Table 1.

The recombinant viruses used in this study and the related mutant amino acid sites

Name	aa mutant sites	Name	aa mutant sites
rBB	No	rBB20s	No
rBB/GP2s	GP2(198G/V)	rBB20s/GP2	GP2(198 V/G)
rBB/GP3s	GP3(69P/S,71 K/R,226S/P)	rBB20s/GP3	GP3(69S/P,71R/K,226P/S)
rBB/GP4s	GP4(43D/N;44 F/S)	rBB20s/GP4	GP4(43 N/D;44S/F)
rBB/Ms	M(70R/K)	rBB20s/M	M(70 K/R)
rBB/Ms-R a	No	rBB20s/M-R b	No

^a The recombinant virus rBB/Ms-R was a revertant virus from rBB/Ms and contained 70R in M. The plasmid was constructed from the full-length infectious cDNA clone pCMV-BB/Ms by using the site-directed mutagenesis described

^b The recombinant virus rBB20s/M-R was a revertant virus from rBB20s/M and contained 70 K in M. The plasmid was constructed from the full-length infectious cDNA clone pCMV-BB20s/M by using the site-directed mutagenesis described