Liu Li, Patel Bhavik, Ghanem Mustafa H, Bundoc Virgilio, Zheng Zhili, Morgan Richard A, Rosenberg Steven A, Dey Barna, Berger Edward A
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Surgery Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
J Virol. 2015 Jul;89(13):6685-94. doi: 10.1128/JVI.00474-15. Epub 2015 Apr 15.
Adoptive transfer of CD8 T cells genetically engineered to express "chimeric antigen receptors" (CARs) represents a potential approach toward an HIV infection "functional cure" whereby durable virologic suppression is sustained after discontinuation of antiretroviral therapy. We describe a novel bispecific CAR in which a CD4 segment is linked to a single-chain variable fragment of the 17b human monoclonal antibody recognizing a highly conserved CD4-induced epitope on gp120 involved in coreceptor binding. We compared a standard CD4 CAR with CD4-17b CARs where the polypeptide linker between the CD4 and 17b moieties is sufficiently long (CD4-35-17b CAR) versus too short (CD4-10-17b) to permit simultaneous binding of the two moieties to a single gp120 subunit. When transduced into a peripheral blood mononuclear cell (PBMC) or T cells thereof, all three CD4-based CARs displayed specific functional activities against HIV-1 Env-expressing target cells, including stimulation of gamma interferon (IFN-γ) release, specific target cell killing, and suppression of HIV-1 pseudovirus production. In assays of spreading infection of PBMCs with genetically diverse HIV-1 primary isolates, the CD4-10-17b CAR displayed enhanced potency compared to the CD4 CAR whereas the CD4-35-17b CAR displayed diminished potency. Importantly, both CD4-17b CARs were devoid of a major undesired activity observed with the CD4 CAR, namely, rendering the transduced CD8(+) T cells susceptible to HIV-1 infection. Likely mechanisms for the superior potency of the CD4-10-17b CAR over the CD4-35-17b CAR include the greater potential of the former to engage in the serial antigen binding required for efficient T cell activation and the ability of two CD4-10-17b molecules to simultaneously bind a single gp120 subunit.
HIV research has been energized by prospects for a cure for HIV infection or, at least, for a "functional cure" whereby antiretroviral therapy can be discontinued without virus rebound. This report describes a novel CD4-based "chimeric antigen receptor" (CAR) which, when genetically engineered into T cells, gives them the capability to selectively respond to and kill HIV-infected cells. This CAR displays enhanced features compared to previously described CD4-based CARs, namely, increased potency and avoidance of the undesired rendering of the genetically modified CD8 T cells susceptible to HIV infection. When adoptively transferred back to the individual, the genetically modified T cells will hopefully provide durable killing of infected cells and sustained virus suppression without continued antiretroviral therapy, i.e., a functional cure.
采用基因工程改造以表达“嵌合抗原受体”（CARs）的CD8 T细胞进行过继性转移，是实现HIV感染“功能性治愈”的一种潜在方法，即停用抗逆转录病毒疗法后可实现持久的病毒学抑制。我们描述了一种新型双特异性CAR，其中CD4片段与17b人单克隆抗体的单链可变片段相连，该抗体可识别gp120上一个高度保守的、参与共受体结合的CD4诱导表位。我们将标准CD4 CAR与CD4-17b CAR进行了比较，其中CD4和17b部分之间的多肽接头足够长（CD4-35-17b CAR）或过短（CD4-10-17b），以允许这两个部分同时与单个gp120亚基结合。当转导到外周血单个核细胞（PBMC）或其T细胞中时，所有三种基于CD4的CAR均对表达HIV-1 Env的靶细胞表现出特异性功能活性，包括刺激γ干扰素（IFN-γ）释放、特异性靶细胞杀伤以及抑制HIV-1假病毒产生。在用基因多样化的HIV-1原代分离株对PBMC进行传播感染的试验中，与CD4 CAR相比，CD4-10-17b CAR表现出更强的效力，而CD4-35-17b CAR表现出较弱的效力。重要的是，两种CD4-17b CAR均没有观察到CD4 CAR所具有的一种主要不良活性，即使转导的CD8(+) T细胞易受HIV-1感染。CD4-10-17b CAR比CD4-35-17b CAR效力更强的可能机制包括前者更有潜力参与有效T细胞激活所需的连续抗原结合，以及两个CD4-10-17b分子能够同时结合单个gp120亚基。
HIV感染治愈前景，或者至少是“功能性治愈”（即停用抗逆转录病毒疗法后病毒不反弹）的前景，为HIV研究注入了活力。本报告描述了一种新型的基于CD4的“嵌合抗原受体”（CAR），当将其进行基因工程改造到T细胞中时，可使T细胞有能力选择性地响应并杀死HIV感染的细胞。与先前描述的基于CD4的CAR相比，这种CAR具有增强的特性，即效力增加，并且避免了基因改造的CD8 T细胞出现易受HIV感染这种不良情况。当过继性转移回个体时，经基因改造的T细胞有望在不进行持续抗逆转录病毒治疗的情况下，即实现功能性治愈，持久地杀死感染细胞并持续抑制病毒。
