New mutational trends in the HA protein of 2009 H1N1 pandemic influenza virus from May 2010 to February 2011

As we enter the year of 2011, the 2009 H1N1 pandemic influenza virus is in the news again. At least 20 people have died of this virus in China since the beginning of 2011 and it is now the predominant flu strain in the country. Although this novel virus was quite stable during its run in the flu season of 2009-2010, a genetic variant of this virus was found in Singapore in early 2010, and then in Australia and New Zealand during their 2010 winter influenza season. Several critical mutations in the HA protein of this variant were uncovered in the strains collected from January 2010 to April 2010. Moreover, a structural homology model of HA from the A/Brisbane/10/2010(H1N1) strain was made based on the structure of A/California/04/2009 (H1N1). The purpose of this study was to investigate mutations in the HA protein of 2009 H1N1 from sequence data collected worldwide from May 2010 to February 2011. A fundamental problem in bioinformatics and biology is to find the similar gene sequences for a given gene sequence of interest. Here we proposed the inverse problem, i.e., finding the exemplars from a group of related gene sequences. With a clustering algorithm affinity propagation, six exemplars of the HA sequences were identified to represent six clusters. One of the clusters contained strain A/Brisbane/12/2010(H1N1) that only differed from A/Brisbane/10/2010 in the HA sequence at position 449. Based on the sequence identity of the six exemplars, nine mutations in HA were located that could be used to distinguish these six clusters. Finally, we discovered the change of correlation patterns for the HA and NA of 2009 H1N1 as a result of the HA receptor binding specificity switch, revealing the balanced interplay between these two surface proteins of the virus.

Stop H5N1 influenza in US cattle now

The relentless march of a highly pathogenic avian influenza virus(HPAIV)strain,known as H5N1,to become an unprecedented panzootic continues unchecked.The leap of H5N1 clade 2.3.4.4b from Eurasia and Africa to North America in 2021 and its further spread to South America and the Antarctic have exposed new avian and mammalian populations to the virus and led to outbreaks on an unrivaled scale.The virus has infected wild birds across vast geographic regions and caused wildlife deaths in some of the world's most biodiverse ecosystems.

Antiviral activity of Basidiomycete mycelia against influenza type A(serotype H1N1) and herpes simplex virus type 2 in cell culture

In this study, we investigated the in vitro antiviral activity of the mycelia of higher mushrooms against influenza virus type A(serotype H1N1) and herpes simplex virus type 2(HSV-2), strain BH. All 10 investigated mushroom species inhibited the reproduction of influenza virus strain A/FM/1/47(H1N1) in MDCK cells reducing the infectious titer by 2.0–6.0 lg ID50. Four species, Pleurotus ostreatus, Fomes fomentarius, Auriporia aurea, and Trametes versicolor, were also determined to be effective against HSV-2 strain BH in RK-13 cells, with similar levels of inhibition as for influenza. For some of the investigated mushroom species—Pleurotus eryngii, Lyophyllum shimeji, and Flammulina velutipes—this is the first report of an anti-influenza effect. This study also reports the first data on the medicinal properties of A. aurea, including anti-influenza and antiherpetic activities. T. versicolor 353 mycelium was found to have a high therapeutic index(324.67), and may be a promising material for the pharmaceutical industry as an anti-influenza and antiherpetic agent with low toxicity. Mycelia with antiviral activity were obtained in our investigation by bioconversion of agricultural wastes(amaranth flour after CO2 extraction), which would reduce the cost of the final product and solve some ecological problems.

