Replication-dead gammaherpesvirus vaccine protects against acute replication, reactivation from latency, and lethal challenge in mice

Abstract

Gammaherpesviruses (GHVs) are oncogenic viruses that establish lifelong infections and are significant causes of human morbidity and mortality. While several vaccine strategies to limit GHV infection and disease are in development, there are no FDA-approved vaccines for human GHVs. As a new approach to gammaherpesvirus vaccination, we developed and tested a replication-dead virus (RDV) platform, using murine gammaherpesvirus 68 (MHV68), a well-established mouse model for gammaherpesvirus pathogenesis studies and preclinical therapeutic evaluations. We employed codon-shuffling-based complementation to generate revertant-free RDV lacking expression of the essential replication and transactivator protein (RTA) encoded by ORF50 to arrest viral gene expression early after de novo infection. Inoculation with RDV-50.stop exposes the host to intact virion particles and leads to limited lytic gene expression in infected cells. Prime-boost vaccination of mice with RDV-50.stop elicited virus-specific neutralizing antibody and effector T cell responses in the lung and spleen. Vaccination with RDV-50.stop resulted in a near complete abolishment of virus replication in the lung 7 days post-challenge and virus reactivation from spleen 16 days post-challenge with WT MHV68. Ifnar1-/- mice, which lack the type I interferon receptor, exhibit severe disease upon infection with WT MHV68. RDV-50.stop vaccination of Ifnar1-/- mice prevented wasting and mortality upon challenge with WT MHV68. These results demonstrate that prime-boost vaccination with a GHV that is unable to undergo lytic replication offers protection against acute replication, reactivation, and severe disease upon WT virus challenge. ImportanceGammaherpesviruses establish chronic infections that place a host at life-long risk for the development of lymphoproliferative disorders. While these viruses are endemic within the adult human population, there are currently no FDA-approved vaccines available to prevent acute infection or the later onset of lymphoproliferative disorders. We report here the use of a prime-boost vaccination strategy utilizing replication-dead virus strains to protect mice from acute disease following challenge with WT virus. We demonstrate that vaccination with replication-dead viruses is both safe and effective within immunocompetent and immunodeficient mice, and protects from viral replication, reactivation, and onset of severe disease.