VP24

Milestone signifies ongoing effort to help prepare for outbreaks of Zaire ebolavirus RAHWAY, N.J.--(BUSINESS WIRE)-- Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced today that the European Commission (EC) has approved an expanded indication for ERVEBO for active immunization of individuals 1 year of age or older to protect against Ebola Virus Disease (EVD) caused by Zaire ebolavirus. The EC’s decision follows the positive opinion from the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) received on July 20, 2023. The vaccine was previously approved for use in the European Union (EU) for individuals 18 years of age or older. The use of ERVEBO should be in accordance with official recommendations. “Ebola virus disease is severe and potentially life-threatening for both children and adults. The European Commission’s expanded approval of ERVEBO for children 1 year of age and older is an important milestone for the prevention of disease caused by Zaire ebolavirus,” said Dr. Eliav Barr, senior vice president, head of global clinical development and chief medical officer, Merck Research Laboratories. “When outbreaks of Ebola virus disease occur, they can quickly become a public health crisis. We are proud to play a role, alongside the global public health community, in helping to prepare for potential outbreaks of Zaire ebolavirus.” In January 2021, Merck confirmed an agreement with UNICEF to establish the world’s first global Ebola vaccine stockpile with ERVEBO to support future Zaire ebolavirus outbreak preparedness and response efforts. To date, over 500,000 doses of the licensed vaccine have been delivered to the stockpile, which is administered by the International Coordinating Group on Vaccine Provision. Selected Safety Information for ERVEBO CONTRAINDICATIONS Do not administer ERVEBO to individuals with a history of a severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine, including rice protein. WARNINGS AND PRECAUTIONS Management of Acute Allergic Reactions Among 18,616 participants vaccinated with at least one dose of ERVEBO in clinical trials, there were two reports of anaphylaxis. Monitor individuals for signs and symptoms of hypersensitivity reactions following vaccination with ERVEBO. Appropriate medical treatment and supervision must be available in case of an anaphylactic event following the administration of ERVEBO. Limitations of Vaccine Effectiveness Vaccination with ERVEBO may not protect all individuals. Vaccinated individuals should continue to adhere to infection control practices to prevent Zaire ebolavirus infection and transmission. Immunocompromised Individuals The safety and effectiveness of ERVEBO have not been assessed in immunocompromised individuals. The effectiveness of ERVEBO in immunocompromised individuals may be diminished. The risk of vaccination with ERVEBO, a live virus vaccine, in immunocompromised individuals should be weighed against the risk of disease due to Zaire ebolavirus. Transmission Vaccine virus RNA has been detected by RT-PCR in blood, saliva, urine, and fluid from skin vesicles of vaccinated individuals. Transmission of vaccine virus is a theoretical possibility. ADVERSE REACTIONS The most commonly reported local and systemic adverse events in clinical trials were: Individuals 18 years of age and older: injection-site pain (70%); headache (55%); feverishness (39%); muscle pain (33%); somnolence, reduced activity, fatigue (26%); joint pain, arthralgia (19%); chills (17%); injection-site