Robert Jacques, Abramowitz Lara, Gantress Jennifer, Morales Heidi D
Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA.
J Wildl Dis. 2007 Oct;43(4):645-52. doi: 10.7589/0090-3558-43.4.645.
Frog virus 3 (FV3) or FV3-like viruses (Iridoviridae) infect a wide range of amphibian species, and they are becoming increasingly and causally associated with amphibian disease outbreaks worldwide. We have established the frog Xenopus laevis as an experimental model to study host defense and pathogenesis of FV3 infection. Although X. laevis adults usually clear FV3 infection within a few weeks, viral DNA has been detected in the kidneys several months after they had been experimentally infected; virus also has been detected in seemingly healthy nonexperimentally infected adults. Based on this information, we hypothesized that covert FV3 infection may occur in Xenopus. We first conducted a survey that detected FV3 by polymerase chain reaction (PCR) in the kidneys (the main site of FV3 infection) in a significant fraction of X. laevis raised in five different locations in the United States. Asymptomatic FV3 carriers also were detected by initiation of an acute systemic FV3 infection in frogs that had been immunosupressed by sublethal gamma-irradiation. Finally, we focused on macrophages as a potential site for viral persistence, and we showed that FV3 can infect peritoneal macrophages in vitro as determined by reverse transcriptase-PCR detection of viral mRNAs. Unlike kidney cell lines that are readily killed by FV3, infected macrophages, like uninfected macrophages, survived up to 12 days. Viral transcription also was detected in macrophages from animals up to 12 days after infection. These results suggest that FV3 can become quiescent in resistant species such as Xenopus, thereby making these species potential viral reservoirs.
蛙病毒3（FV3）或FV3样病毒（虹彩病毒科）可感染多种两栖动物物种，并且它们与全球范围内两栖动物疾病的爆发越来越多地存在因果关联。我们已将非洲爪蟾确立为研究FV3感染的宿主防御和发病机制的实验模型。尽管成年非洲爪蟾通常在几周内清除FV3感染，但在实验感染后的几个月里，在其肾脏中检测到了病毒DNA；在看似健康的未实验感染的成年爪蟾中也检测到了病毒。基于这些信息，我们推测非洲爪蟾可能发生隐性FV3感染。我们首先进行了一项调查，通过聚合酶链反应（PCR）在美国五个不同地点饲养的相当一部分非洲爪蟾的肾脏（FV3感染的主要部位）中检测到了FV3。通过对经亚致死剂量γ射线照射免疫抑制的青蛙引发急性全身性FV3感染，也检测到了无症状FV3携带者。最后，我们将重点放在巨噬细胞作为病毒持续存在的潜在部位，并且我们表明通过逆转录酶 - PCR检测病毒mRNA确定FV3可在体外感染腹膜巨噬细胞。与容易被FV3杀死的肾细胞系不同，受感染的巨噬细胞与未感染的巨噬细胞一样，存活长达12天。在感染后长达12天的动物巨噬细胞中也检测到了病毒转录。这些结果表明FV3可在非洲爪蟾等抗性物种中进入静止状态，从而使这些物种成为潜在的病毒储存宿主。