Molecular Characterization of Avian-like H1N1 Swine Influenza A Viruses Isolated in Eastern China, 2011

Currently, three predominant subtypes of influenza virus are prevalent in pig populations worldwide： H1N1, H3N2, and H1N2. European avian-Hke H1N1 viruses, which were initially detected in European pig populations in 1979, have been circulating in pigs in eastern China since 2007. In this study, six influenza A viruses were isolated from 60 swine lung samples collected from January to April 2011 in eastern China. Based on whole genome sequencing, molecular characteristics of two isolates were determined. Phylogenetic analysis showed the eight genes of the two isolates were closely related to those of the avian-like H1N1 viruses circulating in pig populations, especially similar to those found in China. Four potential glycosylation sites were observed at positions 13, 26, 198, 277 in the HA1 proteins of the two isolates. Due to the presence of a stop codon at codon 12, the isolates contained truncated PB1-F2 proteins. In this study, the isolates contained 591Q, 627E and 701N in the polymerase subunit PB2, which had been shown to be determinants of virulence and host adaptation. The isolates also had a D rather than E at position 92 of the NS1, a marker of mammalian adaptation. Both isolates contained the GPKV motif at the PDZ ligand domain of the 3＇ end of the NS1, a characteristic marker of the European avian-like swine viruses since about 1999, which is distinct from those of avian, human and classical swine viruses. The M2 proteins of the isolates have the mutation （S31N）, a characteristic marker of the European avian-like swine viruses since about 1987, which may confer resistance to amantadine and rimantadine antivirals. Our findings further emphasize the importance of surveillance on the genetic diversity of influenza A viruses in pigs, and raise more concerns about the occurrence of cross-species transmission events.

Influenza virus H1N1 induced apoptosis of mouse astrocytes and the effect on protein expression

Objective:To investigate the effects of influenza A virus H1N1 infection on the proliferation and apoptosis of mouse astrocytes cells and its protein expression.Methods:After mouse astrocytes was infected with purified influenza A virus H1N1 in vitro,viral integration and replication status of the cells were detected by RT-PCR assay,cell proliferation and apoptosis was determined by MTT method and flow cytometry,respectively.Associated protein expression was delected by Western blotting.Results:Agarose gel electrophoresis showed H1N1 virus can infect astrocytes and can be copied.MTT staining showed H1N1 virus infection can inhibit the proliferation of mouse astrocytes,which makes cell viability decreased significantly.Flow cytometry showed that the proportion of Annein V staining positive vascular endothelial cells in the influenza A virus group was significantly higher than that in the control group.Western blot analysis showed after24 h and 32 h of infection,there were cells caspase-3 protein and the expression of its active form(lysed caspase-3 protein)increased.The proportion of Bax/Bcl-2 also increased.Conclusions:Influenza A virus can infect human vascular endothelial cells and proliferation and it can induce apoptosis of endothelial cells.

Structure and Anti-influenza A(H1N1) Virus Activity of Three Polysaccharides from Eucheuma denticulatum

Three polysaccharides （EW, EH and EA） were prepared from a red alga Eucheuma denticulatum by sequential extraction with cold water, hot water and sodium hydroxide water solution. Their monosaccharide compositions, relative molecular mass and structural characterization were determined by gas chromatography, high performance liquid chromatography, fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy methods. EW was hybrid l/k/v-carrageenan （701/17k/13v-car- rabiose）, EH was mainly t-carrageenan, and EA was mainly α-1,4-Glucan （88%） but mixed with small amount of t-carrageenan （12%）. The relative molecular mass ofEW, EH and EA was 480, 580 and 510kDa, respectively. The anti-influenza A （H1N1） virus activity of these three polysaccharides was evaluated using the Madin-Darby canine kidney cells model. EW showed good anti-H1N1 virus activity, its ICso was 276.5 μg mL-1, and the inhibition rate to H1N1 virus was 52% when its concentration was 250 μgmL-1. The ICs0 of t-carrageenan EH was 366.4 μgmL1, whereas EA showed lower anti-H1N1 virus activity （IC50〉430μgmL-1）. Available data obtained give positive evidence that the hybrid carrageenan EW from Eueheuma denticulatum can be used as potential anti-H1N1 virus inhibitor in future.

