Regulation of antibody diversification and production in HIV-1 infection

这项提案的目的是阐明HIV-1逃避的机制， 体液免疫抗体应答，包括类别转换DNA重组 (CSR)和体细胞超突变（SHM）是阻止HIV-1进入和传播的关键。 CSR用IgG或伊加取代IgM，从而赋予抗体新的效应子 增强病毒清除系统性和粘膜进入部位的功能。SHM 在编码抗原结合可变区的基因中引入点突变， 抗体，从而提供用于通过病毒抗原选择的结构相关物， 高亲和力IgG和伊加突变体。CSR和SHM需要激活诱导的胞苷 脱氨酶（AID），一种由B细胞表达的酶，在生殖中心（GC）， 次级淋巴器官这种特殊的微环境包括CD 4 + T细胞 通过CD 154和IL-4激活B细胞。最终，GC B细胞分化为 浆细胞，其分泌大量IgG和伊加抗体。HIV-1损害 对病毒抗原、机会致病菌的全身和粘膜IgG和伊加应答 和疫苗的机制仍然知之甚少。虽然进步 CD 4 + T细胞的丢失当然是重要的，B细胞内在异常，包括差 也涉及B细胞对CD 154的反应性。在本提案中，我们认为， HIV-1蛋白Nef有助于B细胞内在缺陷的发生， HIV-1感染。我们认为Nef减弱CD 154依赖的CSR，SHM以及 作为病毒特异性IgG和伊加的生产系统和粘膜GC。我们也 假设Nef通过长距离隧穿作用靶向B细胞 从HIV-1感染的细胞中发出的纳米管。最后，我们建议，多个Nef 结构域有助于抑制B中转导CD 154和IL-4信号的激酶 细胞提出了三个具体目标。目的1是确定Nef-充分的能力 和Nef缺陷型HIV-1以减弱CSR、SHM和抗原特异性IgG和伊加 在全身和粘膜B细胞中产生。目标2是评估长期- 距离隧道纳米管穿梭膜结合和囊泡相关的Nef 从受感染的细胞到B细胞。目的3是阐明参与的分子相互作用， Nef介导的对B细胞中CD 154和IL-4信号传导的抑制。调查结果来自 这些研究将有助于更好地理解HIV-1的机制， 逃避抗体反应。此外，拟议的研究可能有助于 开发针对HIV-1的新型治疗和疫苗策略。HIV-1严重损害了针对病毒蛋白、机会因子和 疫苗。越来越多的证据表明，这种抗体缺乏不仅是由于损失， CD 4 + T细胞，但也由B细胞的内在缺陷。本申请的目的是阐明 HIV-1导致B细胞功能障碍的机制。最终，研究结果得出 这些研究成果将有助于开发更有效的抗HIV-1疫苗。

The goal of this proposal is to elucidate the mechanisms by which HIV-1 evades humoral immunity. Antibody responses, including class switch DNA recombination (CSR) and somatic hypermutation (SHM), are essential to block HIV-1 entry and spread. CSR substitutes IgM with IgG or IgA, thereby endowing antibodies with novel effector functions that enhance viral clearance systemically and at mucosal sites of entry. SHM introduces point mutations in genes encoding the antigen-binding variable region of antibodies, thereby providing the structural correlate for selection by viral antigens of higher affinity IgG and IgA mutants. CSR and SHM require activation-induced cytidine deaminase (AID), an enzyme expressed by B cells in the germinal center (GC) of secondary lymphoid organs. This specialized microenvironment comprises CD4+ T cells that activate B cells through CD154 and IL-4. Ultimately, GC B cells differentiate into plasma cells, which secrete large amounts of IgG and IgA antibodies. HIV-1 impairs systemic and mucosal IgG and IgA responses to viral antigens, opportunistic pathogens and vaccines through mechanisms that remain poorly understood. Although progressive loss of CD4+ T cells is certainly important, B cell-intrinsic abnormalities, including poor responsiveness of B cells to CD154, are also involved. In this proposal, we argue that the HIV-1 protein Nef contributes to the genesis of B cell-intrinsic defects arising during HIV-1 infection. We contend that Nef attenuates CD154-dependent CSR, SHM as well as virus-specific IgG and IgA production in systemic and mucosal GCs. We also hypothesize that Nef targets B cells by traveling through long-range tunneling nanotubules emanating from HIV-1-infected cells. Finally, we propose that multiple Nef domains contribute to the inhibition of kinases transducing CD154 and IL-4 signaling in B cells. Three specific aims are proposed. Aim 1 is to determine the ability of Nef-sufficient and Nef-deficient HIV-1 to attenuate CSR, SHM and antigen-specific IgG and IgA production in systemic and mucosal B cells. Aim 2 is to assess the ability of long- distance tunneling nanotubules to shuttle membrane-bound and vesicle-associated Nef from infected cells to B cells. Aim 3 is to elucidate the molecular interactions involved in Nef-mediated inhibition of CD154 and IL-4 signaling in B cells. Findings resulting from these studies should lead to a better understanding of the mechanisms whereby HIV-1 evades the antibody response. In addition, the proposed studies might facilitate the development of novel therapeutic and vaccine strategies against HIV-1. HIV-1 profoundly impairs antibody responses against viral proteins, opportunistic agents and vaccines. Growing evidence indicates that this antibody deficiency is caused not only by loss of CD4+ T cells, but also by B cell-intrinsic defects. The goal of this application is to elucidate the mechanisms by which HIV-1 causes B cell dysfunctions. Ultimately, findings deriving from the proposed studies should help develop more effective vaccines against HIV-1.