TMPRSS2

自 COVID-19 大流行爆发以来，全球已研发了数百种针对 SARS-CoV2 的疫苗。大多数已被临床使用的疫苗对相应毒株表现出令人满意的初始保护率。然而，随着时间的推移，新冠疫苗的保护率迅速下降，几乎所有疫苗在 6 个月后都低于 50% 。在这篇研究热点中，厦门大学生命科学学院韩家淮团队分析相关数据，提出新冠疫苗保护率下降迅速与新冠病毒本身性质密切相关。新冠病毒其非系统性呼吸道粘膜病毒的属性、高受体亲和力、短潜伏期和大规模感染导致的高突变速度是疫苗保护率下降的主要原因。它们导致预防新冠感染所需的抗体水平阈值很高，在正常的抗体衰减进程中，新冠疫苗所产生的抗体水平会在相对短的时间内下降至低于所需的保护阈值，因此失去保护性。该报道以题为 “COVID-19 vaccines and beyond” 的论文发表在《Cellular & Molecular Immunology》上。【面对非系统性呼吸道病毒的困境】与新冠疫苗的处境相同，流感疫苗和几个月前获美国 FDA 批准的 RSV 疫苗在达到理想的预防感染效果上存在一定挑战。该领域的专家将流感、RSV 和 SARS-CoV2 等病毒归类为非系统性呼吸道病毒，因为这些病毒主要在粘膜及附近组织复制，很少依赖全身性扩散。非系统性呼吸道病毒的一个共性就是它们倾向表现为反复感染，这些病毒也从未被疫苗有效控制。下一代 SARS-CoV2 疫苗的研发需要着重增强分泌性粘膜免疫和提升 IgA 反应，这已成为该领域内的共识。然而，对于这类呼吸道病毒免疫反应的认知存在不足，这限制了制定有效控制病毒传播新策略的进展。【新冠的高亲和力、短潜伏期、高突变速度】一种常见的说法是，SARS-CoV2 疫苗的短暂保护期与接种后迅速下降的抗体水平有关。比较能产生持久保护效果的HBV 和 HPV 疫苗，HBV 的血清抗体水平在前 6 个月内降低一半大约需要 60-100 天， HPV 大约需要 70-120 天，而 SARS-CoV2 约为 40-90 天，与HBV和HPV疫苗相比，并没有显著更快的趋势。因此，SARS-CoV2 疫苗的保护效果迅速下降不能归因于 SARS-CoV2 抗体水平下降速度超过其他疫苗。SARS-CoV2 的高受体亲和力对疫苗的保护效果提出了挑战。SARS-CoV2 的受体亲和力为 3-40 nM ，高于具有持久疫苗效力的 HBV (67.1 nM) ，麻疹 (80-400 nM) 和脊髓灰质炎病毒 (110-670 nM) 。病毒与受体的亲和力越高，中和抗体就越难有效阻止病毒与宿主细胞的结合。潜伏期差异也可能导致不同病毒之间疫苗效果的差异。SARS-CoV2 的潜伏期约为 2-10 天。流感病毒约为 1-3 天，麻疹病毒约为 9-14 天，乙肝病毒约为 50-150 天， HPV 约为 50-150天。接种疫苗产生血清抗体可以在病毒发展前中和病毒，而潜伏期短不利于抗体阻止感染。另外，短的潜伏期会使得疫苗的记忆反应赶不上病毒的发展。SARS-CoV2 毒株的持续变异是疫苗保护作用降低和病毒再感染的重要原因之一。由于针对之前病毒株产生的抗体可能无法有效结合新出现的突变抗原位点，实际中和抗体滴度迅速下降。随着 Omicron 变异株的出现，这种影响尤为明显。接种疫苗后，针对 Omicron 的中和抗体滴度是针对 Delta 变株的抗体滴度的 1/10 ，疫苗对 Delta 株提供约 90% 的保护率时，对 Omicron 的保护率仅约 50% 。【新冠的高抗体保护阈值】血清抗体水平与保护效力之间存在相关性，维持中和抗体滴度高于阈值是有效保护的必要条件。对于 HBV 感染的保护阈值水平通常为 10 mIU/mL，在完全接种疫苗后，抗体水平超过该阈值数百倍。麻疹的抗体保护阈值被认为是 120 mIU/mL，疫苗将抗体水平提高到约 1000 mIU/mL。保护脊髓灰质炎病毒感染的中和抗体滴度约为 1:4-8，疫苗可将中和抗体滴度提高到约 1:400-5000 。对于 SARS-CoV2 ，感染或接种疫苗的个体血清抗体水平约为 1:200-1000 ，目前仅知 SARS-CoV2 50% 保护率对应的中和抗体滴度在 1:10-40 之间，而其保护阈值应高于该水平。这些数据表明，远高于阈值的初始抗体滴度与长期保护相关 (图 1A)，而 SARS-CoV2 感染的保护阈值相对较高。图1A 抗体防护病毒感染的影响因素【新冠危险性降低的原因】SARS-CoV2 的突变株尤其是 Omicron ，毒力显著降低， Omicron 刺突蛋白对 TMPRSS2 (跨膜蛋白酶丝氨酸 2)的依赖性更小。由于 TMPRSS2 在肺部的表达水平较高，而 ACE2 从上呼吸道到肺部的表达水平逐渐降低，因此 Omicron 倾向于在上呼吸道而不是肺部感染或传播。由于呼吸道的组织损伤通常不会危及生命，而肺部损伤可能具有致命风险，Omicron 危险性较低的原因很可能在于相比先前的毒株，该变异株对肺部的攻击程度较为有限(图 1B)。图1B 感染或扩增位置影响个体死亡结果【小结】该报道通过对各种病毒及疫苗的比较，表明目前新冠疫苗无法提供长期保护是由于病毒的性质， SARS-CoV2 抗体的衰减速度并非主要原因。SARS-CoV2 在全球范围内大规模感染导致的快速突变、对宿主细胞的高亲和力以及短潜伏期是疫苗不尽如人意的主要原因 (图 1A)。尽管新冠疫苗的长期保护效果有限，但新冠疫苗显著降低了死亡风险，为控制 COVID-19 大流行做出了重要贡献。然而，必须保持警惕，因为如果未来的突变导致感染部位再次转移至肺部，危险可能再次出现 (图 1B)。为了长期预防 SARS-CoV2 以及应对类似的未知病毒，必须制定新的免疫策略，以诱导比目前方法更为有效的免疫反应。原文链接：https://www.nature.com/articles/s41423-024-01132-2识别微信二维码，添加生物制品圈小编，符合条件者即可加入生物制品微信群！请注明：姓名+研究方向！版权声明本公众号所有转载文章系出于传递更多信息之目的，且明确注明来源和作者，不希望被转载的媒体或个人可与我们联系(cbplib@163.com)，我们将立即进行删除处理。所有文章仅代表作者观点，不代表本站立场。

New research shows that the recently emerged BA.2.86 omicron subvariant of the virus that causes COVID-19 can be neutralized by bivalent mRNA vaccine-induced antibodies in the blood, which explains why this variant did not cause a widespread surge as previously feared. New research shows that the recently emerged BA.2.86 omicron subvariant of the virus that causes COVID-19 can be neutralized by bivalent mRNA vaccine-induced antibodies in the blood, which explains why this variant did not cause a widespread surge as previously feared. However, the study in cell cultures showed this