OC 10.2 - Antibody-mediated depletion of human CLEC-2 in a novel humanized mouse model

Saturday, July 9, 2022

1:15 PM – 1:30 PM

Location: ExCel Center, ICC Capital Suite Room 6

Presentation Format: In-Person

Co-Author(s)

HB

Helena C. Brown

PhD student
University Hospital Würzburg
Würzburg, Bayern, Germany

Presenting Author(s)

Sarah Beck, PhD

Postdoc
Institute of Experimental Biomedicine - Chair I, University Hospital and Rudolf Virchow Center for Integrative and Translational Bioimaging, Würzburg, Germany
Würzburg, Bayern, Germany

Co-Author(s)

Stefano Navarro, MSc

PhD candidate
University hospital Würzburg
Würzburg, Bayern, Germany
SW

Steve Watson

Professor
University of Birmingham
Birmingham, England, United Kingdom
BN

Bernhard Nieswandt

Professor
Institute of Experimental Biomedicine - Chair I, University Hospital Würzburg and Rudolf Virchow Center for Integrative and Translational Biomaging, University of Würzburg, Germany
Würzburg, Bayern, Germany
David Stegner, PhD

Professor
Institute of Experimental Biomedicine - Chair I, University Hospital and Rudolf Virchow Center for Integrative and Translational Bioimaging, Würzburg, Germany
Würzburg, Bayern, Germany

Background: Platelet C-type lectin-like receptor 2 (CLEC-2) is a unique platelet activation receptor signaling through a hemITAM motif. Due to its roles in thrombosis, tumor metastasis and inflammation CLEC-2 has been suggested as therapeutic target. However, there are currently no methods to test potential human therapeutics targeting CLEC-2, such as antibodies, in vivo.

Aims: We have therefore generated and characterized a humanized CLEC-2 mouse (hCLEC-2KI) and developed a novel monoclonal anti-human CLEC-2 antibody, HEL1, for in vivo testing.

Methods: Murine CLEC-2 was replaced with the human variant and the mice, as well as their platelets characterized in vitro and in vivo. HEL1 was generated by hybridoma technology following immunization of rats with immunoprecipitated human CLEC-2. HEL1 was characterized using human and hCLEC-2KI platelets. CLEC-2 regulation was assessed using the anti-hCLEC-2 monoclonal antibodies AYP1 and HEL1.

Results: hCLEC-2KI mice were viable, fertile and born at Mendelian ratio, without evidence of blood-lymphatic mixing. hCLEC-2KI platelets displayed glycoprotein receptor expression, activation and aggregation comparable to wildtype controls. Likewise, tail bleeding times of hCLEC-2KI mice were like those of WT mice. The novel antibody HEL1 activates platelets upon binding to CLEC-2. However, HEL1-fab fragments neither activate platelets nor affect rhodocytin-induced platelet activation. Challenging hCLEC-2KI mice with HEL1- or AYP1-IgG, which bind different epitopes, resulted in a transient thrombocytopenia as well as CLEC-2 depletion for more than 2 weeks, but did not affect hemostasis.

Conclusion(s): Here, we provide proof of principle that the hCLEC-2KI mouse can be used to test anti-hCLEC-2 agents in vivo. In addition, we demonstrated that hCLEC-2 can be immunodepleted.