Preclinical evaluation of two phylogenetically distant arenavirus vectors for the development of novel immunotherapeutic combination strategies for cancer treatment

BACKGROUND

Engineered arenavirus vectors have recently been developed to leverage the body's immune system in the fight against chronic viral infections and cancer. Vectors based on Pichinde virus (artPICV) and lymphocytic choriomeningitis virus (artLCMV) encoding a non-oncogenic fusion protein of human papillomavirus (HPV)16 E6 and E7 are currently being tested in patients with HPV16+ cancer, showing a favorable safety and tolerability profile and unprecedented expansion of tumor-specific CD8+ T cells. Although the strong antigen-specific immune response elicited by artLCMV vectors has been demonstrated in several preclinical models, PICV-based vectors are much less characterized.

METHODS

To advance our understanding of the immunobiology of these two vectors, we analyzed and compared their individual properties in preclinical in vivo and in vitro systems. Immunogenicity and antitumor effect of intratumoral or intravenous administration of both vectors, as well as combination with NKG2A blockade, were evaluated in naïve or TC-1 mouse tumor models. Flow cytometry, Nanostring, and histology analysis were performed to characterize the tumor microenvironment (TME) and T-cell infiltrate following treatment.

RESULTS

Despite being phylogenetically distant, both vectors shared many properties, including preferential infection and activation of professional antigen-presenting cells, and induction of potent tumor-specific CD8+ T-cell responses. Systemic as well as localized treatment induced a proinflammatory shift in the TME, promoting the infiltration of inducible T cell costimulator (ICOS)+CD8+ T cells capable of mediating tumor regression and prolonging survival in a TC-1 mouse tumor model. Still, there was evidence of immunosuppression built-up over time, and increased expression of H2-T23 (ligand for NKG2A T cell inhibitory receptor) following treatment was identified as a potential contributing factor. NKG2A blockade improved the antitumor efficacy of artARENA vectors, suggesting a promising new combination approach. This demonstrates how detailed characterization of arenavirus vector-induced immune responses and TME modulation can inform novel combination therapies.

CONCLUSIONS

The artARENA platform represents a strong therapeutic vaccine approach for the treatment of cancer. The induced antitumor immune response builds the backbone for novel combination therapies, which warrant further investigation.

Local immunotherapy with the RNA-based immune stimulator CV8102 induces substantial anti-tumor responses and enhances checkpoint inhibitor activity

Immunotherapy has revolutionized cancer treatment in recent years. Although currently approved checkpoint inhibitors (CPIs) yield remarkable anti-tumoral responses in several cancer types, a substantial proportion of patients do not benefit from such therapies. Local activation of innate immune signaling pathways is a promising approach to overcome the immunosuppressive tumor microenvironment, induce anti-tumor immunity, and improve the efficacy of CPI therapies. Here, we assessed the mode of action and efficacy of the RNA-based innate immune stimulator CV8102 for local immunotherapy in preclinical models. Intratumoral (i.t.) administration of CV8102 activated innate immune responses in the tumor microenvironment and draining lymph nodes, resulting in a dose-dependent anti-tumoral response. Combining i.t. CV8102 with systemic anti-programmed death protein 1 (PD-1) treatment further enhanced anti-tumoral responses, inducing tumor infiltration and activation of CD8+ T cells. The resulting memory response prevented tumor growth in rechallenged animals and impaired the growth of non-injected distal tumors. Therefore, i.t. CV8102 delivery is a promising approach for local cancer immunotherapy, especially in combination with CPIs. Clinical testing of CV8102 is ongoing (NCT03291002).

