Removal of Vaccinia Virus Genes That Block Interferon Type I and II Pathways Improves Adaptive and Memory Responses of the HIV/AIDS Vaccine Candidate NYVAC-C in Mice

Abstract

Poxviruses encode multiple inhibitors of the interferon (IFN) system, acting at different levels and blocking the induction of host defense mechanisms. Two viral gene products, B19 and B8, have been shown to act as decoy receptors of type I and type II IFNs, blocking the binding of IFN to its receptor. Since IFN plays a major role in innate immune responses, in this investigation we asked to what extent the viral inhibitors of the IFN system impact the capacity of poxvirus vectors to activate immune responses. This was tested in a mouse model with single and double deletion mutants of the vaccine candidate NYVAC-C, which expresses the HIV-1 Env, Gag, Pol, and Nef antigens. When deleted individually or in double, the type I (B19) and type II (B8) IFN binding proteins were not required for virus replication in cultured cells. Studies of immune responses in mice after DNA prime/NYVAC boost revealed that deletion of B8R and/or B19R genes improved the magnitude and quality of HIV-1-specific CD8 + T cell adaptive immune responses and impacted their memory phase, changing the contraction, the memory differentiation, the effect magnitude, and the functionality profile. For B cell responses, deletion of the viral gene B8R and/or B19R had no effect on antibody levels to HIV-1 Env. These findings revealed that single or double deletion of viral factors (B8 and B19) targeting the IFN pathway is a useful approach in the design of improved poxvirus-based vaccines.

Deletion of the Vaccinia Virus N2L Gene Encoding an Inhibitor of IRF3 Improves the Immunogenicity of Modified Vaccinia Virus Ankara Expressing HIV-1 Antigens

“…Remarkably, compared to MVA-B, the deletion mutant MVA-B ⌬N2L significantly enhanced the adaptive and memory HIV-1-specific T cell immune responses. In both immunization groups, HIV-1-specific CD4 ϩ and CD8 ϩ T cells were activated, but with a higher frequency of HIV-1-specific CD8 ϩ T cells, similar to previous results with MVA or NYVAC vectors containing deletions in VACV genes (42,62,63,80,84). However, MVA-B ⌬N2L significantly enhanced the magnitude of the overall adaptive and memory HIV-1-specific CD4 ϩ and CD8 ϩ T cell responses compared to MVA-B.…”

“…(81), but an additional fifth deletion of the uracil-DNA glycosylase gene (MVA101R) decreased the responses (81). Moreover, NYVAC vectors with a single deletion of a VACV gene encoding a TLR inhibitor (A46R [83]) and with single or double deletions in VACV genes encoding type I and II IFN binding proteins (B19R and B8R, respectively [84][85][86]) were also able to enhance the immune responses to HIV-1 antigens in mice.…”

HIV/AIDS Vaccine Candidates Based on Replication-Competent Recombinant Poxvirus NYVAC-C-KC Expressing Trimeric gp140 and Gag-Derived Virus-Like Particles or Lacking the Viral Molecule B19 That Inhibits Type I Interferon Activate Relevant HIV-1-Specific B and T Cell Immune Functions in Nonhuman Primates

“…In cells infected with a NYVAC vector lacking B19, we have shown enhanced IFN-␣ production, maturation, and expression of IFN-induced pathways, IFN-regulated transcription factors, as well as multiple inflammatory cytokines in human DCs (12). Immunization of mice with NYVAC lacking B19R and expressing Env, Gag, Pol, and Nef clade C (CN54) HIV-1 antigens improved the magnitude and quality of HIV-1-specific CD8 ϩ T cell adaptive immune responses and impacted their memory phase, changing the contraction, the memory differentiation, the magnitude, and the functionality profile, while for B cell responses, B19 had no apparent effect on antibody levels (17). The immunomodulatory effects of B19 were more pronounced in mice than in NHPs.…”

The Canarypox Virus Vector ALVAC Induces Distinct Cytokine Responses Compared to the Vaccinia Virus-Based Vectors MVA and NYVAC in Rhesus Monkeys

“…Differences in immune gene upregulation and induced immune phenotypes were further seen following MVA and NYVAC infections in vitro and in vivo (27)(28)(29)(30). Further studies showed increased innate stimulation by these vectors following expanded deletion of their immune regulatory gene repertoire, highlighting the role of the immune gene repertoire of poxvirus vectors in their innate stimulatory phenotypes (31)(32)(33)(34). However, far less is known about the innate immune profile of ALVAC and its immune regulatory genes (35).…”