Genesis of avian-origin H7N9 influenza A viruses

Influenza H7N9 virus disrupts the monolayer human brain microvascular endothelial cells barrier in vitro

Influenza H7N9 virus causes human infections with about 40% case fatality rate. The severe cases usually present with pneumonia; however, some present with central nervous system complications. Pneumonia syndrome is attributed to the cytokine storm after infection with H7N9, but the pathogenic mechanism of central nervous system complications has not been clarified. This study used immortalized human brain microvascular endothelial cells hCMEC/D3 to simulate the blood-brain barrier. It demonstrated that H7N9 virus could infect brain microvascular endothelial cells and compromise the blood-brain barrier integrity and permeability by down-regulating the expression of cell junction-related proteins, including claudin-5, occludin, and vascular endothelial (VE)-cadherin. These results suggested that H7N9 could infect the blood-brain barrier in vitro and affect its functions, which could be a potential mechanism for the pathogenesis of H7N9 viral encephalopathy.

In Silico Studies Reveal Peramivir and Zanamivir as an Optimal Drug Treatment Even If H7N9 Avian Type Influenza Virus Acquires Further Resistance

An epidemic of avian type H7N9 influenza virus, which took place in China in 2013, was enhanced by a naturally occurring R294K mutation resistant against Oseltamivir at the catalytic site of the neuraminidase. To cope with such drug-resistant neuraminidase mutations, we applied the molecular docking technique to evaluate the fitness of the available drugs such as Oseltamivir, Zanamivir, Peramivir, Laninamivir, L-Arginine and Benserazide hydrochloride concerning the N9 enzyme with single (R294K, R119K, R372K), double (R119_294K, R119_372K, R294_372K) and triple (R119_294_372K) mutations in the pocket. We found that the drugs Peramivir and Zanamivir score best amongst the studied compounds, demonstrating their high binding potential towards the pockets with the considered mutations. Despite the fact that mutations changed the shape of the pocket and reduced the binding strength for all drugs, Peramivir was the only drug that formed interactions with the key residues at positions 119, 294 and 372 in the pocket of the triple N9 mutant, while Zanamivir demonstrated the lowest RMSD value (0.7 Å) with respect to the reference structure.

Analysis of the Codon Usage Pattern of HA and NA Genes of H7N9 Influenza A Virus

Novel H7N9 influenza virus transmitted from birds to human and, since March 2013, it has caused five epidemic waves in China. Although the evolution of H7N9 viruses has been investigated, the evolutionary changes associated with codon usage are still unclear. Herein, the codon usage pattern of two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA), was studied to understand the evolutionary changes in relation to host, epidemic wave, and pathogenicity. Both genes displayed a low codon usage bias, with HA higher than NA. The codon usage was driven by mutation pressure and natural selection, although the main contributing factor was natural selection. Additionally, the codon adaptation index (CAI) and deoptimization (RCDI) illustrated the strong adaptability of H7N9 to Gallus gallus. Similarity index (SiD) analysis showed that Homo sapiens posed a stronger selection pressure than Gallus gallus. Thus, we assume that this may be related to the gradual adaptability of the virus to human. In addition, the host strong selection pressure was validated based on CpG dinucleotide content. In conclusion, this study analyzed the usage of codons of two genes of H7N9 and expanded our understanding of H7N9 host specificity. This aids into the development of control measures against H7N9 influenza virus.

Close Relationship between cIAP2 and Human ARDS Induced by Severe H7N9 Infection

Background

cIAP2 is involved in necroptosis as a key upstream regulation factor. We aimed to investigate the role of cIAP2 in ARDS/ALI induced by H7N9 virus through regulating the RIPK1/3 necroptosis pathway.

