以流感病毒血凝素酶为靶点兼具免疫调节功能的新型抗禽流感病毒肽类化合物的研究

Avian influenza is an infectious disease caused by influenza A viruses (IAV). It is a serious threat to public health. Thus far, there are only two types of drugs available in the clinics, which are M2 ion channel inhibitors and neuraminidase inhibitors. Nevertheless, the emergence of drug-resistant viral strains has been reported, thus it is imperative to develop new and effective anti-IAV drugs with different modes of action. In our previous work, we identified several short lipopeptides (MW<1000) possessing potent and broad anti-IAV activities. The mechanism study indicated that the binding site of these molecules is in the stem region of HA2 subunit of hemagglutinin (HA), by which to interrupt the conformational changes of HA2 and subsequently inhibit the fusion of virus-host cell membranes, thereby blocking the entry of virus. In addition, the study also showed that these peptides were able to reduce the level of NF-κB, as well as the expression of IL-1β and TNF-α, thus possessing the immunomodulatory ability towards host cells. On the basis of these works, this application will continue to investigate these lipopeptides by extensively modifying their structures and studying their structure-activity relationships, by which to obtain more potent candidates for the further investigation. The ongoing study will be carried out by targeting the influenza viral envelop protein of hemagglutinin (HA) and using H5N1 pseudo-typed virus as the screening model. To reduce the cellular toxicities and enhance the selectivity indices of these peptides, a strategy of “complex peptides” which we successfully developed recently will be employed. In addition, to make the candidates more valuable, the modes of action including anti-IAV and immunomodulatory activities will be extensively investigated, by which to establish a solid base for the development of new anti-IAV drugs. As a result, we believe that the successful implementation of this application will bring us one more choice for the treatment of avian influenza infection in the future.

禽流感是由A型流感病毒引起的一种对公共健康构成严重威胁的人畜共患传染病。目前使 用的药物只作用于M2离子通道和神经氨酸酶两个靶点，且面临日益严重的耐药性问题，因此迫切需要研制新的药物。我们前期的工作中发现多个肽类化合物（分子量<1000）具有较好的广谱抗流感病毒活性。这些化合物作用在血凝素酶HA2亚基的茎部，通过阻止HA2亚基在酸性条件下构象的变化进而阻止病毒进入宿主。此外，这些化合物还能降低宿主细胞NF-κB以及IL-1β, TNF-α等炎症因子的表达，因此具有免疫调节作用。以此为基础，本研究拟以流感病毒血凝素酶为靶点，对这些化合物进行深入的结构修饰和构效关系研究，以提高其抗病毒活性，尤其是通过构筑靶向复合肽的方法降低其毒性，提高其选择性，并深入探讨高活性化合物抗病毒及免疫调节作用的机制，为开发新型抗禽流感病毒药物打下基础。本研究的成功实施将对禽流感的治疗具有重要的意义。

本项目以前期发现的多个具有较好的广谱抗流感病毒活性，且能降低宿主细胞NF-κB以及IL-1β,TNF-α等炎症因子表达的肽类化合物为基础，以流感病毒血凝素酶为靶点，对这些化合物进行深入的结构修饰和构效关系研究，以提高其抗病毒活性，对宿主细胞的选择性，并深入探讨高活性化合物抗病毒及免疫调节作用的机制，为开发新型抗禽流感病毒药物打下基础。.为达到这一目标，以前期化合物C12-KKWK为模型，我们首先改变其脂链，合成一系列从C2到C20不同长度的脂肪链取代的KKWK，研究其活性、毒性和结构的关系。结果发现，抗病毒活性随着链长的增加，活性增加。然而，其毒性也随之增加。.随后，我们采用改变其结构骨架的思路来达到目标。为此，我们以KKWK及KWKK为配体，通过构筑树状肽的方法，合成了一系列的四价树状化合物。同时在肽链的N端分别连接上不同长度的脂肪链（C6-C18），不同的芳香基团（萘乙酸，对联苯乙酸，FMOC等），考察这些化合物结构与活性的关系以及对宿主细胞的毒性。.通过这一系列结构改造和修饰，筛选出一四价树状化合物FMOC-4-KKWK，能在保持较高抗病毒活性的同时具有较低细胞毒性。在此基础上，深入探究了该化合物体外抗流感病毒的活性、对宿主细胞的毒性，初步的抗炎活性，以及可能的作用机制和小鼠体内活性。.虽然目前通过用树状结构的分子抑制HA与宿主SA之间多价结合的工作有所报道，但本研究是首次针对HA2亚基，通过构筑多价分子以抑制病毒-细胞膜融合的尝试，这一工作的成功实施为抗流感病毒多肽类药物提供了新的设计思路。