TABLE 1.

Trunk substitutions for the small subset of NP epitopes where specific escape substitutions have been experimentally validated^a

Position in NP	Experimental evidence (reference)	No. of trunk substitutions for human influenza virus (substitution[s] and yr of isolation)
103	K103R escapes recognition by a HLA-B*1503-restricted T cell (21)	2 (K103R in 1981, R103K in 1997)
259	S259L escapes recognition by a HLA-B*4002-restricted T cell (21)	2 (L259S in 1972, S259L in 1990)
384	R384G abrogates MHC binding in HLA-B*2705 (24)	1 (R384G in 1990)
421	D421E escapes recognition by an HLA-B*3501-restricted T cell (22)	1 (D421E in 1977)
425	I425V escapes recognition by an HLA-B*3501-restricted T cell (22)	2 (I425V in 1975, V425I in 1999)

^aThere were no trunk substitutions for swine influenza virus at any of these five sites.