Regulation of antibody diversification and production in HIV-1 infection

描述（由申请人提供）：本提案的目的是阐明HIV-1逃避体液免疫的机制。抗体反应，包括类转换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功能，增强病毒全身清除和粘膜进入部位的清除。SHM在编码抗体的抗原结合可变区的基因中引入点突变，从而为通过病毒抗原选择更高亲和力的IgG和伊加突变体提供结构相关性。CSR和SHM需要激活诱导的胞苷脱氨酶（AID），一种由次级淋巴器官生发中心（GC）中的B细胞表达的酶。这种特殊的微环境包括通过CD 154和IL-4激活B细胞的CD 4 + T细胞。最终，GC B细胞分化成浆细胞，其分泌大量IgG和伊加抗体。HIV-1通过仍知之甚少的机制损害对病毒抗原、机会致病菌和疫苗的全身和粘膜IgG和伊加应答。虽然CD 4 + T细胞的进行性丢失当然很重要，但也涉及B细胞内在异常，包括B细胞对CD 154的反应性差。在这个建议中，我们认为，HIV-1蛋白Nef有助于B细胞的内在缺陷的发生在HIV-1感染。我们认为Nef减弱了全身和粘膜GC中CD 154依赖性CSR、SHM以及病毒特异性IgG和伊加的产生。我们还假设Nef通过从HIV-1感染细胞发出的长距离隧道纳米管来靶向B细胞。最后，我们提出多个Nef结构域有助于抑制B细胞中转导CD 154和IL-4信号的激酶。提出了三个具体目标。目的1是确定Nef充足和Nef缺陷的HIV-1减弱系统和粘膜B细胞中CSR、SHM和抗原特异性IgG和伊加产生的能力。目的2是评估长距离隧穿纳米管将膜结合的和囊泡相关的Nef从感染的细胞穿梭到B细胞的能力。目的3：阐明Nef抑制B细胞中CD 154和IL-4信号转导的分子相互作用。这些研究的结果应该会导致更好地理解HIV-1逃避抗体反应的机制。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。 公共卫生相关性：HIV-1严重损害针对病毒蛋白、机会因子和疫苗的抗体应答。越来越多的证据表明，这种抗体缺乏不仅是由于CD 4 + T细胞的损失，而且也由B细胞内在缺陷引起的。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，从拟议的研究中得出的发现应该有助于开发更有效的艾滋病毒1疫苗。

DESCRIPTION (provided by applicant): 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. PUBLIC HEALTH RELEVANCE: 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.