猪圆环病毒3型衣壳蛋白(Cap)抑制宿主细胞天然免疫应答

Inhibition effect of PCV3 capsid protein on innate immune response of host cells

摘要:

【背景】猪圆环病毒是引起猪圆环病毒病的病原，能够引起严重的免疫抑制和临床症状，给养猪业造成严重的经济损失。【目的】研究猪圆环病毒3型(porcine circovirus 3，PCV3)衣壳蛋白(Capsid protein，Cap)对宿主天然免疫应答的调控作用，解析其免疫抑制机制对阐明猪圆环病毒致病机制具有重要意义。【方法】通过构建Cap真核表达质粒，利用Western blotting进行表达验证，实时荧光定量(RT-PCR)、双荧光素酶基因报告系统和ELISA探究Cap对I型干扰素通路活化的影响，通过免疫共沉淀探索其作用机制。【结果】真核表达质粒成功表达并且证实Cap可以抑制DNA模拟物poly(dA:dT)诱导的I型干扰素通路的活化；Cap可以与天然免疫通路节点分子MITA相互作用。【结论】研究发现PCV3病毒Cap蛋白与干扰素通路节点分子MITA相互作用发挥免疫抑制作用，这为阐明PCV3免疫抑制机制提供了理论依据。

关键词:PCV3，衣壳蛋白(Cap)，干扰素，信号通路

Abstract:

[Background] Porcine circovirus causes porcine circovirus associated disease, severe immunosuppression and clinical symptoms in pigs, causing substantial economic losses. [Objective] To study the role of porcine circovirus 3 (PCV3) capsid protein (Cap) in regulating host innate immune response, we constructed a eukaryotic plasmid expressing PCV3 protein Cap. [Methods] The expression of Cap was verified by Western blotting. The real-time quantification PCR (RT-PCR), dual luciferase gene reporting system and ELISA assay were used to study the effect of Cap on type I interferon pathway activation, and the Co-immunoprecipitation was done to study the involved antagonistic mechanism. [Results] The expression of Cap was verified, suggesting that Cap was highly expressed in the transfected cells, and Cap inhibited the activation of type I interferon signaling pathway stimulated by a synthetic DNA, poly(dA:dT). The interaction of Cap with the adaptor protein MITA of innate immune signaling pathway was identified. [Conclusion] These results indicate that Cap plays an important role in inhibiting the innate immune response of host cells by interacting with MITA. Our study provides a theoretical basis for clarification of the molecular mechanisms for PCV3-mediated immune suppression.

Key words:PCV3, capsid protein (Cap), interferon, signal pathway