Human mastadenovirus type 70: a novel, multiple recombinant species D mastadenovirus isolated from diarrhoeal faeces of a haematopoietic stem cell transplantation recipient

A human mastadenovirus D (HAdV-D) isolated from diarrhoeal faeces of an allogeneic haematopoietic stem cell transplant (SCT) recipient was found to be non-typable by sequencing of loops 1 and 2 of the hexon main neutralization epitope ('imputed serology). In contrast to HAdV-C, HAdV-D infections are rarely observed in SCT patients. Therefore, the whole genome of this isolate was sequenced and phylogenetically analysed. In addition, microneutralization testing with type-specific antisera was performed. A complete genomic sequence of 35.2 kb in length with a GC content of 57 % was obtained and found to be distantly related to HAdV-D27 (96.25 % identity). Imputed serology implicated a new type with a nucleotide sequence identity of only 96.11 % to HAdV-D37 (loop 1) and 95.76 % to HAdV-D30 and HAdV-D37 (loop 2). Microneutralization testing confirmed that this clinical isolate was not neutralized by HAdV-D37- or HAdV-D30-specific antisera. The penton base gene showed a novel sequence, which clustered with HAdV-D38, but bootscan analysis indicated an intra-penton recombination event with HAdV-D60. Another recombination event was detected within the early gene region E3 with the 12.2 kDa and CR1-alpha genes derived from HAdV-D58. Moreover, the E4 region was derived from HAdV-D13, but all these genes had evolved significantly from their ancestors. By contrast, the recombinant fibre gene was almost 100 % identical to HAdV-D29. In conclusion, the genomics of this novel HAdV, designated the HAdV-D70 [P70H70F29] prototype, supported the significance of multiple recombinations in the phylogeny of HAdV-D.