Genetic heterogeneity of recent isolates of adenovirus types 3, 4, and 7.

Restriction endonuclease analysis was carried out on adenovirus types 3, 4, and 7 (Ad3, Ad4, and Ad7, respectively) isolated during a 16-month epidemic period. Most of the isolates were associated with respiratory or ocular infection or both. Forty-four strains of the subtype Ad7b were identified with SmaI; these strains could be further subdivided into three distinct genome groups, designated Ad7b1, Ad7b2, and Ad7b3, by digestion with PvuII, BglI, and SstII. These Ad7b variants occurred at approximately similar frequencies throughout the epidemic and were associated with similar clinical illnesses. Nine distinct intratypic genome groups were identified among 29 Ad3 strains with HindIII, PstI, and SmaI; adenoviruses similar to subtype Ad3a, formerly reported to be uncommon in Europe, were isolated most frequently (41% of strains), and the previously predominant prototype (Ad3p) was not found. Considerable similarities among the genomes of some strains of Ad3 and Ad7 could be demonstrated, and clinical and epidemiological presentations were very similar. The four strains of Ad4 isolated fell into two distinct patterns, i.e., the previously recognized prototype (Ad4p) and a new subtype designated Ad4b. Both of these subtypes were associated with follicular conjunctivitis. Thus we were unable to produce evidence that particular genome types of Ad3, Ad4, and Ad7 are associated with particular clinical presentations. However, restriction endonuclease analysis should prove useful for epidemiological studies on these viruses.