GENOMIC CHARACTERIZATION OF TYPE-3 POLIOVIRUSES ISOLATED FROM VACCINE-ASSOCIATED POLIOMYELITIS CASES IN BRAZIL

Eight strains of P3/Sabin-related polioviruses were analyzed; four fro m persistent paralytic poliomyelitis cases classified as vaccine assoc iated, one from a transient paralysis case classified as transverse my elitis, one from a transient paralysis case classified as Guillain-Bar re syndrome, one from a transient facial paralysis case, and one from a healthy vaccinee. The serotypes of the viral isolates were identifie d by the neutralization test with hyperimmune equine sera and the rela tionship of the isolates with the P3/Sabin strain was demonstrated by molecular hybridization of the viral RNA of the isolates with a P3/Sab in-specific probe. The P3/Sabin relationship was confirmed by PCR, usi ng a pair of specific primers for P3/Sabin-related isolates. The avail able data indicate that a U-->C mutation at nucleotide 472 in the 5' n oncoding region of the genome of the type 3 Sabin strain increases the neurovirulence of this strain and this mutation was observed in all t ype 3 isolates from vaccine-associated cases. These eight P3/Sabin-rel ated isolates were partially sequenced in the 5' noncoding region and seven presented a U-->C mutation at nucleotide 472, except the isolate from a transient paralysis case classified as transverse myelitis, th at maintained a U at nucleotide 472. Although this virus maintaining U at nucleotide 472 may not be the etiological agent of the disease, th e possibility that the virus was the causative agent of the disease co uld not be ruled out.