OligoDOMTM: a T-cell response-enhancing platform applied to cancer immunotherapy

Abstract

Background: Neoepitopes derived (0) from tumors are attractive cancer immunotherapy targets, especially when combined with immune checkpoint inhibitors (CPIs). Vaccines using lipid nanoparticle (LNP)-encapsulated mRNA to deliver neoepitopes have shown encouraging results in patients and animal models, due to T cell-dependent responses. However, a low mutational burden is often a predictor of poor CPI response: the immune response against the few available mutations can be insufficient. An enhanced response to these few mutations could increase CPI efficacy. Here, we investigate the potential of oligoDOM™, a self-assembling sequence, to improve neoepitope immunogenicity and antitumor efficacy in murine cancer models.

Methods: LNP-formulated mRNA constructs encoding short epitope strings fused with oligoDOM™ were tested. Immune responses in mice were compared between constructs with oligoDOM™ and their controls. Specific T-cell responses against four tumor models (MC38, CT26, TC-1, B16-OVA) were measured using ELISpot in naïve mice. Two models (TC-1 and B16-OVA) were further selected for tumor growth efficacy testing.

Results: LNP-formulated neoepitope-oligoDOM™ mRNA constructs induced a significantly superior immune response as compared with the control groups in four neoantigens tested. This increased specific immunogenicity is linked to antitumor growth effects in murine syngeneic cancer models such as the B16-OVA and TC-1. The induced T-cell immune response significantly correlated with tumor growth rate reduction.

Discussion: Combining oligoDOM™ and LNP-mRNA technologies offers a versatile platform that allows for efficient short neoepitope strings delivery. This approach represents a feasible, potentially effective strategy for personalized cancer immunotherapy.

Keywords: cancer; immunotherapy; mRNA; nanoparticles; t cells.

Figure 1

OligoDOM™ in mRNA constructs induces stronger specific T cells IFNg response in the spleen compared to the constructs without this sequence. Naïve C57BL/6 mice (n = 5) were immunized twice (D0, D21) with 50 µL of different mRNA constructs by the IM route. (A) Schematic representation of the constructs used for this study. (B–E) Immune responses evaluated 7 days after the second immunization by measuring specific IFNγ secreting splenocytes (spot-forming cells (SFCs)/1 × 10⁶ cells) using ELISpot after restimulation with specific peptides for 24 hours: (B) MC38 CD8-epitopes Reps1 or Adpgk, (C) CT26 epitopes Mitch 1 (CD8) or Dhx35 (CD4), (D) E7 CD8-epitope and (E) OVA CD8- or CD4-epitopes. Individual data, mean (line), and SD are represented. Differences were assessed by one-way ANOVA followed by Dunn’s multiple comparison test. **p < 0.01.

Figure 2

OligoDOM™ in mRNA constructs induces efficient tumor therapy. (A) Schematic representation of the prophylactic approach. (B) TC-1 tumor growth rate in mice immunized against E7 peptide. Each line refers to the mean tumor volume ± SD of each experimental group (n = 5). (C) Immune response measured at the end of the experiment, against the specific E7 epitope used to immunize the mice. E7 specific IFNγ-secreting CD8 T cells were measured by ELISpot (spot-forming cells (SFCs)/1 × 10⁶ cells) in the spleen. Individual data, mean (line), and SD are represented. Differences were assessed by one-way ANOVA followed by Dunn’s multiple comparison test. *p < 0.05; ** p < 0.01. (D) Schematic representation of the therapeutic approach. (E) B16-OVA tumor growth rate in mice immunized against OVA peptides. Each line refers to the mean tumor volume ± SD of each experimental group (n = 5). (F) Immune response against OVA epitopes at the end of the experiment. CD8- or CD4- peptide specific IFNγ secreting T-cells (spot-forming cells (SFCs)/1 × 10⁶ cells) in the spleen. Individual data, mean (line), and SD were represented. Differences were assessed by one-way ANOVA followed by Dunn’s multiple comparison test. *p < 0.05; ** p < 0.01.

Figure 3

A strong link between the increased immune response triggered by oligoDOM™ and the efficacy against tumor growth is evident. The Spearman correlation graphs illustrate the relationship between specific T cells secreting IFNγ in the spleen and the tumor size across all groups in the HPV prophylactic experiment (A) and OVA therapeutic experiment (B).