Gene Expression Profiles Comparison between 2009 Pandemic and Seasonal H1N1 Influenza Viruses in A549 Cells

Objective To perform gene expression profiles comparison so that to identify and understand the potential differences in pathogenesis between the pandemic and seasonal A （H1N1） influenza viruses. Methods A549 cells were infected with A/California/07/09 （H1N1） and A/GuangdongBaoan/51/08 （H1N1） respectively at the same MOI of 2 and collected at 2, 4, 8, and 24 h post infection （p.i.）. Gene expression profiles of A549 cells were obtained using the 22 K Human Genome Oligo Array, and differentially expressed genes were analyzed at selected time points. Results Microarrays results indicated that both of the viruses suppressed host immune response related pathways including cytokine production while pandemic H1N1 virus displayed weaker suppression of host immune response than seasonal H1N1 virus. Observation on similar anti-apoptotic events such as activation of apoptosis inhibitor and down-regulation of key genes of apoptosis pathways in both infections showed that activities of promoting apoptosis were different in later stage of infection. Conclusion The immuno-suppression and anti-apoptosis events of pandemic H1N1 virus were similar to those seen by seasonal H1N1 virus. The pandemic H1N1 virus had an ability to inhibit biological pathways associated with cytokine responses, NK activation and macrophage recognition .

Integrated analysis of human influenza A(H1N1)virus infectionrelated genes to construct a suitable diagnostic model

The genome characteristics and structural functions of coding proteins correlate with the genetic diversity of the H1N1 virus,which aids in the understanding of its underlying pathogenic mechanism.In this study,analyses of the characteristic of the H1N1 virus infection-related genes,their biological functions,and infection-related reversal drugs were performed.Additionally,we used multi-dimensional bioinformatics analysis to identify the key genes and then used these to construct a diagnostic model for the H1N1 virus infection.There was a total of 169 differently expressed genes in the samples between 21 h before infection and 77 h after infection.They were used during the protein-protein interaction(PPI)analysis,and we obtained a total of 1725 interacting genes.Then,we performed a weighted gene co-expression network analysis(WGCNA)on these genes,and we identified three modules that showed significant potential for the diagnosis of the H1N1 virus infection.These modules contained 60 genes,and they were used to construct this diagnostic model,which showed an effective prediction value.Besides,these 60 genes were involved in the biological functions of this infectious virus,like the cellular response to type I interferon and in the negative regulation of the viral life cycle.However,20 genes showed an upregulated expression as the infection progressed.Other 36 upregulated genes were used to examine the relationship between genes,human influenza A virus,and infection-related reversal drugs.This study revealed numerous important reversal drug molecules on the H1N1 virus.They included rimantadine,interferons,and shikimic acid.Our study provided a novel method to analyze the characteristic of different genes and explore their corresponding biological function during the infection caused by the H1N1 virus.This diagnostic model,which comprises 60 genes,shows that a significant predictive value can be the potential biomarker for the diagnosis of the H1N1 virus infection.

Novel H1N1 influenza A virus infection in a patient with acute rejection after liver transplantation

BACKGROUND:The 2009 H1N1 influenza A virus was first identified in April 2009 and rapidly evolved into a pandemic. Recipients of solid-organ transplants have a higher risk for severe infection because of immunosuppression.There are limited reports of 2009 H1N1 influenza in liver transplant recipients,especially in China. METHODS:We present a case of a 48-year-old male liver transplant recipient with 2009 H1N1 influenza A virus.He received therapy for acute rejection after transplantation and was confirmed with H1N1 virus infection. RESULTS:The patient was started on oseltamivir(75 mg, orally twice daily)and had a benign hospital course,with defervescence and resolution of symptoms within 72 hours. The follow-up chest radiograph after discharge was normal. CONCLUSIONS:The 2009 H1N1 influenza in this hospitalized transplant recipient was relatively mild,and prolonged viral shedding was not noted.Oseltamivir can be a valid measure in immunocompromised individuals.

