scholarly journals Pathogenesis and Transmission Assessments of Two H7N8 Influenza A Viruses Recently Isolated from Turkey Farms in Indiana Using Mouse and Ferret Models

2016 ◽  
Vol 90 (23) ◽  
pp. 10936-10944 ◽  
Author(s):  
Xiangjie Sun ◽  
Jessica A. Belser ◽  
Joanna A. Pulit-Penaloza ◽  
Hui Zeng ◽  
Amanda Lewis ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Influenza A ◽  
Influenza Viruses ◽  
Avian Influenza Viruses ◽  
Highly Pathogenic ◽  
Pathogenic Avian Influenza ◽  
Domestic Poultry ◽  
Commercial Turkey

ABSTRACTAvian influenza A H7 viruses have caused multiple outbreaks in domestic poultry throughout North America, resulting in occasional infections of humans in close contact with affected birds. In early 2016, the presence of H7N8 highly pathogenic avian influenza (HPAI) viruses and closely related H7N8 low-pathogenic avian influenza (LPAI) viruses was confirmed in commercial turkey farms in Indiana. These H7N8 viruses represent the first isolation of this subtype in domestic poultry in North America, and their virulence in mammalian hosts and the potential risk for human infection are largely unknown. In this study, we assessed the ability of H7N8 HPAI and LPAI viruses to replicatein vitroin human airway cells andin vivoin mouse and ferret models. Both H7N8 viruses replicated efficientlyin vitroandin vivo, but they exhibited substantial differences in disease severity in mammals. In mice, while the H7N8 LPAI virus largely remained avirulent, the H7N8 HPAI virus exhibited greater infectivity, virulence, and lethality. Both H7N8 viruses replicated similarly in ferrets, but only the H7N8 HPAI virus caused moderate weight loss, lethargy, and mortality. The H7N8 LPAI virus displayed limited transmissibility in ferrets placed in direct contact with an inoculated animal, while no transmission of H7N8 HPAI virus was detected. Our results indicate that the H7N8 avian influenza viruses from Indiana are able to replicate in mammals and cause severe disease but with limited transmission. The recent appearance of H7N8 viruses in domestic poultry highlights the need for continued influenza surveillance in wild birds and close monitoring of the potential risk to human health.IMPORTANCEH7 influenza viruses circulate in wild birds in the United States, but when the virus emerges in domestic poultry populations, the frequency of human exposure and the potential for human infections increases. An H7N8 highly pathogenic avian influenza (HPAI) virus and an H7N8 low-pathogenic avian influenza (LPAI) virus were recently isolated from commercial turkey farms in Indiana. To determine the risk that these influenza viruses pose to humans, we assessed their pathogenesis and transmissionin vitroand in mammalian models. We found that the H7N8 HPAI virus exhibited enhanced virulence, and although transmission was only observed with the H7N8 LPAI virus, the ability of this H7 virus to transmit in a mammalian host and quickly evolve to a more virulent strain is cause for concern. Our findings offer important insight into the potential for emerging H7 avian influenza viruses to acquire the ability to cause disease and transmit among mammals.

scholarly journals Insertion of a Multibasic Cleavage Motif into the Hemagglutinin of a Low-Pathogenic Avian Influenza H6N1 Virus Induces a Highly Pathogenic Phenotype

2010 ◽  
Vol 84 (16) ◽  
pp. 7953-7960 ◽  
Author(s):  
Vincent J. Munster ◽  
Eefje J. A. Schrauwen ◽  
Emmie de Wit ◽  
Judith M. A. van den Brand ◽  
Theo M. Bestebroer ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Virus Replication ◽  
Influenza A ◽  
Virus Genotype ◽  
Specific Nature ◽  
Highly Pathogenic ◽  
Pathogenic Avian Influenza ◽  
Low Pathogenic Avian Influenza

