Mani Bernhard, Gerber Marco, Lieby Patricia, Boschetti Nicola, Kempf Christoph, Ros Carlos
Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
Transfusion. 2007 Oct;47(10):1765-74. doi: 10.1111/j.1537-2995.2007.01393.x.
B19 virus (B19V) is a human pathogen frequently present in blood specimens. Transmission of the virus occurs mainly via the respiratory route, but it has also been shown to occur through the administration of contaminated plasma-derived products. Parvoviridae are highly resistant to physicochemical treatments; however, B19V is more vulnerable than the rest of parvoviruses. The molecular mechanism governing the inactivation of B19V and the reason for its higher vulnerability remain unknown.
After inactivation of B19V by wet heat and low pH, the integrity of the viral capsid was examined by immunoprecipitation with two monoclonal antibodies directed to the N-terminal of VP1 and to a conformational epitope in VP2. The accessibility of the viral DNA was quantitatively analyzed by a hybridization-extension assay and by nuclease treatment.
The integrity of the viral particles was maintained during the inactivation procedure; however, the capsids became totally depleted of viral DNA. The DNA-depleted capsids, although not infectious, were able to attach to target cells. Comparison studies with other members of the Parvoviridae family revealed a remarkable instability of B19V DNA in its encapsidated state.
Inactivation of B19V by heat or low pH is not mediated by capsid disintegration but by the conversion of the infectious virions into DNA-depleted capsids. The high instability of the viral DNA in its encapsidated state is an exclusive feature of B19V, which explains its lower resistance to inactivation treatments.
B19病毒（B19V）是血液标本中常见的人类病原体。该病毒主要通过呼吸道传播，但也可通过输注受污染的血浆衍生制品传播。细小病毒科对物理化学处理具有高度抗性；然而，B19V比其他细小病毒更脆弱。B19V失活的分子机制及其更高脆弱性的原因尚不清楚。
通过湿热和低pH使B19V失活后，用两种针对VP1 N端和VP2构象表位的单克隆抗体进行免疫沉淀，检测病毒衣壳的完整性。通过杂交延伸试验和核酸酶处理对病毒DNA的可及性进行定量分析。
在失活过程中病毒颗粒的完整性得以维持；然而，衣壳中的病毒DNA完全耗尽。DNA耗尽的衣壳虽无感染性，但仍能附着于靶细胞。与细小病毒科其他成员的比较研究表明，B19V DNA在衣壳化状态下具有显著的不稳定性。
热或低pH对B19V的失活不是由衣壳解体介导的，而是由感染性病毒粒子转化为DNA耗尽的衣壳所致。病毒DNA在衣壳化状态下的高度不稳定性是B19V的独特特征，这解释了其对失活处理的较低抗性。
