Circulation of a novel pattern of infections by enteric adenovirus serotype 41 among children below 5 years of age in Kolkata, India

Abstract

Human adenovirus of strains subgenus F (AdV F) are the most common strains detected in acute gastroenteritis cases in developing countries. Subgenus F is represented by AdV serotype 40 (AdV-40) and AdV-41. Most of the reports have described the predominance of AdV-41 in acute gastroenteritis cases. To gain insight into the epidemiology and genetic variation of AdV-41 strains, we analyzed 1,053 stool specimens from children with diarrhea. Among them, 42 (4.0%) and 56 (5.3%) were positive for enteric adenovirus 40/41 by enzyme-linked immunosorbent assay (ELISA) and PCR, respectively. For 1,305 asymptomatic children, 9 (0.7%) and 22 (1.7%) samples were positive for enteric adenovirus 40/40 by ELISA and PCR, respectively. The age distribution revealed a higher frequency (90%) in children <24 months of age. AdV F infection was observed at a low frequency throughout the year, with an increased incidence occurring during February and March. Sequence analysis of one to three hypervariable regions (HVRs) of the hexon genes of 16 representative AdV-41 strains in this study confirmed circulation of a unique strain with genomic type cluster 1 (GTC1)/GTC2. However, sequence analysis of the fiber genes of these strains confirmed 15 amino acid deletions from the 15th repeat motif of the shaft region. The existence of two GTCs reflects the accumulation of amino acid mutations in the HVR of the hexon gene. The novel AdV-41 strain might follow the same infection pattern as AdV-40. There is no significant variation in the sequences of hexon and fiber genes among strains from symptomatic and asymptomatic children. Our data confirm the circulation of an AdV-41 strain with a novel pattern in Kolkata, India, among children below 5 years of age.

Fig. 1.

Comparison of the detection of enteric adenovirus 40/41 by ELISA and PCR followed by sequencing from stool samples from children in Kolkata, India, collected from December 2007 through December 2009.

Fig. 2.

Seasonal distribution of enteric adenovirus 40/41 during the period from December 2007 to December 2009.

Fig. 3.

Phylogenetic tree based on the nucleotide sequence of the HVR (1 to 3) of the hexon gene (a) and the nucleotide sequence of the shaft region (partial) of the fiber gene (b) of representative AdV-41 strains isolated from children in Kolkata, India, from December 2007 through December 2009. The phylogenetic trees were constructed by the neighbor-joining method with 1,000 bootstrap replications in the Clustal W program (http://www.ddbj.nig.ac.jp/search/clustalw-j.html). The numbers at internal nodes indicate the bootstrap values. The designations indicate the strain name/city name/month of infection/year of infection for the strains detected in this study. GTC1 and GTC2 denote genome type clusters in the hexon gene, as described by Li et al. (24). For the hexon gene, the following reference strains of human adenovirus (GenBank accession numbers are indicated in parentheses) were selected from GenBank: for hexon genes, D1-VN47 (AB103341), D4-VN28 (AB103342), D12-JP3171 (AB103343), D22-Km079 (AB103344), D26-JP31106 (AB103345), D27-JP2149 (AB103346), D25-Ks35 (AB103347), D28-VN1020 (AB103348), and TAK (X51783), with strain Dugan (X51782) used as the outgroup, and for the fiber gene, TAK (X16583) and M60327 (FB585), with strains Dugan (L19443) and GU245891 used as the outgroup.

Fig. 4.

Alignment of the deduced amino acid sequences of the fiber gene shaft region from 14 representative AdV-41 strains. One amino acid that overlaps with the sequence of the reference AdV-41 strain has been shown in boldface.