Development of a novel TB vaccine safer and more effective than BCG based on a precisely controlled replication-limited Mycobacterium tuberculosis engineered for optimal in vivo growth and clearance

基于精确控制的复制限制结核分枝杆菌，开发出比卡介苗更安全、更有效的新型结核疫苗，该疫苗经过精心设计，可实现最佳的体内生长和清除

• 批准号: 10372028
• 负责人: MARCUS AARON HORWITZ
• 金额: $ 78万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-03-15 至 2026-02-28
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10372028
• 关键词: Address; Adolescent; Adult; Aerosols; Affect; Animal Model; Attenuated; Attenuated Vaccines; BCG Vaccine; Bacille Calmette-Guerin vaccination; Bacteria; Cause of Death; Cavia; Cells; Cessation of life; Characteristics; Child; Childhood; Development; Disease; Dose; Engineering; Essential Genes; Generations; Genes; Genetic; Goals; Growth; Heme Iron; Human; Immune response; Immunity; Immunization; Immunize; Immunocompetent; Immunocompromised Host; Immunodominant Antigens; In Vitro; Individual; Infectious Agent; Inflammatory Response; Iron; Knock-out; Life; Mediating; Metabolic Clearance Rate; Modification; Mus; Mutation; Mycobacterium bovis; Mycobacterium tuberculosis; Organism; Pathway interactions; Persons; Public Health; Pulmonary Tuberculosis; Role; SCID Mice; Safety; Siderophores; System; T memory cell; T-Lymphocyte Epitopes; Testing; Time; Tuberculosis; Tuberculosis Vaccines; Vaccinated; Vaccination; Vaccines; Virulence; attenuation; base; booster vaccine; efficacy study; exhaust; expectation; immunogenicity; immunopathology; improved; in vivo; iron metabolism; mortality; mutant; mycobacterial; novel; novel strategies; preservation; prevent; protective efficacy; rBCG; response; vaccine development; vaccine immunogenicity

ABSTRACT Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the world's leading causes of death. BCG, the only licensed vaccine against TB, is an attenuated bacterium highly homologous to Mtb, yet safe in immunocompetent individuals because it has lost several genes that confer virulence. BCG has good efficacy against TB in children, but poor efficacy against TB in adolescents and adults. Hence, a vaccine much more potent than BCG is clearly needed. However, any replacement vaccine will almost certainly need to be based on modified (e.g. recombinant) BCG or attenuated Mtb to preserve the substantial benefits of BCG. The goal of this project is to develop an attenuated Mtb mutant that is safer and more potent than BCG. Our novel strategy involves manipulating two key characteristics of live vaccines: (1) their initial period of growth in the host and (2) their rate of elimination. The inadequate protective efficacy induced by BCG and non-replicating Mtb mutants can be attributed, at least in part, to their lack of replication in the host. Prolonged persistence in the host is also a negative factor, resulting in the generation of primarily effector and effector memory T cells rather than central memory T cells, important for long-term immunity. We hypothesize that limited replication of an Mtb mutant for a brief period after immunization, mimicking the early stage of a natural Mtb infection, followed by rapid clearance will induce a potent immune response and yet avoid the negative inflammatory responses induced by prolonged Mtb infection. To achieve our goal, we first shall engineer an attenuated Mtb mutant defective in both of its iron acquisi- tion pathways - siderophore-mediated iron acquisition (SMIA) and heme-iron acquisition (HIA). Such a mutant will be unable to obtain iron from the host but can be pre-loaded in vitro with the precise amount of iron to allow optimal replication in the host. Thus, an Mtb ∆SMIA ∆HIA mutant will allow us to address the first important factor - controlling the extent of replication in the host. While growth of Mtb ∆SMIA ∆HIA in the host will cease once it exhausts its supply of iron, the organism may persist for a prolonged period. Thus, to address the second important factor, the rate of clearance from the host, we shall further modify Mtb ∆SMIA ∆HIA, via two approaches – 1) knocking out persistence genes and 2) conditional silencing of essential genes. While both should result in improved clearance, conditional silencing likely will result in faster clearance. We shall vaccin- ate mice with persistence and conditional silencing mutants and perform clearance and protective efficacy studies to determine the optimal replication and clearance. We expect a replication- and persistence-limited Mtb mutant with rapid clearance will be much more efficacious than BCG and, in contrast to BCG, safe even in an immunocompromised host. Once we have optimized the vaccine for protective immunity in mice, we shall examine its immunogenicity in mice to assess preliminary correlates of protection, assess its safety in immuno- compromised SCID mice, and examine its safety and efficacy in a second animal model of TB - guinea pigs.

抽象的 结核分枝杆菌（MTB）引起的结核病（TB）是世界上主要的原因之一 死亡。 BCG是唯一针对TB的许可疫苗，是一种与MTB高度同源的衰减细菌 在免疫能力的个体中安全，因为它失去了几种会议病毒的基因。 BCG很好 儿童对结核病的功效，但青少年和成人对结核病的效率较差。因此，一种疫苗 显然需要比BCG更多的潜力。但是，任何替代疫苗几乎肯定都需要 基于修改（例如重组）BCG或减弱MTB，以保留BCG的实质益处。 该项目的目的是开发一种减弱的MTB突变体，比BCG更安全，更有潜力。 我们的新颖策略涉及操纵活疫苗的两个关键特征：（1）它们的初始时期 宿主的增长和（2）消除率。 BCG和 非重复的MTB突变体至少部分归因于它们在宿主中缺乏复制。长时间 主机中的持久性也是一个负因素，导致主要效应子和效应器的产生 记忆T细胞而不是中央记忆T细胞，对长期免疫力很重要。我们假设这一点 免疫后短期内MTB突变体的复制有限，模仿天然的早期阶段 MTB感染，然后进行快速清除将引起潜在的免疫响应，但避免了阴性 长期MTB感染引起的炎症反应。 为了实现我们的目标，我们首先应在其两种铁中设计出衰减的MTB突变体有缺陷 Tion途径 - 侧面介导的铁采集（SMIA）和血红素铁的采集（HIA）。这样的突变体 将无法从宿主那里获得铁，但可以用精确的铁在体外进行预载以允许 主机中的最佳复制。那就是MTB ∆SMIA ∆HIA突变体将使我们能够解决第一个重要 因子 - 控制主机中复制程度。而宿主中MTB ∆SMIA ∆HIA的增长将停止 一旦耗尽了铁的供应，生物体可能会持续一段时间。那是为了解决 第二重要因素是宿主的清除率，我们应通过两个 方法 - 1）淘汰持续基因和2）基本基因的条件沉默。两者兼而有之 应该导致清除率提高，有条件的沉默可能会导致清除速度更快。我们将疫苗接种 - 持久和有条件沉默的突变体和性能清除和保护效率的小鼠吃掉小鼠 研究确定最佳复制和清除率的研究。我们期望复制和持久性限制 MTB突变体具有快速清除率将比BCG高得多，并且与BCG相反，即使在 免疫功能低下的宿主。一旦我们优化了对小鼠的保护免疫史的疫苗，我们将 检查其在小鼠中的免疫原性，以评估保护的初步相关性，评估其在免疫方面的安全性 损害了SCID小鼠，并在第二个TB -Guinea Pigs的动物模型中检查其安全性和效率。