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)在疫苗保护和从病毒感染中恢复是重要的。因此，了解NAB发生的机制可能具有重要的临床和翻译意义。NAB在被称为生发中心(GC)的结构中通过被称为亲和力成熟的过程来发展。在GC中，带有重排免疫球蛋白(Ig)基因的B细胞发生体细胞超突变(SHM)，导致抗体与同源抗原的结合增强。Ig SHM主要由激活诱导脱氨酶(AID)介导，AID是一种在转录Ig DNA过程中将脱氧胞苷脱氨为脱氧尿苷的酶，导致G-A或C-T转变。大多数抗体相对于生殖系有10%的突变，但能够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%)。因此，更好地了解Ig SHM在病毒感染过程中是如何发生的，可能有助于设计针对具有全球重要性的抗原性多样化病毒病原体的通用疫苗。有趣的是，APOBEC3酶在进化上与AID有关。APOBEC3可以通过脱氨基逆转录酶来对抗逆转录病毒，导致致命的G-to-A超突变。6年前，我们报道了APOBEC3编码Rfv3，这是一种经典的小鼠耐药基因，通过刺激更强的NAB反应来促进小鼠从致病的Friend逆转录病毒感染中恢复1。我们最近发现了令人兴奋的证据，APOBEC3可以直接编辑病毒特异性的免疫球蛋白，但与AID2相比，它的序列背景不同。因此，我们揭示了APOBEC3介导的脱氨基作用作为体内抗体多样化的一种新机制。这一基本的免疫学发现引发了关于APOBEC3介导的Ig SHM的大量基本问题，因为这一过程可能是在疫苗接种期间增强NAB反应的一种策略。事实上，我们报道了在活体3中，ApoBEC3可以被干扰素α治疗所调控。此外，我们还获得了试验数据，表明TLR7激动剂可以通过APOBEC3增强疫苗的免疫球蛋白应答。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)评估病毒感染期间APOBEC3介导的Ig SHM的调节检查点；(目的2)研究APOBEC3在疫苗诱导抗体保护中的影响；以及(目的3)确定NAB效力的增加是否源于APOBEC3突变。值得注意的是，小鼠只编码1个APOBEC3基因，但人类有7个。因此，7种人类APOBEC3蛋白可能对Ig SHM有较强的影响。我们将利用一种新型的编码整个人类APOBEC3基因座的转基因小鼠来验证这一假设。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，利用为这项研究专门生成的新型小鼠品系，研究临床批准的疫苗佐剂，并采用创新的纳米颗粒疫苗、单B细胞聚合酶链式反应和下一代测序方法。拟议的研究应该提供关于APOBEC3如何介导免疫球蛋白SHM的更深层次的见解，这可能为通用疫苗策略提供参考。