| 摘要 |
<p>An attenuated poliovirus, suitable for vaccination against poliomyelitis, does not have a base pair mismatch, such as a U-G mismatch, in stem (a) or (b) of domain V of the 5' non-coding region of the poliovirus genome. The corrected base pairing applies at least to mismatches which presently occur in type 3 virus at positions 472/537 and 480/531, in type 2 virus at position 478/527 and in type 1 virus at positions 476/529 and 480/525. Preferably, the virus is a type 3 poliovirus whose 5' non-coding region contains the following U-A base pairs: (a) U-A at positions 472-537, U-A at positions 478-533 and U-A at positions 480-531; (b) U-A at positions 472-537, U-A at positions 480-531 and U-A at positions 481-530; or (c) U-A at positions 472-537, U-A at positions 480-531 and A-U at positions 482-529. The substitution of a U-A pair in place of a C-G pair in each of the viral strains is also proposed, for example at positions 469/534 in type 1 and 2 viruses. Substitutions are achieved by site-directed mutagenesis.</p> |
