A型流感病毒致病性及跨种间传播的分子生物学基础

A型流感病毒在温血动物中广泛存在,也是目前导致人类和各种动物流感疾病的主型。在自然情况下流感病毒感染的宿主范围有一定的特异性,分离自人的流感病毒一般不能在鸡、鸭等禽类体内复制,同样禽流感病毒在灵长类动物体内的复制能力也极差。但近年来不断发生禽流感病毒（包括H5N1,H9N2,H7N7亚型病毒）直接传染给人的事件,而2009年爆发的人类的H1N1流感的病原则是猪源流感病毒重组而来。研究证实,流感病毒的致病性及跨种间传播的深层原因是病毒分子结构差异及其与宿主细胞相互作用。病毒多种结构蛋白和非结构蛋白某些功能位点上氨基酸的差异是病毒致病性及其跨中传播的分子生物学基础。     

流感病毒哺乳动物间传播的研究进展

流感病毒是单股负链有囊膜的RNA病毒,具有8个基因节段,编码11种蛋白。根据病毒粒子核蛋白(NP)和膜蛋白(MP)划分为甲,乙,丙3个型,甲型流感病毒根据其表面蛋白的抗原性又可以划分为16个HA亚型和9个NA亚型。所有亚型的流感病毒均已经在水禽中发现,其中H1～H3亚型的流感病毒在人类历史上爆发过大流行——1918 H1N1、1957 H2N2、1968 H3N2和2009 H1N1,而禽流感病毒(AIV)直接感染人事件的多次出现警示我们AIV一旦获得在人与人之间水平传播的能力将会引发新一轮的流感大流行。本文综述了影响流感病毒在哺乳动     

A型流感病毒跨种传播和致病性相关蛋白研究进展

A型流感病毒是重要的人和动物病原体,每年都会在人群中引发季节性流感流行,偶尔还会引发全球流感大流行,对公共卫生安全构成严重威胁.研究发现,A型流感病毒的跨种传播与该病毒的多个蛋白有关,其中血凝素是该病毒宿主范围的主要限制因素,但聚合酶蛋白和非结构蛋白1(NS1)的作用也不容忽视.A型流感病毒通过不断地适应各类宿主和长期...     

流感病毒与细胞受体相互作用的复杂性

细胞受体是流感病毒感染、复制与传播的生物学基础.病毒血凝素基因的差异和细胞上不同类型的受体是影响病毒受体结合特性的两个重要因素.了解这两个因素有助于人们进一步认识流感的病原学、感染机制、流行病学等内容,对于流感的监测、疫苗研制和公共卫生学都将有借鉴意义.论文就流感病毒基因特点、细胞受体类型差异及二者相互作用的复杂性进行综述.     

流感病毒在人间的传播及防控

禽流感病毒是正粘病毒,流感病毒属的一个成员。流感病毒由特异的不具交叉反应的核糖核蛋白抗原区分为三个不同的抗原型,即A、B、C三型。A型和B型人流感病毒可造成季节性流行,一般出现在10月和5月。野生水禽是所有已知A型流感病毒的天然宿主,特别是某些野鸭、鹅、大雁、天鹅、海鸥、水鸟和燕鸥。     

浅谈微信公众号信息传播的影响因素分析

随着新媒体时代的到来,微信公众号平台成为用户传播信息的一种新模式,传播信息快,社会反应效果非常好。本文对微信公众号传播的影响因素进行了分析,得出影响微信公众号传播有宣传主体、推送标题、推送内容、推送时机等主要因素,最后提出校园信息宣传中运营微信公众号平台的建议与对策。     

流感病毒受体在三种动物气管和肺脏分布的组织化学检测

利用凝集素组织化学染色的方法,对岭南黄鸡、番鸭和BALB/C小鼠的气管和肺脏进行了流感病毒受体分布的检测。结果表明:在岭南黄鸡、番鸭和小鼠的气管粘膜层、粘膜下层、肺脏的细支气管和肺泡上皮细胞均有禽流感病毒受体的分布。番鸭和小鼠气管和肺脏的人流感病毒受体的分布范围和细胞类型与禽流感病毒受体的分布稍有差异,岭南黄鸡气管和肺脏未检测到人流感病毒受体的分布。研究结果为探讨流感病毒的感染机制和宿主特异性的差异提供了基础数据。     

流感病毒的跨种感染

人们通常认为流感只是一种仅持续数天的无害疾病 ,养鸡者对其的了解则比较充分。流感病毒的危害比一般人认为的都大 ,有些类型的流感病毒能够成为家畜乃至人类的杀手而会发生种间传播     

