Enteric adenovirus type 41 : genome organization and specific detection procedures

Abstract: Enteric adenoviruses (EAd) types 40 and 41 (Ad40 and Ad41) representing subgenus F, are primary pathogens of children being second only to rotaviruses as the most important cause of infantile diarrhea.The EAds differ from all other adenoviruses in their inability to grow in most conventional established cell lines and have been suggested to be deficient in some early gene functions since they could be complemented by Ad 5 early regions EIA and E1B. In order to search for differences that could explain its characteristic growth restriction, the early regions EIA and E1B of Ad41 (strain D389) were sequenced, analysed and compared with the corresponding regions of Adl2, Ad7, Ad2, and Ad4. As revealed by the analysis of Ad2, three major mRNAs of 9S, 12S and 13S are generated from region EIA. The EIA region of Ad41 encodes two mRNAs corresponding to the 12S and 13S mRNAs. Only the 13S mRNA is transcribed at detectable levels. This mRNA can be translated into a 251 aa putative protein that contains the three highly conserved domains found in all other human adenoviruses and shown to be responsible for many important regulatory functions during infection.The E1B region of Ad41 encodes three transcripts that correspond to 22S, 14S and 9S mRNA of Ad2. No equivalent to the 13S mRNA of Ad2 E1B is found. In addition the Ad41 14S mRNA exhibits an additional exon of 23 bp created by a donor and an acceptor splice sites not desribed for other adenovirus E1B sequences.Due to their growth restriction in conventional cultures, rapid diagnostic procedures developed for the enteric adenovirus infections have mainly been aimed at the detection of viral antigens or nucleic acids. This thesis also describes several procedures developed for the general detection of adenoviruses and specific detection of the enteric types in stools specimens. General and specific hybridization assays were developed by use of two BamHI clones obtained from the EIA region of Ad41. One- and two-step PCR procedures were also developed for the general detection of adenoviruses using primers corresponding to highly conserved sequences within the hexon gene. Subgenus F specific one- and two-step PCRs were developed by using primers located in the Ad41 E1B region.The one-step PCR systems were tested and validated against isolation in tissue culture, DNA restriction enzyme analysis and a commercial latex agglutination test in the study of 60 specimens obtained from children with rotavirus negative diarrhea. The asymptomatic fecal excretion of adenoviruses was evaluated by two-step PCR amplifications on samples from 50 healthy children, 50 healthy adults, and 50 adults suffering from diarrhea.Finally, a simplified procedure for detection, discrimination and typing of EAd was also designed by combining the one-step PCR amplification of the hexon region with the restriction of the 300 bp product.