Noncytopathic type 2 bovine viral diarrhea virus 96B2222 induces upregulation of type-I interferon and chemokine receptor 4 expression in bovine peripheral blood mononuclear cells during in vitro infection

Abstract

Bovine viral diarrhea virus (BVDV) infection leads to monetary losses in cattle operations due to morbidity and impaired growth. IT is not currently possible to identify pregnant cattle carrying fetuses persistently infected (PI) with BVDV. We previously described a type-I interferon (IFN-I) response to acute non-cytopathic (ncp) BVDV infection in PI fetuses. It was hypothesized that infection of peripheral blood mononuclear cells (PBMC) with ncp-2 96b2222 BVDV would: (1) up-regulate IFN-stimulated genes (IFN-(3, ISG 15), antiviral molecules (retinoic acid inducible gene I, RIG- 1) and chemokine receptor four (CXCR4); (2) viral entry would be mediated through CXCR4; and (3) differentially affect immune cell populations and expression of CXCR4. After optimization of in vitro conditions, PBMCs isolated from a BVDV-naive steer were infected with ncp-2 96b2222 BVDV and treated with AMD3100 and/or CXCR4's ligand, chemokine ligand 12 (CXCL12). Cells were collected and processed for RT-PCR and flow cytometry staining post-infection. At 32 hours post-infection (hpi), mRNA expression of IFN-I pathway genes (IFN-(3, ISG-15), antiviral molecules (RIG-I), CXCR4, CXCLJ 2 and CD8 increased (P < 0.05). Treatment of PBMCs with AMD3100 prior to BVDV infection did not affect BVDV mRNA replication but caused a decrease in CXCR4 mRNA and cell surface expression. CXCL12 treatment increased the concentration of BVDV, CXCR4, IFN- ß, ISG15, and RIG-I transcription. Blocking CXCR4 with AMD3100 and/or CXCL12 did not prevent viral entry and/or replication, but abrogated a BVDV-induced increase in CXCR4 mRNA expression while CXCL12 modulated infection. During PBMC infection in vitro, BVDV may induce release of IFN- ß which then activates ISGs to increase CXCR4 mRNA and protein. Flow cytometry data suggest trends in immune cell populations during ncp-2 96b2222 BVDV infection.