Methods

Lung tissues of 11 patients who died from ARDS-complicated H7N9 infection between 2013 and 2016 were obtained as the H7N9-ARDS group. Lung tissues near benign lung nodules were acquired as the control group. Histological changes were evaluated by H&E staining. Protein levels of cIAP2, RIPK1, RIPK3, p-RIPK3, MLKL, and p-MLKL in the lung tissues were detected by Western Blot. The mRNA levels of cIAP2, RIPK1, and RIPK3 were detected by real-time PCR.

Results

H7N9 virus infection had a high mortality, with ARDS being the leading cause of death. The protein level of cIAP2 in the experimental group was lower than that in the control group (P<0.05). However, the experimental group showed higher RIPK1, RIPK3, and p-RIPK3 protein levels than the control group (P<0.05), as well as the expression level of MLKL and p-MLKL protein, which is a key downstream protein in necroptosis (P<0.05).

Conclusion

In tissues from patients with fatal H7N9, downregulation of cIAP2 and induction of necroptosis was observed. We could speculate that necroptosis of the pulmonary epithelium is associated with severe H7N9 infection leading to ARDS. Thus, necroptosis inhibition may be a novel therapy for H7N9 influenza virus.

Preliminary Proteomic Analysis of A549 Cells Infected with Avian Influenza Virus H7N9 and Influenza A Virus H1N1

A newly emerged H7N9 influenza virus poses high risk to human beings. However, the pathogenic mechanism of the virus remains unclear. The temporal response of primary human alveolar adenocarcinoma epithelial cells (A549) infected with H7N9 influenza virus and H1N1 influenza A virus (H1N1, pdm09) were evaluated using the proteomics approaches (2D-DIGE combined with MALDI-TOF-MS/MS) at 24, 48 and 72 hours post of the infection (hpi). There were 11, 12 and 33 proteins with significant different expressions (P<0.05) at 24, 48 and 72hpi, especially F-actin-capping protein subunit alpha-1 (CAPZA1), Ornithine aminotransferase (OAT), Poly(rC)-binding protein 1 (PCBP1), Eukaryotic translation initiation factor 5A-1 (EIF5A) and Platelet-activating factor acetylhydrolaseⅠb subunit beta (PAFAH1B2) were validated by western-blot analysis. The functional analysis revealed that the differential proteins in A549 cells involved in regulating cytopathic effect. Among them, the down-regulation of CAPZA1, OAT, PCBP1, EIF5A are related to the death of cells infected by H7N9 influenza virus. This is the first time show that the down-regulation of PAFAH1B2 is related to the later clinical symptoms of patients infected by H7N9 influenza virus. These findings may improve our understanding of pathogenic mechanism of H7N9 influenza virus in proteomics.

PB2-588 V promotes the mammalian adaptation of H10N8, H7N9 and H9N2 avian influenza viruses

Human infections with avian influenza H7N9 or H10N8 viruses have been reported in China, raising concerns that they might cause human epidemics and pandemics. However, how these viruses adapt to mammalian hosts is unclear. Here we show that besides the commonly recognized viral polymerase subunit PB2 residue 627 K, other residues including 87E, 292 V, 340 K, 588 V, 648 V, and 676 M in PB2 also play critical roles in mammalian adaptation of the H10N8 virus. The avian-origin H10N8, H7N9, and H9N2 viruses harboring PB2-588 V exhibited higher polymerase activity, more efficient replication in mammalian and avian cells, and higher virulence in mice when compared to viruses with PB2-588 A. Analyses of available PB2 sequences showed that the proportion of avian H9N2 or human H7N9 influenza isolates bearing PB2-588 V has increased significantly since 2013. Taken together, our results suggest that the substitution PB2-A588V may be a new strategy for an avian influenza virus to adapt mammalian hosts.

Is a highly pathogenic avian influenza virus H5N1 fragment recombined in PB1 the key for the epidemic of the novel AIV H7N9 in China, 2013?

BACKGROUND

A novel avian influenza A H7N9 virus that infects humans was identified in China in 2013. This study is the first to comprehensively investigate the characteristics of genomic recombination, rather than reassortment, which has been the subject of investigation in previously reported studies.

