Isolation and Propagation of Enteric Adenoviruses in HEp-2 Cells

Eighty-two stool samples from children with gastroenteritis in Canada, England, and Thailand which had been shown to contain adenovirus antigen (by a group-specific enzyme-linked immunosorbent assay) or adenovirus particles (by electron microscopy) or both, were tested for primary isolation of enteric adenoviruses in HEp-2 and Graham 293 cells. Graham 293 cells are known to support the replication of enteric adenovirus types (Ad40 and Ad41) on primary isolation, whereas HEp-2 cells reportedly do not. Of the 82 adenovirus isolates, 73 could be typed as Ad40 or Ad41 by type-specific monoclonal antibody enzyme-linked immunosorbent assay and by analysis of SmaI endonuclease digests. Of these 73, 30 (41%) could be isolated in HEp-2 cells, which included 43% (9/21) of those typed as Ad40 and 40% (21/52) of those typed as Ad41. On the basis of these results, the growth characteristics of adenoviruses in HEp-2 cell cultures, commonly used to distinguish enteric from nonenteric adenovirus types, are not valid for either diagnosis or epidemiological studies. For the samples studied here, use of these nondefinitive criteria would result in underestimation of the incidence of enteric adenoviruses in viral gastroenteritis.