Underneath the three frequency bars is the corresponding genotype: NHHHHNNNNNNNNNNN, which means that these strains have the human consensus marked ‘H’ at 4 protein positions: 87 NS1, 103 NS1, 207 NS1 and 63 NS2. The remaining 12 4SC-202 positions carry a non-human amino acid variant marked ‘N’. Many of the human markers could be a consequence of persistent founder mutations from the see more ancestral 1918 pandemic strain, which gave rise to current circulating human strains.
It is interesting to observe, however, that avian strains maintain each of the human consensus variants in the NS segment with species specific variation patterns. Twenty-four percent of the avian strains share the human consensus amino acid in position 87 NS1 spanning 35 distinct serotypes. Seventy-seven percent of the avian strains share at least one human consensus at one of the other positions in the NS segment, spanning 65 distinct serotypes. If the two sites evolved independently, 19% of the observed avian genotypes would be expected to share a human consensus at 87 NS1 and at least one of the other NS segment positions, however, only 2% of avian strains show this pattern. Half of these cases involve a collection of H3N2 avian strains that recently acquired the NS segment from a swine virus (Rank 12 in Figure1). For position 70 and 87 in NS1, Lysine and Serine
are the respective consensus amino acids in human. In avian strains, the combinations for the respective positions are Glutamic acid and Serine (58%), Lysine and Proline (26%), Glutamic acid and Proline (9%) and GANT61 molecular weight only rarely Lysine and Serine (2%). Figure 1 Persistent human markers in non-human strains. Each column in the table is a genotype with the bars showing genotype frequency Tacrolimus (FK506) for avian (red), avian to human crossovers (blue) and non-avian non-human strains (orange). A table entry with H (green) means the amino
acid position has the human consensus for the amino acid position, and N means non-human consensus. The last row “”Rank”" labels each genotype and shows its frequency rank among avian strains. Rank is in increasing order with 0 being the most common genotype. Select strain subtypes are shown in the figure, with details given in the text. The columns are grouped so that avian to human crossover genotypes are clustered into three groups labeled at the top of Figure1as: H7 (avian frequency rank 0 and 14), H5N1 beginning in 2003 (rank 2, 8, 3, 16 and 9) [7,16–19] and the H5N1/H9N2 Hong Kong outbreaks from 1997–1999 (rank 13, 15, 6, and 17) [20,21]. Additional similar genotype patterns are placed in adjacent columns. A pattern emerges from the two most common avian genotypes ranked 0 and 1 in Figure1. These two genotypes cover 60% of the sequenced strains and span nearly all of the subtypes including H5N1, H9N2, H7N7 and H7N3.