0 avis
The risk of evolution to high pathogenicity avian influenza is determined by the thermodynamic stability of the HA cleavage site product-template primary sequences within the polymerase catalytic site
Archive ouverte
Edité par CCSD -
International audience. Influenza viruses pose a threat to animal and human health due to their high genetic variability and zoonotic nature.In birds, H5 and H7 subtypes can evolve into highly pathogenic forms, capable of systemic replication. This evolution is characterized by the acquisition of a multi-basic cleavage site (MBCS) in hemagglutinin (HA). The genetic mechanism leading to the appearance of this MBCS is still poorly characterized. We wondered whether all low pathogenic H5Nx viruses have the same evolutionary potential, and whether there are specific features of the HA segment that could influence evolution towards the highly pathogenic form.We have developed a reverse genetics system that generates influenza viruses containing whole HA sequences as a transgene at the end of the PA protein coding segment. In this model, the virus thus has two HA-coding genes: one in transgene form, which will never be expressed, so that no selection pressure is exerted on its protein function, and another, corresponding to the wild-type HA segment, which will be classically expressed. The accumulation of mutations in the HA transgene is therefore studied, based on nucleotide sequence only. We have successfully produced and characterized infectious viruses containing the HA transgene.We tested how different nucleotide environments and different predicted or transient secondary structures could influence viral polymerase errors using this system and high fidelity deep sequencing.We have shown the influence of nucleotide sequence on insertion frequencies. We believe that the mechanism at the origin of insertions and therefore of the emergence of highly pathogenic viruses by insertions is backtracking, mediated by the interaction between the template and the product RNA produced in the catalytic site of the viral polymerase. We believe that this mechanism is dependent on an adenine stretch and the environment of this stretch.
Consulter en ligne
Suggestions
Du même auteur
