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-a 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.

Following a distinct summer heat wave, nine autochthonous cases of West Nile fever and West Nile neuroinvasive disease, including one fatality, were observed in Leipzig, Germany, in August and September 2020. Phylogenetic analysis demonstrated close relationships in viruses from humans, animals and mosquitos in eastern Germany, obtained during the preceding 2 years. The described large cluster of autochthonous West Nile virus infections in Germany indicates endemic seasonal circulation of lineage 2 viruses in the area.

A prerequisite for the intracellular replication process of the Flavivirus West Nile virus (WNV) is the cyclization of the viral RNA genome, which enables the viral replicase to initiate RNA synthesis. Our earlier studies indicated that the p45 isoform of the cellular AU-rich element binding protein 1 (AUF1) has an RNA chaperone activity, which supports RNA cyclization and viral RNA synthesis by destabilizing a stem structure at the WNV RNA's 3 ′ -end. Here we show that in mammalian cells, AUF1 p45 is consistently modified by arginine methylation of its C terminus. By a combination of different experimental approaches, we can demonstrate that the methyltransferase PRMT1 is necessary and sufficient for AUF1 p45 methylation and that PRMT1 is required for efficient WNV replication. Interestingly, in comparison to the nonmethylated AUF1 p45, the methylated AUF1 p45 aDMA exhibits a significantly increased affinity to the WNV RNA termini. Further data also revealed that the RNA chaperone activity of AUF1 p45 aDMA is improved and the methylated protein stimulates viral RNA synthesis considerably more efficiently than the nonmethylated AUF1 p45. In addition to its destabilizing RNA chaperone activity, we identified an RNA annealing activity of AUF1 p45, which is not affected by methylation. Arginine methylation of AUF1 p45 thus represents a specific determinant of its RNA chaperone activity while functioning as a WNV host factor. Our data suggest that the methylation modifies the conformation of AUF1 p45 and in this way affects its RNA binding and restructuring activities.

Species D is the largest of the seven species of human mastadenoviruses (HAdV), but few of its multiple types are associated with asevere disease, e.g. epidemic keratoconjunctivitis. Many other types are hardly ever associated with significant diseases in immunocompetent patients, but have been isolated from the diarrhoeal faeces of terminal AIDS patients suggesting their role as opportunistic pathogens. Three novel HAdV-D strains were isolated from the faeces of three immunocompromised adult patients (clinical diagnoses: lymphoma, myelodysplastic syndrome and AIDS CDC3B, respectively). These strains were not typeable by imputed serology of the hexon and fibre gene and therefore complete genomic sequences were generated by next-generation sequencing (NGS). All three strains were multiple recombinants and fulfilled the criteria for designation as types 73, 74 and 75 with the penton/hexon/fibre genotype codes P67H45F27, P70H74F51 and P75H26F29, respectively. A novel genomic backbone and also a novel hexon neutralization epitope sequence were discovered in type 74, and a novel penton sequence in type 75. At the complete genome level, types 73, 74 and 75 were closely related neither to each other nor to type 70, which was previously isolated in the same region. However, these four HAdV-D types were closely related to each other in single genes and gene regions, e.g. penton, E1 and E4 due to recombination events in their phylogeny. In conclusion, regional co-circulation of opportunistic HAdV-D types facilitated co- and super-infections, which are essential for homologous recombination, and thus resulted in the evolution of novel genotypes by lateral gene transfer.