Characterization of measles virus strains causing SSPE: A study of 11 cases

Eleven subacute sclerosing panencephalitis (SSPE) cases diagnosed in the UK between 1965 and 2000 were investigated. The entire or partial matrix (M), hemagglutinin (H), and nucleoprotein (N) genes of measles virus (MV) were sequenced following direct RT-PCR amplification from brain tissues. All the M genes showed the characteristic biased hypermutations and a premature termination codon was detected in 5/11 M sequences. Based on the more highly conserved H and N genes observed in persistent MV studies, phylogenetic analysis showed that two of three strains from patients likely to have acquired infection in the 1950s were related to clade C (WHO designation) and one appears to be a novel genotype. Three strains from patients infected in the 1960s and 1970s were clearly related to a MV strain isolated in 1974 belonging to genotype D1. Four strains from patients infected in the 1980s clustered with genotype D7 strains. One sequence from a patient infected in 1990s was identified as genotype D6. No vaccine strains were detected although five of these patients had been previously immunized. The sequence data obtained from these historic strains do not support the view that vaccine strains are associated with SSPE and provide valuable information for further studies of MV epidemiology, evolution, and pathogenesis in SSPE.