Strain variation in adenovirus serotypes 4 and 7a causing acute respiratory disease

In order to determine the suitability of vaccine strains established in the 1960s for a new vaccine, a comprehensive study of strain variation of aden ovirus serotype 4 (AV 4) and AV 7 was undertaken. A 1,500-bp region of the hexon gene containing the AV neutralization epitopes from prototype, vaccin e, and community-acquired strains and from wild-type strains from military personnel that cause acute respiratory disease (ARD) was sequenced and anal yzed. The whole hexon gene from prototype strains, vaccine strains, and sel ected isolates was sequenced. AV 7 and AV 7a were found to have distinct ge notypes, and all vaccine and wild-type strains recovered from 1963 to 1997 had the AV 79 genotype, There was no significant strain variation in the ne utralization epitopes of the AV 7a genotype over a 42-year period. The evol ution of AV 4 was more complex, with continuous genetic drift punctuated by replacement with a new strain. The current strain of AV 4, which has been in circulation since 1995, is significantly different from the AV 4 prototy pe and the vaccine strains. Genetic differences were confirmed to be antige nic differences by neutralization tests, which define the new strain as an AV 4 variant. A type-specific PCR for AV 4, AV 7/7a, and AV 21 was develope d, and this PCR facilitated the rapid identification of isolates from outbr eaks of ARD.