Astragalus polysaccharide enhances immunity and inhibits H9N2 avian influenza virus in vitro and in vivo

Abstract Background Diallyl trisulfide (DATS) is a garlic-derived organosulfur compound. As it has been shown to have anti-viral activity, we hypothesized that it may alleviate infections caused by H9N2 avian influenza virus (AIV), which is prevalent in poultry with pandemic potential. Methods Human lung A549 epithelial cells were treated with three different concentrations of DATS 24 h before (pre-treatment) or one hour after (post-treatment) H9N2 AIV infection. Culture supernatants were collected 24 h and 48 h post-infection and analyzed for viral titers and levels of inflammatory and anti-viral immune responses. For in vivo experiments, BABL/c mice were administered daily by intraperitoneal injection with DATS (30 mg/kg) for 2 weeks starting 1 day after H9N2 AIV infection. Clinical signs, lung pathology, and inflammatory and anti-viral immune responses were assessed 2, 4, and 6 days after infection. Results Both pre-treatment and post-treatment of A549 cells with DATS resulted in reduced viral loads, increased expression of anti-viral genes (RIG-I, IRF-3, and interferon-β), and decreased expression of inflammatory cytokines (TNF-α and IL-6). These effects were also observed in H9N2 AIV-infected mice treated with DATS. Such treatment also reduced lung edema and inflammation in mice. Conclusions Results suggest that DATS has anti-viral activity against H9N2 AIV and may be used as an alternative treatment for influenza virus infection.

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A Unique Multibasic Proteolytic Cleavage Site and Three Mutations in the HA2 Domain Confer High Virulence of H7N1 Avian Influenza Virus in Chickens

Journal of Virology ◽

10.1128/jvi.02082-15 ◽

2015 ◽

Vol 90 (1) ◽

pp. 400-411 ◽

Cited By ~ 10

Author(s):

El-Sayed M. Abdelwhab ◽

Jutta Veits ◽

Kerstin Tauscher ◽

Mario Ziller ◽

Jens P. Teifke ◽

...

Keyword(s):

Influenza Virus ◽

Avian Influenza ◽

Avian Influenza Virus ◽

Cleavage Site ◽

Influenza Viruses ◽

Highly Pathogenic ◽

Systemic Spread ◽

H7n1 Virus

ABSTRACT In 1999, after circulation for a few months in poultry in Italy, low-pathogenic (LP) avian influenza (AI) H7N1 virus mutated into a highly pathogenic (HP) form by acquisition of a unique multibasic cleavage site (mCS), PEIPKGSRVRR*GLF (asterisk indicates the cleavage site), in the hemagglutinin (HA) and additional alterations with hitherto unknown biological function. To elucidate these virulence-determining alterations, recombinant H7N1 viruses carrying specific mutations in the HA of LPAI A/chicken/Italy/473/1999 virus (Lp) and HPAI A/chicken/Italy/445/1999 virus (Hp) were generated. Hp with a monobasic CS or carrying the HA of Lp induced only mild or no disease in chickens, thus resembling Lp. Conversely, Lp with the HA of Hp was as virulent and transmissible as Hp. While Lp with a multibasic cleavage site (Lp_CS445) was less virulent than Hp, full virulence was exhibited when HA2 was replaced by that of Hp. In HA2, three amino acid differences consistently detected between LP and HP H7N1 viruses were successively introduced into Lp_CS445. Q450L in the HA2 stem domain increased virulence and transmission but was detrimental to replication in cell culture, probably due to low-pH activation of HA. A436T and/or K536R restored viral replication in vitro and in vivo . Viruses possessing A436T and K536R were observed early in the HPAI outbreak but were later superseded by viruses carrying all three mutations. Together, besides the mCS, stepwise mutations in HA2 increased the fitness of the Italian H7N1 virus in vivo . The shift toward higher virulence in the field was most likely gradual with rapid optimization. IMPORTANCE In 1999, after 9 months of circulation of low-pathogenic (LP) avian influenza virus (AIV), a devastating highly pathogenic (HP) H7N1 AIV emerged in poultry, marking the largest epidemic of AIV reported in a Western country. The HPAIV possessed a unique multibasic cleavage site (mCS) complying with the minimum motif for HPAIV. The main finding in this report is the identification of three mutations in the HA2 domain that are required for replication and stability, as well as for virulence, transmission, and tropism of H7N1 in chickens. In addition to the mCS, Q450L was required for full virulence and transmissibility of the virus. Nonetheless, it was detrimental to virus replication and required A436T and/or K536R to restore replication, systemic spread, and stability. These results are important for better understanding of the evolution of highly pathogenic avian influenza viruses from low-pathogenic precursors.

