Drug-Encoded Biomarkers for Monitoring Biological Therapies

Optimizing oncolytic virotherapy in cancer treatment

In the wake of the success of modern immunotherapy, oncolytic viruses (OVs) are currently seen as a potential therapeutic option for patients with cancer who do not respond or fail to achieve durable responses following treatment with immune checkpoint inhibitors. OVs offer a multifaceted therapeutic platform because they preferentially replicate in tumour cells, can be engineered to express transgenes that augment their cytotoxic and immunostimulatory activities, and modulate the tumour microenvironment to optimize immune-mediated tumour eradication, both at locoregional and systemic sites of disease. Lysis of tumour cells releases tumour-specific antigens that trigger both the innate and adaptive immune systems. OVs also represent attractive combination partners with other systemically delivered agents by virtue of their highly favourable safety profiles. Rational combinations of OVs with different immune modifiers and/or antitumour agents, based on mechanisms of tumour resistance to immune-mediated attack, may benefit the large, currently underserved, population of patients who respond poorly to immune checkpoint inhibition.

Humanized Mice with Subcutaneous Human Solid Tumors for Immune Response Analysis of Vaccinia Virus-Mediated Oncolysis

Oncolytic vaccinia virus (VACV) therapy is an alternative cancer treatment modality that mediates targeted tumor destruction through a tumor-selective replication and an induction of anti-tumor immunity. We developed a humanized tumor mouse model with subcutaneous human tumors to analyze the interactions of VACV with the developing tumors and human immune system. A successful systemic reconstitution with human immune cells including functional T cells as well as development of tumors infiltrated with human T and natural killer (NK) cells was observed. We also demonstrated successful in vivo colonization of such tumors with systemically administered VACVs. Further, a new recombinant GLV-1h376 VACV encoding for a secreted human CTLA4-blocking single-chain antibody (CTLA4 scAb) was tested. Surprisingly, although proving CTLA4 scAb's in vitro binding ability and functionality in cell culture, beside the significant increase of CD56^bright NK cell subset, GLV-1h376 was not able to increase cytotoxic T or overall NK cell levels at the tumor site. Importantly, the virus-encoded β-glucuronidase as a measure of viral titer and CTLA4 scAb amount was demonstrated. Therefore, studies in our "patient-like" humanized tumor mouse model allow the exploration of newly designed therapy strategies considering the complex relationships between the developing tumor, the oncolytic virus, and the human immune system.

Use of Reporter Genes in the Generation of Vaccinia Virus-Derived Vectors

Vaccinia virus (VACV) is one of the most extensively-studied viruses of the Poxviridae family. It is easy to genetically modify, so it has become a key tool for many applications. In this context, reporter genes facilitate the study of the role of foreign genes introduced into the genome of VACV. In this review, we describe the type of reporter genes that have been used to generate reporter-expressing VACV and the applications of the recombinant viruses obtained. Reporter-expressing VACV are currently employed in basic and immunology research, in the development of vaccines and cancer treatment.