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

Abstract

1Vaccines based on live attenuated viruses often induce broad, multifaceted immune 2 responses. However, they also usually sacrifice immunogenicity for attenuation. It is 3 particularly difficult to elicit an effective vaccine for herpesviruses due to an armament of 4 immune evasion genes and a latent phase. Here, to overcome the limitation of 5 attenuation, we developed a rational herpesvirus vaccine in which viral immune evasion 6 genes were deleted to enhance immunogenicity while also attaining safety. To test this 7 vaccine strategy, we utilized murine gammaherpesvirus-68 (MHV-68) as a proof-of-8 concept model for the cancer-associated human -herpesviruses, Epstein-Barr virus and 9Kaposi sarcoma-associated herpesvirus. We engineered a recombinant MHV-68 virus by 10 targeted inactivation of viral antagonists of type I interferon (IFN-I) pathway and deletion 11 of the latency locus responsible for persistent infection. This recombinant virus is highly 12 attenuated with no measurable capacity for replication, latency, or persistence in 13 immunocompetent hosts. It stimulates robust innate immunity, differentiates virus-specific 14 memory T cells, and elicits neutralizing antibodies. A single vaccination affords durable 15 protection that blocks the establishment of latency following challenge with the wild type 16 MHV-68 for at least six months post-vaccination. These results provide a novel approach 17 to effective vaccination against cancer-associated herpesviruses through the elimination 18 of latency and key immune evasion mechanisms from the pathogen. 19 20 Keywords: attenuation, -herpesviruses, immunogenicity, immune evasion, latency, T-21 cell, tumorigenesis, type I interferon, vaccine 22 herpesvirus (KSHV) are associated with cancer, and with no effective vaccine remain a 25 global health challenge. Despite strong innate and adaptive immune responses, once 26 acquired, herpesviruses persist for the rest of the host's life. EBV is associated with 27Burkitt's lymphoma, nasopharyngeal carcinoma (NPC), and Hodgkin'sand non-28Hodgkin's lymphomas 1-3 while KSHV is associated with Kaposi's sarcoma (KS), primary 29 effusion lymphoma (PEL), and multicentric Castleman's disease (MCD). These 30 malignancies frequently develop in AIDS patients 4-6 , but also in immunocompetent 31 people with more than 160,000 annual cancer cases associated with EBV and KSHV 7 . 32Clearly, effective vaccines against human -herpesviruses would dramatically reduce the 33 incidence of malignancies associated with these viruses. 34 35 Herpesviruses establish persistent infections characterized by lytic replication and 36 latency. Lytic replication of -and -herpesviruses results in disease pathologies, such 37 as varicella and herpes zoster for Varicella-Zoster virus (VZV), cold sores and genital 38 lesions for herpes simplex virus (HSV), and congenital defects for cytomegalovirus 39 (CMV). In comparison, malignancies associated with -herpesvirus infection are linked to 40 viral latency. Viral genes expressed during latency promote...

Conquering the Host: Determinants of Pathogenesis Learned from Murine Gammaherpesvirus 68

“…In one case, an MHV68 recombinant lacking ORF73 and genes of the MHV68 unique latency locus was generated (115). In another, a complex recombinant was constructed carrying stop insertions in genes with dual roles in lytic replication and immune evasion (ORF10, ORF36, ORF54, mK3), along with replacement of the MHV68 conserved latency locus (ORF72, M11, ORF73, ORF74) with a constitutive RTA expression construct (116). Both designs provide protection from wildtype virus challenge through induction of synergistic CD4 T cell, CD8 T cell, and antibody responses (115,116).…”

“…In another, a complex recombinant was constructed carrying stop insertions in genes with dual roles in lytic replication and immune evasion (ORF10, ORF36, ORF54, mK3), along with replacement of the MHV68 conserved latency locus (ORF72, M11, ORF73, ORF74) with a constitutive RTA expression construct (116). Both designs provide protection from wildtype virus challenge through induction of synergistic CD4 T cell, CD8 T cell, and antibody responses (115,116). Rational design of attenuated MHV68 viruses shows promise in generating full-spectrum protective immune responses against gammaherpesvirus infections.…”