DataSheet_1_An Intranasal OMV-Based Vaccine Induces High Mucosal and Systemic Protecting Immunity Against a SARS-CoV-2 Infection.docx

The development of more effective, accessible, and easy to administer COVID-19 vaccines next to the currently marketed mRNA, viral vector, and whole inactivated virus vaccines is essential to curtailing the SARS-CoV-2 pandemic. A major concern is reduced vaccine-induced immune protection to emerging variants, and therefore booster vaccinations to broaden and strengthen the immune response might be required. Currently, all registered COVID-19 vaccines and the majority of COVID-19 vaccines in development are intramuscularly administered, targeting the induction of systemic immunity. Intranasal vaccines have the capacity to induce local mucosal immunity as well, thereby targeting the primary route of viral entry of SARS-CoV-2 with the potential of blocking transmission. Furthermore, intranasal vaccines offer greater practicality in terms of cost and ease of administration. Currently, only eight out of 112 vaccines in clinical development are administered intranasally. We developed an intranasal COVID-19 subunit vaccine, based on a recombinant, six-proline-stabilized, D614G spike protein (mC-Spike) of SARS-CoV-2 linked via the LPS-binding peptide sequence mCramp (mC) to outer membrane vesicles (OMVs) from Neisseria meningitidis. The spike protein was produced in CHO cells, and after linking to the OMVs, the OMV-mC-Spike vaccine was administered to mice and Syrian hamsters via intranasal or intramuscular prime-boost vaccinations. In all animals that received OMV-mC-Spike, serum-neutralizing antibodies were induced upon vaccination. Importantly, high levels of spike-binding immunoglobulin G (IgG) and A (IgA) antibodies in the nose and lungs were only detected in intranasally vaccinated animals, whereas intramuscular vaccination only induced an IgG response in the serum. Two weeks after their second vaccination, hamsters challenged with SARS-CoV-2 were protected from weight loss and viral replication in the lungs compared to the control groups vaccinated with OMV or spike alone. Histopathology showed no lesions in lungs 7 days after challenge in OMV-mC-Spike-vaccinated hamsters, whereas the control groups did show pathological lesions in the lung. The OMV-mC-Spike candidate vaccine data are very promising and support further development of this novel non-replicating, needle-free, subunit vaccine concept for clinical testing.

相较于目前已上市的mRNA疫苗（mRNA vaccine）、病毒载体疫苗（viral vector vaccine）与全灭活病毒疫苗（whole inactivated virus vaccine），开发更高效、可及性更强且易于接种的新冠疫苗，对遏制SARS-CoV-2大流行至关重要。当前一大核心关切是，疫苗诱导的免疫保护作用会随新型变异株的出现而减弱，因此或许需要开展加强免疫接种，以拓宽并强化机体免疫应答。目前所有已获批的新冠疫苗以及绝大多数在研新冠疫苗均采用肌肉注射给药方式，旨在诱导系统性免疫。而鼻内疫苗还可诱导局部黏膜免疫，靶向SARS-CoV-2的主要病毒入侵途径，具备阻断病毒传播的潜力。此外，鼻内疫苗在成本与接种便捷性上也更具实用性。当前112款在研新冠疫苗中，仅8款采用鼻内给药方式。本研究团队开发了一款鼻内新冠亚单位疫苗，其基于重组六脯氨酸稳定化且携带D614G突变的SARS-CoV-2刺突蛋白（spike protein，mC-Spike），通过脂多糖结合肽序列mCramp（mC）将该蛋白连接至脑膜炎奈瑟菌（Neisseria meningitidis）来源的外膜囊泡（OMVs）。该刺突蛋白在CHO细胞（中国仓鼠卵巢细胞）中表达，与外膜囊泡结合后，研究人员通过鼻内或肌肉注射的初免-加强免疫策略，将OMV-mC-Spike疫苗接种至小鼠与叙利亚金黄地鼠体内。在所有接种OMV-mC-Spike疫苗的动物体内，接种后均可诱导出血清中和抗体。值得注意的是，仅鼻内接种的动物可在鼻腔与肺部检测到高水平的刺突结合免疫球蛋白G（IgG）与免疫球蛋白A（IgA）抗体，而肌肉注射仅能诱导血清中的IgG应答。在第二次接种两周后，用SARS-CoV-2攻毒的金黄地鼠相较于接种单独外膜囊泡或单独刺突蛋白的对照组，未出现体重减轻，且肺部未检测到病毒复制。组织病理学检测显示，攻毒后7天，接种OMV-mC-Spike疫苗的金黄地鼠肺部无任何病变，而对照组肺部则出现了病理损伤。OMV-mC-Spike候选疫苗的数据表现极具前景，支持进一步推进这一新型非复制型、无针亚单位疫苗理念的临床测试。