Virome Profiling of Bats from Myanmar by Metagenomic Analysis of Tissue Samples Reveals More Novel Mammalian Viruses

He, Biao; Li, Zuosheng; Yang, Fanli; Zheng, Junfeng; Feng, Ye; Guo, Huancheng; Li, Yingying; Wang, Yiyin; Su, Nan; Zhang, Fuqiang; Fan, Quanshui; Tu, Changchun

Comparison is difficult, however, since sequence similarities are identified by BLAST search of the Genbank databases, which are continually expanding [58] . Our results showed that about 2% (26,698/1,649,512) of total contigs were virus-related sequences. However, in previous viromes, the proportions of virus-related sequences in total reads or contigs ranged from 0.1%-58% [10, [35] [36] [37] . Of note is that 45% of viral contigs in our virome classified to vertebrate viruses, while insect viruses and phages constituted only 28% and 27% of viral contigs respectively (Table 3 ). This compares with less than 10% of total viral contigs related to vertebrate viruses in previous viral metagenomes of bats [10, [35] [36] [37] . In addition, among 24 viral families identified here, 54% (13 families) were mammalian viruses, much higher and broader than the rates reported in previous virome studies. This difference may be ascribed to the sample type: various organ tissue samples of all bats, along with intestine contents, were used in our study, while the samples used in previous studies were only feces or feces plus oral and pharyngeal swabs [10, [35] [36] [37] . Mammalian viruses require replication in host cells, with some, but not all, being excreted into the environment through the fecal and/or oral routes. Moreover, excretion of many viruses is intermittent, and therefore the virome obtained from excreted or secreted materials may not represent the complete viral complement of the host. Consequently, mixed tissue samples are likely to provide a more complete virome profile. For instance, since hepadnaviruses are strictly blood-borne viruses and normally not secreted through the fecal and oral routes, this could be the reason why previous metagenomic studies have not found Hepadnaviridae in any bat species. In the present study, sampling of bat livers may have permitted successful identification of a bat hepadnavirus. The fact that this constituted the largest population of mammalian viral sequences ( Table 3 ) additionally indicates that bats are potential reservoirs of hepadnaviruses.