Measuring CMI responses using the PrimeFlow RNA assay; a new method of evaluating BVDV vaccination response in cattle

Authors: Falkenberg, Shollie; Dassanayake, Rohana; Neill, John; WALZ, PAUL - Auburn University; Casas, Eduardo; Ridpath, Julia; ROTH, JAMES - Iowa State University

Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2020
Publication Date: 2/11/2020
Citation: Falkenberg, S.M., Dassanayake, R.P., Neill, J.D., Walz, P., Casas, E., Ridpath, J.F., Roth, J. 2020. Measuring CMI responses using the PrimeFlow RNA assay; a new method of evaluating BVDV vaccination response in cattle. Veterinary Immunology and Immunopathology. 221:110024. https://doi.org/10.1016/j.vetimm.2020.110024.
DOI: https://doi.org/10.1016/j.vetimm.2020.110024

Interpretive Summary: Infection with bovine viral diarrhea virus (BVDV) contributes to a variety of economically important disease outcomes, and vaccination against BVDV is a common practice as a preventative method to protect against infection. Modified live viral (MLV) vaccines have been shown to provide better protection against fetal infections with BVDV than killed BVDV vaccines. This is thought to be due to producing greater immune protection. This study describes a newly developed assay that incorporates cell identification in addition to detection of immune response signals and BVDV inside the cell. Immune response signals are substances called cytokines that affect other immune cells and provide signs to other cells. These signals were found in cells that generally produce these signals as well as a new finding of another cell type that produced these signals in vaccinated calves. This study also showed a decrease in the amount of BVDV inside the cells of vaccinated calves. Data from this study shows a relationship between an increase in immune signals and a decreased in the amount of BVDV in the cells. This new method detects immune signals and also the antiviral effects from these signals. This is the first assay to describe and measure immune signals and the amount of BVDV inside the cell following BVDV vaccination.

Technical Abstract: Current methods for evaluating bovine viral diarrhea virus (BVDV) vaccination response typically rely on measurement of humoral responses as determined by virus neutralizing antibody titers (VNT) against BVDV. While VNT are correlated with increased protection, research has also shown that cell mediated immunity (CMI) is an important component of a protective response against BVDV. For example, improved protection against BVDV by modified-live viral (MLV) vaccines as compared to killed vaccines is thought to be due to better CMI induced by the MLV. The goal of this work was to evaluate the cell mediated response in vaccinated calves using a novel PrimeFlow RNA assay that incorporates cell surface marker staining with intracellular RNA expression of cytokines and viral RNA detection. Results from this study evaluating mRNA for IFN-' and IL-2 at 24 hours post-BVDV stimulation are similar to previous studies in which IFN-' was detected in the CD4+ and CD8+ T cell population. However, a novel observation was the detection of IFN-' mRNA in the NK cell population in vaccinated animals. The NK cell population contributed a significant portion of the IFN-' produced. This study also demonstrated a decrease in the frequency and amount of BVDV in PBMCs, harvested from vaccinated calves and exposed to BVDV in vitro. Collectively data from this study highlights the association between an increase in IFN-' and a decreased infection rate of isolated PBMC’s, based on the frequency and amount of BVDV positive cells following in vitro exposure. This new method combines not only the ability to evaluate cellular responses, but also the ability to understand potential antiviral properties associated with cellular responses. This is the first assay to describe and simultaneously measure CMI responses and intracellular viral RNA quantity as a method to evaluate protective responses associated with vaccination.