Evolutionary consequences of a decade of vaccination against subtype H6N2 influenza.
The evolutionary dynamics of chicken-origin H6N2 viruses isolated in South Africa between 2002 and 2013 were investigated. Sub-lineages I and II continued to co-circulate under vaccination pressure, but sub-lineage I, from which the inactivated vaccine was derived, displayed a markedly higher mutation rate and a three-fold increase in the emergence of potential antigenic sites on the globular head of HA compared to sub-lineage II. Immunological pressure culminated in a critical phenotypic change as four of the five isolates from 2012 to 2013 had lost the ability to haemagglutinate chicken erythrocytes, correlating with a pattern of predicted O-glycosylation sites at residues 134, 137 and 141 within the critical 130 loop of the receptor binding domain site. Coassortment of the HA, NA and M genes in the respective sub-lineages contrasted reassortment of the other internal protein genes, and the vaccine seed strain itself was the probable donor of segments to sub-lineage II field strains.
Deltamune (Pty) Ltd, 248 Jean Avenue, Centurion, Pretoria 0140, South Africa; Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110, South Africa.
Dionne
D
Rauff
Deltamune (Pty) Ltd, 248 Jean Avenue, Centurion, Pretoria 0140, South Africa.
Christine
C
Strydom
Poultry Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110, South Africa. Electronic address: celia.abolnik@up.ac.za.
Celia
C
Abolnik
D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002645:Chickens; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D019143:Evolution, Molecular; D016679:Genome, Viral; D023281:Genomics; D006031:Glycosylation; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007114:Immunization; D009980:Influenza A virus / Q000145:classification* / Q000235:genetics / Q000276:immunology*; D007252:Influenza Vaccines / Q000235:genetics / Q000276:immunology*; D005585:Influenza in Birds / Q000276:immunology* / Q000517:prevention & control*; D008958:Models, Molecular; D010641:Phenotype; D010802:Phylogeny; D011487:Protein Conformation; D016865:Reassortant Viruses / Q000235:genetics / Q000276:immunology; D012641:Selection, Genetic
D000914:Antibodies, Viral; D000956:Antigens, Viral; D000939:Epitopes; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines
Avian influenza; Coassortment; Genetic drift; Glycosylation; H6N2; Reassortment; Vaccine