Elucidating the molecular mechanisms of MxB-mediated restriction of herpes virus infections

疱疹病毒导致严重到危及生命的疾病，特别是在免疫反应不足的患者中，例如移植后、患有艾滋病或由于遗传倾向而导致的疾病。这些疾病包括脑炎和脑膜炎(HSV-1、HSV-2)、带状疱疹(带状疱疹、VZV)、出生缺陷(HCMV)和癌症(EBV、KSHV)。先天免疫系统可以限制生产性疱疹病毒感染。虽然干扰素诱导蛋白在多个部位抑制感染，但疱疹病毒反过来又对抗这些免疫反应。鉴于这些不同的病毒逃避机制，有效对抗疱疹病毒的宿主蛋白仍然缺乏了解。Kochs团队最近发现，由MX2基因编码的干扰素诱导的人类MXB蛋白限制了α、β和伽马疱疹病毒的感染。MXB是一种动力蛋白样大的GTP酶，已被描述为HIV-1的限制因子。我们之前的研究表明，MXB在感染周期的早期阻止病毒复制，MXB可以破坏疱疹病毒衣壳，并且MXB攻击疱疹病毒的机制与HIV-1不同。本项目的目的是阐明MXB介导的抗疱疹病毒活性的分子机制。我们将比较不同物种的MXB蛋白对不同人和动物疱疹病毒的限制作用，以深入了解疱疹病毒感染对MX2基因进化可能的选择压力。我们将确定MXB如何防止传入的病毒衣壳将其基因组释放到细胞核中进行复制，以及MXB是否也攻击新组装的衣壳。通过生化分析，我们将确定MXB的分子决定因素，这些决定因素对于识别和可能破坏病毒衣壳是必要的。此外，通过现代蛋白质相互作用分析，我们将确定MXB结合的病毒蛋白质。最后，我们想要检查MXB是否不仅在体外而且在受感染的细胞中分解衣壳，从而有助于病毒DNA的细胞质传感。通过我们的研究，我们将确定病毒衣壳蛋白和病毒基因组在MXB表达细胞中的命运，并阐明这种广泛作用的细胞内限制因子的分子机制。通过结合我们在Mx-GTPase(AG Kochs)和疱疹病毒感染细胞生物学(AG Sodeik)领域的专业知识，我们拥有了最佳条件来阐明MXB抗疱疹病毒的作用机制。我们希望我们的发现有助于开发治疗危及生命的疱疹病毒感染的新方法。

Herpes viruses cause severe to life-threatening diseases, especially in patients with deficient immune responses, for example after transplantation, with AIDS or by genetic disposition. These include encephalitis and meningitis (HSV-1, HSV-2), shingles (herpes zoster, VZV), birth defects (HCMV) and cancers (EBV, KSHV). The innate immune system can limit productive herpesvirus infections. Although interferon-inducible proteins inhibit the infection at multiple sites, herpesviruses in turn antagonize these immune responses. In view of these diverse viral evasion mechanisms, the host proteins effective against herpesviruses are still poorly understood.The Kochs team has recently shown that the interferon-inducible human MxB protein encoded by the MX2 gene confines infections of alpha, beta and gamma herpesviruses. MxB is a dynamin-like, large GTPase that has already been described to be a restriction factor of HIV-1. Our previous studies show that MxB blocks viral replication early in the infection cycle, that MxB can destroy herpesviral capsids, and that MxB attacks herpesviruses by a different mechanism than HIV-1. The aim of our project is the elucidation of the molecular mechanisms of MxB-mediated antiviral activity against herpesviruses.We will compare the restriction of different human and animal herpes viruses by MxB proteins from different species to gain insights into a possible selection pressure of herpesvirus infections on the evolution of MX2 genes. We will determine how MxB prevents incoming viral capsids from releasing their genomes into the nucleus for replication, and whether MxB attacks newly assembled capsids too. With a biochemical assay, we will identify the molecular determinants of MxB that are necessary for the recognition and possible destruction of viral capsids. Furthermore, through modern protein interaction analyses, we will identify viral proteins to which MxB binds. Finally, we want to check whether MxB breaks up capsids not only in vitro but also in infected cells and thus contributes to the cytoplasmic sensing of the viral DNA. With our studies, we will determine the fate of viral capsid proteins and viral genomes in MxB-expressing cells and elucidate the molecular mechanisms of this broadly-acting intracellular restriction factor. By combining our expertise in the field of Mx-GTPases (AG Kochs) and cell biology of herpesvirus infection (AG Sodeik), we have optimal conditions to elucidate the mechanisms of MxB action against herpesviruses. We hope to contribute our findings to the development of new approaches for the treatment of life-threatening herpesvirus infections.