swelling (17%); decreased appetite (15%); abdominal pain (13%); injection-site redness (12%); nausea (10%); arthritis (5%); vomiting (4%), rash (4%); abnormal sweating (3%) and mouth ulceration (2%). Individuals 12 months through 2 years of age: feverishness (83%); crying (31%); decreased appetite (27%); injection-site pain (26%); somnolence, reduced activity, fatigue (20%); diarrhea (19%); vomiting (17%); irritability (11%); screaming (10%); mouth ulceration (6%); chills (5%); injection-site swelling (5%); headache (4%); abdominal pain (2%); abnormal sweating (2%) and injection-site erythema (1%). Individuals 3 years through 11 years of age: feverishness (65%); headache (50%); injection-site pain (40%); decreased appetite (24%); somnolence, reduced activity, fatigue (22%); abdominal pain (21%); chills (14%); myalgia (12%); vomiting (11%); dizziness (8%); nausea (8%); injection-site pruritus (7%); crying (3%); arthralgia (3%); diarrhea (3%); injection-site swelling (3%); abnormal sweating (1%); mouth ulceration (2%) and irritability (1%). Individuals 12 years through 17 years of age: headache (59%); injection-site pain (52%); feverishness (48%); myalgia (30%); somnolence, reduced activity, fatigue (28%); decreased appetite (21%); chills (19%); dizziness (17%); abdominal pain (16%); arthralgia (16%); nausea (8%); abnormal sweating (5%); diarrhea (4%); vomiting (4%); injection-site pruritus (3%); injection-site swelling (3%) and mouth ulceration (2%). DRUG INTERACTIONS Interference with Laboratory Tests Following vaccination with ERVEBO, individuals may test positive for anti-Ebola glycoprotein (GP) antibody and/or Ebola GP nucleic acid or antigens. GP-based testing may have limited diagnostic value during the period of vaccine viremia, in the presence of vaccine-derived Ebola GP, and following antibody response to the vaccine. USE IN SPECIFIC POPULATIONS There are no adequate and well-controlled studies of ERVEBO in pregnant women, and human data available from clinical trials with ERVEBO are insufficient to establish the presence or absence of vaccine-associated risk during pregnancy. Human data are not available to assess the impact of ERVEBO on milk production, its presence in breast milk, or its effects on the breastfed child. INDICATIONS AND USAGE IN THE U.S. ERVEBO® is indicated for the prevention of disease caused by Zaire ebolavirus in individuals 12 months of age and older. Limitations Of Use The duration of protection conferred by ERVEBO is unknown. ERVEBO does not protect against other species of Ebolavirus or Marburgvirus. Effectiveness of the vaccine when administered concurrently with antiviral medication, immune globulin (IG), and/or blood or plasma transfusions is unknown. About Ebola Virus Disease Ebola virus disease is a rapidly progressive, severe, potentially fatal and transmissible hemorrhagic illness caused by infection with one of the Ebola virus species. While there are six identified Ebola virus species, the Zaire ebolavirus strain has been the leading cause of outbreaks over the last 20 years. The average fatality rate for Ebola virus disease is approximately 50% but has ranged from 25% to 90% in previous outbreaks. Human-to-human transmission can occur via blood or bodily fluids, objects (like needles and syringes), possibly from contact with semen from a man who has recovered from Ebola, or direct contact through broken skin or mucous membranes. About ERVEBO® (Ebola Zaire Vaccine, Live) Suspension for intramuscular