流感病毒受体识别以及流感病毒跨宿主感染的分子机理

近年来禽流感病毒在亚洲流行,使家禽养殖业受到很大冲击。令人担心的是,从东南亚疫情爆发地区还报道了人类感染禽流感病毒的病例,我国湖南等省也有人类感染禽流感病毒。目前疫情虽然已经得到控制,但是H5N1亚型禽流感病毒将长期在亚洲存在。由于流感病毒的自身基因组极易产生变异和亚洲地区家禽业的养殖模式特点,禽流感病毒极有可能进化成可以跨宿主感染的新型流感毒株。本文对流感病毒的受体识别和跨宿主感染的分子机理作一综述,并讨论若出现流感大流行时的药物控制措施。     

流感病毒受体结合与抗原性改变的分子基础

流感病毒的血凝素(HA)与宿主细胞表面糖链末端唾液酸(SA)的结合对流感病毒感染宿主起着至关重要的作用。禽流感病毒对SAα2-3Galβ糖链以及人流感病毒对SAα2-6Galβ糖链的结合特异性使跨种属传播受阻,但不同的流感病毒在猪和陆地家禽等中间宿主体内发生基因重配作用后,可使部分禽流感病毒获得适应性感染人的能力,另一方面,流感病毒自身的基因突变,尤其是受体结合部位周围的特定位点,可导致流感病毒受体结合特异性发生转变,而病毒的变异伴随着自身糖修饰和抗原表位的改变,使机体对其免疫识别结合的能力也随之发生变化。这些分子水平的改变都将对病毒相关的宿主受体结合和免疫应答反应产生影响。     

猪流感病毒的基因组结构及跨种属传播

猪是禽和哺乳动物流感病毒的中间宿主和产生重组病毒的混合器,猪流感病毒基因重排现象非常普遍。从猪流感病毒的形态结构、抗原性、基因组与主要编码蛋白、基因重排与跨种属传播等方面,对其研究情况进行了综述,以期为进一步了解猪流感病毒基因重排及种间传播机制,更好的防控流感疫情提供参考。     

Modeling analysis revealed the distinct global transmission patterns of influenza A viruses and their influencing factors

Influenza A virus has caused huge damage to human health and poultry production worldwide, but its global transmission patterns and influencing factors remain unclear. Here, by using the Nearest Genetic Distance Approach with genetic sequences data, we reconstructed the global transmission patterns of 4 most common subtypes of influenza A virus (H1N1, H3N2, H5N1, and H7N9) and analyzed associations of transmission velocity of these influenza viruses with environmental factors. We found that the transmission patterns of influenza viruses and their associations with environmental factors were closely related to their host properties. H1N1 and H3N2, which are mainly held by humans, are transmitted between regions at high velocity and over long distances, which may be due to human transportation via airplane; while H5N1 and H7N9, which are mainly carried by animals, are transmitted locally at short distances and at low velocity, which may be facilitated by poultry transportation via railways or high ways. H1N1 and H3N2 spread faster in cold seasons, while H5N1 spread faster in both cold and warm seasons, and H7N9 spread faster in wet seasons. H1N1, H3N2, and H5N1 spread faster in places with both high and low human densities. Our study provided novel insights into the global transmission patterns, processes, and management strategies for influenza under accelerated global change.     

Syndromic survey and molecular analysis of influenza viruses at the human–swine interface in two West African cosmopolitan cities suggest the possibility of bidirectional interspecies transmission

Influenza viruses are frequently transmitted between pigs and their handlers, and among pig handlers. However, reports on socio‐environmental variables as potential risk factors associated with transmission of influenza in West African swine production facilities are very scarce. Syndromic survey for influenza was therefore conducted in Ibadan, Nigeria, and Kumasi, Ghana, in order to identify and elucidate selected socio‐environmental variables that may contribute to the occurrence and distribution of influenza‐like illness (ILI) among swine industry workers. In addition, molecular analyses were conducted to elucidate the nature of influenza viruses circulating at the human–swine interface in these cities and better understand the dynamics of their transmission. Influenza viruses were detected by type‐specific and subtype‐specific RT–PCR. Sequencing and phylogenetic analyses were carried out. Socio‐environmental variables were tested by both univariable and multivariable regression methods for significance at p < 0.05. Three risk factors for ILI were identified in each city. These included “frequency of visit of pig handler to pig pen or lairage” (Ibadan: risk ratio [RR] = 1.54, 95% confidence interval [CI] = 1.36–1.79, p = 0.02; Kumasi: RR = 1.28, 95% CI = 1.11–1.71, p = 0.01) and “pig handler's awareness about biosecurity measures” (Ibadan: RR = 7.09, 95% CI = 2.36–21.32, p < 0.001; Kumasi: RR = 4.84, 95% CI = 1.98–11.80, p < 0.001). Influenza A(H1N1)pdm09 viruses, with M genes closely related to those which circulated among pigs in the two cities during the same period, were detected among Nigerian and Ghanaian pig industry workers. These findings suggest the possibility of bidirectional transmission of influenza at the human–swine interface in these cities and underscore the need for more extensive molecular studies. Risk factors identified may assist in the control of human‐to‐human and human‐to‐swine transmission of influenza in the West African swine industry.     