SARS-CoV-2 variant can infect human cells that line the lower lung and engage in virus-host cell membrane fusion more efficiently, two features linked to severe disease symptoms. The study is published today (Jan. 8, 2024) in the journal Cell. The BA.2.86 variant of omicron is the ancestor of the currently dominating JN.1 and has about 60 more spike protein mutations than the original, or parent, coronavirus, including over 30 more than its close omicron relatives -- the early BA.2 variant and the recently dominant XBB.1.5 variant among them. These mutations led scientists to worry that so many changes would make the variant as tough to contain as the initial omicron outbreak in 2021-22. "We found that, surprisingly, despite all those 60 mutations combined together, BA.2.86 is not as immune-evasive as the XBB.1.5 variant, which until recently had been dominating the pandemic for months. That's good news," said Shan-Lu Liu, senior author the study and a virology professor in the Department of Veterinary Biosciences at The Ohio State University. "But BA.2.86 appears to have increased infectivity of human lung epithelial cells compared to all omicron variants, so that's a little worrisome. And, consistent with infectivity, it also has increased fusion activity with human lung epithelial cells," said Liu, also a professor in the Department of Microbial Infection and Immunity. "That raises a potential concern about whether or not this virus is more pathogenic compared to recent omicron variants." The published findings coincide with reports from the Centers for Disease Control and Prevention that after a brief increase in BA.2.86 infections, its derived sublineage JN.1 rapidly gained ground in the United States, responsible for an estimated 44% of COVID-19 cases as of Dec. 23, 2023. First detected in July in Europe and the Middle East, BA.2.86 and its sublineages have since been spreading with increasing frequency in different parts of the world. On Nov. 22, the World Health Organization classified BA.2.86 and sublineages as "variants of interest." The Ohio State researchers analyzed neutralizing antibodies in blood serum samples from health care professionals who had received three monovalent vaccine doses or two monovalent vaccines followed by one bivalent vaccine booster, and from first responders who had COVID-19 infections during the wave dominated by the XBB.1.5 variant. They compared the ability of neutralizing antibodies to block infection by BA.2.86, an XBB-derived variant known as FLip, the parent virus and several omicron variants. Overall, antibodies produced by serum from the bivalent vaccine-dosed health care professionals were more efficient at neutralizing BA.2.86 than they were at neutralizing other omicron variants, including XBB.1.5. In contrast, the three monovalent vaccines and previous XBB.1.5 infection were barely effective in blocking infection by BA.2.86. "People who have had a COVID-19 infection should remember that omicron variants are less virulent compared to prior variants such as delta, meaning they don't make most people very sick," Liu said. "If you have less severe disease, the antibodies generated by infection are low -- almost 10-fold lower than