Abstract 4198: Evaluation of a cancer immunotherapy with engineered arenavirus vectors and 4-1BB agonists in a preclinical tumor model

T cells play a central role in immune responses against cancer. Within the tumor, however, T cells are exposed to a plethora of inactivating factors causing various degrees of dysfunction, changes in metabolism and a generally reduced cellular fitness, eventually leading to tumor progression. To prevent or delay the onset of exhaustion and instead augment effector functions and persistence of functional T cells, costimulatory factors and cytokines are needed. Targeting 4-1BB (CD137), a member of the tumor necrosis factor receptor superfamily, has been shown to represent a promising strategy for inducing an activating signal in CD8+ T cells, resulting in increased pro-inflammatory cytokine secretion, cytotoxic function, and survival. Engineered arenavirus vectors based on lymphocytic choriomeningitis virus (LCMV) or Pichinde virus (PICV) have been shown previously to induce massive infiltration of tumor antigen specific CD8+ T cells into the tumor in several preclinical cancer models. To investigate whether enhanced co-stimulation via 4-1BB further improves T cell responses and/or tumor control, combination therapies with replicating LCMV based vectors (artLCMV) and 4-1BB agonists were explored. A single intravenous treatment of artLCMV encoding the tumor associated antigens (TAA) gp70 or Trp2 in B16.F10 tumor bearing mice induced TAA specific CD8+ T cells in both the periphery and the tumor, resulting in tumor growth delay and some complete responses. Combining artLCMV with agonistic anti-4-1BB significantly improved tumor control and increased the number of complete responders. Analysis of tumor infiltrating lymphocytes revealed higher absolute numbers of TAA specific CD8+ T cells in the combination group compared to the artLCMV alone group. Analyses of the TAA specific cells revealed that more cells expressed granzyme B, Ki67 and Bcl-XL when co-stimulated with anti-4-1BB compared to the group treated with artLCMV alone. Importantly, encoding 4-1BBL in addition to a TAA in artLCMV revealed similar outcomes as just summarized for the combination with agonistic antibodies. Overall, these experiments confirmed the strong antigenicity and T cell inducing capacity of the engineered arenavirus platform, leading to efficient tumor control in a stringent mouse model. Combination with 4-1BB agonists, either in form of antibodies or encoded within the vector genome, was shown to further augment TAA-specific T cell responses within the tumor, leading to better tumor growth control and a higher rate of complete responders.

Citation Format: Judith Strauss, Marilies Scheinost, Theresa Kleissner, Diana Reckendorfer, Kimberly Pojar, Mohamed Habbeddine, Sarah Ahmadi-Erber, Daniela Deutschmann, Sarah Schmidt, Josipa Raguz, Igor Matushansky, Christoph Lampert, Klaus K. Orlinger, Henning Lauterbach. Evaluation of a cancer immunotherapy with engineered arenavirus vectors and 4-1BB agonists in a preclinical tumor model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4198.

Abstract 2048: In vitro and in vivo characterization of non-oncolytic engineered arenavirus vectors for cancer immunotherapy

Cytotoxic CD8+ T cells are paramount for effective cancer immunotherapy. We engineered two distantly related arenaviruses, lymphocytic choriomeningitis virus (LCMV) and Pichinde virus (PICV), encoding the same non-oncogenic HPV16 E7E6 fusion protein to effectively mount and maintain tumor specific CD8+ T cell responses. The designated vectors, HB-201 (LCMV) and HB-202 (PICV), are currently in an ongoing Phase I/II open labelled clinical trial of HB-201 single vector therapy and HB-202/HB-201 alternating two-vector therapy in patients with treatment-refractory HPV16+ cancers (NCT04180215). To characterize the immunogenic properties of both vectors, we designed a comprehensive set of preclinical and translational experiments utilizing human PBMCs, artificial APCs and HPV16 E6 and E7 specific reporter T cells. This was done in conjunction with a preclinical model for HPV16 associated cancer (TC-1). HB-201 (LCMV) and HB-202 (PICV) surrogate vectors encoding GFP readily infected human monocytes, plasmacytoid dendritic, and conventional dendritic cells. In addition, HB-201 and HB-202 vectors successfully induced antigen presentation of E7 and E6 epitopes as evidenced by TCR reporter cells. Innate immune cell activation and cytokine responses to HB-202 were slightly lower compared to HB-201, findings which are consistent with different memory profiles of E7 specific CD8+ T cells in non-tumor bearing mice. In a therapeutic setting of the TC-1 tumor model, both vectors were comparably effective, showing major infiltration of CD8+ T cells into the tumor microenvironment, tumor growth delay and a significantly prolonged survival already after a single administration. In this data set we have confirmed the strong immunogenicity of the engineered arenavirus platform leading to efficient tumor control in a relevant mouse model for HPV16+ cancers, which further supports the clinical development of our novel arenavirus platform.