injection ERVEBO® is indicated for the prevention of disease caused by Zaire ebolavirus in individuals 12 months of age and older. ERVEBO is a live recombinant viral vaccine consisting of a vesicular stomatitis virus (VSV) backbone deleted for the VSV envelope glycoprotein and substituted with the envelope glycoprotein of the Zaire ebolavirus (Kikwit 1995 strain). ERVEBO was initially engineered by scientists from the Public Health Agency of Canada’s National Microbiology Laboratory and the technology was subsequently licensed by a subsidiary of NewLink Genetics Corporation now known as Lumos Pharma, Inc. Merck licensed the vaccine in 2014 and led research and development efforts in collaboration with a number of public health organizations to enable a broad clinical development program. This project has been funded in part with federal funds from the U.S. Department of Health and Human Services, Administration for Strategic Preparedness and Response, Biomedical Advanced Research and Development Authority (BARDA), under contract number HHSO100201700012C. The National Institute of Allergy and Infectious Diseases (NIAID), L’institut National de la Santé et de la Recherche Médicale (INSERM), and the London School of Hygiene and Tropical Medicine (LSHTM) sponsored the PREVAC study, designed to evaluate the safety and immunogenicity of two Ebola virus disease vaccine candidates, including ERVEBO, in adults and children aged 12 months and older. ERVEBO is approved in the European Union, United Kingdom, United States, Canada, Switzerland, and 10 countries in Africa. About Merck At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities. For more information, visit and connect with us on Twitter, Facebook, Instagram, YouTube and LinkedIn. Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA This news release of Merck & Co., Inc., Rahway, N.J., USA (the “company”) includes “forward-looking statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the company’s management and are subject to significant risks and uncertainties. There can be no guarantees with respect to pipeline candidates that the candidates will receive the necessary regulatory approvals or that they will prove to be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements. Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic factors, including interest rate and currency exchange rate fluctuations; the impact of the global outbreak of novel coronavirus disease (COVID-19); the impact of pharmaceutical industry regulation and health care legislation in the United States and internationally; global trends toward health care cost containment; technological advances, new products and patents attained by competitors; challenges inherent in new product development, including obtaining regulatory approval; the company’s ability to accurately predict future market conditions; manufacturing difficulties or delays; financial instability of international economies and sovereign risk; dependence on the effectiveness of the company’s patents and other protections for innovative products; and the exposure to litigation, including patent litigation, and/or regulatory actions. The company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the company’s Annual Report on Form 10-K for the year ended December 31, 2022 and the company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site ( ). Please see Prescribing Information for ERVEBO at and Patient Information for ERVEBO at . View source version on businesswire.com: Contacts Media Contacts: Olivia Finucane 00 / + 44 7881 262476 Kimberly Petrillo (267) 742-2813 Investor Contacts: Alexis Constantine (732) 594-1578 Peter Dannenbaum (732) 594-1579 Source: Merck & Co., Inc. View this news release online at:

Merck continues progress in helping to protect people at risk of Zaire ebolavirus disease RAHWAY, N.J.--(BUSINESS WIRE)-- Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced today that the U.S. Food and Drug Administration (FDA) has approved an expanded indication for ERVEBO, which is now indicated for the prevention of disease caused by Zaire ebolavirus in individuals 12 months of age and older. The vaccine was previously approved for use in individuals 18 years of age and older. ERVEBO does not protect against other species of Ebolavirus or Marburgvirus and the duration of protection conferred by ERVEBO is unknown. The effectiveness of the vaccine when administered concurrently with antiviral medication, immune globulin (IG), and/or blood or plasma transfusions is unknown. ERVEBO includes a contraindication for individuals with a history of a severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine, including rice protein. “Ebola virus disease is contagious and potentially deadly in both children and adults. We’re proud of the approval of ERVEBO for the prevention of disease caused by Zaire ebolavirus in children as young as 12 months old, which is another milestone in our continued commitment to help address the global health threat caused by Zaire ebolavirus,” said Dr. Eliav Barr, senior vice president, head of global clinical development and chief medical officer, Merck Research Laboratories. Separately, on July 20, 2023, the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) recommended the expanded approval of ERVEBO® [Ebola Zaire Vaccine, (rVSVΔG-ZEBOV-GP) live], for active immunization of individuals 1 year of age or older to protect against Ebola Virus Disease (EVD) caused by Zaire ebolavirus. ERVEBO is currently authorized for use in the European Union (EU) for individuals 18 years of age and older. The CHMP opinion will now be considered by the European Commission for amending the marketing authorization, and a final decision is expected in the third quarter of 2023. In January 2021, Merck confirmed an agreement with UNICEF to establish the world’s first global Ebola vaccine stockpile with ERVEBO to support future Zaire ebolavirus outbreak preparedness and response efforts. As of March 2023, over 500,000 doses of the licensed vaccine have been delivered to the stockpile, which is administered by the International Coordinating Group on Vaccine Provision. Selected Safety Information for ERVEBO CONTRAINDICATIONS Do not administer ERVEBO to individuals with a history of a severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine, including rice protein. WARNINGS AND PRECAUTIONS Management of Acute Allergic Reactions Among 18,616 participants vaccinated with at least one dose of ERVEBO in clinical trials, there were two reports of anaphylaxis. Monitor individuals for signs and symptoms of hypersensitivity reactions following vaccination with ERVEBO. Appropriate medical treatment and supervision must be available in case of an anaphylactic event following the administration of ERVEBO. Limitations of Vaccine Effectiveness Vaccination with ERVEBO may not protect all individuals. Vaccinated individuals should continue to adhere to infection control practices to prevent Zaire