ABSTRACT The highly pathogenic avian influenza (HPAI) virus phenotype is restricted to influenza A viruses of the H5 and H7 hemagglutinin (HA) subtypes. To obtain more information on the apparent subtype-specific nature of the HPAI virus phenotype, a low-pathogenic avian influenza (LPAI) H6N1 virus was generated, containing an HPAI H5 RRRKKR↓G multibasic cleavage site (MBCS) motif in HA (the downward arrow indicates the site of cleavage). This insertion converted the LPAI virus phenotype into an HPAI virus phenotype in vitro and in vivo. The H6N1 virus with an MBCS displayed in vitro characteristics similar to those of HPAI H5 viruses, such as cleavage of HA0 (the HA protein of influenza A virus initially synthesized as a single polypeptide precursor) and virus replication in the absence of exogenous trypsin. Studies of chickens confirmed the HPAI phenotype of the H6N1 virus with an MBCS, with an intravenous pathogenicity index of 1.4 and systemic virus replication upon intranasal inoculation, the hallmarks of HPAI viruses. This study provides evidence that the subtype-specific nature of the emergence of HPAI viruses is not at the molecular, structural, or functional level, since the introduction of an MBCS resulted in a fully functional virus with an HPAI virus genotype and phenotype.

scholarly journals Avian influenza: the role of the pig and public health implications

2017 ◽  
Vol 56 (4) ◽  
pp. 339
Author(s):  
C. S. KYRIAKIS (Κ. ΣΠ. ΚΥΡΙΑΚΗΣ) ◽  
K. Van REETH
Keyword(s):  
Influenza Virus ◽  
Avian Influenza ◽  
Influenza A ◽  
H5n1 Virus ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Avian Influenza Viruses ◽  
Highly Pathogenic ◽  
Pathogenic Avian Influenza ◽  
H5n1 Influenza

The huge epizootics of highly pathogenic avian influenza (subtype H5N1) in Southeastern Asia over the last two years and especially the transmission of avian influenza viruses to humans have alerted the international scientific community. Many support that the threat of a new influenza pandemic appears greater today than ever before. During the 20th century, humanity has faced three pandemics, including the "Spanish flu" of 1918-19, which claimed over 20 to 40 million lives, and two less dramatic pandemics in 1957-58 and 1968-69. Influenza A viruses are single stranded RNA viruses belonging to the family Orthomyxoviridae. Their genome expresses only 10 proteins, most important of which are the two surface glycoproteins: haemagglutinin (HA) and neuraminidase (NA). So far, 16 different types of haemagglutinin (HI to Η16) and 9 of neuraminidase (Nl to N9) have been recognized. Influenza A viruses are grouped into "subtypes", according to the HA and NA surface proteins they bear (for example Η I N I , H5N2). Natural reservoirs of influenza A viruses are the wild aquatic birds (migratory waterfowl), from which all types of HA and NA have been isolated. It is important to mention that migratory waterfowl do not show clinical signs of disease, but shed the virus through their excretions.The host range of flu viruses includes domestic poultry, and mammalian species from aquatic mammals to horses, humans and swine. Because of their segmented single stranded RNA genome, influenza viruses have a very high mutation rate (genetic drift) and the possibility to undergo reassortment. Reassortment may occur when more than one virus co-infect the same cell, exchange genes and as a result, provide a totally new influenza virus (genetic shift). At least two subtypes of influenza A viruses are currendy endemic within the human population (H1N1 and H3N2), causing every year outbreaks of disease with very low mortality, especially in elders. Unlike these endemic viruses, pandemic viruses have a much higher morbidity, affecting people of all ages. Η I N I , H3N2 and H1N2 influenza viruses are currently circulating in the European and American swine population. Some of the swine influenza virus subtypes, namely Η I N I and H3N2, are thus similar to those of humans, but there are still important antigenic differences between them. Only rarely swine influenza viruses may be transmitted or cause disease to humans. Unlike mammalian influenza viruses, influenza viruses of domestic birds are grouped in two "pathotypes": low pathogenic avian influenza (LPAI) viruses, which cause localized infections and remain mild or subclinical, and highly pathogenic avian influenza (HPAI) viruses, which cause severe general infection with mortality up to 100% (fowl plague). The majority of avian influenza viruses are low pathogenic and only some, but not all, viruses of H5 and H7 subtypes are highly pathogenic. Occasionally low pathogenic Η5 or H7 viruses from wild birds transmit to poultry. Such viruses can undergo mutations in poultry as a result of which they may acquire a highly pathogenic phenotype. Until the recent avian influenza epizootics in Asia, the predominant theory for the creation of a pandemic virus supported that the pig was likely to act as an intermediate host for transmission of influenza viruses from birds to humans. The fact that genetic reassortment between human and avian viruses has also been shown to occur in pigs in nature, had led to the hypothesis that the pandemic viruses of 1957 and 1968 may have been generated through the pig. More recent data, however, come to question these theories and hypotheses: (a)the direct transmission of the H5N1 and H7N7 avian influenza viruses from birds to humans in Southeastern Asia and The Netherlands, and (b) the presence of cellular receptors recognized preferentially by the haemagglutinin of avian influenza viruses in the human conjunctiva and ciliated respiratory epithelial cells, which support that avian influenza viruses can be transmitted in toto (without reassortment) to and between humans or that humans can be the mixing vessel themselves. Furthermore, there is no solid scientific evidence to prove that any influenza virus reassortants, that have originated in swine, have posed a risk for humans. There are three criteria (conditions) an influenza virus must fulfill in order to be characterized as a pandemic virus: (a) it must be a new virus against which humans are immunologically naive, (b) it must be able to replicate in humans causing severe disease, and (c) it must be efficiendy transmitted among humans, causing wide outbreaks. So far the H5N1 influenza virus only fulfills the first and second condition, and even though it has been sporadically infecting humans for over two years, it has not yet been able to fully adapt to it's new host. Compared to the human population that may have been exposed to the H5N1 influenza virus in Asia, the number of patients and fatalities due to the H5N1 virus is very small. So far, it appears that swine do not play an important role in the epidemiology of this specific virus. Experimental infections of swine with highly pathogenic H5N1 virus have shown that it does not replicate extensively in pigs. Additionally, extensive serological investigations in the swine population of Viet Nam, indicated that the H5N1 virus merely spread to a very small number (~0.25%) of contact animals within the epizootic regions. Nevertheless, it is critical to continue monitor ring pigs and studying the behavior and spread of influenza viruses in these species.

