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

ABSTRACT

Typically, anticancer CD8^pos T cells occur at low frequencies and become increasingly impaired in the tumor micro environment. In contrast, antiviral CD8^pos T cells display a much higher polyclonality, frequency, and functionality. In particular, cytomegalovirus (CMV) infection induces high numbers of ‘inflationary’ CD8^pos 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-ReTARG^pp65 rendered EpCAM-expressing primary patient-derived carcinoma cells highly sensitive to selective elimination by cognate anti-CMV CD8^pos 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-ReTARG^pp65 and EGFR-ReTARG^IE-1 strongly potentiated selective cancer cell elimination owing to the concerted action of the corresponding cognate anti-CMV CD8^pos 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.

KEYWORDS:

• Cancer immunotherapy
• anti-CMV T cells
• T cell-induced cytotoxicity
• EpCAM
• carcinoma

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

All data relevant to the study are included in the article or are uploaded as supplementary information.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/2162402X.2023.2207868.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by Dutch Cancer Society project numbers 13077 (to W.H.) and GSMS-123015 (to I. B.).