Deletion of immune evasion genes provides an effective vaccine design for tumor-associated herpesviruses

Gurpreet Brar,Leming Tong,Wai Wai Lin,Ren Sun,Carl F Ware,Alex K Lam,Ting-Ting Wu,Nisar A Farhat,Tiffany Hsu,Alisa Sukhina,Marcia A Blackman,Yong Hoon Kim

doi:10.1038/s41541-020-00251-x

Abstract

Vaccines based on live attenuated viruses often induce broad, multifaceted immune responses. However, they also usually sacrifice immunogenicity for attenuation. It is particularly difficult to elicit an effective vaccine for herpesviruses due to an armament of immune evasion genes and a latent phase. Here, to overcome the limitation of attenuation, we developed a rational herpesvirus vaccine in which viral immune evasion genes were deleted to enhance immunogenicity while also attaining safety. To test this vaccine strategy, we utilized murine gammaherpesvirus-68 (MHV-68) as a proof-of-concept model for the cancer-associated human γ-herpesviruses, Epstein–Barr virus and Kaposi sarcoma-associated herpesvirus. We engineered a recombinant MHV-68 virus by targeted inactivation of viral antagonists of type I interferon (IFN-I) pathway and deletion of the latency locus responsible for persistent infection. This recombinant virus is highly attenuated with no measurable capacity for replication, latency, or persistence in immunocompetent hosts. It stimulates robust innate immunity, differentiates virus-specific memory T cells, and elicits neutralizing antibodies. A single vaccination affords durable protection that blocks the establishment of latency following challenge with the wild type MHV-68 for at least six months post-vaccination. These results provide a framework for effective vaccination against cancer-associated herpesviruses through the elimination of latency and key immune evasion mechanisms from the pathogen.

Highlights

Human γ-herpesviruses Epstein–Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) are associated with cancer, and with no effective vaccine remain a global health challenge
We show that an murine gammaherpesvirus-68 (MHV-68) virus engineered to be latency- and immune evasion-deficient is highly attenuated in immunocompetent hosts yet a potent inducer of antiviral locus comprising ORF72, ORF73 (LANA), ORF74, and M11 with constitutively expressed RTA driven by the phosphoglycerate kinase 1 (PGK) promoter in a two-tiered approach to prevent persistent infection
These antigens reduced infectious mononucleosis-like symptoms of lymphoproliferation but failed to limit establishment of latency[43,44,45,46,47,48]

Summary

INTRODUCTION

Human γ-herpesviruses Epstein–Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) are associated with cancer, and with no effective vaccine remain a global health challenge. Herpesviruses establish persistent infections characterized by lytic replication and latency. We hypothesized that a recombinant ing LANA expression combined with constitutive RTA expression herpesvirus lacking multiple IFN-I evasion genes and deficient in results in a latency-deficient virus[28]. We show that an MHV-68 virus engineered to be latency- and immune evasion-deficient is highly attenuated in immunocompetent hosts yet a potent inducer of antiviral locus comprising ORF72, ORF73 (LANA), ORF74, and M11 with constitutively expressed RTA driven by the phosphoglycerate kinase 1 (PGK) promoter in a two-tiered approach to prevent persistent infection. Deletion of the latency locus, constitutive RTA expression, and the removal of immune evasion genes created a live attenuated γ-herpesvirus vaccine named DIP (deficient in immune evasion and persistence) (Fig. 1a). Comparison of the in vitro growth kinetics of DIP in NIH3T3 fibroblasts with the wild type (WT) virus showed that DIP

RESULTS

Brar et al 3

DISCUSSION

Findings

METHODS