Rapid evolution of the PB1-F2 virulence protein expressed by human seasonal H3N2 influenza viruses reduces inflammatory responses to infection

Table 1 Presence of full-length and various truncated forms of PB1-F2 in H3N2 viruses isolated in different years

Year of isolation	Total no. isolates	No. isolates with indicated PB1-F2 amino acid sequence length
Year of isolation	Total no. isolates	10–27	34	57–76	79–81	87	90	95	101
Pre-1999	683	3	12 (1.8%)^a	19	12	10	601 (88.0%)	0	26
2000–2009	2291	4	302 (13.2%)	7	20	40	1916 (83.6%)	1	1
2010	408	1	191 (46.8%)	1	0	0	215 (52.7%)	0	0
2011	330	1	182 (55.2%)	0	3	0	144 (43.6%)	0	0
2012	501	1	63 (12.6%)	1	2	0	434 (86.6%)	0	0
2013	396	0	20 (5%)	0	0	2	374 (94.4%)	0	0
All samples	4609	10	770 (16.7%)	28	37	52	3684 (80%)	1	27

^apercentage of total isolates in that time span is shown for the dominant length PB1-F2 proteins

ISSN: 1743-422X