The susceptibility of wild ruminants, especially cervids, to bovine viral diarrhea virus (BVDV) has remained an enigma. Two white-tailed deer (Odocoileus virginianus) were submitted to the Animal Disease Research and Diagnostic Laboratory (ADRDL) in the fall of 2003 by the South Dakota Game Fish and Parks for chronic wasting disease (CWD) testing. Both animals were CWD negative. The animals were necropsied and histopathology, viral antigen detection, and virus isolation were performed. A noncytopathic (NCP) BVDV was isolated from the lungs and several other tissues of both animals. Formalin-fixed ear notches from both animals were positive for BVDV antigen by immunohistochemistry. The BVDV isolates were typed with the use of polymerase chain reaction in 5' untranslated region (UTR) and one isolate was typed a Type 2a and the other a Type 1b. Future field surveys to determine the incidence of BVDV along with experimental studies to determine if white-tailed deer fawns can be persistently infected with BVDV are needed.

Bovine herpesvirus 1 (BHV-1), an alphaherpesvirus, is a major pathogen that causes respiratory and reproductive infections. We observed tyrosine phosphorylation of a 95-kDa viral protein and dephosphorylation of 55- and 103-kDa cellular proteins during the course of BHV-1 infection. We demonstrated BHV-1 glycoprotein E (gE) to be the tyrosine phosphorylated viral protein by immunoprecipitation. Inhibition of phosphorylation of BHV-1 gE by tyrosine kinase inhibitors genistein and tyrphostin AG1478 substantially lowered the viral titer in Madin-Darby bovine kidney cells. The decrease in viral titer was directly proportional to the decrease in phosphorylation of the BHV-1 gE. Interestingly, these kinase inhibitors did not inhibit the replication of the BHV-1 gE deletion mutant virion (BHV-1gEDelta3.1). Our findings suggest that the wild-type BHV-1, with a functional gE protein, uses a different pathway of signaling events than the BHV-1 gE deletion mutant in replication. Our results indicate that the tyrosine phosphorylation of the cytoplasmic tail of BHV-1 gE is an important post-translational modification of the functional protein. An application of this study may be the use of tyrosine kinase inhibitors in controlling the BHV-1 infection.

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.

The innate immune response is a vital part of the body's antiviral defense system. The innate immune response is initiated by various receptor interactions, including danger associated molecular patterns (DAMPs). The S100A9 is a member of the DAMPs protein family and, is released by activated phagocytic cells such as neutrophils, monocytes, macrophages or endothelial cells, and S100A9 induces its effect through TLR4/MyD88 pathway. Bovine viral diarrhea virus (BVDV) is one of the major devastating disease in the cattle industry worldwide. It shows its effect through immunosuppression and develops persistent infection in calves born from infected cows. The current study revealed that BVDV potentially induced immunosuppression by the interaction of BVDV Npro protein with cellular S100A9 protein. The Inhibition of S100A9 protein expression by small interfering RNA (siRNA) enhanced the virus replication in infected cells. Overexpression of bovine S100A9 enhanced the ncpBVDV2a 1373 mediated Type-I interferon production. A co-immunoprecipitation experiment demonstrated a strong interaction between ncp BVDV2a 1373 Npro protein and cellular S100A9 protein. This suggested that BVDV Npro reduced the S100A9 protein availability/activity in infected cells, resulting in reduced Type-I interferon production. A further study of S100A9-BVDV interaction will be need for better understanding of BVDV pathophysiology.

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