vaccine-induced antibodies. That is why you cannot rely on natural infection alone for immunity. "While bivalent vaccine can still neutralize BA.2.86, the efficiency is clearly reduced. Therefore, it is important to get the newest booster vaccine, which is formulated with only XBB.1.5 and has been shown to be effective against BA.2.86," Liu added. However, the researchers were surprised to find that a monoclonal antibody known as S309, which has been shown to inhibit almost all other major omicron variants, does not neutralize BA.2.86. Molecular modeling revealed that some of the BA.2.86 mutations in the spike protein might have changed the conformation and rendered S309 unable to neutralize the new variant, Liu said. Additional experiments pointed to the potential for BA.2.86 to be more likely to cause severe disease than its omicron relatives. Researchers found BA.2.86 was more efficient at infecting a cell line derived from the human lower airway epithelium in the lung. Infection of these cells is greatly facilitated through a cell surface protein, known as TMPRSS2, to promote membrane fusion, and this protein is a known contributor to SARS-CoV-2 infection and disease symptoms in the respiratory tract. First author Panke Qu, a graduate student in Liu's lab, conducted the cell-culture studies using pseudoviruses -- a non-infectious viral core surrounded by different SARS-CoV-2 spike proteins on the surface structured to match known variants. "Because we used a pseudovirus, we need to confirm these findings using the real virus," said Liu, also associate director of Ohio State's Center for Retrovirus Research and a program co-director of the Viruses and Emerging Pathogens Program in Ohio State's Infectious Diseases Institute. "But from our past experience, we know that the infectivity in human epithelial cell lines provides very important information. The concern is whether or not this variant, as well as its descendants including JN.1, will have an increased tendency to infect human lung epithelial cells similar to the parental virus that launched the pandemic in 2020." Liu noted that other labs have recently suggested that JN.1, one of fastest-growing descendants of BA.2.86, is much more resistant to neutralizing antibodies that are effective against BA.2.86. "We know that coronaviruses are prone to viral recombination, which can lead to new variants with huge numbers of mutations that could have increased immune evasion but also disease severity," he said. "That's why surveillance of the variants is still very important, even though we are in the end of year four of the pandemic." This work was supported by anonymous donor funds, the National Institutes of Health, the National Center for Advancing Translational Sciences, the Glenn Barber Fellowship from Ohio State's College of Veterinary Medicine, the Robert J. Anthony Fund for Cardiovascular Research, and Ohio State's Comprehensive Cancer Center and Center for Clinical and Translational Science. Additional co-authors, all from Ohio State, are Kai Xu, Julia Faraone, Negin Goodarzi, Yi-Min Zheng, Claire Carlin, Joseph Bednash, Jeffrey Horowitz, Rama Mallampalli, Linda Saif, Eugene Oltz, Daniel Jones and Richard Gumina.

