Committing Cytomegalovirus-Specific CD8 T Cells to Eliminate Tumor Cells by Bifunctional Major Histocompatibility Class I Antibody Fusion Molecules

Redirector of Vaccine-induced Effector Responses (RoVER) for specific killing of cellular targets

BACKGROUND

In individuals with malignancy or HIV-1 infection, antigen-specific cytotoxic T lymphocytes (CTLs) often display an exhausted phenotype with impaired capacity to eliminate the disease. Existing cell-based immunotherapy strategies are often limited by the requirement for adoptive transfer of CTLs. We have developed an immunotherapy technology in which potent CTL responses are generated in vivo by vaccination and redirected to eliminate target cells using a bispecific Redirector of Vaccine-induced Effector Responses (RoVER).

METHODS

Following Yellow fever (YF) 17D vaccination of 51 healthy volunteers (NCT04083430), single-epitope YF-specific CTL responses were quantified by tetramer staining and multi-parameter flow cytometry. RoVER-mediated redirection of YF-specific CTLs to kill antigen-expressing Raji-Env cells, autologous CD19+ B cells or CD4+ T cells infected in vitro with a full-length HIV-1-eGFP was assessed in cell killing assays. Moreover, secreted IFN-γ, granzyme B, and TNF-α were analyzed by mesoscale multiplex assays.

FINDINGS

YF-17D vaccination induced strong epitope-specific CTL responses in the study participants. In cell killing assays, RoVER-mediated redirection of YF-specific CTLs to autologous CD19+ B cells or HIV-1-infected CD4+ cells resulted in 58% and 53% killing at effector to target ratio 1:1, respectively.

INTERPRETATION

We have developed an immunotherapy technology in which epitope-specific CTLs induced by vaccination can be redirected to kill antigen-expressing target cells by RoVER linking. The RoVER technology is highly specific and can be adapted to recognize various cell surface antigens. Importantly, this technology obviates the need for adoptive transfer of CTLs.

FUNDING

This work was funded by the Novo Nordisk Foundation (Hallas Møller NNF10OC0054577).

Applications of Anti-Cytomegalovirus T Cells for Cancer (Immuno)Therapy

Infection with cytomegalovirus (CMV) is highly prevalent in the general population and largely controlled by CD8pos T cells. Intriguingly, anti-CMV T cells accumulate over time to extraordinarily high numbers, are frequently present as tumor-resident 'bystander' T cells, and remain functional in cancer patients. Consequently, various strategies for redirecting anti-CMV CD8pos T cells to eliminate cancer cells are currently being developed. Here, we provide an overview of these strategies including immunogenic CMV peptide-loading onto endogenous HLA complexes on cancer cells and the use of tumor-directed fusion proteins containing a preassembled CMV peptide/HLA-I complex. Additionally, we discuss conveying the advantageous characteristics of anti-CMV T cells in adoptive cell therapy. Utilization of anti-CMV CD8pos T cells to generate CAR T cells promotes their in vivo persistence and expansion due to appropriate co-stimulation through the endogenous (CMV-)TCR signaling complex. Designing TCR-engineered T cells is more challenging, as the artificial and endogenous TCR compete for expression. Moreover, the use of expanded/reactivated anti-CMV T cells to target CMV peptide-expressing glioblastomas is discussed. This review highlights the most important findings and compares the benefits, disadvantages, and challenges of each strategy. Finally, we discuss how anti-CMV T cell therapies can be further improved to enhance treatment efficacy.

