HIV-1-Specific Chimeric Antigen Receptors Based on Broadly Neutralizing Antibodies

Abstract

Although the use of chimeric antigen receptors (CARs) based on single-chain antibodies for gene immunotherapy of cancers is increasing due to promising recent results, the earliest CAR therapeutic trials were done for HIV-1 infection in the late 1990s. This approach utilized a CAR based on human CD4 as a binding domain and was abandoned for a lack of efficacy. The growing number of HIV-1 broadly neutralizing antibodies (BNAbs) offers the opportunity to generate novel CARs that may be more active and revisit this modality for HIV-1 immunotherapy. We used sequences from seven well-defined BNAbs varying in binding sites and generated single-chain-antibody-based CARs. These CARs included 10E8, 3BNC117, PG9, PGT126, PGT128, VRC01, and X5. Each novel CAR exhibited conformationally relevant expression on the surface of transduced cells, mediated specific proliferation and killing in response to HIV-1-infected cells, and conferred potent antiviral activity (reduction of viral replication in log 10 units) to transduced CD8 ؉ T lymphocytes. The antiviral activity of these CARs was reproducible but varied according to the strain of virus. These findings indicated that BNAbs are excellent candidates for developing novel CARs to consider for the immunotherapeutic treatment of HIV-1. R ecent years have seen a surge in immunotherapeutic approaches for treating malignancy, including numerous promising human trials of chimeric antigen receptor (CAR) gene therapy to generate tumor-specific T cells, based on the importance of CD8 ϩ T lymphocytes (CTLs) in tumor surveillance and malignant cell clearance through cytotoxicity. The general approach has been to identify monoclonal antibodies that bind a tumor cell surface antigen and use a single-chain version of the antibody as an artificial T cell receptor by genetic fusion to the CD3 chain signaling domain. As opposed to native T cell receptors (TCRs), CARs have the advantage of being major histocompatibility complex (MHC) unrestricted and therefore broadly applicable across human individuals and are also unaffected by tumor cell immune evasion through MHC downregulation. IMPORTANCE While chimeric antigen receptors (CARsNotably, one of the earliest tested clinical applications of CARs was for the treatment of HIV-1 infection. In 1994, Roberts et al. designed two virus-specific CARs using CD4 or a single-chain antibody as the binding domain for recombinant gp120 on the surface of cells (1), and these CARs were shown subsequently to have the direct capacity to kill HIV-1-infected cells and suppress viral replication at levels similar to those of HIV-1-specific CTL clones isolated from infected persons (2). Based on these data, the CD4-based CAR, consisting of the CD4 extracellular and transmembrane domains fused to the CD3 intracellular signaling domain (CD4 Ϫ ), was advanced to clinical trials starting in the late 1990s, using retroviral transduction of autologous peripheral blood T lymphocytes and reinfusion. Unfortunately, this effort was abandoned after these trials showed...

Engineering HIV-Resistant, Anti-HIV Chimeric Antigen Receptor T Cells

“…PGT128 CAR T cells, in contrast, exhibited lower rates of CD137 expression after co-culture with HIV pos targets and appeared to clear HIV pos cells less well than other HIV-CAR T cells but produced cytokines after stimulation with cells expressing an alternative HIV envelope. Ali et al 58 recently compared the potency of bNAb-based HIV CARs against HIV-1 NL4-3 -infected T2 cells and found the CAR based on the PGT128 bNAb to be the www.moleculartherapy.org least effective, whereas that based on the 10E8 bNAb was the most potent. Here we observed that 10E8 HIVCAR T cells exhibited an activation profile that varied between donors and killed less potently than PGT145-and VRC07-523-HIVCAR T cells in our target cell assays.…”

Chimeric Antigen Receptor T Cells Guided by the Single-Chain Fv of a Broadly Neutralizing Antibody Specifically and Effectively Eradicate Virus Reactivated from Latency in CD4 + T Lymphocytes Isolated from HIV-1-Infected Individuals Receiving Suppressive Combined Antiretroviral Therapy

“…Previous reports have described the generation of HIV-1-specific CAR-T cells by connection of an extracellular antigenbinding domain to intracellular T cell activation domains (e.g., CD3 and CD28). The former can be a single-chain variable fragment (scFv) (26)(27)(28)(29)(30) or a natural molecule, such as CD4 (26,27,(31)(32)(33)(34)(35)(36), capable of directly inducing the death of cells expressing the viral envelope glycoprotein (Env). However, it remains to be determined whether these CAR-T cells can be used to kill the reactivated HIV-1 latently infected cells from the infected individuals receiving suppressive cART.…”

Engineering HIV-Specific Immunity with Chimeric Antigen Receptors

“…[30][31][32] The use of this CD4fCAR has important advantages, in that it has been found to be a safe reagent in multiple long-term clinical trials with over 500 patient years of clinical safety data 33,34 and this is strong evidence that it does not induce cytokine storms that have been an unwanted element with other CAR-based approaches in treating malignancies. 35,36 It is also unlikely to generate escape variants of HIV envelope as the loss of CD4 binding of an escape variant will likely have a dramatic effect on viral fitness.…”

“…We and others have done extensive testing of the antiviral function of CD8 + T cells transduced with CD4f CAR, finding that transduced cells are capable of killing HIV-infected cells and suppressing viral replication [30][31][32]34,37 and (unlike the HIV-specific TCR) that this activity is independent of HLA-I molecules. 38 CARs can also function in CD4 + T cells to act as HIV-1-specific helper cells.…”

“…32,42 Some of these CARs also contain additional signaling sequences, which provide costimulatory capability upon ligand binding, to achieve a more robust activation event upon ligation with the target epitope. Upon assessment in a suite of assays, each of these CARs is functional; however, efficiency varies with each ligand-binding moiety, each assay used, and the virus strain being employed.…”