[Genetic changes in strains of poliovirus type 2 isolated from patients with vaccine-associated paralytic poliomyelitis].

INTRODUCTION

Poliomyelitis is currently a rare disease in developed countries, where only vaccinal strains seem to be in circulation, which replace wild poliovirus. Nevertheless, it is still a serious disease for children in underdeveloped countries of Asia and Africa.

PATIENTS AND

METHODS

We analysed nine strains of poliovirus type 2 isolated from the faecal matter of patients with vaccine associated paralytic poliomyelitis (VAPP), from the beginning of anti polio vaccination campaigns in our country. These strains were submitted to sequencing of a fragment of 114 base pairs from the 5 NTR (non traductional region), where one of the main determinants of attenuation/reversion to the neurovirulence of poliovirus lies in the position of nucleotide 481.

RESULTS

In this position it was observed how guanine had been replaced by adenine in all the strains that were sequenced, so that it coincided with the homologous sequence of the wild strain, as well as with that of strains obtained from healthy children immunised with the live vaccine. This presupposes that other changes must occur or that other factors must be involved for VAPP to occur or not, and we therefore suggest the sequencing of other regions of the genome in search of other possible differential changes in nucleotides.