Infectivity and transmissibility of H9N2 avian influenza virus in chickens and wild terrestrial birds

Iqbal, Munir; Yaqub, Tahir; Mukhtar, Nadia; Shabbir, Muhammad Zubair; McCauley, John W.

doi:10.1186/1297-9716-44-100

Cited by 75 publications

(47 citation statements)

References 46 publications

(47 reference statements)

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“…[34] and experimentally with Iqbal et al . [35]. This strongly supports the role of a terrestrial wild bird such as crows in transmission of the infection.…”

Section: Discussionsupporting

confidence: 65%

Investigation of avian influenza infection in wild birds in Ismailia and Damietta cities, Egypt

Fadel

Afifi

2017

Vet World

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Aim:This study was carried out to monitor avian influenza (AI) infection in wild birds in Egypt.Materials and Methods:A total of 135 wild birds were examined for the presence of H5, H7, and H9 hemagglutination inhibition antibodies. Organs and swab samples of 75 birds were screened by multiplex real-time reverse transcriptase-polymerase chain reaction (RRT-PCR) to detect AI subtypes H5, H7, and H9 matrix genes.Results:The highest seropositive result was recorded in cattle egrets (90.9%) followed by crows (88.6%), semi-captive pigeons (44.8%), and moorhens (39.1%). In cattle egrets, semi-captive pigeons and moorhens, H5 antibodies predominated. In crows, H9 antibodies predominated. Multiple infections with two or three virus subtypes were highest in crows (6/39, 15.4%) followed by cattle egrets (3/30, 10%) and moorhens’ (1/9, 11.1%) positive samples. Multiplex RRT-PCR results revealed two positive samples in cattle egrets and moorhens.Conclusion:The results indicated high seropositive rates against AI virus subtypes H5 and H9 in the examined wild birds. Multiple infections with more than one AI virus (AIV) subtypes were detected in some birds. This requires a collaboration of efforts to monitor AIV infection in wild birds and implement suitable early intervention measures.

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“…[34] and experimentally with Iqbal et al . [35]. This strongly supports the role of a terrestrial wild bird such as crows in transmission of the infection.…”

Section: Discussionsupporting

confidence: 65%

Investigation of avian influenza infection in wild birds in Ismailia and Damietta cities, Egypt

Fadel

Afifi

2017

Vet World

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“…To understand the role of the PB1-F2 protein in the poultry host, we used a LPAI virus strain that is representative of a H9N2 major lineage (G1-like) that circulates in the enzootic Pakistan region of the Middle East (Iqbal et al , 2013). A reverse genetics system for the A/chicken/Pakistan/UDL01/08 (UDL01) H9N2 strain used previously (Long et al , 2016) was rescued as infectious virus using standard techniques (Hoffmann et al , 2000).…”

Section: Resultsmentioning

confidence: 99%

Influenza A virus PB1-F2 protein prolongs viral shedding in chickens lengthening the transmission window

James

Howard

Iqbal

et al. 2016

Journal of General Virology

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Avian influenza is a significant economic burden on the poultry industry in geographical regions where it is enzootic. It also poses a public health concern when avian influenza subtypes infect humans, often with high mortality. Understanding viral genetic factors which positively contribute to influenza A virus (IAV) fitness – infectivity, spread and pathogenesis – is of great importance both for human and livestock health. PB1-F2 is a small accessory protein encoded by IAV and in mammalian hosts has been implicated in a wide range of functions that contribute to increased pathogenesis. In the avian host, the protein has been understudied despite high-level full-length conservation in avian IAV isolates, which is in contrast to the truncations of the PB1-F2 length frequently found in mammalian host isolates. Here we report that the presence of a full-length PB1-F2 protein, from a low pathogenicity H9N2 avian influenza virus, prolongs infectious virus shedding from directly inoculated chickens, thereby enhancing transmission of the virus by lengthening the transmission window to contact birds. As well as extending transmission, the presence of a full-length PB1-F2 suppresses pathogenicity evidenced by an increased minimum lethal dose in embryonated chicken eggs and increasing survival in directly infected birds when compared to a virus lacking an ORF for PB1-F2. We propose that there is a positive pressure to maintain a full-length functional PB1-F2 protein upon infection of avian hosts as it contributes to the effective transmission of IAV in the field.

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“…H9N2 influenza viruses circulate in poultry populations worldwide (37)(38)(39)(40), and isolation from pigs has been reported (41,42). Human infections by H9N2 strains have been observed occasionally (8,43,44).…”

Section: Discussionmentioning

confidence: 99%

Mutations during the Adaptation of H9N2 Avian Influenza Virus to the Respiratory Epithelium of Pigs Enhance Sialic Acid Binding Activity and Virulence in Mice

Yang

Punyadarsaniya

Lambertz

et al. 2017

J Virol

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The natural reservoir for influenza viruses is waterfowl, and from there they succeeded in crossing the barrier to different mammalian species. We analyzed the adaptation of avian influenza viruses to a mammalian host by passaging an H9N2 strain three times in differentiated swine airway epithelial cells. Using precisioncut slices from the porcine lung to passage the parental virus, isolates from each of the three passages (P1 to P3) were characterized by assessing growth curves and ciliostatic effects. The only difference noted was an increased growth kinetics of the P3 virus. Sequence analysis revealed four mutations: one each in the PB2 and NS1 proteins and two in the HA protein. The HA mutations, A190V and T212I, were characterized by generating recombinant viruses containing either one or both amino acid exchanges. Whereas the parental virus recognized ␣2,3-linked sialic acids preferentially, the HA190 mutant bound to a broad spectrum of glycans with ␣2,6/8/9-linked sialic acids. The HA212 mutant alone differed only slightly from the parental virus; however, the combination of both mutations (HA190ϩHA212) increased the binding affinity to those glycans recognized by the HA190 mutant. Remarkably, only the HA double mutant showed a significantly increased pathogenicity in mice. In contrast, none of those mutations affected the ciliary activity of the epithelial cells which is characteristic for virulent swine influenza viruses. Taken together, our results indicate that shifts in the HA receptor affinity are just an early adaptation step of avian H9N2 strains; further mutational changes may be required to become virulent for pigs.IMPORTANCE Swine play an important role in the interspecies transmission of influenza viruses. Avian influenza A viruses (IAV) of the H9N2 subtype have successfully infected hosts from different species but have not established a stable lineage. We have analyzed the adaptation of IAV-H9N2 virus to target cells of a new host by passaging the virus three times in differentiated porcine respiratory epithelial cells. Among the four mutations detected, the two HA mutations were analyzed by generating recombinant viruses. Depending on the infection system used, the mutations differed in their phenotypic expression, e.g., sialic acid binding activity, replication kinetics, plaque size, and pathogenicity in inbred mice. However, none of the mutations affected the ciliary activity which serves as a virulence marker. Thus, early

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Infectivity and transmissibility of H9N2 avian influenza virus in chickens and wild terrestrial birds

Cited by 75 publications

References 46 publications

Investigation of avian influenza infection in wild birds in Ismailia and Damietta cities, Egypt

Investigation of avian influenza infection in wild birds in Ismailia and Damietta cities, Egypt

Influenza A virus PB1-F2 protein prolongs viral shedding in chickens lengthening the transmission window

Mutations during the Adaptation of H9N2 Avian Influenza Virus to the Respiratory Epithelium of Pigs Enhance Sialic Acid Binding Activity and Virulence in Mice

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