Receptor-binding profiles of H7 subtype influenza viruses in different host species

Influenza viruses of gallinaceous poultry and wild aquatic birds usually have distinguishable receptor-binding properties. Here we used a panel of synthetic sialylglycopolymers and solid-phase receptor-binding assays to characterize receptor-binding profiles of about 70 H7 influenza viruses isolated from aquatic birds, land-based poultry, and horses in Eurasia and America. Unlike typical duck influenza viruses with non-H7 hemagglutinin (HA), all avian H7 influenza viruses, irrespective of the host species, displayed a poultry-virus-like binding specificity, i.e., preferential binding to sulfated oligosaccharides Neu5Acα2-3Galβ1-4(6-O-HSO(3))GlcNAc and Neu5Acα2-3Galβ1-4(Fucα1-3)(6-O-HSO(3))GlcNAc. This phenotype correlated with the unique amino acid sequence of the amino acid 185 to 189 loop of H7 HA and seemed to be dependent on ionic interactions between the sulfate group of the receptor and Lys193 and on the lack of sterical clashes between the fucose residue and Gln222. Many North American and Eurasian H7 influenza viruses displayed weak but detectable binding to the human-type receptor moiety Neu5Acα2-6Galβ1-4GlcNAc, highlighting the potential of H7 influenza viruses for avian-to-human transmission. Equine H7 influenza viruses differed from other viruses by preferential binding to the N-glycolyl form of sialic acid. Our data suggest that the receptor-binding site of contemporary H7 influenza viruses in aquatic and terrestrial birds was formed after the introduction of their common precursor from ducks to a new host, presumably, gallinaceous poultry. The uniformity of the receptor-binding profile of H7 influenza viruses in various wild and domestic birds indicates that there is no strong receptor-mediated host range restriction in birds on viruses with this HA subtype. This notion agrees with repeated interspecies transmission of H7 influenza viruses from aquatic birds to poultry.     

Isolation and characterization of H4N6 avian influenza viruses from pigs with pneumonia in Canada

In October 1999, H4N6 influenza A viruses were isolated from pigs with pneumonia on a commercial swine farm in Canada. Phylogenetic analyses of the sequences of all eight viral RNA segments demonstrated that these are wholly avian influenza viruses of the North American lineage. To our knowledge, this is the first report of interspecies transmission of an avian H4 influenza virus to domestic pigs under natural conditions.     

The pattern of influenza virus attachment varies among wild bird species

The ability to attach to host cells is one of the main determinants of the host range of influenza A viruses. By using virus histochemistry, we investigate the pattern of virus attachment of both a human and an avian influenza virus in colon and trachea sections from 12 wild bird species. We show that significant variations exist, even between closely related avian species, which suggests that the ability of wild birds to serve as hosts for influenza viruses strongly varies among species. These results will prove valuable to assess the possibilities of interspecies transmission of influenza viruses in natural environments and better understand the ecology of influenza.     

Replication and adaptive mutations of low pathogenic avian influenza viruses in tracheal organ cultures of different avian species

Transmission of avian influenza viruses (AIV) between different avian species may require genome mutations that allow efficient virus replication in a new species and could increase virulence. To study the role of domestic poultry in the evolution of AIV we compared replication of low pathogenic (LP) AIV of subtypes H9N2, H7N7 and H6N8 in tracheal organ cultures (TOC) and primary embryo fibroblast cultures of chicken, turkey, Pekin duck and homing pigeon. Virus strain-dependent and avian species-related differences between LPAIV were observed in growth kinetics and induction of ciliostasis in TOC. In particular, our data demonstrate high susceptibility to LPAIV of turkey TOC contrasted with low susceptibility of homing pigeon TOC. Serial virus passages in the cells of heterologous host species resulted in adaptive mutations in the AIV genome, especially in the receptor-binding site and protease cleavage site of the hemagglutinin. Our data highlight differences in susceptibility of different birds to AIV viruses and emphasizes potential role of poultry in the emergence of new virus variants.     

2015-2020年大连市流感病毒分离鉴定情况分析

对2015-2020年大连市流感病毒分离鉴定情况进行对比分析, 为大连市流感防控工作提供参考。

采集大连市2家国家级流感监测哨点医院的流感样病例咽拭子样本, 用MDCK细胞和鸡胚分别进行病毒分离培养, 并采用HA试验和HI试验对分离的病毒滴度和型别进行鉴定。

2015-2020年共分离培养流感病毒核酸检测阳性的咽拭子1 055份, 其中MDCK细胞分离出流感病毒501株, 鸡胚分离出流感病毒72株, 总体病毒分离率54.31%。MDCK细胞分离出A(H1N1)、A(H3N2)、B(Victoria)和B(Yamagata)型病毒, 鸡胚对A(H3N2)型病毒不敏感, 但可以分离出A(H1N1)、B(Victoria)和B(Yamagata)型病毒。每年的优势毒株虽不同, 但分离流感病毒的月份均在流行季内, 与北方流行形势一致。

MDCK细胞与鸡胚的流感病毒分离率不同。大连市每年流感流行的优势株和流行程度虽不同, 但流行程度处于相对平稳状态。

     

