Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America.
Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
PLoS Pathog. 2014 Feb 6;10(2):e1003912. doi: 10.1371/journal.ppat.1003912. eCollection 2014 Feb.
Effects of polyomavirus SV40 microRNA on pathogenesis of viral infections in vivo are not known. Syrian golden hamsters are the small animal model for studies of SV40. We report here effects of SV40 microRNA and influence of the structure of the regulatory region on dynamics of SV40 DNA levels in vivo. Outbred young adult hamsters were inoculated by the intracardiac route with 1×10⁷ plaque-forming units of four different variants of SV40. Infected animals were sacrificed from 3 to 270 days postinfection and viral DNA loads in different tissues determined by quantitative real-time polymerase chain reaction assays. All SV40 strains displayed frequent establishment of persistent infections and slow viral clearance. SV40 had a broad tissue tropism, with infected tissues including liver, kidney, spleen, lung, and brain. Liver and kidney contained higher viral DNA loads than other tissues; kidneys were the preferred site for long-term persistent infection although detectable virus was also retained in livers. Expression of SV40 microRNA was demonstrated in wild-type SV40-infected tissues. MicroRNA-negative mutant viruses consistently produced higher viral DNA loads than wild-type SV40 in both liver and kidney. Viruses with complex regulatory regions displayed modestly higher viral DNA loads in the kidney than those with simple regulatory regions. Early viral transcripts were detected at higher levels than late transcripts in liver and kidney. Infectious virus was detected infrequently. There was limited evidence of increased clearance of microRNA-deficient viruses. Wild-type and microRNA-negative mutants of SV40 showed similar rates of transformation of mouse cells in vitro and tumor induction in weanling hamsters in vivo. This report identified broad tissue tropism for SV40 in vivo in hamsters and provides the first evidence of expression and function of SV40 microRNA in vivo. Viral microRNA dampened viral DNA levels in tissues infected by SV40 strains with simple or complex regulatory regions.
SV40 微小 RNA 对体内病毒感染发病机制的影响尚不清楚。叙利亚金仓鼠是研究 SV40 的小动物模型。我们在此报告 SV40 微小 RNA 的作用以及调控区结构对体内 SV40 DNA 水平动态的影响。通过心内途径接种四种不同 SV40 变体的 1×107 噬菌斑形成单位的杂交成年幼仓鼠。感染动物从感染后 3 天到 270 天处死，并通过定量实时聚合酶链反应测定不同组织中的病毒 DNA 载量。所有 SV40 株均频繁建立持续性感染和缓慢清除病毒。SV40 具有广泛的组织嗜性，感染的组织包括肝脏、肾脏、脾脏、肺和脑。肝脏和肾脏中的病毒 DNA 载量较高；尽管在肝脏中也保留了可检测的病毒，但肾脏是长期持续性感染的首选部位。在野生型 SV40 感染组织中证明了 SV40 微小 RNA 的表达。在肝脏和肾脏中，微 RNA 缺失突变病毒的病毒 DNA 载量始终高于野生型 SV40。具有复杂调控区的病毒在肾脏中的病毒 DNA 载量略高于具有简单调控区的病毒。早期病毒转录本在肝脏和肾脏中的水平高于晚期转录本。很少检测到感染性病毒。微 RNA 缺失病毒清除率增加的证据有限。SV40 的野生型和微 RNA 缺失突变体在体外转化小鼠细胞和体内诱导幼仓鼠肿瘤方面显示出相似的速度。本报告确定了 SV40 在体内仓鼠中的广泛组织嗜性，并首次提供了 SV40 微 RNA 在体内表达和功能的证据。病毒微 RNA 减弱了简单或复杂调控区 SV40 感染组织中的病毒 DNA 水平。
