Changes in Borna disease virus genome with adaptation to host

The CRNP5 variant of Borna disease virus (BDV) has stronger pathogenesis than the CRP3 variant in which only 4 nucleotides in the whole genome are different. The CRP3 is produced by 3 passages in rat brains of BDV, whereas the CRNP5 is produced by 5 passages in mouse brains after 2 passages in rat brains of the BDV. Thymidylic acids at nt 3608 and 3673 were replaced by cytidylic acids during 3 passages in mice. Three passages in mice caused replacement of adenylic acid at nt 7936 by guanylic acid. No replacement at nt 8742 occurred during passages in mice.