Kanda Takehiro, Santos Pauline Dianne, Höper Dirk, Beer Martin, Rubbenstroth Dennis, Tomonaga Keizo
Laboratory of RNA Viruses, Department of Virus Research, Institute for Life and Medical Science, Kyoto University, Kyoto, Japan.
Department of Molecular Virology, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Npj Viruses. 2025 Apr 17;3(1):31. doi: 10.1038/s44298-025-00117-w.
Mammalian orthobornaviruses, such as Borna disease virus 1 (BoDV-1) and variegated squirrel bornavirus 1, are zoonotic pathogens that cause fatal encephalitis in humans. BoDV-2, another mammalian orthobornavirus with high genetic homology to BoDV-1, is believed to share the same geographical distribution as BoDV-1, indicating its potential risk to human health. However, due to the limited number of isolations, the virological characteristics of BoDV-2, such as pathogenicity and infectivity, remain largely unexplored. Here, we re-evaluated the whole-genome sequence of BoDV-2 and established a reverse genetics system to investigate its virological properties. Compared to the published reference sequence, we identified two nonsynonymous nucleotide substitutions in the large (L) gene, one of which was critical for restoring polymerase activity, enabling the successful recovery of recombinant BoDV-2 (rBoDV-2). Additionally, we identified two nonsynonymous single-nucleotide polymorphisms (SNPs) in the L gene and one in the phosphoprotein (P) gene. Substitution of these SNPs significantly enhanced the growth ability of rBoDV-2. Furthermore, our studies demonstrated that BoDV-2 does not induce superinfection exclusion in cells, allowing the persistence of low-fitness genome variants for an extended period of time. These findings help to characterize the virological properties of BoDV-2 and shed light on how bornaviruses maintain genetic diversity in infected cells.
哺乳动物正涎病毒，如博尔纳病病毒1型（BoDV-1）和杂色松鼠涎病毒1型，是人畜共患病原体，可导致人类致命性脑炎。BoDV-2是另一种与BoDV-1具有高度遗传同源性的哺乳动物正涎病毒，据信其地理分布与BoDV-1相同，表明其对人类健康具有潜在风险。然而，由于分离株数量有限，BoDV-2的病毒学特征，如致病性和传染性，在很大程度上仍未得到探索。在此，我们重新评估了BoDV-2的全基因组序列，并建立了反向遗传学系统来研究其病毒学特性。与已发表的参考序列相比，我们在大（L）基因中鉴定出两个非同义核苷酸替换，其中一个对于恢复聚合酶活性至关重要，从而使重组BoDV-2（rBoDV-2）得以成功拯救。此外，我们在L基因中鉴定出两个非同义单核苷酸多态性（SNP），在磷蛋白（P）基因中鉴定出一个。这些SNP的替换显著增强了rBoDV-2的生长能力。此外，我们的研究表明，BoDV-2不会在细胞中诱导超感染排斥，从而使低适应性基因组变体能够长时间持续存在。这些发现有助于表征BoDV-2的病毒学特性，并揭示涎病毒如何在受感染细胞中维持遗传多样性。