Novel Fab-peptide-HLA-I fusion proteins for redirecting pre-existing anti-CMV T cell immunity to selective eliminate carcinoma cells

Typically, anticancer CD8pos T cells occur at low frequencies and become increasingly impaired in the tumor micro environment. In contrast, antiviral CD8pos T cells display a much higher polyclonality, frequency, and functionality. In particular, cytomegalovirus (CMV) infection induces high numbers of 'inflationary' CD8pos T cells that remain lifelong abundantly present in CMV-seropositive subjects. Importantly, these so-called inflationary anti-CMV T cells increase with age, maintain a ready-to-go state, populate tumors, and do not become exhausted or senescent. Given these favorable attributes, we devised a novel series of recombinant Fab-peptide-HLA-I fusion proteins and coined them 'ReTARGs'. A ReTARG fusion protein consists of a high-affinity Fab antibody fragment directed to carcinoma-associated cell surface antigen EpCAM (or EGFR), fused in tandem with soluble HLA-I molecule/β2-microglobulin, genetically equipped with an immunodominant peptide derived from CMV proteins pp65 (or IE-1). Decoration with EpCAM-ReTARGpp65 rendered EpCAM-expressing primary patient-derived carcinoma cells highly sensitive to selective elimination by cognate anti-CMV CD8pos T cells. Importantly, this treatment did not induce excessive levels of proinflammatory T cell-secreted IFNγ. In contrast, analogous treatment with equimolar amounts of EpCAM/CD3-directed bispecific T-cell engager solitomab resulted in a massive release of IFNγ, a feature commonly associated with adverse cytokine-release syndrome. Combinatorial treatment with EpCAM-ReTARGpp65 and EGFR-ReTARGIE-1 strongly potentiated selective cancer cell elimination owing to the concerted action of the corresponding cognate anti-CMV CD8pos T cell clones. In conclusion, ReTARG fusion proteins may be useful as an alternative or complementary form of targeted cancer immunotherapy for 'cold' solid cancers.

Antibody-mediated delivery of a viral MHC-I epitope into the cytosol of target tumor cells repurposes virus-specific CD8+ T cells for cancer immunotherapy

Background

Redirecting pre-existing virus-specific cytotoxic CD8⁺ T lymphocytes (CTLs) to tumors by simulating a viral infection of the tumor cells has great potential for cancer immunotherapy. However, this strategy is limited by lack of amenable method for viral antigen delivery into the cytosol of target tumors. Here, we addressed the limit by developing a CD8⁺T cell epitope-delivering antibody, termed a TEDbody, which was engineered to deliver a viral MHC-I epitope peptide into the cytosol of target tumor cells by fusion with a tumor-specific cytosol-penetrating antibody.

Methods

To direct human cytomegalovirus (CMV)-specific CTLs against tumors, we designed a series of TEDbodies carrying various CMV pp65 antigen-derived peptides. CMV-specific CTLs from blood of CMV-seropositive healthy donors were expanded for use in in vitro and in vivo experiments. Comprehensive cellular assays were performed to determine the presentation mechanism of TEDbody-mediated CMV peptide-MHC-I complex (CMV-pMHCI) on the surface of target tumor cells and the recognition and lysis by CMV-specific CTLs. In vivo CMV-pMHCI presentation and antitumor efficacy of TEDbody were evaluated in immunodeficient mice bearing human tumors.

Results

TEDbody delivered the fused epitope peptides into target tumor cells to be intracellularly processed and surface displayed in the form of CMV-pMHCI, leading to disguise target tumor cells as virally infected cells for recognition and lysis by CMV-specific CTLs. When systemically injected into tumor-bearing immunodeficient mice, TEDbody efficiently marked tumor cells with CMV-pMHCI to augment the proliferation and cytotoxic property of tumor-infiltrated CMV-specific CTLs, resulting in significant inhibition of the in vivo tumor growth by redirecting adoptively transferred CMV-specific CTLs. Further, combination of TEDbody with anti-OX40 agonistic antibody substantially enhanced the in vivo antitumor activity.

Conclusion

Our study offers an effective technology for MHC-I antigen cytosolic delivery. TEDbody may thus have utility as a therapeutic cancer vaccine to redirect pre-existing anti-viral CTLs arising from previously exposed viral infections to attack tumors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01574-0.

