Intratypic differentiation & partial nucleotide sequencing of poliovirus isolates of northern India

The potential resolving power of molecular epidemiological studies has enha nced the precision and reliability of poliovirus (PV) surveillance. PV has an error prone RNA polymerase responsible for rapid evolution of genome (si milar to 10(-2)nt substitution/site/year), during inter and intra-human pas sages. The present study included a serotyped panel of 60 PV (42 PV type-1, 13 PV type-2 and 5 PV type-3) isolated during 1997. They were differentiat ed into vaccine (Sabin) and wild strains by two methods viz., genotype spec ific RNA probe hybridization (Rpro-Hy) based on genotypic variability; and EI,ISA that uses cross-absorbed antiserum (Pab-E) based on phenotypic varia bility. For obtaining information on molecular epidemiology, partial nucleo tide sequencing (VP1/2A region) of five clinical PV isolates was also done. Three of the 60 isolates (two PV type-1 and one PV type-3) intratyped, cou ld not be differentiated correctly by either method. Genotypic characteriza tion of PV isolates was done for confirmation of intratyping results. All f ive wild PV1 sequenced belonged to the same genotype (>85% homology) and se quence divergence among the strains was less than or equal to 4.5 per cent. This indicated circulation of a single genetic lineage in the area.