Structural and antigenic variance between novel influenza A/H1N1/2009 and influenza A/H1N1/2008 viruses.
BACKGROUND
The emergence of influenza A/H1N1/2009 is alarming. The severity of previous epidemics suggests that the susceptibility of the human population to H1N1 is directly proportional to the degree of changes in hemagglutinin/HA and neuraminidase/NA; therefore, H1N1/2009 and H1N1/2008 were analyzed for their sequence as well as structural divergence.


METHODS
The structural and sequence divergence of H1N1/2009 and H1N1/2008 strains were analyzed by aligning HA and NA amino acid sequences by using ClustalW and ESyPred3D software. To determine the variations in sites of viral attachment to host cells, a comparison between amino acid sequences of HA and NA glycosylation sites was performed with NetNGlyc software. The antigenic divergence was executed by CTL epitope prediction method.


RESULTS
The amino acid homology levels of H1N1/2009 were 20.32% and 18.73% compared to H1N1/2008 for HA and NA genes, respectively. In spite of the high variation in HA and NA amino acid composition, there was no significant difference in their structures. Antigenic analysis proposes that great antigenic differences exist between both the viral strains, but no addition of a new site of glycosylation was observed.


CONCLUSIONS
To our knowledge, this is the first report suggesting that the circulating novel influenza virus A/H1N1/2009 attaches to the same glycosylation receptor sites as its predecessor influenza A/H1N1/2008 virus, but is antigenically different and may have the potential for initiating a significant pandemic. Our study may facilitate the development of better therapeutics and preventive strategies, as well as impart clues for novel H1N1 diagnostic and vaccine development.
Centre for Cellular and Molecular Biology, Hyderabad 500 007, India. shailen@ccmb.res.in
Shailendra K
SK
Saxena
Niraj
N
Mishra
Rakhi
R
Saxena
M L Arvinda
ML
Swamy
Pranshu
P
Sahgal
Shailja
S
Saxena
Shrish
S
Tiwari
Asha
A
Mathur
Madhavan P
MP
Nair
D000595:Amino Acid Sequence; D000940:Antigenic Variation; D000956:Antigens, Viral / Q000737:chemistry / Q000235:genetics; D006031:Glycosylation; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D007251:Influenza, Human / Q000276:immunology / Q000821:virology*; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D011487:Protein Conformation; D020539:Sequence Analysis, Protein; D017385:Sequence Homology; D013997:Time Factors; D014774:Virulence; D053585:Virus Attachment
D000956:Antigens, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009439:Neuraminidase