Publications by Year: 2014

Influenza viruses remain a critical global health concern. More efficacious vaccines are needed to protect against influenza virus, yet few adjuvants are approved for routine use. Specialized proresolving mediators (SPMs) are powerful endogenous bioactive regulators of inflammation, with great clinical translational properties. In this study, we investigated the ability of the SPM 17-HDHA to enhance the adaptive immune response using an OVA immunization model and a preclinical influenza vaccination mouse model. Our findings revealed that mice immunized with OVA plus 17-HDHA or with H1N1-derived HA protein plus 17-HDHA increased Ag-specific Ab titers. 17-HDHA increased the number of Ab-secreting cells in vitro and the number of HA-specific Ab-secreting cells present in the bone marrow. Importantly, the 17-HDHA-mediated increased Ab production was more protective against live pH1N1 influenza infection in mice. To our knowledge, this is the first report on the biological effects of ω-3-derived SPMs on the humoral immune response. These findings illustrate a previously unknown biological link between proresolution signals and the adaptive immune system. Furthermore, this work has important implications for the understanding of B cell biology, as well as the development of new potential vaccine adjuvants.

UNLABELLED: Viral infection frequently triggers activation of host innate immune pathways that attempt to limit viral spread. The NF-κB pathway is a critical component that governs this response. We have found that the human cytomegalovirus (HCMV) U(L)26 protein antagonizes NF-κB activation. Upon infection, an HCMV strain lacking the U(L)26 gene (ΔU(L)26) induced the nuclear translocation of the NF-κB RelB subunit and activated expression and secretion of interleukin-6 (IL-6), an NF-κB target gene. The ΔU(L)26 mutant was also more sensitive to challenge with tumor necrosis factor alpha (TNF-α), a canonical NF-κB inducer. Further, expression of U(L)26 in the absence of other viral proteins blocked NF-κB activation induced by either TNF-α treatment or infection with Sendai virus (SeV). Our results indicate that U(L)26 expression is sufficient to block TNF-α-induced NF-κB nuclear translocation and IκB degradation. Last, U(L)26 blocks TNF-α-induced IκB-kinase (IKK) phosphorylation, a key step in NF-κB activation. Combined, our results indicate that U(L)26 is part of a viral program to antagonize innate immunity through modulation of NF-κB signaling.

IMPORTANCE: The NF-κB signaling pathway regulates innate immunity, an integral host process that limits viral pathogenesis. Viruses have evolved mechanisms to modulate NF-κB signaling to ensure their replication. HCMV is a major cause of birth defects and disease in immunosuppressed populations. HCMV is known to actively target the NF-κB pathway, which is important for HCMV infection. Our results indicate that the HCMV U(L)26 gene is a key modulator of NF-κB pathway activity. We find the U(L)26 gene is both necessary and sufficient to block NF-κB activation upon challenge with antiviral cytokines. Further, U(L)26 attenuates the phosphorylation and activation of a key NF-κB activating kinase complex, IKK. Our study provides new insight into how HCMV targets the NF-κB pathway. Given its importance to viral infection, the mechanisms through which viruses target the NF-κB pathway highlight areas of vulnerability that could be therapeutically targeted to attenuate viral replication.

Human cytomegalovirus (HCMV) induces numerous changes to the host metabolic network that are critical for high-titer viral replication. We find that HCMV infection substantially induces de novo pyrimidine biosynthetic flux. This activation is important for HCMV replication because inhibition of pyrimidine biosynthetic enzymes substantially decreases the production of infectious virus, which can be rescued through medium supplementation with pyrimidine biosynthetic intermediates. Metabolomic analysis revealed that pyrimidine biosynthetic inhibition considerably reduces the levels of various UDP-sugar metabolites in HCMV-infected, but not mock-infected, cells. Further, UDP-sugar biosynthesis, which provides the sugar substrates required for glycosylation reactions, was found to be induced during HCMV infection. Pyrimidine biosynthetic inhibition also attenuated the glycosylation of the envelope glycoprotein B (gB). Both glycosylation of gB and viral growth were restored by medium supplementation with either UDP-sugar metabolites or pyrimidine precursors. These results indicate that HCMV drives de novo-synthesized pyrimidines to UDP-sugar biosynthesis to support virion protein glycosylation. The importance of this link between pyrimidine biosynthesis and UDP-sugars appears to be partially shared among diverse virus families, because UDP-sugar metabolites rescued the growth attenuation associated with pyrimidine biosynthetic inhibition during influenza A and vesicular stomatitis virus infection, but not murine hepatitis virus infection. In total, our results indicate that viruses can specifically modulate pyrimidine metabolic flux to provide the glycosyl subunits required for protein glycosylation and production of high titers of infectious progeny.