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: 10115911
• 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/10115911
• 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; 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

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 结核病 (TB) 由结核分枝杆菌 (Mtb) 引起，是世界上导致结核病的主要原因之一 卡介苗是唯一获得许可的结核病疫苗，它是一种与结核分枝杆菌高度同源的减毒细菌。 对于免疫功能正常的个体来说是安全的，因为它丢失了一些赋予卡介苗良好毒力的基因。 对儿童结核病有效，但对青少年和成人结核病疗效较差，因此，疫苗的作用很大。 显然需要比卡介苗更有效的疫苗，但是几乎肯定需要任何替代疫苗。 基于改良（例如重组）BCG 或减毒 Mtb，以保留 BCG 的实质性益处。 该项目的目标是开发一种比 BCG 更安全、更有效的 Mtb 减毒突变体。 我们的新策略涉及操纵活疫苗的两个关键特征：（1）它们的初始阶段 (2) BCG 引起的保护功效不足和 (2) 其消除率。 非复制型 Mtb 突变体至少部分归因于它们在宿主体内缺乏复制。 在宿主体内的持久性也是一个负面因素，导致主要效应子和效应子的产生 记忆 T 细胞而不是中枢记忆 T 细胞，对长期免疫很重要。 免疫后短时间内，结核分枝杆菌突变体的复制受到限制，模仿了自然突变体的早期阶段 结核分枝杆菌感染，随后快速清除，将诱发有效的免疫反应，同时避免负面影响 长期 Mtb 感染引起的炎症反应。 为了实现我们的目标，我们首先应设计一种减毒 Mtb 突变体，该突变体在铁获取方面均存在缺陷。 化途径 - 铁载体介导的铁获取（SMIA）和血红素铁获取（HIA）这样的突变体。 将无法从宿主获得铁，但可以在体外预先装载精确量的铁，以允许 因此，Mtb ΔSMIA ΔHIA 突变体将使我们能够解决第一个重要问题。 因素 - 控制宿主中复制的程度，而宿主中 Mtb ΔSMIA ΔHIA 的生长将停止。 一旦耗尽了铁的供应，有机体可能会持续很长一段时间，因此，要解决这个问题。 第二个重要因素，宿主的清除率，我们将进一步修改 Mtb ΔSMIA ΔHIA，通过两个 方法 – 1) 敲除持久性基因和 2) 有条件地沉默必需基因。 应该会导致清除率提高，有条件的沉默可能会导致更快的清除率。 食用具有持久性和条件性沉默突变体的小鼠并发挥清除和保护功效 研究以确定最佳的复制和清除，我们期望复制和持久性受到限制。 具有快速清除能力的 Mtb 突变体将比 BCG 更有效，并且与 BCG 相比，即使在 一旦我们优化了小鼠的保护性免疫疫苗，我们就应该 检查其在小鼠中的免疫原性，以评估保护作用的初步相关性，评估其免疫安全性 受损的 SCID 小鼠，并在第二种结核病动物模型 - 豚鼠中检查其安全性和有效性。