Sequence variation within an outbreak of measles virus in the Coventry area during spring/summer 1993

Measles virus (MV) was isolated from throat swab samples collected during the spring/summer 1993 in the Coventry area. Viral RNA was reverse transcribed and cDNA prepared using oligo-T primer. Using MV-specific primers the area encoding the external region of the haemagglutinin glycoprotein was amplified using nested PCR and cycle sequenced. Comparisons were made with the Edmonston strain and current MMR vaccine strain. It was found that a high degree of homology existed between all strains examined, but that a majority of clinical samples shared a premature termination signal that potentially shortened the haemagglutinin protein by 35 amino acids. The single clinical sample that lacked this early termination signal appeared to be closely related to the MMR strain and may result from a vaccine-related illness. Truncation of the haemagglutinin protein may have allowed MV to escape the immune response induced by vaccination with the current MMR vaccine.