人類微小病毒B19感染與抗磷脂質抗體之研究

人類微小病毒B19 (Human parvovirus B19, B19)屬於微小病毒科，已知會造成許多人類疾病。B19病毒的殼體蛋白是由VP1及VP2組成，其中VP1比VP2在N端多出227個胺基酸，此段區域被命名為結構蛋白獨立區域[VP1-unique region, VP1u]。文獻已知VP1u具有sPLA2酵素活性，與病毒感染有關，並且能引起IgG抗體產生。先前研究發現B19感染會引起抗磷脂質抗體產生，並且與抗磷脂質症候群密切相關。而其中B19-VP1u病毒蛋白更被發現可誘發抗磷脂質抗體產生。為了深入瞭解VP1u蛋白作用機制，我們利用不同長度片段的B19-VP1u重組蛋白進行研究分析，結果發現VP1u區域中(1)61-227a.a.片段具有較高的sPLA2酵素活性;(2) 82-227a.a.片段與抗磷脂質抗體作用密切相關；(3)注射31-227a.a.及61-227a.a.抗體的Balb/c老鼠，會導致血小板減少和aPTT凝血時間延長;(4)注射21-227a.a.、51-227a.a.抗體的Balb/c老鼠會促進腹腔巨噬細胞遷徙能力增加；(5)注射VP1u片段抗體的Balb/c老鼠會促進CD8+/CD4+/Th17/Treg/NK/B細胞表現。綜合以上結果，我們更明確瞭解B19-VP1u在B19病毒感染與抗磷脂質抗體產生的致病機制重要角色。

Human parvovirus B19 (B19) is classified as Parvoviridae family and known causing disease in humans. The virus capsid is composed of two structural proteins, VP1 and VP2, which are identical except for 227 amino acids at the amino-terminal end of the VP1-protein, the so-called VP1-unique region (VP1u). B19-VP1u proteins have secretary phospholipase A2 (sPLA2) activity, which is essential for viral infectivity and as the region to neutralize the immune response (VP1u-IgG). Previous studies show B19-VP1u induces the production of anti-phospholipid antibody. To further understand the pathogenesis of B19- VP1u, we used different region of B19-VP1u recombinant proteins to analysis. The results indicated that (1) VP1u region of 61-227a.a. has higher sPLA2 activity; (2) 82-227a.a. region has higher association with anti-phospholipid antibody; (3) Passive immunization mice which injecting 31-227a.a. and 61-227a.a. antibodies may cause thrombocytopenia and aPTT prolong; (4) Passive immunization mice which injecting 21-227a.a and 51-227a.a antibodies may activate the macrophages migration; (5)The different VP1u region can stimulate CD8+/CD4+/Th17/Treg/NK/B cells expression. All together, we firstly demonstrated the region of B19-VP1u in B19 infection and the pathogenesis of anti-phospholipid antibodies in vivo.