Detection of viral sequences in archival spinal cords from fatal cases of poliomyelitis in 1951-1952.

Poliovirus (PV) subjected to genetic characterization is often isolated from faecal carriage. Such virus is not necessarily identical to the virus causing paralytic disease since genetic modifications may occur during replication outside the nervous system. We have searched for poliovirus genomes in the 14 fatal cases occurring during the last epidemics in Norway in 1951-1952. A method was developed for isolation and analysis of poliovirus RNA from formalin-fixed and paraffin-embedded archival tissue. RNA was purified by incubation with Chelex-100 and heating followed by treatment with the proteinase K and chloroform extraction. Viral sequences were amplified by a reverse transcriptase-polymerase chain reaction (RT-PCR), the products subjected to TA cloning and sequenced. RNA from the beta-actin gene, as a control, was identified in 13 cases, while sequences specific for poliovirus were achieved in 11 cases. The sequences from the 2C region of poliovirus were rather conserved while those in the 5'-untranslated region were variable. The developed method should be suitable also for other genetic studies of old archival material.