Bioinsecticidas Microbianos, Instituto de Agrobiotecnología, CSIC-UPNA, Gobierno de Navarra, Mutilva Baja, Navarra, Spain.
J Virol. 2014 Mar;88(6):3548-56. doi: 10.1128/JVI.02974-13. Epub 2014 Jan 8.
Superinfection exclusion is the ability of an established virus to interfere with a second virus infection. This effect was studied in vitro during lepidopteran-specific nucleopolyhedrovirus (genus Alphabaculovirus, family Baculoviridae) infection. Homologous interference was detected in Sf9 cells sequentially infected with two genotypes of Autographa californica multiple nucleopolyhedrovirus (AcMNPV), each one expressing a different fluorescent protein. This was a progressive process in which a sharp decrease in the signs of infection caused by the second virus was observed, affecting not only the number of coinfected cells observed, but also the level of protein expression due to the second virus infection. Superinfection exclusion was concurrent with reorganization of cytoplasmic actin to F-actin in the nucleus, followed by budded virus production (16 to 20 h postinfection). Disruption of actin filaments by cell treatment with cytochalasin D resulted in a successful second infection. Protection against heterologous nucleopolyhedrovirus infection was also demonstrated, as productive infection of Sf9 cells by Spodoptera frugiperda nucleopolyhedrovirus (SfMNPV) was inhibited by prior infection with AcMNPV, and vice versa. Finally, coinfected cells were observed following inoculation with mixtures of these two phylogenetically distant nucleopolyhedroviruses--AcMNPV and SfMNPV--but at a frequency lower than predicted, suggesting interspecific virus interference during infection or replication. The temporal window of infection is likely necessary to maintain genotypic diversity that favors virus survival but also permits dual infection by heterospecific alphabaculoviruses.
Infection of a cell by more than one virus particle implies sharing of cell resources. We show that multiple infection, by closely related or distantly related baculoviruses, is possible only during a brief window of time that allows additional virus particles to enter an infected cell over a period of ca. 16 h but then blocks multiple infections as newly generated virus particles begin to leave the infected cell. This temporal window has two important consequences. First, it allows multiple genotypes to almost simultaneously infect cells within the host, thus generating genetically diverse virus particles for transmission. Second, it provides a mechanism by which different viruses replicating in the same cell nucleus can exchange genetic material, so that the progeny viruses may be a mosaic of genes from each of the parental viruses. This opens a completely new avenue of research into the evolution of these insect pathogens.
超级感染排除是指已建立的病毒干扰第二种病毒感染的能力。这种效应在鳞翅目特异性核多角体病毒（属α-杆状病毒，杆状病毒科）感染的体外研究中得到了研究。在依次感染两种基因型的美洲棉铃虫核多角体病毒（AcMNPV）的 Sf9 细胞中检测到了同源干扰，每个病毒都表达了不同的荧光蛋白。这是一个渐进的过程，观察到第二种病毒引起的感染迹象急剧下降，不仅影响了观察到的共感染细胞的数量，还影响了由于第二种病毒感染而导致的蛋白质表达水平。超级感染排除与细胞质肌动蛋白在核中的重新组织为 F-肌动蛋白同时发生，随后产生芽生病毒（感染后 16 至 20 小时）。用细胞松弛素 D 处理细胞以破坏肌动蛋白丝会导致第二次成功感染。还证明了对异源核多角体病毒感染的保护，因为 Sf9 细胞的 Spodoptera frugiperda 核多角体病毒（SfMNPV）的有效感染被 AcMNPV 预先感染所抑制，反之亦然。最后，在接种这些两种系统发育上遥远的核多角体病毒（AcMNPV 和 SfMNPV）混合物后观察到共感染细胞，但频率低于预测值，这表明在感染或复制过程中存在种间病毒干扰。感染的时间窗口可能是维持有利于病毒存活的基因型多样性所必需的，但也允许异源α杆状病毒的双重感染。
一个细胞被多个病毒粒子感染意味着共享细胞资源。我们表明，通过密切相关或远缘相关的杆状病毒进行多次感染仅在大约 16 小时的时间内是可能的，在此期间，允许更多的病毒粒子进入感染的细胞，但随后阻止了多次感染，因为新生成的病毒粒子开始离开感染的细胞。这个时间窗口有两个重要的后果。首先，它允许多个基因型几乎同时感染宿主内的细胞，从而产生用于传播的遗传上多样化的病毒粒子。其次，它提供了一种机制，通过该机制，在同一细胞核中复制的不同病毒可以交换遗传物质，因此，后代病毒可能是来自每个亲本病毒的基因的嵌合体。这为研究这些昆虫病原体的进化开辟了一个全新的途径。
