Monoclonal Antibodies and Nanobodies to the Immune Checkpoint ligand VISTA

 

The V-domain immunoglobulin suppressor of T-cell activation know as VISTA is a newly discovered  immune checkpoint molecule regulating T-cell activation. It is widely expressed within the hematopoietic compartment, with the highest expression found on myeloid cells. VISTA acts as both a receptor and a ligand on immune cells.  In terms of sequence homology, PD-L1 is the closer homologue of the VISTA extracellular domain. The VISTA pathway however operates through a distinct mechanistic pathway than PD-1:PD-L1 immune axis.  VISTA does not bind to itself, nor to PD-1 or PD-L1 and despites the fact that VISTA has been shown to bind to several ligands (VSIG3, PSGL-1 and Syndecan-2), it remains unclear if any of these ligands are true receptors.   Activating the VISTA pathway either with VISTA as a ligand or with agonistic mAbs to VISTA blocks T cell activation and proliferation events.  As such, we and others have shown that these agents are immunosuppressive in many murine models of inflammatory diseases. In order to further study the mechanism of action of VISTA, our laboratory has recently generated nanobodies and mouse mAbs to the human VISTA IgV domain with most of them behaving as agonistic mAbs.  We have also generated rat mAbs that recognize both murine and human VISTA IgV domain. These reagents are available for collaboration (1).

 
What are Bispecific Proteins ?

Bispecific proteins have two binding domains for binding two distinct targets. These proteins have versatile properties that make them advantageous for use as tools in biochemical techniques or as therapeutics. Our current research includes designing novel soluble reagents for improving in vitro techniques and to design and assess novel bispecific therapeutics with immunomodulatory properties. 

T-CEP (T-Cell Expansion Protein) constructs

 
T-CEP (T-Cell Expansion Protein) combines a single chain variable fragment (ScFV) against CD28 with a ScFV against CD3 in one small soluble protein to produce a highly potent small ex vivo T-cell activator and expander. This technology improves on currently available soluble method for T-cell expansion, and has potential for application in the field of adoptive cell therapy, where efficient expansion of effective T-cells is needed (2).

CD28-CD3-bispecific_5_ptm_seed_0_relaxed-color-coded-cropped-for-website.png

Figure 1. Side view of CD28-CD3 ScFV bispecific construct ribbon structure as predicted using Deepmind Alphafold 2.0 under a Google Colab iteration [CD28 ScFV, CD3 ScFV, scFv heavy and light chain, general linker, 6x His Tag]    (https://colab.research.google.com/github/sokrypton/ColabFold/blob/main/beta/AlphaFold2_advanced.ipynb#scrollTo=KAZj6CBZTkJM) 

Bispecific proteins for tissue-specific targeting and accumulation

The use of the bispecific protein format for tissue-specific accumulation of therapeutic cargo is also being explored. By selecting two appropriate domains, we are studying the effectiveness of delivering immunomodulatory proteins to a specific antigen as means of potentiating the therapeutic effect and reducing systemic side effects in the treatment of inflammatory diseases.

Selected publication from our group:

1. Ma YV, Sparkes A, Romão E, Saha S, Gariépy J. (2021) Agonistic nanobodies and antibodies to human VISTA. MAbs. 13(1):2003281 

2.  Matus EI, Sparkes A, Gariépy J (2020) A soluble activator that favors the ex vivo expansion of CD8+CD27+ T cells. JCI Insight. 5(22):e141293

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Last updated on September-12-2021