现有的抗新冠病毒小分子药物主要靶向病毒主蛋白酶或RNA聚合酶，但由于新冠病毒为高突变的RNA病毒，存在产生耐药性的风险。因此，如何应对病毒的耐药性，仍是备受瞩目的关键科学问题。2023年11月21日，复旦大学生物医学研究院孙蕾研究员与上海科技大学免疫化学研究所杨海涛教授、姜标教授，广州实验室陈新文研究员、武汉病毒所张磊砢研究员等团队合作，于Nature系列期刊Nature Communications发表题为“Structure-based discovery of dual pathway inhibitors for SARS-CoV-2 entry”的基于宿主蛋白酶进行抗新冠病毒药物开发的最新研究成果，报道了多种靶向新冠病毒入侵过程中关键宿主蛋白酶TMPRSS2和CTSB/CTSL的抑制剂及其分子机制，并证实同时抑制以上蛋白酶可协同产生更有效的抗病毒作用。该研究为基于宿主蛋白酶的抗新冠病毒广谱性药物开发奠定了重要基础。新冠病毒在入侵过程中，既能通过质膜融合直接入侵(图1左，途径A)，也能在细胞内吞途径中完成膜融合(图1右，途径B)，释放病毒基因组。在两条入侵通路中，膜融合过程的发生分别需要依赖TMPRSS2和CTSB/CTSL对病毒刺突蛋白进行切割并激活其构象，从而介导后续的膜融合反应。由于宿主蛋白酶在新冠病毒的入侵过程中不可或缺的重要地位及其作为宿主蛋白相较于病毒蛋白保守性高，不易突变的特性，被认为是抗新冠病毒广谱性药物开发的理想靶点。图1. 新冠病毒入侵的两条途径及靶向其中宿主蛋白酶的抑制剂研究团队以TMPRSS2和CTSB/CTSL为研究对象，通过高通量筛选发现了多种具有靶向能力的强效抑制剂，并在细胞水平上展现出nM量级的抗病毒效果。研究团队进一步利用X-射线晶体学方法解析了上述多种抑制剂与其相应蛋白靶点的复合物结构，揭示了抑制剂靶向抑制的分子机制。值得一提的是，其中TMPRSS2与抑制剂的复合物结构首次揭示了TMPRSS2完整胞外域的结构信息。此外，研究团队发现联合使用靶向TMPRSS2和CTSB/CTSL的抑制剂分子nafamostat和K777，在抗病毒实验中具有更好的抗病毒效果(EC50=0.9 nM)，表现出“1+1>>2”的协同效应，表明同时抑制两条入侵通路是抗新冠药物开发的有效策略。在上述结构与抗病毒研究基础上，研究团队进一步设计了同时靶向TMPRSS2和CTSB/CTSL的“双活性”抑制剂212-148(图1)，其不仅在酶活试验中展现出双重抑制能力，同时也在细胞水平上展现出对不同新冠病毒突变株如Delta与Omicron感染的拮抗效果。上海科技大学免化所博士后王镐锋、广州实验室副研究员杨琪、上海科技大学免化所博士生刘小策、许孜立、硕士生邵茂林为论文的并列第一作者。上海科技大学杨海涛教授、复旦大学孙蕾研究员、上海科技大学姜标教授，广州实验室陈新文研究员、武汉病毒研究所张磊砢研究员为本文的共同通讯作者。注：文中插图源于 Nature Communications原文链接：https://doi.org/10.1038/s41467-023-42527-5本文仅用于学术分享，转载请注明出处。若有侵权，请联系微信：bioonSir 删除或修改！