Association of serum antibody levels following vaccination with a modified live BVDV vaccine and protection from clinical disease upon challenge

Authors: Falkenberg, Shollie; Ridpath, Julia; Tait Jr, Richard; VANDER LEY, B - University Of Missouri; BAUERMANN, F - Universidade Federal De Santa Maria; REECY, J - Iowa State University

Submitted to: Journal of Vaccines and Vaccination
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2015
Publication Date: 3/5/2015
Publication URL: http://handle.nal.usda.gov/10113/61242
Citation: Falkenberg, S.M., Ridpath, J.F., Tait Jr, R.G., Vander Ley, B., Bauermann, F.V., Reecy, J.M. 2015. Association of serum antibody levels following vaccination with a modified live BVDV vaccine and protection from clinical disease upon challenge. Jacobs Journal of Vaccines and Vaccination. 1(1):002.

Interpretive Summary: Vaccination is a common management practice for beef calves prior to arrival at a stocker or feedlot facility used to boost the immune system as a method to prevent and reduce the incidence of disease. Calves entering the beef production system are challenged with a number of pathogens when comingled at these facilities, which can lead to an increased incidence of disease. A common agent included in many of the commercially available vaccines to control viral pathogens associated with the BRDC is bovine viral diarrhea virus (BVDV). While vaccination confers a level of herd protection it is not successful at effectively eliciting protection for each individual animal. Animals with a weak response to vaccination are more susceptible to infection and could potentially keep the pathogens circulating in the herd. Cattle were categorized into low, mid and high antibody titer response groups following vaccination and exposed to a high virulent BVDV. Clinical presentation (pyrexia), viremia and immunosuppression (leukopenia) were compared in these cattle following challenge. Cattle with a low response to vaccination tended to have a greater decline in circulating WBC and potentially making them more susceptible. Vaccination did not elicit sterilizing immunity with all response groups shedding the virus. Understanding variation in response to vaccination, while broadly categorized in this study, is a step in identifying potentially more susceptible cattle as a result of lack of protection.

Technical Abstract: : Measurements of antigen specific serum antibodies following vaccination of cattle with a modified live vaccine (MLV) were conducted to examine the range of responses elicited against bovine viral diarrhea virus type 2 (BVDV2). Cattle averaging 130 weeks of age were housed in a commercial setting and received two doses of vaccine 20 days apart. The level of virus neutralizing serum antibodies (VNSA) required for prevention of clinical disease was determined by challenging calves that differed in levels of VNSA with a high virulence BVDV2 field strain. This study was run in two replicates (Rep 1 and Rep 2). For Rep 1, bovine viral diarrhea virus (BVDV) VNSA titers were determined on 216 spring born beef calves (177.03 ± 30.05 kg body weight) 20 day after the booster vaccination with a commercial MLV. Antibody titers against bovine viral diarrhea virus (BVDV) was also measured using a commercial enzyme-linked immunosorbent assay (ELISA) and association with VNSA titers was evaluated. Rep 2 utilized 120 fall born beef calves (141.06 ± 29.43 kg body weight) that followed the same vaccination protocol in Rep 1. For Rep 2, titers against BVDV were initially determined using the commercial ELISA. In both trials, all calves were stratified into low, medium and high response groups based on standard deviations from the mean value obtained from the ELISA. Twelve calves, for each trial, were selected to represent low, medium and high response groups (n = 4 calves per group). After selection, serum from selected calves was collected and evaluated for BVDV antibody response by virus neutralizing test. The VNSA values for the three groups (n = 4) were as follows; low (titer < 1:4), mid range (titer 1:4 to 1:16) and high (titer > 1:16). Calves were moved to BL2 containment and challenged with a high virulence BVDV2 strain 101 days after the initial vaccination. A group of non-vaccinated colostrum-deprived, BVDV antibody negative and BVDV antigen negative calves were used to established pathogenic level of inoculum prior to the start of the challenge study. Blood samples were collected on days -2, 2, 4, 6, 9, 11 and 13 post challenge to determine levels of circulating white blood cells, viral shed and levels of BVDV VNSA. While, overt respiratory or enteric disease was not observed in any of the vaccinated calves, challenge did result in a decrease in circulating white blood cells (WBC) in some vaccinated calves. However, the extent of clinical symptoms including decreases in WBC and pyrexia, were more severe in the non-vaccinated animals which indicates vaccination did provide a level of protection. Further, clinical symptoms were more likely to be observed in calves with lower BVDV VNSA levels following the BVDV challenge demonstrating significant association between VNSA levels and clinical protection.