Interfacing Biomaterials with Synthetic T Cell Immunity

The clinical success of cancer immunotherapy is providing exciting opportunities for the development of new methods to detect and treat cancer more effectively. A new generation of biomaterials is being developed to interface with molecular and cellular features of immunity and ultimately shape or control anti-tumor responses. Recent advances that are supporting the advancement of engineered T cells are focused here. This class of cancer therapy has the potential to cure disease in subsets of patients, yet there remain challenges such as the need to improve response rates and safety while lowering costs to expand their use. To provide a focused overview, recent strategies in three areas of biomaterials research are highlighted: low-cost cell manufacturing to broaden patient access, noninvasive diagnostics for predictive monitoring of immune responses, and strategies for in vivo control that enhance anti-tumor immunity. These research efforts shed light on some of the challenges associated with T cell immunotherapy and how engineered biomaterials that interface with synthetic immunity are gaining traction to solve these challenges.

A biomimetic assay platform for the interrogation of antigen-dependent anti-tumor T-cell function

Overcoming tumor-mediated immunosuppression and enhancing cytotoxic T-cell activity within the tumor microenvironment are two central goals of immuno-oncology (IO) drug discovery initiatives. However, exploratory assays involving immune components are often plagued by low-throughput and poor clinical relevance. Here we present an innovative ultra-high-content assay platform for interrogating T-cell-mediated killing of 3D multicellular tumor spheroids. Employing this assay platform in a chemical genomics screen of 1800 annotated compounds enabled identification of small molecule perturbagens capable of enhancing cytotoxic CD8⁺ T-cell activity in an antigen-dependent manner. Specifically, cyclin-dependent kinase (CDK) and bromodomain (BRD) protein inhibitors were shown to significantly augment anti-tumor T-cell function by increasing cytolytic granule and type II interferon secretion in T-cells in addition to upregulating major histocompatibility complex (MHC) expression and antigen presentation in tumor cells. The described biotechnology screening platform yields multi-parametric, clinically-relevant data and can be employed kinetically for the discovery of first-in-class IO therapeutic agents.

Vaccine-induced CD8 T cells are redirected with peptide-MHC class I-IgG antibody fusion proteins to eliminate tumor cells in vivo

Simulating a viral infection in tumor cells is an attractive concept to eliminate tumor cells. We previously reported the molecular design and the in vitro potency of recombinant monoclonal antibodies fused to a virus-derived peptide MHC class I complex that bypass the peptide processing and MHC loading pathway and directly displays a viral peptide in an MHC class I complex on the tumor cell surface. Here, we show that a vaccination-induced single peptide-specific CD8 T cell response was sufficient to eliminate B16 melanoma tumor cells in vivo in a fully immunocompetent, syngeneic mouse tumor model when mice were treated with mouse pMHCI-IgGs fusion proteins targeting the mouse fibroblast activation protein. Tumor growth of small, established B16 lung metastases could be controlled. The pMHCI-IgG had similar potency as an analogous pan-CD3 T-cell bispecific antibody. In contrast to growth control of small tumors, none of the compounds controlled larger solid tumors of MC38 cancer cells, despite penetration of pMHCI-IgGs into the tumor tissue and clear attraction and activation of antigen-specific CD8 T cells inside the tumor. pMHCI-IgG can have a similar potency as classical pan-T-cell recruiting molecules. The results also highlight the need to better understand immune suppression in advanced solid tumors.

Rhesus Cytomegalovirus-Specific CD8+ Cytotoxic T Lymphocytes Do Not Become Functionally Exhausted in Chronic SIVmac239 Infection