Fate of 130 hemagglutinins from different influenza A viruses

In this study, we use our probabilistic models to analyze 130 hemagglutinins from different influenza A virus in order to gain the insight into their fate. The results provide three lines of evidence regarding the H5, H6, and H9 hemagglutinins: (i) the H5 hemagglutinins are more sensitive to mutations, this is the current state of the H5, H6, and H9 hemagglutinins; (ii) the H5 hemagglutinins had experienced more mutations in the past, this is the history of the H5, H6, and H9 hemagglutinins; and (iii) the H6 hemagglutinins has a bigger potential towards future mutations, this is the future of the H5, H6, and H9 hemagglutinins. Furthermore, this study gives two clues on the mutation tendency that is a degeneration process and the species susceptibility that is the chickens and ducks.     

The ecology of influenza. Isolation of type 'A' influenza viruses from Australian pelagic birds

Three different type A influenza viruses have been isolated from pelagic birds nesting on islands of the Great Barrier Reef. One of these, isolated in 1972, was of subtype Hav6Nav5. The other two, which are described in this paper, were isolated in 1975 and belonged to subtypes Hav5Nav2 and Hav3Nav6. Of eight isolates of the latter virus, seven were recovered from cloacal swabs and only one from the trachea.     

Transmission of avian influenza A viruses among species in an artificial barnyard

Waterfowl and shorebirds harbor and shed all hemagglutinin and neuraminidase subtypes of influenza A viruses and interact in nature with a broad range of other avian and mammalian species to which they might transmit such viruses. Estimating the efficiency and importance of such cross-species transmission using epidemiological approaches is difficult. We therefore addressed this question by studying transmission of low pathogenic H5 and H7 viruses from infected ducks to other common animals in a quasi-natural laboratory environment designed to mimic a common barnyard. Mallards (Anas platyrhynchos) recently infected with H5N2 or H7N3 viruses were introduced into a room housing other mallards plus chickens, blackbirds, rats and pigeons, and transmission was assessed by monitoring virus shedding (ducks) or seroconversion (other species) over the following 4 weeks. Additional animals of each species were directly inoculated with virus to characterize the effect of a known exposure. In both barnyard experiments, virus accumulated to high titers in the shared water pool. The H5N2 virus was transmitted from infected ducks to other ducks and chickens in the room either directly or through environmental contamination, but not to rats or blackbirds. Ducks infected with the H7N2 virus transmitted directly or indirectly to all other species present. Chickens and blackbirds directly inoculated with these viruses shed significant amounts of virus and seroconverted; rats and pigeons developed antiviral antibodies, but, except for one pigeon, failed to shed virus.     

MDCK cell-cultured influenza virus vaccine protects mice from lethal challenge with different influenza viruses

Influenza epidemics are major health concern worldwide. Vaccination is the major strategy to protect the general population from a pandemic. Currently, most influenza vaccines are manufactured using chicken embroynated eggs, but this manufacturing method has potential limitations, and cell-based vaccines offer a number of advantages over the traditional method. We reported here using the scalable bioreactor to produce pandemic influenza virus vaccine in a Madin-Darby canine kidney cell culture system. In the 7.5-L bioreactor, the cell concentration reached to 3.2 × 10(6) cells/mL and the highest virus titers of 256 HAU/50 μL and 1 × 10(7) TCID50/mL. The HA concentration was found to be 11.2 μg/mL. The vaccines produced by the cell-cultured system induced neutralization antibodies, cross-reactive T-cell responses, and were protective in a mouse model against different lethal influenza virus challenge. These data indicate that microcarrier-based cell-cultured influenza virus vaccine manufacture system in scalable bioreactor could be used to produce effective pandemic influenza virus vaccines.     

Endocytosis of influenza viruses

Receptor-mediated endocytosis is known to play an important role in the entry of many viruses into host cells. However, the exact internalization mechanism has, until recently, remained poorly understood for many medically important viruses, including influenza. Developments in real-time imaging of single viruses as well as the use of dominant-negative mutants to selectively block specific endocytic pathways have improved our understanding of the influenza infection process.     

Isolation and characterization of avian influenza viruses, including highly pathogenic H5N1, from poultry in live bird markets in Hanoi, Vietnam, in 2001

Since 1997, outbreaks of highly pathogenic (HP) H5N1 and circulation of H9N2 viruses among domestic poultry in Asia have posed a threat to public health. To better understand the extent of transmission of avian influenza viruses (AIV) to humans in Asia, we conducted a cross-sectional virologic study in live bird markets (LBM) in Hanoi, Vietnam, in October 2001. Specimens from 189 birds and 18 environmental samples were collected at 10 LBM. Four influenza A viruses of the H4N6 (n = 1), H5N2 (n = 1), and H9N3 (n = 2) subtypes were isolated from healthy ducks for an isolation frequency of over 30% from this species. Two H5N1 viruses were isolated from healthy geese. The hemagglutinin (HA) genes of these H5N1 viruses possessed multiple basic amino acid motifs at the cleavage site, were HP for experimentally infected chickens, and were thus characterized as HP AIV. These HA genes shared high amino acid identities with genes of other H5N1 viruses isolated in Asia during this period, but they were genetically distinct from those of H5N1 viruses isolated from poultry and humans in Vietnam during the early 2004 outbreaks. These viruses were not highly virulent for experimentally infected ducks, mice, or ferrets. These results establish that HP H5N1 viruses with properties similar to viruses isolated in Hong Kong and mainland China circulated in Vietnam as early as 2001, suggest a common source for H5N1 viruses circulating in these Asian countries, and provide a framework to better understand the recent widespread emergence of HP H5N1 viruses in Asia.     