First isolation and identification of H1N1 swine influenza viruses in Colombian pig farms

The pig industry in Colombia has grown 30% in the last decade achieving high levels of technology and efficiency;in spite of that, respiratory diseases remain a constraint. Since 1970, serological evidence and histological findings suggested the role of swine influenza virus (SIV) as part of the porcine respiratory disease complex;nevertheless, elusive and molecular typing isolates are missing. This study was aimed at isolating SIV from intensive pig farms and to achieve molecular characterization to determine strains circulating in the field. In order to accomplish this goal, 242 samples were taken from nasal swabs, 25 from bronchial washes and 8 from lung tissue. Samples were collected during a period of three years, between 2008 and 2010 and were originated from 78 farms of the three main pig production regions of the country. The samples were transported in BHI broth with 2% antibiotic and antimycotic solution and stored at –70?C until processed. The swabs were inoculated in 9 - 11 days old embryo chicken eggs and in MDCK (Madin Darby Canine Kidney) cell cultures with the addition of trypsin. The isolates were identified by the HA (hemoagglutination) test and by RT-PCR targeting the HA (hemagglutinin), NA (Neuraminidase) and M (Matrix) genes. Full length sequence of the HA and NA glycoproteins from four selected virus isolates was conducted (Macrogen?. USA). As a result, fifteen SIV isolates from nine farms distributed in the three regions were obtained. Twelve of the isolates are related to the swine origin H1N1 virus that caused the 2009 influenza pandemic. The remaining three viruses were related to classical swine influenza viruses.

Subtle differences in receptor binding specificity and gene sequences of the 2009 pandemic H1N1 influenza virus

A recent phylogenetic inference indicated that the 2009 pandemic H1N1 strains circulating from March 2009 to September 2009 could be divided into two closely related but distinct clusters. Cluster one contained most strains from Mexico, Texas, and California, and cluster two had most strains from New York, both of which were reported to co-circulate in all continents. The same study further revealed nine nucleotide changes in six gene segments of the new virus specific for the two clusters. In the current study, the informational spectrum method (ISM), a bioinformatics technique, was employed to study the receptor binding patterns of the two clusters. It discovered that while both groups shared the same primary human binding affinity, their secondary binding preferences were different. Cluster one favored swine binding as its secondary binding pattern, whereas cluster two mostly exhibited the binding specificity of A/South Carolina/1/18 (H1N1) (one of the 1918 flu pandemic strains) as its secondary binding pattern. Besides all the nine nucleotide changes found in the previous study, Random Forests were applied to uncover several new nucleotide polymorphisms in 10 genes of the strains between the two clusters, and several amino acid changes in the HA protein that might be accountable for the discrepancy of the secondary receptor binding patterns of the two clusters. Finally, entropy analysis was conducted to present a global view of gene sequence variations between the two clusters, which illustrated that cluster one had much higher genetic divergence than cluster two. Furthermore, it suggested a significant overall correspondence between the nucleotide positions of high importance in differentiating the two clusters and nucleotide positions of high entropy in cluster one.

Receptor binding specificity and origin of 2009 H1N1 pandemic influenza virus

Recently, a genetic variant of 2009 H1N1 has become the predominant virus circulating in the southern hemisphere, particularly Australia and New Zealand, and in Singapore during the winter of 2010. It was associated with several vaccine breakthroughs and fatal cases. We analyzed three reported mutations D94N, N125D, and V250A in the HA protein of this genetic variant. It appeared that the reason for D94N and V250A to occur in pairs was to maintain the HA binding to human type receptor, so the virus could replicate in humans efficiently. Guided by this interpretation, we discovered a new mutation V30A that could compensate for N125D as V250A did for D94N. We demonstrated that the presence of amino acids 30A and 125N in HA enhanced the binding to human type receptor, while 30V and 125D favored the receptors of avian type and of A/South Carolina/1/18 (H1N1). Furthermore, a combination of 94D, 125D, and 250V made the primary binding preference similar to that of A/South Carolina/1/18 (H1N1) and a combination of 94N, 125D, and 250A resulted in the primary binding affinity for avian type receptor, which clearly differed from that of A/California/07/2009 (H1N1), a strain used in the vaccine for 2009 H1N1. We also re-examined the origin of 2009 H1N1 to refine our knowledge of this important issue. Although the NP, PA, PB1, and PB2 of 2009 H1N1 were closest to North American swine H3N2 in sequence identity, their interaction patterns were closest to swine H1N1 in North America.

