GEOGRAPHICAL GENOTYPES (GEOTYPES) OF POLIOVIRUS CASE ISOLATES FROM THE FORMER SOVIET-UNION - RELATEDNESS TO OTHER KNOWN POLIOVIRUS GENOTYPES

A 150 nucleotide long region corresponding to adjoining segments of th e genes encoding polypeptides VP1 and 2A of 84 poliovirus strains rece ntly isolated from patients with paralytic poliomyelitis over the terr itory of the former Soviet Union (FSU) were characterized by sequencin g and/or PCR amplification using specially designed primers. Eighteen isolates were found to be very closely related to one or another of th e three Sabin vaccine strains. Three distinct classes of geographical genotypes (geotypes) were discerned among 42 wildtype (non-Sabin) stra ins of serotype 1. One such geotype (called A) was widely circulating in 1990-91 in the Caucasian (Azerbaijan and Georgia) as well as Asian (Kyrgyzstan and Turkmenistan) Republics; this geotype exhibited only w eak relatedness to known strains isolated outside the FSU. On the othe r hand, a subset of strains belonging to another geotype (T) of seroty pe 1, which circulated in 1991 in Tajikistan, demonstrated very close relatedness to contemporaneous strains isolated in Pakistan, India and Jordan. Strains that were somewhat different, but belonging to the sa me T-geotype, were found also in Moldova and Georgia. Strikingly, the primary structure of the VP1/2A junction of certain T-geotype isolates differed from the corresponding region of Sabin 1 only in 13-15% of p ositions, thereby not reaching the upper limit accepted for a geotype. This observation raises, though does not prove, the possibility that at least the relevant segment of the T-geotype RNA originated from the vaccine strain. The third geotype of serotype 1 was represented by a single, perhaps imported, isolate. Four distinct subsets of a common g eotype (C) were discerned among 24 wildtype isolates belonging to sero type 3. These strains exhibited a broad geographical distribution bein g found, in particular, in Armenia, Azerbaijan, Georgia, Turkmenistan and Tajikistan; on the other hand, the C-geotype strains exhibited onl y a relatively distant relatedness to a strain isolated outside of the FSU (in Oman).