Citation Format: Josipa Raguz, Theresa Kleissner, Sandra Rosskopf, Mohamed Habbeddine, Katharina Lechner, Valentin Just, Donna Edwards, Igor Matushansky, Christoph Lampert, Klaus K. Orlinger, Henning Lauterbach. In vitro and in vivo characterization of non-oncolytic engineered arenavirus vectors for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2048.

Live-attenuated lymphocytic choriomeningitis virus-based vaccines for active immunotherapy of HPV16-positive cancer

Infection with human papillomavirus (HPV) is associated with a variety of cancer types and limited therapy options. Therapeutic cancer vaccines targeting the HPV16 oncoproteins E6 and E7 have recently been extensively explored as a promising immunotherapy approach to drive durable antitumor T cell immunity and induce effective tumor control. With the goal to achieve potent and lasting antitumor T cell responses, we generated a novel lymphocytic choriomeningitis virus (LCMV)-based vaccine, TT1-E7E6, targeting HPV16 E6 and E7. This replication-competent vector was stably attenuated using a three-segmented viral genome packaging strategy. Compared to wild-type LCMV, TT1-E7E6 demonstrated significantly reduced viremia and CNS immunopathology. Intravenous vaccination of mice with TT1-E7E6 induced robust expansion of HPV16-specific CD8⁺ T cells producing IFN-γ, TNF-α and IL-2. In the HPV16 E6 and E7-expressing TC-1 tumor model, mice immunized with TT1-E7E6 showed significantly delayed tumor growth or complete tumor clearance accompanied with prolonged survival. Tumor control by TT1-E7E6 was also achieved in established large-sized tumors in this model. Furthermore, a combination of TT1-E7E6 with anti-PD-1 therapy led to enhanced antitumor efficacy with complete tumor regression in the majority of tumor-bearing mice that were resistant to anti-PD-1 treatment alone. TT1-E7E6 vector itself did not exhibit oncolytic properties in TC-1 cells, while the antitumor effect was associated with the accumulation of HPV16-specific CD8⁺ T cells with reduced PD-1 expression in the tumor tissues. Together, our results suggest that TT1-E7E6 is a promising therapeutic vaccine for HPV-positive cancers.

Unmodified mRNA in LNPs constitutes a competitive technology for prophylactic vaccines

mRNA represents a promising new vaccine technology platform with high flexibility in regard to development and production. Here, we demonstrate that vaccines based on sequence optimized, chemically unmodified mRNA formulated in optimized lipid nanoparticles (LNPs) are highly immunogenic and well tolerated in non-human primates (NHPs). Single intramuscular vaccination of NHPs with LNP-formulated mRNAs encoding rabies or influenza antigens induced protective antibody titers, which could be boosted and remained stable during an observation period of up to 1 year. First mechanistic insights into the mode of action of the LNP-formulated mRNA vaccines demonstrated a strong activation of the innate immune response at the injection site and in the draining lymph nodes (dLNs). Activation of the innate immune system was reflected by a transient induction of pro-inflammatory cytokines and chemokines and activation of the majority of immune cells in the dLNs. Notably, our data demonstrate that mRNA vaccines can compete with licensed vaccines based on inactivated virus or are even superior in respect of functional antibody and T cell responses. Importantly, we show that the developed LNP-formulated mRNA vaccines can be used as a vaccination platform allowing multiple, sequential vaccinations against different pathogens. These results provide strong evidence that the mRNA technology is a valid approach for the development of effective prophylactic vaccines to prevent infectious diseases.