ebolavirus infection and transmission. Immunocompromised Individuals The safety and effectiveness of ERVEBO have not been assessed in immunocompromised individuals. The effectiveness of ERVEBO in immunocompromised individuals may be diminished. The risk of vaccination with ERVEBO, a live virus vaccine, in immunocompromised individuals should be weighed against the risk of disease due to Zaire ebolavirus. Transmission Vaccine virus RNA has been detected by RT-PCR in blood, saliva, urine, and fluid from skin vesicles of vaccinated individuals. Transmission of vaccine virus is a theoretical possibility. ADVERSE REACTIONS The most commonly reported local and systemic adverse events in clinical trials were: Individuals 18 years of age and older: injection‑site pain (70%); headache (55%); feverishness (39%); muscle pain (33%); somnolence, reduced activity, fatigue (26%); joint pain, arthralgia (19%); chills (17%); injection-site swelling (17%); decreased appetite (15%); abdominal pain (13%); injection-site redness (12%); nausea (10%); arthritis (5%); vomiting (4%), rash (4%); abnormal sweating (3%) and mouth ulceration (2%). Individuals 12 months through 2 years of age: feverishness (83%); crying (31%); decreased appetite (27%); injection-site pain (26%); somnolence, reduced activity, fatigue (20%); diarrhea (19%); vomiting (17%); irritability (11%); screaming (10%); mouth ulceration (6%); chills (5%); injection-site swelling (5%); headache (4%); abdominal pain (2%); abnormal sweating (2%) and injection-site erythema (1%). Individuals 3 years through 11 years of age: feverishness (65%); headache (50%); injection-site pain (40%); decreased appetite (24%); somnolence, reduced activity, fatigue (22%); abdominal pain (21%); chills (14%); myalgia (12%); vomiting (11%); dizziness (8%); nausea (8%); injection-site pruritus (7%); crying (3%); arthralgia (3%); diarrhea (3%); injection-site swelling (3%); abnormal sweating (1%); mouth ulceration (2%) and irritability (1%). Individuals 12 years through 17 years of age: headache (59%); injection-site pain (52%); feverishness (48%); myalgia (30%); somnolence, reduced activity, fatigue (28%); decreased appetite (21%); chills (19%); dizziness (17%); abdominal pain (16%); arthralgia (16%); nausea (8%); abnormal sweating (5%); diarrhea (4%); vomiting (4%); injection-site pruritus (3%); injection-site swelling (3%) and mouth ulceration (2%). DRUG INTERACTIONS Interference with Laboratory Tests Following vaccination with ERVEBO, individuals may test positive for anti-Ebola glycoprotein (GP) antibody and/or Ebola GP nucleic acid or antigens. GP-based testing may have limited diagnostic value during the period of vaccine viremia, in the presence of vaccine-derived Ebola GP, and following antibody response to the vaccine. USE IN SPECIFIC POPULATIONS There are no adequate and well-controlled studies of ERVEBO in pregnant women, and human data available from clinical trials with ERVEBO are insufficient to establish the presence or absence of vaccine-associated risk during pregnancy. Human data are not available to assess the impact of ERVEBO on milk production, its presence in breast milk, or its effects on the breastfed child. INDICATIONS AND USAGE ERVEBO® is indicated for the prevention of disease caused by Zaire ebolavirus in individuals 12 months of age and older. Limitations Of Use The duration of protection conferred by ERVEBO is unknown. ERVEBO does not protect against other species of Ebolavirus or Marburgvirus. Effectiveness