APOBEC3/Rfv3 and Immunoglobulin Somatic Hypermutation

APOBEC3/Rfv3 和免疫球蛋白体细胞超突变

• 批准号: 9179597
• 负责人: Mario Luis Santiago
• 金额: $ 49.35万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-12-01 至 2020-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9179597
• 关键词: Acute; Acute Erythroblastic Leukemia; Adjuvant; Affinity; Agonist; Antibodies; Antibody Affinity; Antibody Response; Antigens; Antiviral Agents; Attenuated; Automobile Driving; B-Lymphocytes; Binding; Biology; Clinical; Communicable Diseases; Complex; DNA; Data; Deaminase; Deamination; Deoxycytidine; Deoxyuridine; Development; Disease; Enzymes; Exhibits; Family; Friend Murine Leukemia Virus; Friends; GTP-Binding Protein alpha Subunits, Gs; Gammaretrovirus; Genes; HIV-1; Human; Immune; Immunoglobulin Class Switching; Immunoglobulin G; Immunoglobulin Genes; Immunoglobulin M; Immunoglobulin Somatic Hypermutation; Immunoglobulins; Immunologics; Infection; Influenza; Interferon-alpha; Interferons; Link; Mediating; Modeling; Molecular; Mus; Mutate; Mutation; Pathogenicity; Pathway interactions; Plasma Cells; Process; Proteins; Purines; Pyrimidine; Reaction; Recovery; Reporting; Resistance; Retroviridae; Retroviridae Infections; Role; Signal Transduction; Splenomegaly; Structure; Structure of germinal center of lymph node; Study models; Subunit Vaccines; TLR7 gene; Testing; Therapeutic; Transcript; Transgenic Mice; Vaccination; Vaccine Adjuvant; Vaccines; Viral; Viral Vaccines; Viremia; Virion; Virus; Virus Diseases; Virus-like particle; Work; activation-induced cytidine deaminase; base; design; human morbidity; human mortality; in vivo; innovation; insight; interest; nanoparticle; neutralizing antibody; next generation sequencing; novel; particle; pathogen; preference; public health relevance; repaired; resistance gene; response; vaccine-induced immunity

 DESCRIPTION (provided by applicant): Neutralizing antibodies (NAb) are important in vaccine protection and recovery from viral infection. Thus, understanding the mechanisms governing NAb development could have significant clinical and translational implications. NAbs develop through a process known as affinity maturation in structures known as Germinal Centers (GCs). In GCs, B cells with rearranged immunoglobulin (Ig) genes undergo somatic hypermutation (SHM), leading to enhanced antibody binding to cognate antigens. Ig SHM is primarily mediated by Activation Induced Deaminase (AID), an enzyme that deaminates deoxycytidines into deoxyuridines in transcribing Ig DNA, resulting in G-to-A or C-to-T transitions. Most antibodies have mutations <10% relative to germline, but antibodies that can broadly neutralize global influenza and HIV-1 strains exhibit unusually high SHM levels (up to 33%). Thus, a better understanding of how Ig SHM occurs during viral infections may inform the design of universal vaccines against antigenically-diverse viral pathogens of global importance. Interestingly, the APOBEC3 enzymes are evolutionarily related to AID. APOBEC3 could counteract retroviruses by deaminating reverse transcripts, leading to lethal G-to-A hypermutation. We reported 6 years ago that APOBEC3 encodes Rfv3, a classical resistance gene in mice that promotes recovery from pathogenic Friend retrovirus infection by stimulating a stronger NAb response1. We recently discovered exciting evidence that APOBEC3 could directly edit virus-specific IgG, but in a different sequence context compared to AID2. Thus, we unraveled APOBEC3- mediated deamination as a novel mechanism for antibody diversification in vivo. This fundamental immunological finding unleashed a plethora of basic questions on APOBEC3-mediated Ig SHM, as this process may be a strategy to augment NAb responses during vaccination. In fact, we reported that APOBEC3 can be regulated by IFNα treatment in vivo3. Moreover, we obtained pilot data showing that a TLR7 agonist may augment vaccine IgG responses via APOBEC3. To expand our understanding of APOBEC3-mediated Ig SHM, we therefore propose to: (Aim 1) evaluate regulatory checkpoints for APOBEC3-mediated Ig SHM during viral infection; (Aim 2) investigate the impact of APOBEC3 in vaccine-induced antibody protection; and (Aim 3) determine if increased NAb potency are due to APOBEC3 mutations. Of note, mice encode only 1 APOBEC3 gene, but humans have seven. Thus, the 7 human APOBEC3 proteins may have a stronger impact on Ig SHM. We will utilize a novel transgenic mouse encoding the entire human APOBEC3 locus to test this hypothesis. We will capitalize on our expertise in the Friend retrovirus infection model, utilize novel murine lines specifically generated for the study, investigate clinically-approved vaccine adjuvants and employ innovative nanoparticle vaccines, single B cell PCR and next-generation sequencing approaches. The proposed studies should provide deeper insights on how APOBEC3 mediates Ig SHM that may inform universal vaccine strategies.