次生林不同类型森林边缘的鸟类物种丰富度及个体多度比较

边缘效应对动物的分布及行为会产生一定的影响,在鸟类生态学研究中已证实某些鸟类在森林内部和森林边缘区域存在着物种丰富度和个体多度的差异。于1999至2001年的春夏季,在吉林省左家自然保护区对阔叶林/农田边缘、阔叶林/灌丛边缘及阔叶林/针叶林边缘3种不同类型边缘地带的鸟类物种丰富度及个体多度进行了比较研究。结果表明,不同年间鸟类物种丰富度无显著变化,但个体多度存在着一定的波动。不同类型森林边缘的鸟类物种丰富度存在着一定的差异,阔叶林/灌丛边缘的鸟类物种丰富度最高,而阔叶林/针叶林边缘的鸟类物种丰富度最低。鸟类个体多度的总体趋势在3种不同类型的边缘差异不显著,但存在种间差异,灰椋鸟、灰头啄木鸟和喜鹊在阔叶林/农田边缘的个体多度最高,斑啄木鸟、黄胸、三道眉草和日本树莺在阔叶林/灌丛边缘的个体多度最高,而沼泽山雀、冕柳莺和山在阔叶林/针叶林边缘的个体多度最高。     

Sphingolipids of influenza viruses.

Total lipid of four egg grown influenza viruses (A2-Asia, A2-England, A2-Taiwan and fowl plague virus) were extracted with chloroform-methanol. After mild alkali treatment of the extracts, glycosphingolipids and sphingomyelin were separated by a silicic acid column, and finally purified by thin layer chromatography. Fatty acid, sphingosine and carbohydrate components of individual lipid classes were then analysed by gas-liquid chromatography. Nearly identical results were obtained with all viruses investigated. Approximately 20% of the total lipid was monohexosylceramide, distributed equally between glucosyl- and galactosyl- analogues. Lactosylceramide and oligohexosylceramides were found in much smaller concentrations (approx. 2%). About 15% of the total lipid was attributed to sphingomyelin. A large proportion of fatty acids (around 25% in sphingomyelin and 60% in glycolipids) belonged to the long chain (C19-C26) normal- and 2-hydroxy series. C18-sphingosine was found to be the only base present in all lipid classes investigated.     

Sialic acid species as a determinant of the host range of influenza A viruses

The distribution of sialic acid (SA) species varies among animal species, but the biological role of this variation is largely unknown. Influenza viruses differ in their ability to recognize SA-galactose (Gal) linkages, depending on the animal hosts from which they are isolated. For example, human viruses preferentially recognize SA linked to Gal by the alpha2,6(SAalpha2,6Gal) linkage, while equine viruses favor SAalpha2,3Gal. However, whether a difference in relative abundance of specific SA species (N-acetylneuraminic acid [NeuAc] and N-glycolylneuraminic acid [NeuGc]) among different animals affects the replicative potential of influenza viruses is uncertain. We therefore examined the requirement for the hemagglutinin (HA) for support of viral replication in horses, using viruses whose HAs differ in receptor specificity. A virus with an HA recognizing NeuAcalpha2,6Gal but not NeuAcalpha2,3Gal or NeuGcalpha2,3Gal failed to replicate in horses, while one with an HA recognizing the NeuGcalpha2,3Gal moiety replicated in horses. Furthermore, biochemical and immunohistochemical analyses and a lectin-binding assay demonstrated the abundance of the NeuGcalpha2,3Gal moiety in epithelial cells of horse trachea, indicating that recognition of this moiety is critical for viral replication in horses. Thus, these results provide evidence of a biological effect of different SA species in different animals.     

Detection of low pathogenic avian influenza viruses in wild ducks from Canada: comparison of two sampling methods

Surveillance for avian influenza viruses in wild birds was initiated in Canada in 2005. In 2006, in order to maximize detection of highly pathogenic avian influenza viruses, the sampling protocol used in Canada's Inter-agency Wild Bird Influenza Survey was changed. Instead of collecting a single cloacal swab, as previously done in 2005, cloacal and oropharyngeal swabs were combined in a single vial at collection. In order to compare the two sampling methods, duplicate samples were collected from 798 wild dabbling ducks (tribe Anatini) in Canada between 24 July and 7 September 2006. Low pathogenic avian influenza viruses were detected significantly more often (P<0.0001) in combined oropharyngeal and cloacal samples (261/798, 33%) than in cloacal swabs alone (205/798, 26%). Compared to traditional single cloacal samples, combined samples improved virus detection at minimal additional cost.