of the vaccine when administered concurrently with antiviral medication, immune globulin (IG), and/or blood or plasma transfusions is unknown. About Ebola Virus Disease Ebola virus disease is a rapidly progressive, severe, potentially fatal and transmissible hemorrhagic illness caused by infection with one of the Ebola virus species. While there are six identified Ebola virus species, the Zaire ebolavirus strain has been the leading cause of outbreaks over the last 20 years. The average fatality rate for Ebola virus disease is approximately 50% but has ranged from 25% to 90% in previous outbreaks. Human-to-human transmission can occur via blood or bodily fluids, objects (like needles and syringes), possibly from contact with semen from a man who has recovered from Ebola, or direct contact through broken skin or mucous membranes. About ERVEBO® (Ebola Zaire Vaccine, Live) Suspension for intramuscular injection ERVEBO® is indicated for the prevention of disease caused by Zaire ebolavirus in individuals 12 months of age and older. ERVEBO is a live recombinant viral vaccine consisting of a vesicular stomatitis virus (VSV) backbone deleted for the VSV envelope glycoprotein and substituted with the envelope glycoprotein of the Zaire ebolavirus (Kikwit 1995 strain). ERVEBO was initially engineered by scientists from the Public Health Agency of Canada’s National Microbiology Laboratory and the technology was subsequently licensed by a subsidiary of NewLink Genetics Corporation now known as Lumos Pharma, Inc. Merck licensed the vaccine in 2014 and led research and development efforts in collaboration with a number of public health organizations to enable a broad clinical development program. This project has been funded in part with federal funds from the U.S. Department of Health and Human Services, Administration for Strategic Preparedness and Response, Biomedical Advanced Research and Development Authority (BARDA), under contract number HHSO100201700012C. The National Institute of Allergy and Infectious Diseases (NIAID), L’institut National de la Santé et de la Recherche Médicale (INSERM), and the London School of Hygiene and Tropical Medicine (LSHTM) sponsored the PREVAC study, designed to evaluate the safety and immunogenicity of two Ebola virus disease vaccine candidates, including ERVEBO, in adults and children aged 12 months and older. ERVEBO is approved in the European Union, United Kingdom, United States, Canada, Switzerland, and 10 countries in Africa. About Merck At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities. For more information, visit and connect with us on Twitter, Facebook, Instagram, YouTube and LinkedIn. Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA This news release of Merck & Co., Inc., Rahway, N.J., USA (the “company”) includes “forward-looking statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the company’s management and are subject to significant risks and uncertainties. There can be no guarantees with respect to pipeline candidates that the candidates will receive the necessary regulatory approvals or that they will prove to be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements. Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic factors, including interest rate and currency exchange rate fluctuations; the impact of the global outbreak of novel coronavirus disease (COVID-19); the impact of pharmaceutical industry regulation and health care legislation in the United States and internationally; global trends toward health care cost containment; technological advances, new products and patents attained by competitors; challenges inherent in new product development, including obtaining regulatory approval; the company’s ability to accurately predict future market conditions; manufacturing difficulties or delays; financial instability of international economies and sovereign risk; dependence on the effectiveness of the company’s patents and other protections for innovative products; and the exposure to litigation, including patent litigation, and/or regulatory actions. The company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the company’s Annual Report on Form 10-K for the year ended December 31, 2022 and the company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site ( ). Please see Prescribing Information for ERVEBO at and Patient Information for ERVEBO at . ​ View source version on businesswire.com: Contacts Media: Julie Cunningham (617) 519-6264 Kimberly Petrillo (267) 742-2813 Investors: Alexis Constantine (732) 594-1578 Peter Dannenbaum (732) 594-1579 Source: Merck & Co., Inc. ​ View this news release online at:

从 2014 年到 2016 年，在西非地区出现的埃博拉疫情，是自 1976 年首次发现埃博拉病毒以来，爆发规模最大，最严重的一次埃博拉疫情。埃博拉病毒（EBOV）一种烈性病原体，感染人体后，可引发严重的出血热，平均致死率为 50%，以往疫情中的致死率为 25%-90%之间。如同埃博拉病毒（EBOV）和新冠病毒一样，绝大多数新出现的病毒也是从动物传播到人体，这使得我们很难预测何时何地会爆发感染何种病毒引发的疫情。全球化和交通的改善，让人们可以触达世界上各种偏远的地区，这也使得新型病毒引发疫情的频率和规模大幅增加，因此，人们必须要加强快速研发预防性病毒疫苗的能力。2022 年 10 月 24 号，BioNTech 公司 CEO Ugur Sahin 在 Molecular Therapy 发表文章：Self-amplifying RNA vaccine protects mice against lethal Ebola virus infection，他们从抗原的组成和接种路线出发，成功开发出预防 EBOV 感染致死的自复制 RNA（saRNA）疫苗。用单独表达 GP 或者共表达 NP 的 saRNA 疫苗免疫小鼠能触发抗原特异性的免疫反应，产生具有中和活性的 GP 特异性抗体，特异性的 CD4+T 细胞和 CD8+T 细胞。同时，采用肌肉注射 EBOV 自复制 RNA 疫苗要比皮内注射能够更好地触发免疫效果。最后，他们发现接种两针表达二价自复制疫苗(5ug GP-saRNA+2.5ug NP-saRNA)或者单价自复制疫苗（5ug GP-saRNA）能够保护感染 EBOV 的小鼠免于死亡。此外，他们还发现即便接种一针表达 GP+NP 抗原的二价自复制疫苗也能保护小鼠免于 EBOV 感染带来的致死效应。总体来看，表达 EBOV 抗原的自复制 RNA 疫苗是一种非常有前景的疫苗。本期分享围绕这款埃博拉病毒自复制 RNA 疫苗展开，我们主要进行以下几个方面的探讨:埃博拉病毒 GP 和 NP 抗原的结构和功能。基于病毒载体的埃博拉病毒疫苗埃博拉病毒自复制 RNA 疫苗的小鼠体内免疫数据1   EBOV 抗原的结构和功能EBOV（埃博拉病毒）属于丝状病毒科，是一个有包膜的，单链负链 RNA 病毒。EBOV 基因组长达 19kb，由 7 个结构蛋白基因组成：NP，VP35,VP40,GP,VP30,VP24,L。然而，由于 GP 基因的 RNA 编辑和翻译后修饰，EBOV 能够合成的蛋白种类要超过 7 个。GP 基因可以编码 3 种蛋白：sGP，GP，ssGP。图 1：埃博拉病毒的基因组结构以及编码的抗原。1.1   sGP 抗原sGP 是一个由 363 个氨基酸组成的非结构蛋白，称为分泌型 GP（sGP）。sGP 的前体会被 Furin 切割产生成熟的 sGP 和一个高度 O-连接糖基化的，分泌型的小单体非结构蛋白，称为△-peptide。两个相互平行的 sGP 单体通过两个二硫键连接（Cys53-Cys53 和 Cys306-Cys306）。在感染 EBOV 的病人血清中会检测到大量的 sGP。幸存者血清中的抗体对于 sGP 的识别能力要优于 GP。因此，sGP 通过结合 EBOV 感染机体后触发的抗体，在 EBOV 逃脱体液免疫方面发挥着非常重要的作用。1.2   GP 抗原GP 基因的一个发卡 Loop 结构内有 7 个连续的腺嘌呤核苷酸，当 L 聚合酶转录至此时会发生卡顿，可能会插入一个额外的腺嘌呤核苷酸，引发移码，最终翻译产生 676 个氨基酸的 I 型跨膜糖蛋白 Pre-GP。由于发生移码突变，GP 和 sGP 在 N 端具有相同的 295 个氨基酸，在 C 端具有不同的序列。不同的 C 末端会导致不同的二硫键模式和不同的蛋白结构。尽管 sGP 是一个二聚体形式，但是 GP 的最终结构是一个三聚体。preGP 被 Furin 切割产生两个亚基：GP1 与 GP2，这两个亚基之间通过 GP1 的 Cys53 和 GP2 的 Cys609 之间的二硫键连接。GP1+GP2 异源二聚体组装成位于病毒粒子表面的 450KDa 的三聚体。TNF-α转化酶（TACE）通过靠近跨膜锚定区域的切割位点能够将附着在病毒粒子表面的 GP 释放。GP 是唯一附着在 EBOV 病毒粒子表面的蛋白，介导 EBOV 进入宿主细胞的过程。GP1 介导病毒附着在宿主细胞表面，而 GP2 参与膜融合过程。在 HEK293T 细胞中，过表达 GP 蛋白会引发细胞毒性，这种细胞毒性由 GP 蛋白中富含 N-或者 O-糖苷键修饰的结构域决定，称为类粘蛋白结构域（mucin-like domain）。1.3   ssGP 抗原当 GP 基因转录时额外插入腺嘌呤核苷酸会产生 GP，缺失一个或者添加 2 个腺嘌呤核苷酸时会产生第三个蛋白，称为 ssGP，是一个非结构的单体小 sGP，与 sGP，GP 具有共同的 295 个 N 末端氨基酸，但是 C 端具有不同的氨基酸组成。EBOV 最为独特的特征是感染期间，会从细胞中释放可溶解形式的糖蛋白。在感染 EBOV 的病人和动物血清中会检测到大量的 sGP 和截断的表面蛋白 GP。由于 sGP 缺乏跨膜锚定结构域，因此可通过经典的分泌途径从细胞中释放出来。位于病毒粒子表面的 GP 会被 TACE 切割，称为脱落 GP。溶解形式的脱落 GP 能够结合和隔离靶向病毒粒子表面 GP 的中和抗体。图 2：埃博拉病毒 GP 抗原的转录和翻译后加过程。