Lintala Annika, Szirovicza Leonóra, Sander Willem, Ekström Eveliina, Kipar Anja, Hetzel Udo, Hepojoki Jussi
Department of Virology, Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
J Gen Virol. 2024 Dec;105(12). doi: 10.1099/jgv.0.002052.
Boid inclusion body disease (BIBD) caused by reptarenaviruses affects captive constrictor snake collections worldwide. The disease manifests by the formation of cytoplasmic inclusion bodies in various tissues. Curiously, a snake with BIBD nearly always carries a swarm of reptarenavirus small and large segments rather than a single pair, and the composition of the swarm can vary between tissues. The role of reptarenavirus coinfections in BIBD pathogenesis remains unknown, and it is unclear whether reptarenavirus infection affects the susceptibility to superinfection or to secondary infections. For mammarenaviruses, co- and/or superinfection can occur if the infecting viruses are genetically divergent enough, and we hypothesized reptarenaviruses to behave similarly. To study this hypothesis, we employed boa constrictor kidney- and brain-derived cell cultures to perform a set of co- and superinfection experiments with one hartmanivirus and five reptarenavirus isolates. While all tested viruses replicated well in the boid kidney cells, experiments on the brain-derived cells showed differences in the replication efficacy between the viruses, suggesting that reptarenaviruses could differ in their target cell spectra. The quantification of viral RNA released from infected cells as a proxy for virus replication did not reveal overt differences between mono- and coinfections. Passaging of coinfected cell cultures revealed that one of the reptarenavirus isolates requires a coinfecting reptarena- or hartmanivirus to establish a persistent infection. Superinfection experiments on persistently reptarenavirus-infected cell lines suggested some interference between genetically similar viruses. We hypothesized that such interference would be mediated by the viral Z protein (ZP) specifically locking the genetically similar viral polymerase in a catalytically inactive state. Curiously, experiments on ZP-expressing cell lines indicated ZP overexpression not to significantly affect the amount of released viral RNA. Our experiments showed very little co- or superinfection interference between genetically dissimilar reptarenaviruses, reflecting the naturally occurring reptarenavirus coinfections in snakes with BIBD.
由爬行动物沙粒病毒引起的蟒类包涵体病（BIBD）影响着全球圈养的蟒蛇种群。该病通过在各种组织中形成细胞质包涵体来表现。奇怪的是，患有BIBD的蛇几乎总是携带一群爬行动物沙粒病毒的小片段和大片段，而不是一对，并且这群病毒的组成在不同组织之间可能会有所不同。爬行动物沙粒病毒共感染在BIBD发病机制中的作用仍然未知，并且尚不清楚爬行动物沙粒病毒感染是否会影响对重叠感染或继发感染的易感性。对于哺乳动物沙粒病毒，如果感染的病毒在基因上差异足够大，就可能发生共感染和/或重叠感染，我们推测爬行动物沙粒病毒的行为方式类似。为了研究这一假设，我们利用蟒蛇肾脏和大脑来源的细胞培养物，用一种哈特曼病毒和五种爬行动物沙粒病毒分离株进行了一系列共感染和重叠感染实验。虽然所有测试病毒在蟒类肾脏细胞中都能很好地复制，但在大脑来源细胞上进行的实验显示病毒之间的复制效率存在差异，这表明爬行动物沙粒病毒的靶细胞谱可能不同。将从感染细胞中释放的病毒RNA定量作为病毒复制的指标，并未揭示单感染和共感染之间的明显差异。对共感染细胞培养物进行传代培养发现，其中一种爬行动物沙粒病毒分离株需要与一种共感染的爬行动物沙粒病毒或哈特曼病毒共同感染才能建立持续感染。对持续感染爬行动物沙粒病毒的细胞系进行重叠感染实验表明，基因相似的病毒之间存在一些干扰。我们推测这种干扰将由病毒Z蛋白（ZP）介导，该蛋白会特异性地将基因相似的病毒聚合酶锁定在催化无活性状态。奇怪的是，在表达ZP的细胞系上进行的实验表明，ZP的过表达并不会显著影响释放的病毒RNA的量。我们的实验表明，基因不同的爬行动物沙粒病毒之间几乎没有共感染或重叠感染干扰，这反映了患有BIBD的蛇体内自然发生的爬行动物沙粒病毒共感染情况。
