A replication-defective variant of Sabin 3 poliovirus.

A variant of Sabin type 3 poliovirus, 265B, only produces 2-3% of the yields of control virus and has a protracted growth cycle in HeLa cells. Attachment and penetration do not appear to account for defective growth of 265B. Viral protein and RNA syntheses are reduced, and blockage of cell protein synthesis is delayed considerably as compared with the parent virus. Nucleotide sequence analysis failed to detect mutations in protein 2AProt or changes in the 5'-noncoding region that could account for growth properties of the virus. However, a Thr-to-Ala substitution was found in viral peptide 2B of 265B, and this alteration is probably responsible for the replication defect.