J Virol. 2015; pii: JVI.03061-14.

Delaloye J, Filali-Mouhim A, Cameron MJ, Haddad EK, Harari A, Goulet JP, Gomez CE, Perdiguero B, Esteban M, Pantaleo G, Roger T, Sékaly RP, Calandra T.

NYVAC, a highly attenuated, replication-restricted poxvirus, is a safe and immunogenic vaccine vector. Deletion of immune evasion genes encoded by poxviruses is an attractive strategy for improving their immunogenic properties.

Using system biology approaches, we herein describe the enhanced immunological profile of NYVAC vectors expressing the HIV-1 clade C env-gag-pol-nef genes (NYVAC-C) with single or double deletion of genes encoding type I (ΔB19R) or type II (ΔB8R) interferon (IFN)-binding proteins. Transcriptomic analyses of human monocytes infected with NYVAC-C, NYVAC-C-ΔB19R or NYVAC-C-ΔB8RB19R revealed a concerted up-regulation of innate immune pathways (IFN-stimulated genes [ISGs]) of increasing magnitude with NYVAC-C-ΔB19R and NYVAC-C-ΔB8RB19R relative to NYVAC-C. Deletion of B8R and B19R resulted in an enhanced activation of IRF3, IRF7 and STAT1, robust production of type I IFN and of ISGs whose expressions were inhibited by anti-type I IFN antibodies. Interestingly, NYVAC-C -ΔB8RB19R induced the production of much higher levels of pro-inflammatory cytokines (TNF, IL-6 and IL-8) than NYVAC-C or NYVAC-C-ΔB19R as well as a strong inflammasome response (caspase-1 and IL-1β) in infected monocytes. Top network analyses showed that this broad ΔB8RB19R-mediated response was organized around two up-regulated gene expression nodes (TNF and IRF7).

Consistent with these findings, monocytes infected with NYVAC-C-ΔB8RB19R induced a stronger type I IFN-dependent and IL-1-dependent allogenic CD4⁺-T-cell response than NYVAC-C or NYVAC-C-ΔB19R. Dual deletion of type I and type II IFN immune evasion genes in NYVAC markedly enhanced its immunogenic properties via an increased expression of type I IFNs and IL-1β and make it an attractive candidate HIV vaccine vector.