Department of Medical Biology, Faculty of Medicine, University of Szeged, Hungary.
BMC Microbiol. 2010 Dec 6;10:311. doi: 10.1186/1471-2180-10-311.
Herpesvirus genes are classified into distinct kinetic groups on the basis of their expression dynamics during lytic growth of the virus in cultured cells at a high, typically 10 plaque-forming units/cell multiplicity of infection (MOI). It has been shown that both the host response and the success of a pathogen are dependent on the quantity of particles infecting an organism. This work is a continuation of an earlier study 1, in which we characterized the overall expression of PRV genes following low-MOI infection. In the present study, we have addressed the question of whether viral gene expressions are dependent on the multiplicity of infection by comparing gene expressions under low and high-MOI conditions.
In the present study, using a real-time RT-PCR assay, we address the question of whether the expression properties of the pseudorabies virus (PRV) genes are dependent on the number of virion particles infecting a single cell in a culture. Our analysis revealed a significant dependence of the gene expression on the MOI in most of these genes. Specifically, we found that most of the examined viral genes were expressed at a lower level at a low MOI (0.1) than at a high MOI (10) experiment in the early stage of infection; however, this trend reversed by six hour post-infection in more than half of the genes. Furthermore, in the high-MOI infection, several PRV genes substantially declined within the 4 to 6-h infection period, which was not the case in the low-MOI infection. In the low-MOI infection, the level of antisense transcript (AST), transcribed from the antiparallel DNA strand of the immediate-early 180 (ie180) gene, was comparable to that of ie180 mRNA, while in the high-MOI experiment (despite the 10 times higher copy number of the viral genome in the infected cells) the amount of AST dropped by more than two log values at the early phase of infection. Furthermore, our analysis suggests that adjacent PRV genes are under a common regulation. This is the first report on the effect of the multiplicity of infection on genome-wide gene expression of large DNA viruses, including herpesviruses.
Our results show a strong dependence of the global expression of PRV genes on the MOI. Furthermore, our data indicate a strong interrelation between the expressions of ie180 mRNA and AST, which determines the expression properties of the herpesvirus genome and possibly the replication strategy (lytic or latent infection) of the virus in certain cell types.
疱疹病毒基因根据其在高感染复数（MOI）下培养细胞中的病毒裂解生长过程中的表达动态，分为不同的动力学群。已经表明，宿主反应和病原体的成功都取决于感染生物体的颗粒数量。这项工作是早期研究的延续，我们在该研究中描述了低 MOI 感染后 PRV 基因的整体表达。在本研究中，我们通过比较低 MOI 和高 MOI 条件下的基因表达，研究了病毒基因表达是否依赖于 MOI。
在本研究中，我们使用实时 RT-PCR 检测，解决了在单个培养细胞中感染的病毒粒子数量是否影响伪狂犬病病毒（PRV）基因表达特性的问题。我们的分析表明，在这些基因中，大多数基因的表达都明显依赖于 MOI。具体而言，我们发现大多数被检测到的病毒基因在感染早期的低 MOI（0.1）下表达水平低于高 MOI（10）实验；然而，在感染后 6 小时，超过一半的基因的这种趋势发生了逆转。此外，在高 MOI 感染中，一些 PRV 基因在 4 到 6 小时的感染过程中显著下降，而在低 MOI 感染中则没有这种情况。在低 MOI 感染中，从立即早期 180（ie180）基因的反平行 DNA 链转录的反义转录本（AST）的水平与 ie180 mRNA 的水平相当，而在高 MOI 实验中（尽管感染细胞中的病毒基因组拷贝数高 10 倍）AST 的量在感染早期阶段下降了两个对数级以上。此外，我们的分析表明，相邻的 PRV 基因受到共同调控。这是关于 MOI 对大型 DNA 病毒（包括疱疹病毒）全基因组基因表达影响的第一个报告。
我们的结果表明，PRV 基因的整体表达强烈依赖于 MOI。此外，我们的数据表明，ie180 mRNA 和 AST 的表达之间存在很强的相关性，这决定了疱疹病毒基因组的表达特性，并且可能决定了病毒在某些细胞类型中的复制策略（裂解或潜伏感染）。