Pathogenicity and transmission of H5N1 avian influenza viruses in different birds

In this study, we selected three H5N1 highly pathogenic avian influenza viruses (HPAIVs), A/Goose/Guangdong/1/1996 (clades 0), A/Duck/Guangdong/E35/2012 (clade 2.3.2.1) and A/Chicken/Henan/B30/2012 (clade 7.2) isolated from different birds in China, to investigate the pathogenicity and transmission of the viruses in terrestrial birds and waterfowl. To observe the replication and shedding of the H5N1 HPAIVs in birds, the chickens were inoculated intranasally with 10⁶ EID₅₀ of GSGD/1/96, 10³ EID₅₀ of DkE35 and CkB30, and the ducks and geese were inoculated intranasally with 10⁶ EID₅₀ of each virus. Meanwhile, the naive contact groups were set up to detect the transmission of the viruses in tested birds. Our results showed that DkE35 was highly pathogenic to chickens and geese, but not fatal to ducks. It could be detected from all the tested organs, oropharyngeal and cloacal swabs, and could transmit to the naive contact birds. GSGD/1/96 could infect chickens, ducks and geese, but only caused death in chickens. It could transmit to the chickens and ducks, but was not transmittable to geese. CkB30 was highly pathogenic to chickens, low pathogenic to ducks and not pathogenic to geese. It could be transmitted to the naive contact chickens, but not to the ducks or geese. Our findings suggested that H5N1 HPAIVs from different birds show different host ranges and tissue tropisms. Therefore, we should enhance serological and virological surveillance of H5N1 HPAIVs, and pay more attention to the pathogenic and antigenic evolution of these viruses.     

The mouse model is suitable for the study of viral factors governing transmission and pathogenesis of highly pathogenic avian influenza (HPAI) viruses in mammals

Highly pathogenic avian influenza (HPAI) viruses of the H5 and H7 subtype pose a major public health threat due to their capacity to cross the species barrier and infect mammals, for example dogs, cats and humans. In the present study we tested the capacity of selected H7 and H5 HPAI viruses to infect and to be transmitted from infected BALB/c mice to contact sentinels. Previous experiments have shown that viruses belonging to both H5 and H7 subtypes replicate in the respiratory tract and central nervous system of experimentally infected mice. In this study we show that selected H7N1 and H5N1 HPAI viruses can be transmitted from mouse-to-mouse by direct contact, and that in experimentally infected animals they exhibit a different pattern of replication and transmission. Our results can be considered as a starting point for transmission experiments involving other influenza A viruses with α 2-3 receptor affinity in order to better understand the viral factors influencing transmissibility of these viruses in selected mammalian species.     

Perceptions and attitudes of swine exhibitors towards recommendations for reducing zoonotic transmission of influenza A viruses

Since 2011, there have been 468 cases of variant influenza A virus (IAV) reported in the United States, many of which were associated with youth swine exhibition. In an effort to mitigate risk associated with exposure to IAV in swine, the “Measures to Minimize Influenza Transmission at Swine Exhibitions” (MtM) was developed for show organizers, volunteers and exhibitors. These recommendations are updated annually; however, it is not clear if youth swine exhibitors are aware of the recommendations; support the recommendations; and would be willing to practise recommended behaviours. Therefore, a cross‐sectional survey method was used to assess swine exhibitor perceptions and their adoption of swine production practices aimed at reducing the transmission of IAV at the human–animal interface. In addition, the survey asked participants their state of residence and the number of shows they would attend in 2017. In all, 155 participants who showed swine on a regular basis (x? = 11 shows per year), from at least 18 states within the US, completed the survey. At least, 67% of participants believed each statement was a good recommendation, with 6 of 11 recommendations being supported by >90% of participants. When asked if recommendations could be implemented, 65%–94% of respondents agreed, and 21%–89% of participants had already implemented each recommendation, respectively. Although significant efforts have been made to increase signage at swine exhibitions (warning of risks associated with eating/drinking in animal areas), a majority of respondents report eating/drinking in the barn and are unwilling to change their behaviours. This study provides evidence that developing and disseminating static recommendations to reduce zoonotic disease transmission is not enough to change human behaviour to prevent future variant IAV infections associated with swine exhibitions.     

