POLIOVIRUS TYPE-1 ISOLATED FROM A VACCINE-ASSOCIATED CASE OF PARALYTIC POLIOMYELITIS IN BRAZIL

This study reports a type 1 poliovirus strain isolated in Brazil from a case classified as vaccine-associated paralytic poliomyelitis (VAPP) . After serotyping of the viral isolate with hyperimmune equine sera, PCR and molecular hybridization techniques characterized the strain as P1/Sabin-derived. The isolate was partially sequenced to identify mut ations at nucleotides 480, 525 and 6203, which are important for rever sion of the P1/Sabin strain to neurovirulence. In a recent study, a P1 /Sabin-derived strain isolated from the central nervous system of a VA PP case did not mutate at these positions, but maintained 480-G and 52 5-U (and 6203-C), suggesting that these mutations are not essential fo r the occurrence of disease (Georgescu et al., (1994), Journal of Viro logy, 68:8089-8101). Although the Brazilian strain also maintained 480 -G and 525-U (and 6203-C) and was isolated from the stool, the possibi lity that this isolate invaded the central nervous system after replic ating in the gut, causing the paralysis, cannot be ruled out. This is the first report of a type 1 VAPP case in Brazil, although some cases caused by type 2 and type 3 strains have been described.