In silico modification of oseltamivir as neuraminidase inhibitor of influenza A virus subtype H1N1

This research focused on the modification of the functional groups of oseltamivir as neuraminidase inhibitor against influenza A virus subtype H1N1.Interactions of three of the best ligands were evaluated in the hydrated state using molecular dynamics simulation at two different temperatures.The docking result showed that AD3BF2 D ligand（N-[（1S,6R）-5-amino-5-{[（2R,3S,4S）-3,4-dihydroxy-4-（hydroxymethyl） tetrahydrofuran-2-yl]oxy}-4-formylcyclohex-3-en-1-yl]acetamide-3-（1-ethylpropoxy）-1-cyclohexene-1-carboxylate） had better binding energy values than standard oseltamivir.AD3BF2 D had several interactions,including hydrogen bonds,with the residues in the catalytic site of neuraminidase as identified by molecular dynamics simulation.The results showed that AD3BF2 D ligand can be used as a good candidate for neuraminidase inhibitor to cope with influenza A virus subtype H1N1.

Transcriptomic analyses reveal new genes and networks response to H5N1 influenza viruses in duck(Anas platyrhynchos)

H5N1 influenza represents one of the great challenges to public health.Some H5N1 viruses(i.e.,A/goose/Hubei/65/05,GS/65) are weakly pathogenic,while the others(i.e.,A/duck/Hubei/49/05,DK/49) are highly pathogenic to their natural hosts.Here,we performed brain and spleen transcriptomic analyses of control ducks and ones infected by the DK/49 or the GS/65 H5N1 virus.We demonstrated that,compared to the GS/65 virus,the DK/49 virus infection changed more numerous immune genes’ expression and caused continuous increasing of immune pathways(i.e.,RIG-I and MDA5) in ducks.We found that both H5N1 virus strains might escape or subvert host immune response through affecting alternative translation of immune genes,while the DK/49 virus seemed to induce alternative translation of more immune genes than the GS/65 virus.We also identified five co-expressional modules associated with H5N1 virus replication through the weight correlation network analysis(WGCNA).Moreover,we first demonstrated that the duck BCL2 L15 and DCSTAMP in one of these five modules inhibited both the highly pathogenic and weakly pathogenic H5N1 virus replication efficiently.These analyses,in combination with our comprehensive transcriptomic data,provided global view of the molecular architecture for the interaction between host and H5N1 viruses.

Novel host markers in the 2009 pandemic H1N1 influenza a virus

The winter of 2009 witnessed the concurrent spread of 2009 pandemic H1N1 with 2009 seasonal H1N1. It is clinically important to develop knowledge of the key features of these two different viruses that make them unique. A robust pattern recognition technique, Random Forests, was employed to uncover essential amino acid markers to differentiate the two viruses. Some of these markers were also part of the previously discovered genomic signature that separate avian or swine from human viruses. Much research to date in search of host markers in 2009 pandemic H1N1 has been primarily limited in the context of traditional markers of avian-human or swine-human host shifts. However, many of the molecular markers for adaptation to human hosts or to the emergence of a pandemic virus do not exist in 2009 pandemic H1N1, implying that other previously unrecognized molecular determinants are accountable for its capability to infect humans. The current study aimed to explore novel host markers in the proteins of 2009 pandemic H1N1 that were not present in those classical markers, thus providing fresh and unique insight into the adaptive genetic modifications that could lead to the generation of this new virus. Random Forests were used to find 18 such markers in HA, 15 in NA, 9 in PB2, 11 in PB1, 13 in PA, 10 in NS1, 1 in NS2, 11 in NP, 3 in M1, and 1 in M2. The amino acids at many of these novel sites in 2009 pandemic H1N1 were distinct from those in avian, human, and swine viruses that were identical at these positions, reflecting the uniqueness of these novel sites.