CD8⁺ cytotoxic T lymphocytes (CTLs) exert potent antiviral activity after HIV/SIV infection. However, efforts to harness the antiviral efficacy of CTLs for HIV/SIV prophylaxis and therapy have been severely hindered by two major problems: viral escape and exhaustion. By contrast, CTLs directed against human cytomegalovirus (HCMV), a ubiquitous chronic herpesvirus, seldom select for escape mutations and remain functional and refractory to exhaustion during chronic HCMV and HIV infection. Recently, attempts have been made to retarget HCMV-specific CTLs for cancer immunotherapy. We speculate that such a strategy may also be beneficial in the context of HIV/SIV infection, facilitating CTL-mediated control of HIV/SIV replication. As a preliminary assessment of the validity of this approach, we investigated the phenotypes and functionality of rhesus CMV (RhCMV)-specific CTLs in SIVmac239-infected Indian rhesus macaques (RMs), a crucial HIV animal model system. We recently identified two immunodominant, Mamu-A^∗02-restricted CTL epitopes derived from RhCMV proteins and sought to evaluate the phenotypic and functional characteristics of these CTL populations in chronic SIVmac239 infection. We analyzed and directly compared RhCMV- and SIVmac239-specific CTLs during SIVmac239 infection in a cohort of Mamu-A^∗01 ⁺ and Mamu-A^∗02 ⁺ RMs. CTL populations specific for at least one of the RhCMV-derived CTL epitopes were detected in ten of eleven Mamu-A^∗02 ⁺ animals tested, and both populations were detected in five of these animals. Neither RhCMV-specific CTL population exhibited significant changes in frequency, memory phenotype, granzyme B expression, exhaustion marker (PD-1 and CTLA-4) expression, or polyfunctionality between pre- and chronic SIVmac239 infection timepoints. In chronic SIVmac239 infection, RhCMV-specific CTLs exhibited higher levels of granzyme B expression and polyfunctionality, and lower levels of exhaustion marker expression, than SIVmac239-specific CTLs. Additionally, compared to SIVmac239-specific CTLs, greater proportions of RhCMV-specific CTLs were of the terminally differentiated effector memory phenotype (CD28^- CCR7^-) during chronic SIVmac239 infection. These results suggest that, in contrast to SIVmac239-specific CTLs, RhCMV-specific CTLs maintain their phenotypes and cytolytic effector functions during chronic SIVmac239 infection, and that retargeting RhCMV-specific CTLs might be a promising SIV immunotherapeutic strategy.

Protease-activation using anti-idiotypic masks enables tumor specificity of a folate receptor 1-T cell bispecific antibody

T-cell bispecific antibodies (TCBs) crosslink tumor and T-cells to induce tumor cell killing. While TCBs are very potent, on-target off-tumor toxicity remains a challenge when selecting targets. Here, we describe a protease-activated anti-folate receptor 1 TCB (Prot-FOLR1-TCB) equipped with an anti-idiotypic anti-CD3 mask connected to the anti-CD3 Fab through a tumor protease-cleavable linker. The potency of this Prot- FOLR1-TCB is recovered following protease-cleavage of the linker releasing the anti-idiotypic anti-CD3 scFv. In vivo, the Prot-FOLR1-TCB mediates antitumor efficacy comparable to the parental FOLR1-TCB whereas a noncleavable control Prot-FOLR1-TCB is inactive. In contrast, killing of bronchial epithelial and renal cortical cells with low FOLR1 expression is prevented compared to the parental FOLR1-TCB. The findings are confirmed for mesothelin as alternative tumor antigen. Thus, masking the anti-CD3 Fab fragment with an anti-idiotypic mask and cleavage of the mask by tumor-specific proteases can be applied to enhance specificity and safety of TCBs.

Soluble MHC class I complexes for targeted immunotherapy

Major histocompatibility complexes (MHC) have been used for more than two decades in clinical and pre-clinical approaches of tumor immunotherapy. They have been proven efficient for detecting anti-tumor-specific T cells when utilized as soluble multimers, immobilized on cells or artificial structures such as artificial antigen-presenting cells (aAPC) and have been shown to generate effective anti-tumor responses. In this review we summarize the use of soluble MHC class I complexes in tumor vaccination studies, highlighting the different strategies and their contradicting results. In summary, we believe that soluble MHC class I molecules represent an exciting tool with great potential to impact the understanding and development of immunotherapeutic approaches on many levels from monitoring to treatment.