METHODS

Novel avian influenza virus (AIV) H7N9 genome sequences were obtained from the NCBI Influenza Virus Sequence Database and the Global Initiative on Sharing Avian Influenza Database (GISAID) and a representative isolate was subjected to homogeneity analysis. A phylogenetic tree was constructed. Eight segments of the isolate were analyzed to identify segments with recombination events, the corresponding recombination fragments, and breakpoints. The evolutionary history of the recombined fragments was tracked by constructing phylogenetic trees of the recombination fragments.

RESULTS

Among the eight segments of the novel AIV H7N9 analyzed, only the PB1 segment showed a marked recombination phenomenon, with 11 recombination events; these included five actual recombination events and six possible misalignment artifact recombination events. The most notable was the recombination of a 291-nucleotide (nt) fragment at the 490-780 nt site that was affiliated to a highly pathogenic avian influenza virus (HPAIV) H5N1 (A/tree sparrow/Thailand/VSMU-16-RBR/2005). The phylogenetic tree of the 291-nt recombination fragment on the PB1 segment showed that the novel AIV H7N9 had a close genetic relationship to H9N2 and H5N1.

CONCLUSIONS

The novel AIV H7N9 might have reassorted its PB1 segment from H9N2 circulating in China, and this H9N2 PB1 might have been recombined into a highly pathogenic fragment from HPAIV H5N1, which could be the reason for the high fatality rate among patients with AIV H7N9 influenza.

Chinese travellers visiting friends and relatives--A review of infectious risks

BACKGROUND

Travellers are potential vectors in the transmission of infectious diseases across international borders. Travellers visiting friends and relatives (VFR) have a particularly high risk of acquiring certain infections during travel. Chinese VFR travellers account for a substantial proportion of all travel in Western countries with high migrant populations.

METHODS

A literature review was undertaken regarding major infectious disease risks for VFR travellers visiting China. This included an examination of the previous pandemics arising in China, the likelihood of future outbreaks in China from H5N1 and H7N9 avian influenza viruses, the potential role of travellers in disease transmission, and the special risks for VFR travellers.

RESULTS

China has been the origin of several influenza pandemics in past few decades, and the origin of several emerging infectious diseases with pandemic potential, including SARS. Travel to and from China has the potential for global spread of emergent infectious diseases, as seen in the SARS outbreak in 2003. For VFR travellers, the risk of other infectious diseases may also be greater in China compared to their countries of migration, including hepatitis A and B, dengue fever, typhoid, and other diseases.

CONCLUSIONS

VFR travel to China may be associated with increased risk of acquiring a range of infectious diseases, and also poses a potential risk for importation of future pandemics to other countries. Chinese VFR travellers need to be cognisant of these risks and health professionals should consider educational interventions to minimise these risks.

The application of pseudotypes to influenza pandemic preparedness

ABSTRACT 

Human and animal populations are constantly exposed to multiple influenza strains due to zoonotic spillover and rapid viral evolution driven by intrinsic error-prone replication and immunological pressure. In this context, antibody responses directed against the hemagglutinin protein on the surface of the virus are of importance since they have been shown to correlate with protective immunity. Serological techniques, detecting these responses, play a critical role in influenza pandemic preparedness in particular with regard to the measurement of vaccine immunogenicity. As the recent human pandemics (H1N1) and avian influenza outbreaks (H5 and H7) have demonstrated, there is an urgent need to be better prepared to assess the contribution of the antibody response to protection against newly emerged viruses and to evaluate the extent of pre-existing heterosubtypic immunity in populations. This review compares pseudotype-based assays with wild-type and virus-like particle virus assays and discusses their place in the pandemic preparedness against the influenza virus. It additionally addresses the state-of-the-art developments of pseudotype-based assays (chimeric hemagglutinins, multiplex and post-attachment) including the development and future deployment of assay kits and approaches toward standardization to both preclinical and clinical endpoints. Progress toward the development of an influenza pseudotype library for the purposes of pandemic preparedness is also outlined and discussed.

