Arming an Oncolytic Herpes Simplex Virus Type 1 with a Single-chain Fragment Variable Antibody against PD-1 for Experimental Glioblastoma Therapy

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d2836978e316">Purpose</h5> <p id="P10">Glioblastoma (GBM) is resistant to standard of care. Immune checkpoints inhibitors (such as anti-PD-1 mAbs) efficiently restore antitumor T-cell activity. We engineered a new oncolytic herpes simplex virus (oHSV) expressing a single-chain antibody against PD-1 (scFvPD-1) to evaluate its efficacy in mouse models of GBM. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d2836978e321">Experimental Design</h5> <p id="P11">NG34scFvPD-1 expresses the human GADD34 gene transcriptionally controlled by the Nestin promoter to allow replication in GBM cells and a scFvPD-1 cDNA transcriptionally controlled by the CMV promoter. ELISA assays were performed to detect binding of scFvPD-1 to mouse and human PD-1. <i>In vitro</i> cytotoxicity and replication assays were performed to measure NG34scFvPD-1 oncolysis, and scFvPD-1 expression and secretion were determined. <i>In vivo</i> survival studies using orthotopic mouse GBM models were performed to evaluate the therapeutic potency of NG34scFvPD-1. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d2836978e332">Results</h5> <p id="P12">NG34scFvPD-1–infected GBM cells express and secrete scFvPD-1 that binds mouse PD-1. The introduction of the scFvPD-1 sequence in the viral backbone does not alter the oncolytic properties of NG34scFvPD-1. <i>In situ</i> NG34scFvPD-1 treatment improved the survival with a tail of durable survivorship in 2 syngeneic immunocompetent mouse models of GBM. Mice that survived the first GBM challenge rejected the second challenge of GBM when implanted in the contralateral hemisphere. However, this was not true when athymic mice were employed as the recipients of the second challenge, consistent with the need for an intact immune system to obtain a memory response. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d2836978e340">Conclusions</h5> <p id="P13">NG34scFvPD-1 treatment induces a durable antitumor response in 2 preclinical mouse models of GBM with evidence for antitumor memory. </p> </div>