抗粘病毒蛋白（Myxovirus resistance，Mx）家族是干扰素诱导的细胞自身天然抗病毒的重要效应分子， MxA具有广谱的抗病毒活性，但并不影响人类免疫缺陷病毒的复制。我们另外两个实验室及最新研究表明MxB具有抑制HIV-1复制的活性，研究发现MxB可以抑制HIV-1病毒基因组的入核及整合从而抑制HIV-1的感染。但是对于MxB是如何抑制病毒感染的，其具体机制并不清楚。本申请将从MxA与MxB的结构特点及研究与MxA或MxB相互作用的细胞蛋白出发，进一步研究它们在MxA或MxB抗病毒过程中发挥的作用，研究内容包括：1）阐明MxB识别HIV-1衣壳的机制；2）研究MxB抑制HIV-1病毒复制过程中的入核机制；3）探索HIV-1病毒逃逸MxB抑制作用的具体过程。通过阐明MxB抗病毒及病毒逃逸机制，可以帮助研究人员更好的理解HIV-1致病机理，同时为抗艾滋的药物研发提供新的方向。

MxB is a recently discovered HIV-1 restriction factor. MxB and its ortholog MxA are both large GTPases from the dynamin superfamily. In contrast to MxA that inhibits many RNA and DNA viruses, the antiviral function of MxB was established only recently by studies of our lab and two other groups. This discovery resulted from the pursuit of interferon-stimulated gene (ISG) products that cause interferon-induced inhibition of HIV-1.MxB is distinguished from other known HIV-1 restriction factors (including APOBEC3G, TRIM5, SAMHD1 and tetherin) by its unique anti-HIV-1 mechanism. MxB inhibits the nuclear import of HIV-1 DNA. MxB does so through interacting with HIV-1 capsid protein and, as a result, dampens the function of viral capsid in HIV-1 nuclear import. .Current data support the model that MxB binds to HIV-1 capsid and inhibits the nuclear import of viral DNA. However, it is unclear how MxB recognizes HIV-1 capsid and how MxB binding to viral capsid impedes viral nuclear import. In addition, it is also unclear how HIV-1 develops resistance to MxB in infected individuals. The following studies are proposed to answer these questions. Aim 1. Determine how MxB recognizes HIV-1 capsid. We propose studies to determine which amino acids in the MxB N-terminal region govern the interaction with HIV-1 capsid. We will also utilize the MxB-resistant viral capsid mutations as the guide to determine which amino acids in viral capsid interact with MxB. Aim 2. Elucidate how MxB inhibits HIV-1 nuclear import. We will perform the in vitro HIV-1 capsid core stability assays to measure the effect of MxB on the stability of HIV-1 capsid cores that can either be prepared from mature HIV-1 particles or assembled using the recombinant viral capsid proteins. We will also perform co-immunoprecipitation assays to determine how MxB affects the association of HIV-1 capsid with CypA, NUP153, NUP358, TNPO3 and CPSF6that have been shown to associate with HIV-1 capsid and modulate HIV-1 nuclear import. Aim 3. Understand how HIV-1 evades MxB restriction. We hypothesize that these capsid mutations may act by, 1) disrupting MxB binding to viral capsid, 2) altering the stability of viral cores, or 3) impeding the interaction of viral capsid with cellular factors. We will also study how the individual differences in MxB expression levels and the single nucleotide polymorphisms (SNPs) in the MxB gene affect the development of viral resistance to MxB, modulate viral loads and alter the course of disease progression. .MxB restriction of HIV-1 infection may have important clinical implications, since significantly higher levels of MxB, but not MxA, were reported in the highly exposed HIV-1 seronegative Kenyan women cohort compared to the high-risk control group. A more complete understanding of the antiviral property of MxB is expected to advance our knowledge of host antiviral defense and inspire the development of new HIV therapeutics.

抗粘病毒蛋白（Myxovirus resistance，Mx）家族是干扰素诱导的细胞自身天然抗病毒的重要效应分子，其中MxA具有广谱的抗病毒活性，但并不影响人类免疫缺陷病毒（Human immunodeficiency virus，HIV）的复制。而MxB可以抑制HIV-1病毒基因组的入核及整合从而抑制HIV-1的感染。但是对于MxB是如何抑制病毒感染的，其具体机制并不清楚。本研究根据MxB的结构域特征以及与MxA蛋白序列的差异，分别对MxB的N端25个氨基酸、GTPase结构域、Loop4区域和stalk结构域进行了序列和功能的突变。结果表明MxB的N端25个氨基酸以及负责其二聚化的stalk结构域中残基L661的突变导致了其抗HIV-1的功能缺失；其GTPase活性和Loop4区域对于其抗病毒功能没有影响。本研究利用在线预测工具对MxB中可能存在的出核信号（Nuclear export signal，NES）进行预测，并对预测出的5段候选序列进行了缺失分析。结果表明，51-68位氨基酸的缺失导致MxB在核中的定位增加，提示此区域可能存在出核信号。令人意外的是，我们发现，缺失MxB 505-527位氨基酸后其抗病毒作用消失，并且在细胞中的定位发生改变。对该区域的进一步细化，我们发现MxB的515-519位氨基酸通过调节与HIV-1 CA的结合，而对其抗病毒功能至关重要。此外，对MxB与核输入蛋白的研究表明，MxB可以与KPNA7和KPNB1相互作用，提示MxB是通过核输入蛋白KPNA7和KPNB1转运至核而发挥作用的。这些结果为为病毒与宿主间相互关系的研究提供新的数据。