Synthetic saccharides to study immunological properties of Streptococcus pneumoni

描述（由申请人提供）：复杂糖结构参与各种损伤和愈合过程已经被基于碳水化合物的疫苗和疗法的发展所承认。肺炎链球菌（SPn）已成为老年人、免疫功能低下者，尤其是幼儿中肺炎、菌血症和脑膜炎的最常见病因之一。在所有细菌性传染病中，SPn对公共卫生和经济的影响最大。全世界每年有200多万儿童死于肺炎，占五岁以下儿童死亡人数的近20%，其中一半以上死于急性呼吸道感染。在90多种已知的SPn血清型中，6A和6B几乎是同样重要的细菌感染原因。SPn6A和6B血清型分别占美国所有侵袭性肺炎球菌病病例的4.7%和7%，spn6血清型在全球范围内一直排在侵袭性肺炎球菌病的前三大病因之列。由于SPn细菌细胞被多糖胶囊包围，预防性接种是对抗细菌入侵的可行工具。通常，血清型特异性抗体会在反应中形成；尽管如此，由于SPn6A和6B的碳水化合物核心结构相似，被诱导的抗体会发生交叉反应。因此，只有水解稳定的SPn6B被包括在所有目前许可的多组分疫苗中。最近的研究对交叉反应性的假设提出了质疑，并认识到在未来几代抗spn疫苗中加入SPn6A偶联物的重要性。然而，由于许多原因，实现这一目标具有挑战性，其中主要是纯分离物的可用性低。本文提出了一种快速的策略来获得spn6血清群及其偶联物的合成等价物，以确保可靠和可重复的免疫学研究。最近发现了一种新的血清型6C，它与6B有两个结构单位的不同，这引起了对血清组SPn6的额外兴趣。据推测，与目前使用的血清型SPn6B的显著结构差异可能导致对6C的交叉保护较弱，并可能导致6C衍生肺炎球菌感染的爆发，就像之前发生的血清型SPn19A一样。本文提出了用于协同免疫学研究的新出现的血清型寡糖及其偶联物的首次全合成。PI研究的长期目标是使合成复杂的碳水化合物和糖缀合物更容易被普通化学、生化和工业用户使用，以跟上糖生物学爆炸式发展的步伐。该项目的最终目标是开发一种完全合成的疫苗成分，针对SPn6A和6C血清型（或适用于6血清型），适合在未来几代多血清型抗spn疫苗中实施。在初步结果的支持下，本文提出了一种新的硫咪酯糖基化方法在糖结构合成中的应用，以研究SPn6A的免疫学特性。然后将合成的糖转化为多价糖缀合物，其免疫特性将与伯明翰阿拉巴马大学的Moon Nahm教授合作确定。本应用程序的目的是开发一种合成结构上与spn6 -血清群相关的新型糖缀合物的通用方法，spn6 -血清群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发现对抗人类细菌感染的新的有效糖疗法的潜力。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缀合物进行排序，从而创造了新的化学方法来应对现代医学科学的主要挑战。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得到培训。在他们的实验室经验，他们不仅学习重要的工具，使化学家合成，修改和分析有机分子，而且还开发新的合成方法，并参与阐述最先进的多步合成。研究人员接触到解决各种生物医学难题的策略开发和协作生物实验，因此，在化学，生物学和医学之间建立了重要的桥梁。

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.