The Serum Profile of Hypercytokinemia Factors Identified in H7N9-Infected Patients can Predict Fatal Outcomes

The novel avian origin influenza A (H7N9) virus has caused severe diseases in humans in eastern China since the spring of 2013. Fatal outcomes of H7N9 infections are often attributed to the severe pneumonia and acute respiratory distress syndrome (ARDS). There is urgent need to discover biomarkers predicting the progression of disease and fatal outcome of potentially lethal flu infections, based on sound statistical analysis. We discovered that 34 of the 48 cytokines and chemokines examined in this study were significantly elevated in the plasma samples from patients infected with H7N9. We report for the first time that the levels of MIF, SCF, MCP-1, HGF, and SCGF-β are highly positively linked to disease severity and the profile of mediators MIF, SCF, MCP-1, HGF, SCGF-β, IP-10, IL-18, and IFN-γ is an independent outcome predictor.

Impact of route of exposure and challenge dose on the pathogenesis of H7N9 low pathogenicity avian influenza virus in chickens

H7N9 influenza A first caused human infections in early 2013 in China. Virus genetics, histories of patient exposures to poultry, and previous experimental studies suggest the source of the virus is a domestic avian species, such as chickens. In order to better understand the ecology of this H7N9 in chickens, we evaluated the infectious dose and pathogenesis of A/Anhui/1/2013 H7N9 in two common breeds of chickens, White Leghorns (table-egg layers) and White Plymouth Rocks (meat chickens). No morbidity or mortality were observed with doses of 10(6) or 10(8)EID50/bird when administered by the upper-respiratory route, and the mean infectious dose (10(6) EID50) was higher than expected, suggesting that the virus is poorly adapted to chickens. Virus was shed at higher titers and spread to the kidneys in chickens inoculated by the intravenous route. Challenge experiments with three other human-origin H7N9 viruses showed a similar pattern of virus replication.

Discovery of potential drugs for human-infecting H7N9 virus containing R294K mutation

Background

After the first epidemic wave from February through May 2013, the influenza A (H7N9) virus emerged and has followed a second epidemic wave since June 2013. As of June 27, 2014, the outbreak of H7N9 had caused 450 confirmed cases of human infection, with 165 deaths included. The case-fatality rate of all confirmed cases is about 36%, making the H7N9 virus a significant threat to people’s health. At present, neuraminidase inhibitors are the only licensed antiviral medications available to treat H7N9 infections in humans. Oseltamivir is the most commonly used inhibitor, and it is also a front-line drug for the threatening H7N9. Unfortunately, it has been reported that patients treated with oseltamivir can induce R294K (Arg294Lys) substitution in the H7N9 virus, which is a rare mutation and can reduce the antiviral efficacy of inhibitors. Even worse, deaths caused by such mutation after oseltamivir treatment have already been reported, indicating that the need to find substitutive neuraminidase inhibitors for currently available drugs to treat drug-resistant H7N9 is really pressing.

Materials and methods

First, the structure of H7N9 containing the R294K substitution was downloaded from the Protein Data Bank, and structural information of approved drugs was downloaded from the ZINC (ZINC Is Not Commercial) database. Taking oseltamivir carboxylate as a reference drug, we then filtered these molecules through virtual screening to find out potential inhibitors targeting the mutated H7N9 virus. For further evaluation, we carried out a 14 ns molecular dynamic simulation for each H7N9–drug complex and calculated the binding energy for each candidate drug.

Results

We found five inhibitors that could be candidate drugs for treating the mutated H7N9 virus. Docking poses showed these drugs could bind to the virus effectively, with the contribution of hydrogen bonds and hydrophobic interactions. With regard to the molecular dynamic simulations, receptor–ligand complexes formed by these candidate drugs were more stable than the one formed by oseltamivir carboxylate. The binding energy of oseltamivir carboxylate was −122.4 kJ/mol, while those for these potential inhibitors were −417.5, −404.7, −372.2, −304.3, and −289.9 kJ/mol, much better than the reference drug.

