Labuda M, Austyn J M, Zuffova E, Kozuch O, Fuchsberger N, Lysy J, Nuttall P A
Institute of Zoology, Slovak Academy of Sciences, Bratislava, Slovakia.
Virology. 1996 May 15;219(2):357-66. doi: 10.1006/viro.1996.0261.
Arboviruses are transmitted to vertebrates by the "bite" of infected arthropods. Events at the site of virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) virus transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus). Virus transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels > or = 2.0 log10 ic mouse LD50/0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE virus transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne virus transmission.
虫媒病毒通过受感染节肢动物的“叮咬”传播给脊椎动物。尽管越来越多的证据表明吸血节肢动物会对其取食的皮肤部位进行免疫调节，但病毒沉积部位的情况在很大程度上仍不为人知。这个问题对于需要吸食数天血液的硬蜱来说尤为重要。为了研究在模拟蜱传脑炎（TBE）病毒自然传播的条件下（即受感染和未受感染的蓖麻硬蜱在同一动物身上取食）所发生的情况，将受感染的成年蜱和未受感染的若蜱放置在一个容纳腔室（皮肤部位A）中，将未受感染的若蜱放置在两只自然宿主动物（黄颈姬鼠（Apodemus flavicollis）和大林姬鼠（Clethrionomys glareolus））身体后部的第二个腔室（皮肤部位B）中。从受感染的共同取食蜱向未受感染的蜱的病毒传播与蜱取食皮肤部位的感染相关。此外，与未被蜱叮咬的皮肤部位相比，病毒优先聚集在蜱取食的部位。病毒血症与皮肤的全身性感染并不对应；在12/13只病毒血症水平≥2.0 log10 ic小鼠LD50/0.02 ml血液的自然宿主的未被蜱叮咬的皮肤部位（C）中未检测到病毒。为了鉴定受感染的细胞，用受感染的蜱感染实验室小鼠品系，然后从选定的皮肤部位取出外植体并漂浮在培养基上。发现大量白细胞从蜱取食部位的皮肤外植体迁移出来。双色免疫细胞化学显示迁移的朗格汉斯细胞和中性粒细胞中存在病毒抗原；此外，迁移的单核细胞/巨噬细胞被证明能产生传染性病毒。结果表明，蜱取食的局部皮肤部位是蜱传播TBE病毒后早期病毒复制的重要场所。蜱取食部位的细胞浸润以及细胞从此类部位的迁移，可能为受感染和未受感染的共同取食蜱之间的传播提供一种媒介，这种传播与明显的病毒血症无关。这些数据支持病毒血症是蜱传病毒传播的产物而非前提条件这一假说。