1.4   NP 抗原NP 是与病毒基因组连接在一起的核蛋白（nucleoprotein），能够与聚合酶辅因子（VP35），转录激活因子（VP30），依赖于 RNA 的 RNA 聚合酶（L）组装成螺旋形的核衣壳（nucleocapsid，NC）。构成核衣壳的病毒蛋白与病毒基因组的复制和转录有关。VP24 是一个极小的病毒基质蛋白，对于核衣壳复合物的组装也是必需的。当 NP 单独在细胞中表达时，会同细胞内的 RNA 形成一个松弛的类似线圈装的结构（coli-like structure）。当 NP 和 VP24 以及 VP25 在细胞中共表达时，能够在细胞质中形成类似核衣壳的结构，这种结构与 EBOV 感染的细胞中观察的核衣壳结构在形态上没有差异。EBOV 病毒基因组负链 RNA 转录形成 mRNA，释放到细胞质中，翻译出病毒蛋白。NP 与 VP35，VP40，VP30，VP24 形成小包涵体（small inclusions），这种包涵体在靠近细胞核的位置会变得更大。在包涵体的边缘位置，形成核衣壳。VP40 与核衣壳结合在一起，有助于将其运输到细胞膜。另外一种情况是，核衣壳初始的时候就会结合很多 VP40，然后被转运到细胞质膜，然后被膜结合型的 VP40 包封。GP 经过内质网，核糖体，转移至细胞膜，组装形成病毒颗粒。图 3：埃博拉病毒在宿主细胞内的组装过程。2   EBOV 疫苗研发进展目前，存在 4 种能够引发致命性疾病的埃博拉病毒：SUDV，BDBV，TAFV，EBOV。在埃博拉疫苗研发的近期进展中，有 5 款基于病毒载体的埃博拉病毒疫苗走在最前面:Ervebo(rVSV-EBOV)，是一款由 Merck 生产的表达 EBOV GP 抗原的单价疫苗，也是唯一一款被证实有临床效果的疫苗，已获得 FDA 和 EMA 的批准。Zabdeno/Mvabea，是一款由 Johnson&Johnson 生产的多价疫苗，初始免疫接种表达 EBOV GP 抗原的 Zabdeno 疫苗，加强免疫接种表达多种混合抗原的 Mvabea 疫苗，在某些特定情况下被 EMA 批准使用。ChAd3-EBOZ/MVA-BN-Filo，是一款由 GlaxoSmithKline 合作研发的多价疫苗，初始免疫接种表达 EBOV GP 抗原的 cAd3-EBOZ/EBOV 疫苗，加强免疫接种表达多种混合抗原的 Mvabea 疫苗，目前还未被 FDA 或者 EMA 批准使用。Ad5-EBOV，是一款由康希诺和军事医学院研发的单价疫苗，于 2017 年取得 1 类生物制品新药注册证书。GamEvac，是一款俄罗斯流行病学和微生物研究生开发的异源疫苗，通过 rVSV 和 Ad5 表达 EBOV GP 抗原。图 4:基于病毒载体的处于领先地位的 EBOV 疫苗。3   BioNtech 开发的 EBOV 自复制 RNA 疫苗3.1   细胞水平抗原表达BioNtech 设计的 saRNA，采用 ARCA 共转录加帽的方式。将 2ug GP-saRNA，NP-saRNA 或者编码 GP/NP 的质粒转染 HuH7 细胞，24h 以后，可以看到 NP（绿色）位于细胞核附近不同大小的包涵体中，而 GP（红色）定位于细胞质膜上病毒出芽的位置。通过 WB 分析病毒蛋白的表达情况，发现能够检测到两条 GP 带，180KDa 的 GP1 亚基和 110KDa 的 GP 前体。图 5：saRNA 编码的 GP 或者 NP 抗原可以在细胞中高效表达。3.2   体液免疫和细胞免疫将 LNP 包封的共表达 GP+NP 抗原的 saRNA 二价疫苗或者只表达 GP 抗原的 saRNA 单价疫苗免疫小鼠，均能够触发特异性的 GP 或者 NP 血清结合抗体，而且这两种抗原相对于靶向彼此的体液免疫不存在相互干扰。同时，还在血清中检测到非常强的靶向 EBOV 中和抗体。此外，研究人员还发现添加 NP 抗原能够加强 CD8+T 细胞免疫反应。图 6：LNP 包封的 EBOV 自复制 RNA 疫苗在小鼠体内的免疫原性。3.3   两种接种路线免疫效果的差异通过皮内注射 1/5 标准肌肉注射剂量的流感疫苗能够触发相似或者更好的免疫效果。因此，研究人员想保持 GP:NP-saRNA 为 2:1，测试高剂量 7.5ug saRNA 和低剂量 1.5ug saRNA 通过肌肉注射和皮内注射两种接种路线免疫小鼠所触发的免疫效果差异。结果发现，不同接种剂量和接种路线触发的血清结合抗体存在差异：高剂量肌肉注射>低剂量肌肉注射>高剂量皮内注射，血清中和抗体活性也存在类似的想象。非常有意思的是，研究人员发现皮内注射自复制 RNA 疫苗引发的 CD8+ T 细胞反应要明显低于同等剂量的肌肉注射的。图 7：肌肉注射 EBOV 自复制 RNA 疫苗触发的免疫效果要优于皮内注射。3.4   有效保护 EBOV 感染小鼠免于死亡小鼠肌肉注射两针表达 GP，NP 或者 GP+NP 的高剂量 saRNA，结果发现，注射 GP 或者 GP+NP saRNA 疫苗的小鼠体内产生的血清结合抗体 IgG 是相当的，然而注射 NP saRNA 疫苗的小鼠血清中靶向 NP 的血清结合抗体 IgG 要明显低于注射 GP+NP saRNA 疫苗。注射 GP 或者 GP+NP saRNA 疫苗的小鼠血清中检测到中和抗体活性，但是，在注射 NP saRNA 疫苗的小鼠血清中并没有检测到中和抗体的活性。用 GP 或者 GP+NP saRNA 疫苗免疫小鼠后，在 EBOV 感染后的第 5 天或者第 14 天，在血清中并没有发现感染性的病毒。而且，在这些小鼠的脾脏和肝脏中也没有检测到病毒基因组。相反，在用 NP saRNA 疫苗免疫小鼠后，在 EBOV 感染后的第 5 天处死小鼠后，在血清和脏器中检测到病毒 RNA 和感染性病毒的存在。研究人员用只表达 GP 抗原或者共表达 NP 抗原的 saRNA 疫苗初始免疫和加强免疫小鼠，发现能够保护感染 EBOV 的小鼠免于死亡。尽管 NP 可以触发特异性的 CD8+T 细胞反应，但是，单独接种表达 NP 抗原的 saRNA 疫苗，无法保护感染 EBOV 的小鼠免于死亡。最后，研究人员还惊喜地发现，接种一针 GP+NP saRNA 疫苗的小鼠感染 EBOV 病毒后，也可免于死亡。图 8：用 GP 或者 NP 或者 GP+NP 自复制 RNA 疫苗二次免疫小鼠，可保护感染 EBOV 的小鼠免于死亡。4   结论BioNTech 开发的 EBOV 自复制 RNA 疫苗充分展现出自复 RNA 技术的巨大优势，可以完全保护接种疫苗的小鼠感染 EBOV 后，免于死亡。自复制 RNA 疫苗之所以可以触发效果更好的免疫效果，主要是两个方面的原因造成的：首先，自复制 RNA 在宿主细胞中发生复制后会产生大量的病毒抗原，最终耗尽宿主细胞的资源，造成宿主细胞的死亡和裂解，然后释放出来的抗原能够持续刺激 B 细胞，产生大量的特异性抗体。其次，自复制 RNA 在宿主细胞中的复制过程会刺激天然免疫反应，充当佐剂，提升适应性免疫反应。总的来说，编码抗原的 RNA 在宿主细胞内的大量复制和复制过程对天然免疫反应的刺激促使自复制 RNA 疫苗能够以极低的剂量触发强烈的免疫反应。此外，尽管 EBOV 自复制 RNA 疫苗在小鼠模型中具有非常好的免疫效果，但是，鉴于其他类型的 EBOV 疫苗，例如灭活疫苗或者重组蛋白疫苗，无法在非人灵长类动物身上取得良好的免疫效果，所以，BioNTech 开发的这款 EBOV 自复制 RNA 疫苗还需要在非人灵长类动物身上进行进一步的测试。题图来自：https://medicalxpress.com/news/2022-09-stem-cells-liver-ebola-virus.html.参考文献：1.Current state of Ebola virus vaccines: A snapshot.2.The spatio-temporal distribution dynamics of Ebola virus proteins and RNA in infected cells.3.Ebolavirus glycoprotein structure and mechanism of entry.4.Shed GP of Ebola Virus Triggers Immune Activation and Increased Vascular Permeability.