Immunotherapies: Exploiting the Immune System for Cancer Treatment

Cancer is a condition that has plagued humanity for thousands of years, with the first depictions dating back to ancient Egyptian times. However, not until recent decades have biological therapeutics been developed and refined enough to safely and effectively combat cancer. Three unique immunotherapies have gained traction in recent decades: adoptive T cell transfer, checkpoint inhibitors, and bivalent antibodies. Each has led to clinically approved therapies, as well as to therapies in preclinical and ongoing clinical trials. In this review, we outline the method by which these 3 immunotherapies function as well as any major immunotherapeutic drugs developed for treating a variety of cancers.

Oncolytic Adenoviral Delivery of an EGFR-Targeting T-cell Engager Improves Antitumor Efficacy

Antiviral immune responses present a major hurdle to the efficacious use of oncolytic adenoviruses as cancer treatments. Despite the existence of a highly immunosuppressive tumor environment, adenovirus-infected cells can nonetheless be efficiently cleared by infiltrating cytotoxic T lymphocytes (CTL) without compromising tumor burden. In this study, we tested the hypothesis that tumor-infiltrating T cells could be more effectively activated and redirected by oncolytic adenoviruses that were armed with bispecific T-cell-engager (BiTE) antibodies. The oncolytic adenovirus ICOVIR-15K was engineered to express an EGFR-targeting BiTE (cBiTE) antibody under the control of the major late promoter, leading to generation of ICOVIR-15K-cBiTE, which retained its oncolytic properties in vitro cBiTE expression and secretion was detected in supernatants from ICOVIR-15K-cBiTE-infected cells, and the secreted BiTEs bound specifically to both CD3⁺ and EGFR⁺ cells. In cell coculture assays, ICOVIR-15K-cBiTE-mediated oncolysis resulted in robust T-cell activation, proliferation, and bystander cell-mediated cytotoxicity. Notably, intratumoral injection of this cBiTE-expressing adenovirus increased the persistence and accumulation of tumor-infiltrating T cells in vivo, compared with the parental virus lacking such effects. Moreover, in two distinct tumor xenograft models, combined delivery of ICOVIR-15K-cBiTE with peripheral blood mononuclear cells or T cells enhanced the antitumor efficacy achieved by the parental counterpart. Overall, our results show how arming oncolytic adenoviruses with BiTE can overcome key limitations in oncolytic virotherapy. Cancer Res; 77(8); 2052-63. ©2017 AACR.

A New Class of Bifunctional Major Histocompatibility Class I Antibody Fusion Molecules to Redirect CD8 T Cells

Bifunctional antibody fusion proteins engaging effector T cells for targeted elimination of tumor cells via CD3 binding have shown efficacy in both preclinical and clinical studies. Different from such a polyclonal T-cell recruitment, an alternative concept is to engage only antigen-specific T-cell subsets. Recruitment of specific subsets of T cells may be as potent but potentially lead to fewer side effects. Tumor-targeted peptide-MHC class I complexes (pMHCI-IgGs) bearing known antigenic peptides complexed with MHC class I molecules mark tumor cells as antigenic and utilize the physiologic way to interact with and activate T-cell receptors. If, for example, virus-specific CD8(+) T cells are addressed, the associated strong antigenicity and tight immune surveillance of the effector cells could lead to efficacious antitumor treatment in various tissues. However, peptide-MHC class I fusions are difficult to express recombinantly, especially when fused to entire antibody molecules. Consequently, current formats are largely limited to small antibody fragment fusions expressed in bacteria followed by refolding or chemical conjugation. Here, we describe a new molecular format bearing a single pMHCI complex per IgG fusion molecule characterized by enhanced stability and expression yields. This molecular format can be expressed in a full immunoglobulin format and can be designed as mono- or bivalent antibody binders. Mol Cancer Ther; 15(9); 2130-42. ©2016 AACR.

Activation of cytomegalovirus-specific CD8+ T-cell response by antibody-mediated peptide-major histocompatibility class I complexes

Imposing antigenicity on tumor cells is a key step toward successful cancer-immunotherapy. A cytomegalovirus-derived peptide recombinantly fused to a major histocompatibility class I complex and a monoclonal antibody can be targeted to tumor cells by antibody-mediated delivery and activate a strong and specific CD8⁺ T cell response.