor seroprotection but allosensitization after adjuvanted pandemic influenza H1N1 vaccine in kidney transplant recipients

Seasonal and pandemic influenza virus infections in renal transplant patients are associated with poor outcomes. During the pandemic of 2009-2010, the AS03-adjuvanted monovalent H1N1 influenza vaccine was recommended for transplant recipients, although its immunogenicity in this population was unknown. We sought to determine the safety and immunogenicity of an adjuvant-containing vaccine against pandemic influenza A H1N1 2009 (pH1N1) administered to kidney transplant recipients. We prospectively enrolled 124 adult kidney transplant recipients in the fall of 2009 at two transplant centers. Cohort 1 (n=42) was assessed before and after pH1N1 immunization, while Cohort 2 (n=82) was only assessed post immunization. Humoral response was measured by the hemagglutination inhibition assay. Vaccine safety was assessed by adverse event reporting, graft function, and human leukocyte antigen (HLA) alloantibody measurements. Cohort 1 had a low rate of baseline seroprotection to pH1N1 (7%) and a low rate of seroprotection after immunization (31%). No patient <6months post transplant (n=5) achieved seroprotection. Seroprotection rate was greater in patients receiving double as compared with triple immunosuppression (80% vs. 24%, P=0.01). In Cohort 2, post-immunization seroprotection was 35%. In both cohorts, no confirmed cases of pH1N1 infection occurred. No difference was seen in estimated glomerular filtration rate before (54.3mL/min/1.73m(2) ) and after (53.8mL/min/1.73m(2) ) immunization, and no acute rejections had occurred after immunization at last follow-up. In Cohort 1, 11.9% of patients developed new anti-HLA antibodies. An adjuvant-containing vaccine to pH1N1 provided poor seroprotection in renal transplant recipients. Receiving triple immunosuppression was associated with a poor seroresponse. Vaccination appeared safe, but some patients developed new anti-HLA antibodies post vaccination. Alternative strategies to improve vaccine responses are necessary.