Vaccines based on mRNA provoke strong immune responses after a single dose. mRNA is commonly known as the ‘genetic messenger’ cousin of DNA and a crucial mediator of protein production. Now, research led by Mariola Fotin-Mleczek, of Germany’s CureVac AG, demonstrates that mRNA can be developed to produce virus fragments, called antigens, that can prime a vaccinee’s immune system against a pathogen. Testing their vaccine platform, the team created mRNA coding for rabies and influenza antigens, and used intramuscular injection to inoculate non-human primates. A single dose elicited strong immune responses, which the team then successfully maintained through booster vaccinations for an observation period of 1 year. The responses outperformed those of licensed vaccines against rabies and influenza type H3N2. This research shows that mRNA has promise as a versatile, cost-effective, rapidly scalable vaccine technology.

Soluble ectodomain CD163 and extracellular vesicle-associated CD163 are two differently regulated forms of 'soluble CD163' in plasma

CD163 is the macrophage receptor for uptake of hemoglobin-haptoglobin complexes. The human receptor can be shed from the macrophage surface owing to a cleavage site for the inflammation-inducible TACE/ADAM17 enzyme. Accordingly, plasma ‘soluble CD163’ (sCD163) has become a biomarker for macrophage activity and inflammation. The present study disclosed that 10% of sCD163 in healthy persons is actually extracellular vesicle (EV)-associated CD163 not being cleaved and shed. Endotoxin injection of human volunteers caused a selective increase in the ectodomain CD163, while septic patients exhibited high levels of both soluble ectodomain CD163 and extracellular vesicle (EV) CD163, the latter representing up 60% of total plasma CD163. A poor prognosis of septic patients measured as the sequential organ failure assessment (SOFA) score correlated with the increase in membrane-associated CD163. Our results show that soluble ectodomain CD163 and EV CD163 in plasma are part of separate macrophage response in the context of systemic inflammation. While that soluble ectodomain CD163 is released during the acute systemic inflammatory response, this is not the case for EV CD163 that instead may be released during a later phase of the inflammatory response. A separate measurement of the two forms of CD163 constituting ‘soluble CD163’ in plasma may therefore add to the diagnostic and prognostic value.

Bone marrow-specific knock-in of a non-activatable Ikkα kinase mutant influences haematopoiesis but not atherosclerosis in Apoe-deficient mice

Background

The Ikkα kinase, a subunit of the NF-κB-activating IKK complex, has emerged as an important regulator of inflammatory gene expression. However, the role of Ikkα-mediated phosphorylation in haematopoiesis and atherogenesis remains unexplored. In this study, we investigated the effect of a bone marrow (BM)-specific activation-resistant Ikkα mutant knock-in on haematopoiesis and atherosclerosis in mice.

Methods and Results

Apolipoprotein E (Apoe)-deficient mice were transplanted with BM carrying an activation-resistant Ikkα gene (Ikkα^AA/AAApoe^−/−) or with Ikkα^+/+Apoe^−/− BM as control and were fed a high-cholesterol diet for 8 or 13 weeks. Interestingly, haematopoietic profiling by flow cytometry revealed a significant decrease in B-cells, regulatory T-cells and effector memory T-cells in Ikkα^AA/AAApoe^−/− BM-chimeras, whereas the naive T-cell population was increased. Surprisingly, no differences were observed in the size, stage or cellular composition of atherosclerotic lesions in the aorta and aortic root of Ikkα^AA/AAApoe^−/− vs Ikkα^+/+Apoe^−/− BM-transplanted mice, as shown by histological and immunofluorescent stainings. Necrotic core sizes, apoptosis, and intracellular lipid deposits in aortic root lesions were unaltered. In vitro, BM-derived macrophages from Ikkα^AA/AAApoe^−/− vs Ikkα^+/+Apoe^−/− mice did not show significant differences in the uptake of oxidized low-density lipoproteins (oxLDL), and, with the exception of Il-12, the secretion of inflammatory proteins in conditions of Tnf-α or oxLDL stimulation was not significantly altered. Furthermore, serum levels of inflammatory proteins as measured with a cytokine bead array were comparable.