 描述（由申请人提供）：中和抗体（NAb）对于疫苗保护和病毒感染恢复非常重要，因此，了解控制 NAb 发育的机制可能具有重要的临床和转化意义。生发中心 (GC) 在 GC 中，具有重排免疫球蛋白 (Ig) 基因的 B 细胞会发生体细胞超突变 (SHM)，导致抗体与同源蛋白的结合增强。 Ig SHM 主要由激活诱导脱氨酶 (AID) 介导，这种酶在 Ig DNA 转录过程中将脱氧胞苷脱氨基为脱氧尿苷，导致 G 到 A 或 C 到 T 的转变，大多数抗体的突变相对小于 10%。种系，但可以广泛中和全球流感和 HIV-1 毒株的抗体表现出异常高的 SHM 水平（高达 33%）。关于 Ig SHM 在病毒感染过程中如何发生的信息可能会为针对具有全球重要性的抗原多样性病毒病原体的通用疫苗的设计提供信息，APOBEC3 酶在进化上与 AID 相关，可以通过使逆转录物脱氨基来对抗逆转录病毒，从而产生致命的 G-。 6 年前，我们报道了 APOBEC3 编码 Rfv3，这是小鼠中的一种经典抗性基因，可通过刺激更强的抵抗力来促进致病性 Friend 逆转录病毒感染的恢复。 NAb 反应1。我们最近发现了令人兴奋的证据，表明 APOBEC3 可以直接编辑病毒特异性 IgG，但与 AID2 相比，其序列背景不同。因此，我们揭示了 APOBEC3 介导的脱氨基作用是体内抗体多样化的新机制。引发了关于 APOBEC3 介导的 Ig SHM 的大量基本问题，因为这个过程可能是在疫苗接种过程中增强 NAB 反应的策略。事实上，我们报道过 APOBEC3 可以。此外，我们获得的初步数据显示 TLR7 激动剂可以通过 APOBEC3 增强疫苗 IgG 反应，因此，为了扩大我们对 APOBEC3 介导的 Ig SHM 的理解，我们建议：（目标 1）评估监管检查点。病毒感染期间 APOBEC3 介导的 Ig SHM；（目标 2）研究 APOBEC3 在疫苗诱导的抗体保护中的影响；以及（目标 3）确定是否增加NAb 效力归因于 APOBEC3 突变。值得注意的是，小鼠仅编码 1 个 APOBEC3 基因，但人类有 7 个基因，因此，7 种人类 APOBEC3 蛋白可能对 Ig SHM 产生更强的影响。我们将利用我们在 Friend 逆转录病毒感染模型方面的专业知识，利用专门为该研究生成的新型小鼠品系，研究临床批准的疫苗佐剂并采用创新的 APOBEC3 基因座来检验这一假设。纳米颗粒疫苗、单 B 细胞 PCR 和下一代测序方法应提供有关 APOBEC3 如何介导 Ig SHM 的更深入见解，从而为通用疫苗策略提供信息。