Genetic analysis of human and swine influenza A viruses isolated in Northern Italy during 2010–2015

Influenza A virus (IAV) infection in swine plays an important role in the ecology of influenza viruses. The emergence of new IAVs comes through different mechanisms, with the genetic reassortment of genes between influenza viruses, also originating from different species, being common. We performed a genetic analysis on 179 IAV isolates from humans (n. 75) and pigs (n. 104) collected in Northern Italy between 2010 and 2015, to monitor the genetic exchange between human and swine IAVs. No cases of human infection with swine strains were noticed, but direct infections of swine with H1N1pdm09 strains were detected. Moreover, we pointed out a continuous circulation of H1N1pdm09 strains in swine populations evidenced by the introduction of internal genes of this subtype. These events contribute to generating new viral variants—possibly endowed with pandemic potential—and emphasize the importance of continuous surveillance at both animal and human level.     

Seroprevalence and risk factors for influenza A viruses in pigs in Peninsular Malaysia

Following a series of H5N1 cases in chickens and birds in a few states in Malaysia, there was much interest in the influenza A viruses subtypes that circulate among the local pig populations. Pigs may act as a mixing vessel for avian and mammal influenza viruses, resulting in new reassorted viruses. This study investigated the presence of antibodies against influenza H1N1 and H3N2 viruses in pigs from Peninsular Malaysia using Herdcheck Swine Influenza H1N1 and H3N2 Antibody Test Kits. At the same time, the presence of influenza virus was examined from the nasal swabs of seropositive pigs by virus isolation and real time RT-PCR. The list of pig farms was obtained from the headquarters of the Department of Veterinary Services, Malaysia, and pig herds were selected randomly from six of 11 states in Peninsular Malaysia. A total of 727 serum and nasal swab samples were collected from 4- to 6-month-old pigs between May and August 2005. By ELISA, the seroprevalences of swine influenza H1N1 and H3N2 among pigs were 12.2% and 12.1% respectively. Seropositivity for either of the virus subtypes was detected in less than half of the 41 sampled farms (41.4%). Combination of both subtypes was detected in 4% of all pigs and in 22% of sampled farms. However, no virus or viral nucleic acid was detected from nasal samples. This study identified that the seropositivity of pigs to H1N1 and H3N2 based on ELISA was significantly associated with factors such as size of farm, importation or purchase of pigs, proximity of farm to other pig farms and the presence of mammalian pets within the farm.     

Novel reassortant H5N6 highly pathogenic influenza A viruses in Vietnamese quail outbreaks

Avian influenza A H5N6 virus is a highly contagious infectious agent that affects domestic poultry and humans in South Asian countries. Vietnam may be an evolutionary hotspot for influenza viruses and therefore could serve as a source of pandemic strains. In 2015, two novel reassortant H5N6 influenza viruses designated as A/quail/Vietnam/CVVI01/2015 and A/quail/Vietnam/CVVI03/2015 were isolated from dead quails during avian influenza outbreaks in central Vietnam, and the whole genome sequences were analyzed. The genetic analysis indicated that hemagglutinin, neuraminidase, and polymerase basic protein 2 genes of the two H5N6 viruses are most closely related to an H5N2 virus (A/chicken/Zhejiang/727079/2014) and H10N6 virus (A/chicken/Jiangxi/12782/2014) from China and an H6N6 virus (A/duck/Yamagata/061004/2014) from Japan. The HA gene of the isolates belongs to clade 2.3.4.4, which caused human fatalities in China during 2014–2016. The five other internal genes showed high identity to an H5N2 virus (A/chicken/Heilongjiang/S7/2014) from China. A whole-genome phylogenetic analysis revealed that these two outbreak strains are novel H6N6-like PB2 gene reassortants that are most closely related to influenza virus strain A/environment/Guangdong/ZS558/2015, which was detected in a live poultry market in China. This report describes the first detection of novel H5N6 reassortants in poultry during an outbreak as well as genetic characterization of these strains to better understand the antigenic evolution of influenza viruses.