Conclusion

Given the current and future threat of the mutated H7N9 virus, it is urgent that potent drugs and effective antiviral therapeutics be found. Our study therefore is able to complement currently available drugs for influenza A infectors and helps to prevent the ongoing threat of H7N9 virus.

Ultrastructural fingerprints of avian influenza A (H7N9) virus in infected human lung cells

In this study, we investigated the ultrastructural modifications induced by influenza A (H7N9) virus in human lung epithelial cells. One particular characteristic of H7N9 viral infection is the formation of numerous M1-associated striated tubular structures within the nucleus and the cytoplasm, which have only previously been observed for a limited number of influenza A viruses, notably the 2009 pandemic (H1N1) virus.

Preliminary success in the characterization and management of a sudden breakout of a novel H7N9 influenza A virus

Influenza has always been one of the major threats to human health. The Spanish influenza in 1918, the pandemic influenza A/H1N1 in 2009, and the avian influenza A/H5N1 have brought about great disasters or losses to mankind. More recently, a novel avian influenza A/H7N9 broke out in China and until December 2, 2013, it had caused 139 cases of infection, including 45 deaths. Its risk and pandemic potential attract worldwide attention. In this article, we summarize epidemiology, virology characteristics, clinical symptoms, diagnosis methods, clinical treatment and preventive measures about the avian influenza A/H7N9 virus infection to provide a reference for a possible next wave of flu outbreak.

H7N9 influenza: something old, something new …

In February 2013, two patients living in Shanghai were admitted to the Shanghai Fifth Hospital with fever, cough and respiratory tract infection, followed by severe pneumonia, respiratory distress and multiorgan dysfunction(1). While the first patient, an 87-year-old man, did not present a history of exposure to live birds during the preceding 2 weeks, the second patient, a 27-year-old man,was a butcher at a market selling live birds. A 35-year-old female from the Anhui Province of China, the third patient who became infected, visited a chicken market a week before her symptoms started (2,3). All three patients died, and their infections did not appear to be epidemiologically linked (4).

H9N2 avian influenza infection altered expression pattern of sphiogosine-1-phosphate receptor 1 in BALB/c mice

Background

The pathological damage inflicted by virulent AIV strains is often caused by inducing a positive feedback loop of cytokines in immune cells that cause excessive inflammation. Previous research has shown that a G protein-coupled receptor, sphingosine-1-phosphate receptor 1 (S1PR1), plays a crucial role in the development of excessive inflammation in influenza virus infection (Cell 146:861–862, 2011; Cell 146:980–991, 2011). BALB/c mice are common laboratory animals used in research of influenza virus; however the effects of influenza infections on expression patterns of S1PR1 in mice are unknown.

Methods

We investigated the expression patterns of S1PR1 in normal BALB/c mice and those infected by two distinct H9N2 AIV strains, one (A/chicken/Guangdong/V/2008,V) highly pathogenic, and the other (A/chicken/Guangdong/Ts/2004,Ts), non-pathogenic in mice, using quantitative PCR and immunohistochemistry (IHC) to detect S1PR1 mRNA and protein, respectively.

Results

S1PR1 mRNA was ubiquitously expressed in all the tissues examined, and significant differences were seen in mRNA expression between infected Ts, V and control mice in detected tissues, heart, liver, spleen, kidney and brain. S1PR1 protein was expressed in the cytoplasm and also demonstrated quantitative changes in expression in the various tissues between mice infected with the two strains of AIV.

Conclusions

Our results provided the first look at differences in S1PR1 expression patterns in BALB/c mice infected by non-pathogenic and highly pathogenic H9N2 influenza viruses. This information will not only be helpful in designing experiments to better understand the role of S1PR1 in virus-host interactions but also in developing novel anti-influenza agents to minimize the mortality and morbidity associated with highly virulent strains in avian and human populations.

