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Table 5 Dynamics of HA and NA glycosylation for pH1N1 viruses isolated from MENA region during 2009–2017. In total, glycosylation patterns of 512 HA and 343 NA sequences of pH1N1 virus were analyzed. Numbers between brackets represent the percentage of sequences expressing glycosylation sequon in corresponding year while conserved glycosylation sites are indicated in bold

From: Epidemiological and genetic characterization of pH1N1 and H3N2 influenza viruses circulated in MENA region during 2009–2017

Localization of potential glycosylation sequons in HA and NA of pH1N1 viruses
HA
   Amino acid position
Year Number of sequences analyzed Stem Head Stem
2009 132 28 40 104   304   498 557
2010 68 28 40 104   304   498 557
2011 36 28 40 104 179 (2%) 304   498 557
2012 27 28 40 104   304   498 557
2013 33 28 40 104   304 489* (18%) 498 557
2014 25 28 40 104   304   498 557
2015 157 28 40 104 179 (85%) 304   498 557
2016 60 28 40 104 179 (99%) 304 489* (2%) 498 557
NA
Year Number of sequences analyzed Amino acid position
2009 97    44 (11%) 50 58 63 68 88 146 235 386
2010 42   42 (36%)   50 58 63 68 88 146 235 386
2011 36   42 (100%)   50 58 63 68 88 146 235 386*
2012 29 28 (7%) 42 (100%)   50 58 63 68 88 146 235 386
2013 32   42 (100%)   50 58 63 68 88 146 235 386
2014 25   42 (100%)   50 58 63 68 88 146 235 386
2015 79   42 (100%)   50 58 63 68 88 146 235 386
2016 3   42 (100%)   50 58 63 68 88 146 235  
  1. HA Glycosylation: glycosylation site, N489, was detected in sequences isolated from Iran. Glycosylation sequons at N28, N104, N498 and N557 were lost from viruses isolate from Iran at different time periods. In 2015, for example, N28 and N557 sequons were missing from 1.5 and 5% of HA sequences, respectively. NA Glycosylation: N386 glycosylation sequon was missing from one sequence in 2011, however, during following years more NA sequences were found to lack 386 glycosylation (31% of sequences in 2012; 80% in 2014; 77% in 2015) before disappearing completely from NA sequences in 2016