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- Naguib, Mahmoud, et al.
(författare)
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Comparison of genomic and antigenic properties of Newcastle Disease virus genotypes II, XXI and VII from Egypt do not point to antigenic drift as selection marker
- 2022
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Ingår i: Transboundary and Emerging Diseases. - : John Wiley & Sons. - 1865-1674 .- 1865-1682. ; 69:2, s. 849-863
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Tidskriftsartikel (refereegranskat)abstract
- Newcastle disease (ND), caused by avian orthoavulavirus type-1 (NDV), is endemic in poultry in many regions of the world and causes continuing outbreaks in poultry populations. In the Middle East, genotype XXI, used to be present in poultry in Egypt but has been replaced by genotype VII. We investigated whether virus evolution contributed to superseding and focussed on the antigenic sites within the hemagglutinin-neuraminidase (HN) spike protein. Full-length sequences of an NDV genotype VII isolate currently circulating in Egypt was compared to a genotype XXI isolate that was present as co-infection with vaccine-type viruses (II) in a historical virus isolated in 2011. Amino acid differences in the HN glycoprotein for both XXI and VII viruses amounted to 11.7% and 11.9%, respectively, compared to the La Sota vaccine type. However, mutations within the globular head (aa 126-570), bearing relevant antigenic sites, were underrepresented (a divergence of 8.8% and 8.1% compared to 22.4% and 25.6% within the protein domains encompassing cytoplasmic tail, transmembrane part and stalk regions (aa 1-125) for genotypes XXI and VII, respectively). Nevertheless, reaction patterns of HN-specific monoclonal antibodies inhibiting receptor binding revealed differences between vaccine-type viruses and genotype XXI and VII viruses for epitopes located in the head domain. Accordingly, compared to Egyptian vaccine-type isolates and the La Sota vaccine reference strain, single aa substitutions in 6 of 10 described neutralizing epitopes of HN were found. However, the same alterations in neutralization sensitive epitopes were present in old genotype XXI as well as in newly emerged genotype VII isolates. In addition, isolates were indistinguishable by polyclonal chicken sera raised against different genotypes including vaccine viruses. These findings suggest that factors other than antigenic differences within the HN protein account for facilitating the spread of genotype VII versus genotype XXI viruses in Egypt.
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| 3. |
- Wille, Michelle
(författare)
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Viruses on the wing : evolution and dynamics of influenza A virus in the Mallard reservoir
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores the evolution of avian influenza A viruses (IAV), as well as host-pathogen interactions between these viruses and their main reservoir host, the Mallard (Anas platyrhynchos). IAV is a genetically diverse, multi-host virus and wild birds, particularly dabbling ducks, are the natural reservoir. At our study site, up to 30% of migratory Mallards are infected with IAV during an autumn season, and host a large number of virus subtypes. IAV diversity is driven by two main mechanisms: mutation, driving genetic drift; and reassortment following co-infection, resulting in genetic shift. Reassortment is pervasive within an autumn season, both across multiple subtypes and within a single subtype. It is a key genetic feature in long-term maintenance of common subtypes, as it allows for independent lineage turn-over, generating novel genetic constellations. I hypothesize that the decoupling of successful constellations and generation of novel annual constellations enables viruses to escape herd immunity; these genetic changes must confer antigenic change for the process to be favourable. Indeed, in an experiment utilizing vaccines, circulating viruses escaped homosubtypic immunity, resulting in the proliferation of infections with the same subtype as the vaccine. While the host plays an important role in shaping IAV evolutionary genetics, one must consider that Mallards are infected with a multitude of other microorganisms. Here, Mallards were infected with IAV, gamma coronaviruses, and avian paramyxovirus type 1 simultaneously, and we found a putative synergistic interaction between IAV and gamma coronaviruses. Mallards occupy the interface between humans, poultry, and wild birds, and are the reservoir of IAV diversity. New incursions of highly pathogenic H5 viruses to both Europe and North America reaffirms the role of wild birds, particularly waterfowl, in diffusion of viruses spatially. Using European low pathogenic viruses and Mallard model, this thesis contributes to aspects of epidemiology, ecology, and evolutionary dynamics of waterfowl viruses, particularly IAV
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