Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Microbiol Spectr. 2023 Jun 15;11(3):e0506522. doi: 10.1128/spectrum.05065-22. Epub 2023 May 22.
Reptarenaviruses cause boid inclusion body disease (BIBD), a fatal disease particularly impacting captive boa constrictor collections. The development of cytoplasmic inclusion bodies (IBs) comprising reptarenavirus nucleoprotein (NP) in many cell types of affected snakes is characteristic of BIBD. However, snakes can harbor reptarenaviruses without showing IBs, hence representing carriers and a potential source of transmission. The RNA genome of reptarenaviruses comprises a small (S) and a large (L) segment, and the snakes with BIBD commonly carry a swarm of reptarenavirus segments. To design sensitive and reliable tools for the diagnosis of reptarenavirus infection in snake colonies, we used metatranscriptomics to determine the reptarenavirus segments present in a large boa constrictor breeding colony. The analysis identified one reptarenavirus S segment and three L segments in the colony. The sequence data served to design real-time reverse transcription-PCR (RT-PCR) targeting the found S segment. This allowed us to identify all infected animals and to quantify the S segment RNA levels, which we found to correlate with the presence of IBs. We further found a positive correlation between the number of L segments and the S segment RNA level, which could suggest that L segment excess also contributes to the IB formation. Information on cohousing of the snakes showed a clear association of reptarenavirus infection with cohousing in general and cohousing with infected animals. Information on breeding and offspring confirmed that vertical transmission occurred. Furthermore, our data suggest that some animals might be able to clear the infection or at least exhibit transient or intermittent viremia. Boid inclusion body disease (BIBD) is caused by reptarenavirus infection, and while reptarenavirus nucleoprotein is the main component of the inclusion bodies (IBs) characteristic of BIBD, not all reptarenavirus-infected snakes demonstrate IBs in their cells. Identification of infected individuals is critical for controlling the spread of the disease; however, the genetic divergence of reptarenaviruses complicates reverse transcription-PCR (RT-PCR)-based diagnostics. Here, we tested a next-generation-sequencing-based approach to establish a tailored "colony-specific" set of diagnostic tools for the detection of reptarenavirus small (S) and large (L) genome segments. With this approach, we could demonstrate that an S-segment-specific RT-PCR is highly effective in identifying the infected individuals. We further found the S segment RNA level to positively correlate with the presence of IBs and the number of L segments, which could direct future studies to identify the BIBD pathogenetic mechanisms.
爬行动物仁病毒引起巨蟒包涵体病（BIBD），这是一种致命疾病，尤其影响圈养蟒科动物。受感染蛇类多种细胞类型中的细胞质包涵体（IB）包含爬行动物仁病毒核蛋白（NP），这是 BIBD 的特征。然而，蛇类可能携带爬行动物仁病毒而不显示包涵体，因此是携带者，也是潜在的传播源。爬行动物仁病毒的 RNA 基因组由一个小（S）和一个大（L）片段组成，患有 BIBD 的蛇通常携带大量的爬行动物仁病毒片段。为了设计用于蛇类群体中爬行动物仁病毒感染的敏感和可靠工具，我们使用宏转录组学来确定大型蟒科动物养殖群体中存在的爬行动物仁病毒片段。分析在该群体中鉴定出一个爬行动物仁病毒 S 片段和三个 L 片段。该序列数据被用于设计针对发现的 S 片段的实时逆转录 PCR（RT-PCR）。这使我们能够识别所有感染动物，并定量 S 片段 RNA 水平，我们发现该水平与包涵体的存在相关。我们还发现 L 片段数量与 S 片段 RNA 水平之间存在正相关，这可能表明 L 片段过剩也有助于包涵体的形成。关于蛇类共居的信息显示，爬行动物仁病毒感染与一般共居以及与感染动物的共居明显相关。关于繁殖和后代的信息证实了垂直传播的发生。此外，我们的数据表明，一些动物可能能够清除感染，或者至少表现出短暂或间歇性的病毒血症。巨蟒包涵体病（BIBD）由爬行动物仁病毒感染引起，虽然爬行动物仁病毒核蛋白是 BIBD 特征性包涵体（IB）的主要成分，但并非所有感染爬行动物仁病毒的蛇类在其细胞中都显示包涵体。鉴定感染个体对于控制疾病传播至关重要；然而，爬行动物仁病毒的遗传差异使基于逆转录 PCR（RT-PCR）的诊断复杂化。在这里，我们测试了一种基于下一代测序的方法，以建立一种针对检测爬行动物小（S）和大（L）基因组片段的“群体特异性”定制诊断工具。通过这种方法，我们可以证明 S 片段特异性 RT-PCR 非常有效地识别感染个体。我们还发现 S 片段 RNA 水平与包涵体的存在和 L 片段的数量呈正相关，这可能指导未来的研究以确定 BIBD 的发病机制。
