Abstract
BackgroundDendritic cells (DC) are important antigen presentation cells that monitor, process, and present antigen to T cells. Viruses that infect DC can have a devastating impact on the immune system. In this study, the ability of bovine viral diarrhea virus (BVDV) to replicate and produce infectious virus in monocyte-derived dendritic cells (Mo-DC) and monocytes was studied. The study also examined the effect of BVDV infection on Mo-DC expression of cell surface markers, including MHCI, MHCII, and CD86, which are critical for DC function in immune response.MethodsPeripheral blood mononuclear cells (PBMCs) were isolated from bovine blood through gradient centrifugation. The adherent monocytes were isolated from PBMCs and differentiated into Mo-DC using bovine recombinant interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GMCSF). To determine the effect of BVDV on Mo-DC, four strains of BVDV were used including the severe acute non-cytopathic (ncp) BVDV2a-1373; moderate acute ncp BVDV2a 28508-5; and a homologous virus pair [i.e., cytopathic (cp) BVDV1b TGAC and ncp BVDV1b TGAN]. The Cooper strain of bovine herpesvirus 1 (BHV1) was used as the control virus. Mo-DC were infected with one of the BVDV strains or BHV-1 and were subsequently examined for virus replication, virus production, and the effect on MHCI, MHCII, and CD86 expression.ResultsThe ability of monocytes to produce infectious virus reduced as monocytes differentiated to Mo-DC, and was completely lost at 120 hours of maturation. Interestingly, viral RNA increased throughout the course of infection in Mo-DC, and the viral non-structural (NS5A) and envelope (E2) proteins were expressed. The ncp strains of BVDV down-regulated while cp strain up-regulated the expression of the MHCI, MHCII, and CD86 on Mo-DC.ConclusionsThe study revealed that the ability of Mo-DC to produce infectious virus was reduced with its differentiation from monocytes to Mo-DC. The inability to produce infectious virus may be due to a hindrance of virus packaging or release mechanisms. Additionally, the study demonstrated that ncp BVDV down-regulated and cp BVDV up-regulated the expression of Mo-DC cell surface markers MHCI, MHCII, and CD86, which are important in the mounting of immune responses.
Highlights
Dendritic cells (DC) are important antigen presentation cells that monitor, process, and present antigen to T cells
Characterization of monocyte-derived dendritic cells (Mo-DC) Freshly collected monocytes were positive for MHCI (96.62 ± 0.50%), MHCII (80.58 ± 19.69%), and CD14 (16.54 ± 1.49%) (Figure 1)
After 7 days of differentiation from monocytes to Mo-DC, the Mo-DC were positive for MHCI (98.58 ± 0.34%), MHCII (94.1 ± 2.81%), CD205 (55.97 ± 45.48%), and CD86 (77.83 ± 17.83%), and were negative for CD21 (3.42 ± 0.19%) and CD14 (1.025 ± 0.45) (Figure 2)
Summary
Dendritic cells (DC) are important antigen presentation cells that monitor, process, and present antigen to T cells. The ability of bovine viral diarrhea virus (BVDV) to replicate and produce infectious virus in monocyte-derived dendritic cells (Mo-DC) and monocytes was studied. The study examined the effect of BVDV infection on Mo-DC expression of cell surface markers, including MHCI, MHCII, and CD86, which are critical for DC function in immune response. Genotypes are divided into Type 1 (BVDV1) or Type 2 (BVDV2), and are distinguishable using monoclonal antibodies [2], while BVDV biotypes are classified as either cytopathic (cp) or non-cytopathic (ncp), based on the effect the virus has on cell culture [3]. The ability of BVDV to replicate and produce infectious virus in monocytes and Mo-DC was investigated along with the effect of BVDV infection on MHCI, MHCII, or CD86 expression. Four strains of BVDV were used in this study including the severe acute ncp BVDV2a 1373 strain, the moderate acute ncp BVDV2a 28508-5 strain, and a virus pair (cp BVDV1b TGAC and ncp BVDV1b TGAN) recovered from an animal that died of mucosal disease
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