Modi Tapasvi, Gervais David, Smith Stuart, Miller Julie, Subramaniam Shaan, Thalassinos Konstantinos, Shepherd Adrian
Porton Biopharma Limited, Development, Porton Down, Salisbury, Wiltshire, UK.
Institute of Structural and Molecular Biology, Division of Biosciences, Darwin Building Room 101A, University College London, London, UK.
Hum Vaccin Immunother. 2021 Mar 4;17(3):747-758. doi: 10.1080/21645515.2020.1799668. Epub 2020 Sep 8.
The manufacture of the UK Anthrax vaccine (AVP) focuses on the production of Protective Antigen (PA) from the Sterne strain. Although used for decades, several of AVP's fundamental properties are poorly understood, including its exact composition, the extent to which proteins other than PA may contribute to protection, and whether the degree of protection varies between individuals.This study involved three innovative investigations. Firstly, the composition of AVP was analyzed using liquid chromatography tandem mass-spectrometry (LC-MS/MS), requiring the development of a novel desorption method for releasing proteins from the vaccine's aluminum-containing adjuvant. Secondly, computational MHC-binding predictions using NetMHCIIpan were made for the eight most abundant proteins of AVP, for the commonest HLA alleles in multiple ethnic groups, and for multiple strains. Thirdly, antibody levels and toxin neutralizing antibody (TNA) levels were measured in sera from AVP human vaccinees for both PA and Lethal Factor (LF).It was demonstrated that AVP is composed of at least 138 proteins, including PA (65%), LF (8%) and Edema Factor (EF) (3%), using LC-MS/MS. NetMHCIIpan predicted that peptides from all eight abundant proteins are likely to be presented to T cells, a pre-requisite for protection; however, the number of such peptides varied considerably between different HLA alleles.These analyses highlight two important properties of the AVP vaccine that have not been established previously. Firstly, the effectiveness of AVP within humans may not depend on PA alone; there is compelling evidence to suggest that LF has a protective role, with computational predictions suggesting that additional proteins may be important for individuals with specific HLA allele combinations. Secondly, in spite of differences in the sequences of key antigenic proteins from different strains, these are unlikely to affect the cross-strain protection afforded by AVP.
英国炭疽疫苗（AVP）的生产主要集中于从斯特恩菌株生产保护性抗原（PA）。尽管已使用数十年，但AVP的一些基本特性仍了解不足，包括其确切成分、除PA之外的蛋白质对保护作用的贡献程度，以及个体之间的保护程度是否存在差异。本研究涉及三项创新性调查。首先，使用液相色谱串联质谱法（LC-MS/MS）分析AVP的成分，这需要开发一种新型解吸方法，以从疫苗含铝佐剂中释放蛋白质。其次，使用NetMHCIIpan对AVP的八种最丰富蛋白质、多个种族群体中最常见的HLA等位基因以及多个菌株进行了计算性MHC结合预测。第三，测量了AVP人类疫苗接种者血清中针对PA和致死因子（LF）的抗体水平和毒素中和抗体（TNA）水平。使用LC-MS/MS证明，AVP由至少138种蛋白质组成，包括PA（65%）、LF（8%）和水肿因子（EF）（3%）。NetMHCIIpan预测，所有八种丰富蛋白质的肽段都可能呈递给T细胞，这是产生保护作用的前提条件；然而，不同HLA等位基因之间此类肽段的数量差异很大。这些分析突出了AVP疫苗以前未被确定的两个重要特性。首先，AVP在人体内的有效性可能并非仅取决于PA；有令人信服的证据表明LF具有保护作用，计算预测表明，对于具有特定HLA等位基因组合的个体，其他蛋白质可能也很重要。其次，尽管不同菌株的关键抗原蛋白序列存在差异，但这些差异不太可能影响AVP提供的跨菌株保护作用。
