Using Cystine Knot Proteins as a Novel Approach to Retarget Oncolytic Measles Virus

Area of Science:

• Virology
• Oncology
• Protein Engineering

Background:

• Modified measles virus (MV) shows preclinical oncolytic activity against various cancers.
• Cystine knot proteins (CKPs) are high-affinity binding polypeptides with potential for targeted delivery.
• Integrins (αvβ3, αvβ5, α5β1) are cell surface receptors often overexpressed in tumors.

Purpose of the Study:

• To investigate the retargeting of MV using CKPs to enhance oncolytic virotherapy.
• To evaluate the efficacy of a CKP-retargeted MV (MV-CKPint) against integrin-expressing cancer cells.
• To assess the potential of MV-CKPint for intravenous delivery and therapeutic application.

Main Methods:

• Engineered MV to display a CKP targeting αvβ3, αvβ5, and α5β1 integrins (MV-CKPint).
• Assessed MV-CKPint's infectivity, replication, and cytolytic activity against human glioblastoma, medulloblastoma, DIPG, and melanoma cell lines in vitro.
• Evaluated the effect of echistatin (integrin inhibitor) and protease cleavage on viral activity.
• Administered MV-CKPint intravenously (i.v.) in a glioblastoma tumor model to assess tumor targeting and efficacy.

Main Results:

• MV-CKPint effectively infected, replicated in, and killed target cancer cells expressing αvβ3, αvβ5, and α5β1 integrins in vitro.
• Viral activity was confirmed to be integrin-dependent and mediated by the CKP, as shown by echistatin blocking and abrogation upon protease cleavage.
• Intravenous delivery of MV-CKPint successfully reached a subcutaneous glioblastoma tumor and induced cytopathic effects comparable to intratumoral injection.
• The retargeted virus demonstrated potential for effective therapy via i.v. administration due to targeting of tumor vascular endothelium.

Conclusions:

• Cystine knot proteins can successfully retarget measles virus to specific cellular receptors like integrins.
• MV-CKPint exhibits potent oncolytic activity against multiple integrin-positive cancer types, including glioblastoma and melanoma.
• The study provides proof of principle for using CKPs to retarget enveloped viruses for oncolytic and gene therapy, with potential for i.v. delivery.