Conclusion

Our data reveal an important and previously unrecognized role of haematopoietic Ikkα kinase activation in the homeostasis of B-cells and regulatory T-cells. However, transplantation of Ikkα^AA mutant BM did not affect atherosclerosis in Apoe^−/− mice. This suggests that the diverse functions of Ikkα in haematopoietic cells may counterbalance each other or may not be strong enough to influence atherogenesis, and reveals that targeting haematopoietic Ikkα kinase activity alone does not represent a therapeutic approach.

CD1d-restricted NKT cells modulate placental and uterine leukocyte populations during chlamydial infection in mice

Invariant CD1d-restricted natural killer T cells play an important immunoregulatory role and can influence a broad spectrum of immunological responses including against bacterial infections. They are present at the fetal-maternal interface and although it has been reported that experimental systemic iNKT cell activation can induce mouse abortion, their role during pregnancy remain poorly understood. In the present work, using a physiological Chlamydia muridarum infection model, we have shown that, in vaginally infected pregnant mice, C. muridarum is cleared similarly in C57BL/6 wild type (WT) and CD1d(-/-) mice. We have also shown that infected- as well as uninfected-CD1d(-/-) mice have the same litter size as WT counterparts. Thus, CD1d-restricted cells are required neither for the resolution of chlamydial infection of the lower-genital tract, nor for the maintenance of reproductive capacity. However, unexpected differences in T cell populations were observed in uninfected pregnant females, as CD1d(-/-) placentas contained significantly higher percentages of CD4(+) and CD8(+) T cells than WT counterparts. However, infection triggered a significant decrease in the percentages of CD4(+) T cells in CD1d(-/-) mice. In infected WT pregnant mice, the numbers of uterine CD4(+) and CD8(+) T cells, monocytes and granulocytes were greatly increased, changes not observed in infected CD1d(-/-) mice. An increase in the percentage of CD8(+) T cells seems independent of CD1d-restricted cells as it occurred in both WT and CD1d(-/-) mice. Thus, in the steady state, the lack of CD1d-restricted NKT cells affects leukocyte populations only in the placenta. In Chlamydia-infected pregnant mice, the immune response against Chlamydia is dampened in the uterus. Our results suggest that CD1d-restricted NKT cells play a role in the recruitment or homeostasis of leukocyte populations at the maternal-fetal interface in the presence or absence of Chlamydia infection.

Role of NKT cells in the placenta and uterus of pregnant mice infected by Chlamydia trachomatis (42.5)

In order to study the role of maternal NKT cells against a Chlamydia infection during pregnancy, we have compared CD1d-deficient, C57Bl/6 (B6) mice to wild type controls, in the presence or absence of a Chlamydia infection. We have examined the expression of several molecules known to be important for NKT cell function, in the uterus and placenta. We focused our study on NKG2A, NKG2C and NKG2D receptors, their ligands Qa-1 and Rae-1 and their co-receptors CD94, DAP10 and DAP12. We also studied perforin, granzyme B, osteopontin and cytokines such as TNF alpha, interferon gamma and IL1 beta, Our results suggest that CD1d-restricted NKT cells do not play a major role in the control of infection, as the intensity and duration of infection were comparable in CD1d-deficient and wild type mice. However, we found that Chlamydia infection caused an increase of invariant NKT (iNKT) cells in the placenta and uterus of B6 mice, measured by the expression of their characteristic TCR Valpha14-Jalpha18 invariant chain. Correlatively, Chlamydia infection in CD1d-deficient mice lead to organ-specific modulations in the expression of several NKT cell markers, which differed from those observed in B6 mice.

Supported by NIH grant number 5 R21 A1060725-02, CNRS and Universities Paris 6 and 7.