scholarly journals Isolation of a Novel Reassortant Highly Pathogenic Avian Influenza (H5N2) Virus in Egypt

Viruses ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 565 ◽  
Author(s):  
Naglaa M. Hagag ◽  
Ahmed M. Erfan ◽  
Mohamed El-Husseiny ◽  
Azhar G. Shalaby ◽  
Mohamed A. Saif ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Highly Pathogenic Avian Influenza ◽  
Influenza Viruses ◽  
Avian Influenza Viruses ◽  
Highly Pathogenic ◽  
Pathogenic Avian Influenza ◽  
H5n2 Virus ◽  
Domestic Poultry ◽  
Hpai H5n1 ◽  
Avian Influenza H9n2

Highly pathogenic avian influenza (HPAI) H5N1 and H5N8 have become endemic among domestic poultry in Egypt since 2006 and 2016, respectively. In parallel, the low pathogenic avian influenza H9N2 virus has been endemic since 2010. Despite the continuous circulation of these subtypes for several years, no natural reassortant has been detected so far among the domestic poultry population in Egypt. In this study, the HPAI (H5N2) virus was isolated from a commercial duck farm, giving evidence of the emergence of the first natural reassortment event in domestic poultry in Egypt. The virus was derived as a result of genetic reassortment between avian influenza viruses of H5N8 and H9N2 subtypes circulating in Egypt. The exchange of the neuraminidase segment and high number of acquired mutations might be associated with an alteration in the biological propensities of this virus.

Opposite outcomes of the within-host competition between highly and low pathogenic H5N8 avian influenza viruses in chickens compared to ducks

2021 ◽  
Author(s):  
Pierre Bessière ◽  
Thomas Figueroa ◽  
Amelia Coggon ◽  
Charlotte Foret-Lucas ◽  
Alexandre Houffschmitt ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Reverse Genetics ◽  
Highly Pathogenic Avian Influenza ◽  
Viral Evolution ◽  
Influenza Viruses ◽  
Poultry Production ◽  
Avian Influenza Viruses ◽  
Highly Pathogenic ◽  
Pathogenic Avian Influenza ◽  
Low Pathogenic Avian Influenza

