Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 12, 2011
Publication Date: November 17, 2011
Citation: Schaut, R.G., McGill, J.L., Neill, J.D., Ridpath, J.F., Sacco, R.E. 2011. Bovine viral diarrhea virus modulations of monocyte derived macrophages [abstract]. In: Proceedings of the U.S. Bovine Viral Diarrhea Virus Symposium, November 17-18, 2011, San Diego, Calfornia. p. 69. Technical Abstract: Bovine viral diarrhea virus (BVDV) is a single stranded, positive sense RNA virus and is the causative agent of bovine viral diarrhea (BVD). Disease can range from persistently infected (PI) animals displaying no clinical symptoms of disease to an acute, severe disease. Presently, limited studies have focused on specific immune cell function or cytokine response to BVDV, especially in regard to paired biotypes. The objective of this study is to examine the effects of paired BVDV2 biotypes (cytopathic [CP], noncytopathic [NCP], high virulence [HV] and low virulence [LV]) on monocyte-derived macrophages (MDM) both in an in vitro and in vivo setting, and to elucidate the mechanisms by which BVDV can contribute to immunosuppression. For in vitro MDM experiments, eight BVDV-negative Holstein calves (age 6 months) were bled via jugular venipuncture. Peripheral blood mononuclear cells (PBMCs) were harvested and adherent cells isolated. Cells were plated after a seven-day incubation into 96-well tissue plates at 5x10**5 cells per well. Virus was added at a multiplicity of infection (MOI) of 1. Mock inoculated wells were included as controls. Cell supernatants were harvested at 2, 6, 18, and 24 h post inoculation. RNA was harvested for qPCR analysis. Cell supernatants were analyzed for cytokine protein via Searchlight, an immobilized antibody array. In a set of three in vivo experiments, 21 clinically healthy, colostrum-deprived Holstein calves (ages 2-5 weeks) were assigned to three groups: 1373 (HV), RS886 (LV), and control. Blood was collected beginning day -2 post infection and days 2, 4, 8, and 12 for monocytes and MDM. RNA and cell supernatants were collected with similar protocols to in vitro experiments. In vitro, we found that most cytokines measured (IL-1beta, TNF-alpha, IL-12p40, IL-8) were induced at a significantly higher level in the MDMs inoculated with the CP strain. The CP strain induced an initial (2 h) increase in IL-1beta and TNF-alpha mRNA in MDMs followed by a decrease over 6-24 h. When comparing an HV (1373) to LV (28508) strain, we found that 1373 rarely induced a response at 2 h in MDMs. Unlike the other strains, 1373 tended to induce a sustained mRNA response of IL-1beta, TNF-alpha and IL-12p40, which occurred beginning at 6 h post inoculation. In contrast to gene transcription, protein secretion by MDMs was impaired, especially TNF-alpha and IL-1beta. In vivo MDMs response to LPS stimulation was impaired at the level of transcription as well as protein secretion. Moreover, calves infected with the HV strain showed a greater impairment at an earlier timepoint than the calves infected with the LV strain. Loss of function in MDMs is one means by which BVDV could modulate the immune response to infection with secondary pathogens. These studies indicate that infection of MDM with BVDV in vitro can be used to model alterations in immunoregulatory pathways that lead to immunosuppression similar to that observed in an in vivo setting.