Shiqi herbal tea reduces the susceptibility to H1N1 influenza virus in stressed mice

Objective:It is well known that stress plays a critical role in immune response and susceptibility to diseases.Among many stressors,restraint stress has been shown to suppress immune function and increase susceptibility to infections.In this study,we employed a restraint-mouse model to investigate the effect and preliminary mechanism of ShiQi herbal tea(SQHT),a traditional Chinese medicine,on H1N1 virus infection.Methods:Mice were exposed to restraint stress and infected with H1N1 influenza virus by intranasal inoculation.SQHT(936 and 1872 mg/kg/d)was orally administrated to mice for 7 days from the first day of restraint stress.The survival rate of mice in each group was monitored daily for 21 days.Histopathological changes,inflammatory cells infiltration,and virus titer in lungs were examined.For the study of mechanisms,we investigated whether SQHT could promote interferon-β(IFN-β)generation and interferon stimulated genes(ISG)expression.Results:Our results suggested that SQHT(936 mg/kg/d)significantly reduced H1N1-induced mortality,the level of complement C5a and lung tissue inflammation,and viral replication in restraint-stressed mice.Further results revealed that in restraint-stressed mice model,SQHT(936 mg/kg/d)administration markedly improved IFN-βgeneration,and increased MX1 and IFITM3 gene expression.Conclusion:Our study demonstrates that SQHT reduces restraint stress-induced susceptibility to H1N1 infection via improving IFN-βantiviral pathway,which provides a certain basis for the clinical use of SQHT to treat H1N1 infection.

Seroprevalence study of infection with influenza A(H1N1)pdm09 virus in San Felipe Town, Chile

Objective: To know the natural history of the first wave of pandemic influenza A(H1N1)pdm09 in the Southern hemisphere, through the detection of antibodies against influenza A(H1N1)pdm09 in a selected community, to estimate the population attack rate and its variations, the consultation rates, hospitallization and mortality rates. Methodology: A representative random sample of the population of a commune in Chile (San Felipe) was interviewed and taken blood samples between January and March 2010. A study against the antibodies of the influenza A(H1N1) pdm09 virus was conducted, by the technique of the Hemaglutination Inhibition (HAI) according to standardized methodology. Subjects with antibody titers ≥1:40 were considered positive. Results: 13.5% of the population of San Felipe had antibodies against influenza A(H1N1)pdm09;this percentage reached 30% of the population between 0 and 18 years and 6.1% among those over 19 years. The age variable was the only factor that evidenced significant differences in the prevalence of antibodies. There were no significant differences related to gender, vaccination history against seasonal inluenza, or comorbidity. 51% of people with positive serology showed IN-FLUENZA-LIKE SYMPTOMS. Conclusions: A relevant percentage of subclinical disease was detected in the first pandemic wave in Chile and the proportion of people with SARI and deaths was small. Data from epidemiological surveillance were useful to estimate the trend of TSI but not its magnitude.