Highly pathogenic avian influenza viruses (HPAIV) emerge from low pathogenic avian influenza viruses (LPAIV) through the introduction of basic amino acids at the hemagglutinin (HA) cleavage site. Following viral evolution, the newly formed HPAIV likely represents a minority variant within the index host, predominantly infected with the LPAIV precursor. Using reverse-genetics engineered H5N8 viruses differing solely at the HA cleavage, we tested the hypothesis that the interaction between the minority HPAIV and the majority LPAIV could modulate the risk of HPAIV emergence and that the nature of the interaction could depend on the host species. In chickens, we observed that the H5N8 LP increased H5N8 HP replication and pathogenesis. By contrast, the H5N8 LP antagonized H5N8 HP replication and pathogenesis in ducks. Ducks mounted a more potent antiviral innate immune response than chickens against the H5N8 LP , which correlated with H5N8 HP inhibition. These data provide experimental evidence that HPAIV may be more likely to emerge in chickens than in ducks and underscore the importance of within-host viral variants interactions in viral evolution. IMPORTANCE Highly pathogenic avian influenza viruses represent a threat to poultry production systems and to human health because of their impact on food security and because of their zoonotic potential. It is therefore crucial to better understand how these viruses emerge. Using a within-host competition model between highly and low pathogenic avian influenza viruses, we provide evidence that highly pathogenic avian influenza viruses could be more likely to emerge in chickens than in ducks. These results have important implications for highly pathogenic avian influenza virus emergence prevention and they underscore the importance of within-host viral variants interactions in virus evolution.

scholarly journals Novel Highly Pathogenic Avian A(H5N2) and A(H5N8) Influenza Viruses of Clade 2.3.4.4 from North America Have Limited Capacity for Replication and Transmission in Mammals

mSphere ◽  
2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Bryan S. Kaplan ◽  
Marion Russier ◽  
Trushar Jeevan ◽  
Bindumadhav Marathe ◽  
Elena A. Govorkova ◽  
...  
Keyword(s):  
North America ◽  
Avian Influenza ◽  
North American ◽  
Influenza Viruses ◽  
Morbidity And Mortality ◽  
Avian Influenza Viruses ◽  
Highly Pathogenic ◽  
The North ◽  
Domestic Poultry ◽  
The Impact

ABSTRACT Highly pathogenic H5 influenza viruses have been introduced into North America from Asia, causing extensive morbidity and mortality in domestic poultry. The introduced viruses have reassorted with North American avian influenza viruses, generating viral genotypes not seen on other continents. The experiments and analyses presented here were designed to assess the impact of this genetic diversification on viral phenotypes, particularly as regards mammalian hosts, by comparing the North American viruses with their Eurasian precursor viruses. Highly pathogenic influenza A(H5N8) viruses from clade 2.3.4.4 were introduced to North America by migratory birds in the fall of 2014. Reassortment of A(H5N8) viruses with avian viruses of North American lineage resulted in the generation of novel A(H5N2) viruses with novel genotypes. Through sequencing of recent avian influenza viruses, we identified PB1 and NP gene segments very similar to those in the viruses isolated from North American waterfowl prior to the introduction of A(H5N8) to North America, highlighting these bird species in the origin of reassortant A(H5N2) viruses. While they were highly virulent and transmissible in poultry, we found A(H5N2) viruses to be low pathogenic in mice and ferrets, and replication was limited in both hosts compared with those of recent highly pathogenic avian influenza (HPAI) H5N1 viruses. Molecular characterization of the hemagglutinin protein from A(H5N2) viruses showed that the receptor binding preference, cleavage, and pH of activation were highly adapted for replication in avian species and similar to those of other 2.3.4.4 viruses. In addition, North American and Eurasian clade 2.3.4.4 H5NX viruses replicated to significantly lower titers in differentiated normal human bronchial epithelial cells than did seasonal human A(H1N1) and highly pathogenic A(H5N1) viruses isolated from a human case. Thus, despite their having a high impact on poultry, our findings suggest that the recently emerging North American A(H5N2) viruses are not expected to pose a substantial threat to humans and other mammals without further reassortment and/or adaptation and that reassortment with North American viruses has not had a major impact on viral phenotype. IMPORTANCE Highly pathogenic H5 influenza viruses have been introduced into North America from Asia, causing extensive morbidity and mortality in domestic poultry. The introduced viruses have reassorted with North American avian influenza viruses, generating viral genotypes not seen on other continents. The experiments and analyses presented here were designed to assess the impact of this genetic diversification on viral phenotypes, particularly as regards mammalian hosts, by comparing the North American viruses with their Eurasian precursor viruses.

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