Synthetic saccharides to study immunological properties of Streptococcus pneumoni

描述(由申请人提供)：碳水化合物疫苗和疗法的发展已经认识到复杂的糖结构参与了各种损伤和愈合过程。肺炎链球菌(SPN)已经成为老年人肺炎、菌血症和脑膜炎最常见的原因之一，免疫功能低下，尤其是在幼儿中。在所有细菌传染病中，SPN具有最大的公共卫生和经济影响之一。全世界每年有200多万儿童死于肺炎，占五岁以下儿童死亡的近20%，其中一半以上的死亡是由肺炎引起的。在90多个已阐明的SPN血清型中，6A和6B几乎是细菌感染的重要原因。在美国，SPn6A和6B血清型分别占所有侵袭性肺炎球菌病病例的4.7%和7%，SPn6血清型一直被列为全球侵袭性肺炎球菌病的前三大病因之一。由于SPN细菌细胞被多糖壳包围，预防性疫苗接种是对抗细菌入侵的可行工具。通常，在反应中会形成血清型特异性抗体；即使如此，由于SPn6A和6B的碳水化合物核心结构相似，引发的抗体也会产生交叉反应。因此，目前所有获得许可的多组分疫苗中只包含了具有稳定水解性的SPn6B。最近的研究挑战了交叉反应假说，并承认了在未来几代抗SPN疫苗中包括SPn6A结合物的重要性。然而，由于许多原因，实现这一目标具有挑战性，主要原因是纯分离株的可获得性较低。在此，建议开发一种快速策略来获得SPn6-血清组的糖类及其结合物的合成等价物，以确保可靠和可重复性的免疫学研究。最近发现了一种新的6C血清型，它与6B有两个结构单位不同，这吸引了人们对SPn6血清组的额外兴趣。据推测，与目前使用的SPn6B血清型的显著结构差异可能导致对6C的弱交叉保护，并可能导致6C衍生肺炎球菌感染的爆发，就像以前发生的SPn19A血清型一样。首次提出了新出现的血清型寡糖及其结合物的全合成，用于协同免疫学研究。PI研究的长期目标是使普通化学、生物化学和工业受众更容易获得合成复杂碳水化合物和糖共轭化合物，以跟上糖生物学爆炸性领域的步伐。拟议项目的最终目标是开发一种完全合成的疫苗成分，专用于血清型SPn6A和6C型(或对血清型6通用)，适合在未来几代多血清型抗SPN疫苗中实施。在有希望的初步结果的支持下，提出了一种新的硫代亚胺糖基化方法在糖结构合成中的应用，以研究SPn6A的免疫学性质。然后，合成的糖将被转化为多价糖共轭化合物，其免疫学特性将与阿拉巴马大学伯明翰分校的穆恩·纳姆教授合作确定。这项应用的目的是开发一种通用的方法来合成结构上与SPn6-血清组相关的新型糖偶联物，SPn6-血清组是细菌感染的重要原因。公共卫生相关性：拟议研究的健康益处包括有可能发现新的有效的糖疗法来对抗人类的细菌感染。生物医学界的其他好处包括发现了新的有效的合成策略来对复杂的碳水化合物和糖共轭化合物进行排序，从而创造了新的化学方法来应对现代医学的重大挑战。这项研究的一个重要方面是从事这些项目的年轻研究人员将接受的培训。在他们的实验室经验中，他们不仅学习重要的工具，使化学家能够合成、修饰和分析有机分子，而且还开发新的合成方法，并参与最先进的多步合成的阐述。研究人员接触到战略开发和协作生物实验，以解决各种生物医学难题，因此，在化学、生物学和医学之间建立了一座重要的桥梁。

DESCRIPTION (provided by applicant): Involvement of complex glycostructures in a variety of damaging and healing processes has already been acknowledged by development of carbohydrate-based vaccines and therapeutics. The bacteria Streptococcus pneumoniae (SPn) have become one of the most frequent causes of pneumonia, bacteremia, and meningitis in the elderly, immunocompromised, and especially in young children. SPn has one of the largest public health and economic impacts amongst all bacterial infectious diseases. Over 2 million children die annually worldwide due to pneumonia, accounting for almost 20% of deaths under age five with more than half of these deaths attributed to SPn. Amongst over ninety elucidated SPn serotypes, 6A and 6B are nearly equally important causes of bacterial infections. Serotypes SPn6A and 6B account for 4.7 and 7%, respectively, of all cases of invasive pneumococcal disease in the US and the SPn6-serogroup has been consistently ranked within the top three causes of invasive pneumococcal disease worldwide. Since the SPn bacterial cell is surrounded by a polysaccharide capsule, preventive vaccination is a viable tool against the bacterial invasion. Usually, serotype-specific antibodies are formed in response; even so it was believed that due to similarity in the carbohydrate core structures of SPn6A and 6B, the elicited antibodies would be cross-reactive. As a result, only hydrolytically stable SPn6B was included in all currently licensed multi-component vaccines. Recent studies challenged hypothesis of the cross-reactivity and the importance of including the SPn6A conjugates in the future generations of anti-SPn vaccines has been acknowledged. However, the achievement of this is challenging for a number of reasons, major of which is low availability of pure isolates. Herein, development of an expeditious strategy to obtain synthetic equivalents of saccharides of SPn6-serogroup and conjugates thereof to ensure reliable and reproducible immunological studies is proposed. Additional interest to the serogroup SPn6 has recently been drawn by a discovery of a new serotype 6C that differs by two structural units from 6B. It has been postulated that the significant structural difference from the currently used serotype SPn6B may lead to a weak cross-protection against 6C and could result in an outbreak of 6C-derived pneumococcal infections, just as it previously occurred for serotype SPn19A. The first total synthesis of oligosaccharides of the newly arisen serotype and conjugates thereof for collaborative immunological studies is proposed herein. The long-term goal of the PI's research is to make synthetic complex carbohydrates and glycoconjugates more accessible to general chemical, biochemical, and industrial audiences to keep pace with the exploding area of glycobiology. The ultimate goal of the proposed project is to develop a fully synthetic vaccine component, specific to the serotypes SPn6A and 6C (or universal for serogroup 6), suitable for implementing in the future generations of multi-serotype anti-SPn vaccines. Supported by promising preliminary results, the application of a new thioimidate glycosylation method in the synthesis of glycostructures to study immunological properties of SPn6A is proposed. The synthetic saccharides will be then converted into polyvalent glycoconjugates whose immunological properties will be determined in collaboration with Professor Moon Nahm at the University of Alabama at Birmingham. The objective of this application is to develop a general approach to the synthesis of novel glycoconjugates structurally related to SPn6-serogroup, an important cause of bacterial infections. PUBLIC HEALTH RELEVANCE: The health benefits of the proposed research include the potential to discover new and effective glycotherapeutics to fight bacterial infections in humans. Other benefits to the biomedical community include the discovery of new effective synthetic strategies to sequence complex carbohydrates and glycoconjugates, thereby creating new chemical ways to approach major challenges of modern medical sciences. An important aspect of this research is the training that young researchers working on these projects will receive. During their laboratory experience they do not only learn important tools that allow chemists to synthesize, modify and analyze organic molecules, but also develop new synthetic methodologies and participate in the elaboration of state of the art multi-step syntheses. The researchers are exposed to strategy development and collaborative biological experimentations to solve various biomedical puzzles, therefore, building an essential bridge between chemistry, biology, and medicine.