Genome type analysis of adenovirus types 3 and 7 isolated during successive outbreaks of lower respiratory tract infections in children

Abstract

Adenovirus is an important cause of respiratory infections in infants and children. Fifty-one serotypes have been identified, and adenovirus type 3 (Ad3) and Ad7 have often been associated with outbreaks of severe respiratory tract infections. Each serotype can be further divided into genome types based on the patterns of digestion of their DNAs with restriction enzymes. DNA restriction analysis was performed with 56 strains of Ad3 and 98 strains of Ad7 by using 12 restriction enzymes recognizing 6 bp (BamHI, BclI, BglI, BglII, BstEII, EcoRI, HindIII, HpaI, SalI, SmaI, XbaI, and XhoI). The virus strains were isolated during outbreaks of lower respiratory tract infections in children during an 11-year period from 1990 to 2000 in Seoul, Korea. Among the Ad3 strains, seven genome types were identified; Ad3a and six novel types (Ad3a13, Ad3a14, Ad3a15, Ad3a16, Ad3a17, and Ad3a18). Multiple genome types cocirculated during outbreaks, and some of these were isolated during the 11-year observation period, while others were restricted to particular outbreaks. For Ad7, two genome types, Ad7d and Ad7l, the latter of which is a novel genome type, were identified. A shift in genome types occurred from Ad7d to Ad7l during successive outbreaks. Mortality was 3.6% among children with Ad3 infections and 18% among children infected with either of the Ad7 genome types. In conclusion, the data confirm that Ad3 genome types are more diverse than those of Ad7 and suggest that shifts of genome types may occur during successive outbreaks of Ad3 and Ad7.

FIG. 1.

Temporal distributions of genome types of Ad3 isolated at Seoul National University Children's Hospital from November 1990 to July 2000. Note that the time frame for each bar represent a 2-month period. From left to right, months are shown as follows: N, November; J, January; M, March; M, May; J, July; and S, September.

FIG. 2.

Temporal distributions of genome types of Ad7 isolated at Seoul National University Children's Hospital from November 1990 to July 2000. Time frames and months are as described in the legend to Fig. 1. The number of Ad7 isolates during May-June 1996 was 44.

FIG. 3.

Restriction fragment analysis of DNAs of Ad3 (four left panels) and Ad7 (one right panel). Viral DNAs were digested with the indicated enzymes and separated by 0.8% agarose electrophoresis. Lanes M, DNA molecular size markers.

FIG. 4.

Phylogenetic trees of eight genome types of Ad3 and five genome types of Ad7 according to relatedness defined as percent pairwise comigrating restriction fragments.