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Correction for Jeong et al., “In Vitro Profiling of Laninamivir-Resistant Substitutions in N3 to N9 Avian Influenza Virus Neuraminidase Subtypes and Their Association with In Vivo Susceptibility”

Journal of Virology ◽

10.1128/jvi.02275-20 ◽

2021 ◽

Vol 95 (6) ◽

Author(s):

Ju Hwan Jeong ◽

Won-Suk Choi ◽

Khristine Joy C. Antigua ◽

Young Ki Choi ◽

Elena A. Govorkova ◽

...

Keyword(s):

Influenza Virus ◽

Avian Influenza ◽

Avian Influenza Virus ◽

Influenza Virus Neuraminidase

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A Well-Defined H9N2 Avian Influenza Virus Genotype with High Adaption in Mammals was Prevalent in Chinese Poultry Between 2016 to 2019

Viruses ◽

10.3390/v12040432 ◽

2020 ◽

Vol 12 (4) ◽

pp. 432 ◽

Cited By ~ 2

Author(s):

Zhaokun Chen ◽

Qinghua Huang ◽

Shaohua Yang ◽

Shuai Su ◽

Baoquan Li ◽

...

Keyword(s):

Influenza Virus ◽

Avian Influenza ◽

Avian Influenza Virus ◽

Mdck Cells ◽

Replication Capacity ◽

Virus Genotype ◽

Influenza Pandemics ◽

Mouse Lungs

H9N2 subtype avian influenza virus (AIV) is widely prevalent in poultry, and the virus is becoming adaptive to mammals, which poses pandemic importance. Here, BALB/c mice were employed as a model to evaluate the adaption in mammals of 21 field H9N2 viruses isolated from avian species between 2016 to 2019 in China. The replication capacity of the viruses was evaluated in the lungs of mice. The pathogenicity of the viruses were compared by weight loss and lung lesions from infected mice. The whole genomic sequences of the viruses were further characterized to define the associated phenotypes of the H9N2 viruses in vitro and in vivo. The results showed that most viruses could replicate well and cause lesions in the mouse lungs. The propagation capacity in MDCK cells and damage to respiratory tissues of the infected mice corresponded to relative viral titers in the mouse lungs. Further genome analysis showed that all of the H9N2 viruses belonged to the same genotype, G57, and contained a couple of amino acid substitutions or deletions that have been demonstrated as avian-human markers. Additionally, nine amino acids residues in seven viral proteins were found to be correlated with the replication phenotypes of the H9N2 viruses in mammals. The study demonstrated that a well-defined H9N2 AIV genotype with high adaption in mammals was prevalent in China in recent years. Further investigations on the role of the identified residues and continuous surveillance of newly identified mutations associated with host adaption should be strengthened to prevent any devastating human influenza pandemics.

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Mutations in PB2 and HA enhanced pathogenicity of H4N6 avian influenza virus in mice

Journal of General Virology ◽

10.1099/jgv.0.001192 ◽

2020 ◽

Vol 101 (9) ◽

pp. 910-920 ◽

Cited By ~ 2

Author(s):

Guanlong Xu ◽

Fang Wang ◽

Qiuchen Li ◽

Guoxia Bing ◽

Shijie Xie ◽

...

Keyword(s):

Public Health ◽

Influenza Virus ◽

Avian Influenza ◽

Avian Influenza Virus ◽

Point Mutations ◽

Polymerase Activity ◽

Potential Threat ◽

Gain Adaptation

The H4 subtype avian influenza virus (AIV) continues to circulate in both wild birds and poultry, and occasionally infects mammals (e.g. pigs). H4-specific antibodies have also been detected in poultry farm workers, which suggests that H4 AIV poses a potential threat to public health. However, the molecular mechanism by which H4 AIVs could gain adaptation to mammals and whether this has occurred remain largely unknown. To better understand this mechanism, an avirulent H4N6 strain (A/mallard/Beijing/21/2011, BJ21) was serially passaged in mice and mutations were characterized after passaging. A virulent mouse-adapted strain was generated after 12 passages, which was tentatively designated BJ21-MA. The BJ21-MA strain replicated more efficiently than the parental BJ21, both in vivo and in vitro. Molecular analysis of BJ21-MA identified four mutations, located in proteins PB2 (E158K and E627K) and HA (L331I and G453R, H3 numbering). Further studies showed that the introduction of E158K and/or E627K substitutions into PB2 significantly increased polymerase activity, which led to the enhanced replication and virulence of BJ21-MA. Although individual L331I or G453R substitutions in HA did not change the pathogenicity of BJ21 in mice, both mutations significantly enhanced virulence. In conclusion, our data presented in this study demonstrate that avian H4 virus can adapt to mammals by point mutations in PB2 or HA, which consequently poses a potential threat to public health.

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