In vivo engineering of B cells for the secretion of HIV broadly neutralizing antibodies

项目摘要 我们已经开发了一种新的基因治疗方法来实现HIV功能性治愈，其中广泛地 将中和抗体（bnAb）基因靶向B细胞中的内源性重链基因座用于表达 作为功能性抗原受体（BCR）。这利用了基因编辑的精确性， CRISPR-Cas9试剂和同源定向基因编辑。我们已经证明，这些广泛中和的 BCR通过信号传导克隆扩增和BCR的生发中心成熟来应答HIV Env免疫原。 工程细胞，从而产生持久的，同种型转换的记忆bnAb反应， 用于长期控制艾滋病毒。我们的基因保留了B细胞的这些生物学特征 编辑方法，我们假设血清中可以产生足够的中和抗体滴度， 非常少的工程改造的B细胞，包括通过直接体内递送基因组编辑试剂所达到的水平 到目标细胞。为了支持这种方法，我们现在已经表明，可以引发高滴度的bnAb应答， 在小鼠中，当动物注射转录靶向的 携带bnAb编辑试剂的双AAV载体系统。与注射重组bnAb或AAV不同， 将bnAb-IgG表达盒载体化递送至肝脏或肌肉以从病毒中长期分泌 附加体，预期响应于疫苗接种从体内基因编辑的B细胞产生的bnAb具有 以下优点：1）根据需要，响应于病毒抗原是可加强的，2）表达bnAb， 效应同种型，以扩大抗病毒免疫，3）亲和力成熟或演变的bnAb反应，以跟上 一种快速进化的病毒，以及4）被免疫系统更好地耐受。为了进一步发展这种方法，我们 我组建了一个团队，汇集了B细胞工程、载体开发、艾滋病毒疫苗 设计和动物模型，以进一步开发这种体内递送方法， B细胞在体内，并评估这种方法作为一种体内艾滋病毒治愈。

PROJECT SUMMARY We have developed a novel gene therapeutic approach to achieve an HIV functional cure, wherein broadly neutralizing antibody (bnAb) genes are targeted to the endogenous heavy chain locus in B cells for expression as functional antigen-receptors (BCRs). This takes advantage of the precision of gene editing conferred by CRISPR-Cas9 reagents and homology-directed gene editing. We have shown that these broadly neutralizing BCRs respond to HIV Env immunogens by signaling clonal expansion and germinal center maturation of the engineered cells and thereby generate durable, isotype-switched memory bnAb responses that could be deployed for long-term control of HIV. Given these features of B cell biology, which are preserved by our gene editing approach, we hypothesize that sufficient neutralizing antibody titers in serum could be generated from very few engineered B cells, including the levels achieved by in vivo delivery of genome-editing reagents directly to the target cells. In support of this approach, we have now shown that high-titer bnAb responses can be elicited in mice by vaccination with HIV-Env immunogens when the animals are injected with a transcriptionally-targeted dual-AAV vector system carrying the bnAb editing reagents. Unlike injection of recombinant bnAbs, or AAV- vectored delivery of bnAb-IgG expression cassettes to liver or muscle for long-term secretion from viral episomes, bnAbs generated from in vivo gene-edited B cells in response to vaccination are expected to have the following advantages: 1) be boostable, as needed, in response to viral antigen, 2) express bnAbs as all effector isotypes to expand antiviral immunity, 3) affinity-mature or evolve the bnAb response to keep-pace with a rapidly evolving virus, and 4) be better tolerated by the immune system. To further develop this approach, we have assembled a team that brings together expertise in B cell engineering, vector development, HIV vaccine design, and animal models to further develop this in vivo delivery approach to specifically and efficiently engineer B cells in vivo and to evaluate this approach as an in vivo HIV cure.