Prevalent Enteric Adenovirus Variant Not Detected By Commercial Monoclonal Antibody Enzyme Immunoassay
A commercial monoclonal antibody enzyme immunoassay for the detection of enteric adenovirus type 40 and 41 (Ad40 and Ad41) in stool specimens was evaluated. Twenty-one stool specimens from children with gastroenteritis, with adenovirus particles visible by electron microscopy, and reference strains Ad40 Dugan and Ad41 Tak were tested by Ad40- and Ad41-specific and adenovirus group-reactive immunoassays. All stool specimens tested positive in the group-reactive immunoassay. However, only six specimens, containing isolates of Ad40 strain Hovi-X, an Ad40 genomic variant, and Ad41 strain Tak, reacted with the specific immunoassay, besides the reference strains. Fifteen stool specimens determined by restriction analysis to contain a genomic variant of Ad41 were negative by specific immunoassay. The positions of restriction site differences from the prototype strain Ad41 Tak were analyzed, and four mutations were mapped within the hexon gene; two others may occur in the fiber gene. The Ad41 genomic variant not detected by the enteric test is presently the most frequent cause of local adenoviral gastroenteritis. Highly specific monoclonal antibodies can fail to detect genomic variants of enteric adenoviruses, probably because of alteration of external neutralizable epitopes under immunological pressure to vary.