Andrade Ana Cláudia Dos Santos Pereira, Rodrigues Rodrigo Araújo Lima, Oliveira Graziele Pereira, Andrade Kétyllen Reis, Bonjardim Cláudio Antônio, La Scola Bernard, Kroon Erna Geessien, Abrahão Jônatas Santos
Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Laboratório de Imunopatologia de Doenças Virais, Centro de Pesquisas René Rachou-Fiocruz, Minas Gerais, Brazil.
J Virol. 2017 Oct 27;91(22). doi: 10.1128/JVI.01335-17. Print 2017 Nov 15.
Since the discovery of mimivirus, its unusual structural and genomic features have raised great interest in the study of its biology; however, many aspects concerning its replication cycle remain uncertain. In this study, extensive analyses of electron microscope images, as well as biological assay results, shed light on unclear points concerning the mimivirus replication cycle. We found that treatment with cytochalasin, a phagocytosis inhibitor, negatively impacted the incorporation of mimivirus particles by , causing a negative effect on viral growth in amoeba monolayers. Treatment of amoebas with bafilomicin significantly impacted mimivirus uncoating and replication. In conjunction with microscopic analyses, these data suggest that mimiviruses indeed depend on phagocytosis for entry into amoebas, and particle uncoating (and stargate opening) appears to be dependent on phagosome acidification. In-depth analyses of particle morphogenesis suggest that the mimivirus capsids are assembled from growing lamellar structures. Despite proposals from previous studies that genome acquisition occurs before the acquisition of fibrils, our results clearly demonstrate that the genome and fibrils can be acquired simultaneously. Our data suggest the existence of a specific area surrounding the core of the viral factory where particles acquire the surface fibrils. Furthermore, we reinforce the concept that defective particles can be formed even in the absence of virophages. Our work provides new information about unexplored steps in the life cycle of mimivirus. Investigating the viral life cycle is essential to a better understanding of virus biology. The combination of biological assays and microscopic images allows a clear view of the biological features of viruses. Since the discovery of mimivirus, many studies have been conducted to characterize its replication cycle, but many knowledge gaps remain to be filled. In this study, we conducted a new examination of the replication cycle of mimivirus and provide new evidence concerning some stages of the cycle which were previously unclear, mainly entry, uncoating, and morphogenesis. Furthermore, we demonstrate that atypical virion morphologies can occur even in the absence of virophages. Our results, along with previous data, allow us to present an ultimate model for the mimivirus replication cycle.
自从发现巨型病毒以来，其不同寻常的结构和基因组特征引发了人们对其生物学研究的浓厚兴趣；然而，关于其复制周期的许多方面仍不明确。在本研究中，对电子显微镜图像的广泛分析以及生物学检测结果，揭示了巨型病毒复制周期中一些不明确的要点。我们发现，用吞噬作用抑制剂细胞松弛素处理会对巨型病毒颗粒被[具体细胞或生物体]摄取产生负面影响，进而对变形虫单层中的病毒生长产生负面影响。用巴弗洛霉素处理变形虫会显著影响巨型病毒的脱壳和复制。结合显微镜分析，这些数据表明巨型病毒进入变形虫确实依赖吞噬作用，并且颗粒脱壳（以及星门打开）似乎依赖吞噬体酸化。对颗粒形态发生的深入分析表明，巨型病毒衣壳由不断生长的层状结构组装而成。尽管先前的研究提出基因组获取发生在纤丝获取之前，但我们的结果清楚地表明基因组和纤丝可以同时获取。我们的数据表明，在病毒工厂核心周围存在一个特定区域，颗粒在此获取表面纤丝。此外，我们强化了这样一个概念，即即使在没有病毒卫星的情况下也能形成缺陷颗粒。我们的工作提供了关于巨型病毒生命周期中未探索步骤的新信息。研究病毒生命周期对于更好地理解病毒生物学至关重要。生物学检测和显微镜图像的结合使我们能够清晰地了解病毒的生物学特征。自从发现巨型病毒以来，已经进行了许多研究来表征其复制周期，但仍有许多知识空白有待填补。在本研究中，我们对巨型病毒的复制周期进行了新的研究，并为该周期中一些先前不明确的阶段提供了新证据，主要是进入、脱壳和形态发生。此外，我们证明即使在没有病毒卫星的情况下也会出现非典型病毒体形态。我们的结果与先前的数据一起，使我们能够提出一个巨型病毒复制周期的最终模型。
