Inhibition of human tumor growth in mice by an oncolytic herpes simplex virus designed to target solely HER-2-positive cells

Abstract

Oncolytic virotherapy exploits the ability of viruses to infect, replicate into, and kill tumor cells. Among the viruses that entered clinical trials are HSVs. HSVs can be engineered to become tumorspecific by deletion of selected genes or retargeting to tumorspecific receptors. A clinically relevant surface molecule is HER-2, hyperexpressed in one fourth of mammary and ovary carcinomas, and associated with high metastatic ability. As a previously undescribed strategy to generate HSV recombinants retargeted to HER-2 and detargeted from natural receptors, we replaced the Ig-folded core in the receptor-binding virion glycoprotein gD with anti-HER-2 single-chain antibody. The recombinant entered cells solely via HER-2 and lysed HER-2-positive cancer cells. Because of the high specificity, its safety profile in i.p. injected mice was very high, with a LD 50 >5 ؋ 10 8 pfu, a figure at least 10,000-fold higher than that of corresponding WT-gD carrying virus (LD 50 Ϸ 5 ؋ 10 4 pfu). When administered intratumorally to nude mice bearing HER-2-hyperexpressing human tumors, it strongly inhibited progressive tumor growth. The results provide a generally applicable strategy to engineer HSV recombinants retargeted to a wide range of receptors for which a single-chain antibody is available, and show the potential for retargeted HSV to exert target-specific inhibition of human tumor growth. Therapy with HER-2-retargeted oncolytic HSV could be effective in combined or sequential protocols with monoclonal antibodies and small inhibitors, particularly in patients resistant to HER-2-targeted therapy because of alterations in HER-2 signaling pathway, or against brain metastases inaccessible to anti-HER-2 antibodies. mammary carcinoma ͉ ovary carcinoma ͉ retarget ͉ tropism

A Double Mutation in Glycoprotein gB Compensates for Ineffective gD-Dependent Initiation of Herpes Simplex Virus Type 1 Infection

“…To expand the observation that gB:N/T facilitates the use of atypical entry receptors, we used a transient complementation approach to determine whether the double mutation can enhance infection via an unrelated receptor. HSV can be retargeted by ablation of the native receptor recognition functions of gD and insertion of recognition elements for novel receptors (41,42,57), but the efficiency of retargeted infection tends to be lower than that of natural infection through authentic receptors. We generated a gD-null derivative of K-gB:wt, designated K-gB: wt⌬gD, by replacement of the gD ORF with that of enhanced GFP (EGFP), as done earlier to produce K-gB:N/T⌬gD.…”

Cross Talk among the Glycoproteins Involved in Herpes Simplex Virus Entry and Fusion: the Interaction between gB and gH/gL Does Not Necessarily Require gD

“…gD serves as the receptorbinding glycoprotein, able to interact with alternative receptors, nectin1, herpesvirus entry mediator (HVEM) and, in some cells, modified heparan sulfate (9,13,30,39). It can also be engineered to accept heterologous ligands able to interact with selected receptors present on tumor cells and thus represents a tool to redirect HSV tropism (21,28,29,42). The heterodimer gH/gL and gB execute fusion and constitute the conserved fusion apparatus across the Herpesviridae family.…”

A Herpes Simplex Virus Vector System for Expression of Complex Cellular cDNA Libraries

“…HSV has a large transgene capacity (12), transduces most cell types with high efficiency (4,13), and can be retargeted for selective infection of cells bearing specific receptors (17,23). The availability of large expression libraries in vectors capable of efficient gene delivery and expression in a broad range of cell types provides an opportunity to develop methods to select or screen for functions that affect a variety of cellular processes.…”