Targeting the latent human cytomegalovirus reservoir for T-cell-mediated killing with virus-specific nanobodies

Timo W M De Groof,Ian J Groves,Mark Wills,Eleanor Y Lim,Martine J Smit,Nick D Bergkamp,John H Sinclair,Raimond Heukers,Elizabeth G Elder

doi:10.1038/s41467-021-24608-5

Abstract

Latent human cytomegalovirus (HCMV) infection is characterized by limited gene expression, making latent HCMV infections refractory to current treatments targeting viral replication. However, reactivation of latent HCMV in immunosuppressed solid organ and stem cell transplant patients often results in morbidity. Here, we report the killing of latently infected cells via a virus-specific nanobody (VUN100bv) that partially inhibits signaling of the viral receptor US28. VUN100bv reactivates immediate early gene expression in latently infected cells without inducing virus production. This allows recognition and killing of latently infected monocytes by autologous cytotoxic T lymphocytes from HCMV-seropositive individuals, which could serve as a therapy to reduce the HCMV latent reservoir of transplant patients.

Highlights

Latent human cytomegalovirus (HCMV) infection is characterized by limited gene expression, making latent HCMV infections refractory to current treatments targeting viral replication
We developed a new partial inverse agonistic US28-targeting nanobody in the hope that it would inhibit US28 function and efficiently induce IE gene expression for subsequent targeting by host IE-specific cytotoxic T lymphocytes (CTLs)
We tested the functional effect of VUN100bv on NFAT (Nuclear Factor of Activated T cells) signaling, which is induced by US28 wildtype (WT) receptor and several US28 mutants in HEK293T cells (Fig. 1c)[18]

Summary

Introduction

Latent human cytomegalovirus (HCMV) infection is characterized by limited gene expression, making latent HCMV infections refractory to current treatments targeting viral replication. We report the killing of latently infected cells via a virus-specific nanobody (VUN100bv) that partially inhibits signaling of the viral receptor US28. VUN100bv reactivates immediate early gene expression in latently infected cells without inducing virus production. This allows recognition and killing of latently infected monocytes by autologous cytotoxic T lymphocytes from HCMV-seropositive individuals, which could serve as a therapy to reduce the HCMV latent reservoir of transplant patients. In immunocompromised or immunosuppressed individuals, this control of reactivation is lost, and for both solid organ and stem cell transplant patients, HCMV reactivation frequently results in a disseminated viral infection that is a major cause of transplant rejection and mortality[3]. VUN100bv treatment drives recognition and killing of latently infected monocytes by CTLs, and demonstrates the efficacy of VUN100bv for lowering latent viral loads in ex vivo experimentally infected peripheral blood mononuclear cells (PBMCs)

Methods

Results

Conclusion