A Review on 2009 Influenza A Virus

[Objective] The paper was to introduce the research progress of 2009 influenza A virus. [Method] 2009 influenza A virus was introduced from the aspects of classification and host, virology, molecular characteristics and vaccine. [Result] A novel influenza A/H1N1 virus emerged in early April 2009 quickly spread worldwide through human-to-human transmission. The virus contained a group of novel gene segments, the nearest known precursor was the virus found in swine. The virus appeared to retain the potential to infect swine again and thus continued reassort with swine viruses. All registered 2009 influenza A vaccines were tested for safety and immunogenicity in clinical trials on human volunteers, and all vaccines were found to be safe, single dose of vaccine could cause protective antibody responses. [Conclusion] The paper provided basis for further study on 2009 influenza A virus.

Cloning and Phylogenetic Analysis of NS1 Genes from Different Isolates of H9N2 Subtype Duck Influenza Virus

[ Objective] The study aimed to lay a foundation for the further studies on function mechanism of NS1 protein in the interspecies transmission of waterfowl influenza virus. [Method] Using the serologic assay and the specific RT-PCR method, some strains of H9 subtype waterfowl influenza virus were isolated from the 12 to 20 day-old muscovy duck flocks without any clinical symptoms in different areas of Guangdong Province. Four of these strains, including A/duck/ZQ/303/2007（H9N2） （A3 for short）, A/Duck/FJ/301/2007 （H9N2） （C1 for short）, A/Duck/NH/306/2007（H9N2） （ D6 for short）, A/duck/SS/402/2007（H9N2） （ E2 for short）, and a strain named A/duck/ZC/2007（H9N2） （L1 for short） from a muscovy duck died of avian influenza virus （AIV）, were used for NSl gene cloning and sequencing. Subsequently, the obtained NSl gene sequences were compared with other NS1 sequences registered in GenBank, and the phylogenetic analysis was also conducted. [Result] When compared with the H9N2 AIV NS1 sequences in GenBank, the NSl genes of the four AIV strains A3, C1, 136 and E2 displayed homologies ranging from 99% to 100% at nucleotide level, and 95% to 100% at amino acid level; while the NSl gene of L1 strain displayed homology ranging from 94% to 97% at nucleotide level, and 93% to 98% at amino acid level. The phylogenetic tree demonstrated that A3, C1, D6 and E2 were highly resemblant, and L1 was closest to AY66473 （chicken, 2003）. By comparison with the NS1 gene sequences of L1, AF523514 （duck）, AY664743 （chicken） and EF155262.1 （quail） using DNAstar, A3, C1, D6 and E.2 presented nucleotide variations at site 21 （ R→Q）, 70, 71 （ KE→EG）, 86 （ A→S）, 124 （V→M） and 225 （ S→N）, and amino acid variations at site 21,70, 71 and 86 in dsRNA- dependent protein kinase （PKR） binding domain of NSl gene, which induced the evident variations of antigenic determinant and surface proba- bility plot of NS1 protein. [ Conclusion] This study suggested that the amino acid sequence variation in PKR binding domain of NS1 protein had something to do with the virus pathogenicity.

H5N1 influenza viruses： outbreaks and biological properties

All known subtypes of influenza A viruses are maintained in wild waterfowl, the natural reservoir of these viruses. Influenza A viruses are isolated from a variety of animal species with varying morbidity and mortality rates. More importantly, influenza A viruses cause respiratory disease in humans with potentially fatal outcome. Local or global outbreaks in humans are typically characterized by excess hospitalizations and deaths. In 1997, highly pathogenic avian influenza viruses of the H5N1 subtype emerged in Hong Kong that transmitted to humans, resulting in the first documented cases of human death by avian influenza virus infection. A new outbreak started in July 2003 in poultry in Vietnam, Indonesia, and Thailand, and highly pathogenic avian H5N1 influenza viruses have since spread throughout Asia and into Europe and Africa. These viruses continue to infect humans with a high mortality rate and cause worldwide concern of a looming pandemic. Moreover, H5N1 virus outbreaks have had devastating effects on the poultry industries throughout Asia. Since H5N1 virus outbreaks appear to originate from Southern China, we here examine H5N1 influenza viruses in China, with an emphasis on their biological properties.