3D Molecular Modelling Study of the H7N9 RNA-Dependent RNA Polymerase as an Emerging Pharmacological Target

Currently not much is known about the H7N9 strain, and this is the major drawback for a scientific strategy to tackle this virus. Herein, the 3D complex structure of the H7N9 RNA-dependent RNA polymerase has been established using a repertoire of molecular modelling techniques including homology modelling, molecular docking, and molecular dynamics simulations. Strikingly, it was found that the oligonucleotide cleft and tunnel in the H7N9 RNA-dependent RNA polymerase are structurally very similar to the corresponding region on the hepatitis C virus RNA-dependent RNA polymerase crystal structure. A direct comparison and a 3D postdynamics analysis of the 3D complex of the H7N9 RNA-dependent RNA polymerase provide invaluable clues and insight regarding the role and mode of action of a series of interacting residues on the latter enzyme. Our study provides a novel and efficiently intergraded platform with structural insights for the H7N9 RNA-dependent RNA Polymerase. We propose that future use and exploitation of these insights may prove invaluable in the fight against this lethal, ongoing epidemic.

Rapid and sensitive detection of H7N9 avian influenza virus by use of reverse transcription-loop-mediated isothermal amplification

An epidemic of human H7N9 influenza virus infection recently emerged in China whose clinical features include high mortality and which has also resulted in serious economic loss. The novel reassortant avian-origin influenza A (H7N9) virus which was the causative agent of this epidemic raised the possibility of triggering a large-scale influenza pandemic worldwide. It seemed likely that fast molecular detection assays specific for this virus would be in great demand. Here, we report a one-step reverse transcription-loop-mediated isothermal amplification (RT-LAMP) method for rapid detection of the hemagglutinin (HA) and neuraminidase (NA) genes of H7N9 virus, the minimum detection limit of which was evaluated using in vitro RNA transcription templates. In total, 135 samples from clinical specimens (from either patients or poultry) were tested using this method in comparison with the real-time PCR recommended by the World Health Organization (WHO). Our results showed that (i) RT-LAMP-based trials can be completed in approximately 12 to 23 min and (ii) the detection limit for the H7 gene is around 10 copies per reaction, similar to that of the real-time PCR, whereas the detection limit for its counterpart the N9 gene is 5 copies per reaction, a 100-fold-higher sensitivity than the WHO-recommended method. Indeed, this excellent performance of our method was also validated by the results for a series of clinical specimens. Therefore, we believe that the simple, fast, and sensitive method of RT-LAMP might be widely applied for detection of H7N9 infections and may play a role in prevention of an influenza pandemic.

Human H7N9 avian influenza virus infection: a review and pandemic risk assessment

China is undergoing a recent outbreak of a novel H7N9 avian influenza virus (nH7N9) infection that has thus far involved 132 human patients, including 37 deaths. The nH7N9 virus is a reassortant virus originating from the H7N3, H7N9 and H9N2 avian influenza viruses. nH7N9 isolated from humans contains features related to adaptation to humans, including a Q226L mutation in the hemagglutinin cleavage site and E627K and D701N mutations in the PB2 protein. Live poultry markets provide an environment for the emergence, spread and maintenance of nH7N9 as well as for the selection of mutants that facilitate nH7N9 binding to and replication in the human upper respiratory tract. Innate immune suppression conferred by the internal genes of H9N2 may contribute to the virulence of nH7N9. The quail may serve as the intermediate host during the adaptation of avian influenza viruses from domestic waterfowl to gallinaceous poultry, such as chickens and related terrestrial-based species, due to the selection of viral mutants with a short neuraminidase stalk. Infections in chickens, common quails, red-legged partridges and turkeys may select for mutants with human receptor specificity. Infection in Ratitae species may lead to the selection of PB2-E627K and PB2-D701N mutants and the conversion of nH7N9 to a highly pathogenic avian influenza virus.