ABSTRACT
Objective@#To analyze the distribution and the molecular biological characteristics of variant subtypes (H5, H7 and H9) of avian influenza virus (AIV) in the live poultry related external environment of Quanzhou form 2014 to 2017, and provide regional references for the prevention, control and early-warning of human infections.@*Methods@#Samples from monitoring sites of live poultry were collected in Quanzhou from 2014 to 2017. Influenza A and variant subtypes of AIV (H5, H7 and H9) were detected by real time RT-PCR, and the detection results were further analyzed statistically. Furthermore, the HA and NA genes of four representative H7N9 strains were sequenced, and the results were further analyzed with DNAstar and MEGA7.0.@*Results@#Among the samples from external environment, the positive rate of nucleic acid of influenza A was 29.04% (377/1 289), of which the positive rates of H5, H7 and H9 subtypes were 3.80%, 13.34% and 12.02%, respectively. The positive rate of H7N9 was higher than those of the other subtypes in all monitored years, of which the highest rate was found in 2017 (21.88%). As to the different types of samples, chopping board possessed the highest positive rate of influenza A (65.4%), followed by waste water (59.3%) and drinking water for the poultry (29.6%). Among the different monitoring sites, the positive rate of poultry farm is 6.94%, far lower than that in the open air (61.7%) and the live poultry trading market (52.8%). Sequencing of the HA and NA genes of four strains of H7N9 showed that the strains from external environment and the strains from H7N9 patients belonged to Pearl River Delta and Yangtze River Delta lineage, respectively. The cleavage sites of HA proteins of these four strains were all PKGR/G without highly pathogenic mutation. Meanwhile, they were low pathogenic H7N9 without oseltamivir resistant mutation (R292 K in NA), while they all possessed the E627 K mutation in the PB2 genes associated with virulence.@*Conclusions@#H7N9 AIV existed in the live poultry related external environment of Quanzhou, especially the farmers’ and the live poultry trading market, so that more persistent surveillance could be needed in the future.
ABSTRACT
Although previous publications suggest the 2009 pandemic influenza A(H1N1)virus was reassorted from swine viruses of North America and Eurasia, the immediate ancestry still remains elusive due to the big evolutionary distance between the 2009 H1N1 virus and the previously isolated strains. Since the unveiling of the2009 H1N1 influenza, great deal of interest has been drawn to influenza, consequently a large number of influenza virus sequences have been deposited into the public sequence databases. Blast analysis demonstrated that the recently submitted 2007 South Dakota avian influenza virus strains and other North American avian strains contained genetic segments very closely related to the 2009 H1N1 virus, which suggests these avian influenza viruses are very close relatives of the 2009 H1N1 virus. Phylogenetic analyses also indicate that the2009 H1N1 viruses are associated with both avian and swine influenza viruses circulating in North America. Since the migrating wild birds are preferable to pigs as the carrier to spread the influenza viruses across vast distances, it is very likely that birds played an important role in the inter-continental evolution of the 2009 H1N1virus. It is essential to understand the evolutionary route of the emerging influenza virus in order to find a way to prevent further emerging cases. This study suggests the close relationship between 2009 pandemic virus and the North America avian viruses and underscores enhanced surveillance of influenza in birds for understanding the evolution of the 2009 pandemic influenza.
ABSTRACT
Chicken embryo fibroblasts(CEFs)are among the most commonly used cells for the study of interactions between chicken hosts and H5N1 avian influenza virus(AIV).In this study,the expression of eleven housekeeping genes typically used for the normalization of quantitative real-time PCR(QPCR)analysis in mammals were compared in CEFs infected with H5N1 AIV to determine the most reliable reference genes in this system.CEFs cultured from 10-day-old SPF chicken embryos were infected with 100 TCID50 of H5N1 AIV and harvested at 3,12,24 and 30 hours post-infection.The expression levels of the eleven reference genes in infected and uninfected CEFs were determined by real-time PCR.Based on expression stability and expression levels,our data suggest that the ribosomal protein L4(RPL4)and tyrosine 3-monooxygenase tryptophan 5-monooxygenase activation protein zeta polypeptide(YWHAZ)are the best reference genes to use in the study of host cell response to H5N1 AIV infection.However,for the study of replication levels of H5N1 AIV in CEFs,the β-actin gene(ACTB)and the ribosomal protein L4(RPL4)gene are the best references.
ABSTRACT
avian influenza virus (AIV) can not only infect avian and cause pandemics,but also result infection and initiate pandemics in humans and other mammal animals,crossing the species barrier.There have been some advance in research into the nonspecific species barrier of human respiratory tract against AIV infection and the mechanism of the infection of AIV in humans in recent years.