|DOWNEY-SLINKER, E - Texas A&M University|
|SAWYER, J - Texas A&M Agrilife|
|SKOW, L - Texas A&M University|
|HERRING, A - Texas A&M Agrilife|
Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2016
Publication Date: 9/3/2016
Publication URL: http://handle.nal.usda.gov/10113/5509549
Citation: Downey-Slinker, E.D., Ridpath, J.F., Sawyer, J.E., Skow, L.C., Herring, A.D. 2016. Antibody titers to vaccination are not predictive of level of protection against a BVDV type 1b challenge in Bos indicus - Bos taurus steers. Vaccine. 34:5053-5059. doi: 10.1016/j.vaccine.2016.08.087.
Interpretive Summary: While vaccines are frequently used by producers to reduce the risk of infection and increase the health of the herd, they are very few ways available for a producer or practitioner to measure how well their vaccine program is working. One of the common methods in use is the measurement of antibodies in blood serum. The goal of the studies described in this manuscript was to determine if different levels of antibodies in serum reflect different levels of protection. To do this, steers in each of 4 successive years were divided into 3 groups. The first group got no vaccination; the second group was vaccinated with a type of vaccine called a killed virus (KV) vaccine; and the third group received a type of vaccine called a modified live virus (MLV) vaccine. The levels of antibodies in serum was measured and then the steers were exposed to a virus (in this case a virus called bovine viral diarrhea virus type 1). It was found that, based on proportion of the steers that developed antibodies and the level of antibodies found, the MLV vaccine elicited a better response to vaccination that the KV vaccine. Further, it was found that steers exposed to virus after being vaccinated with a MLV vaccine suffered fewer symptoms than cattle vaccinated with a KV vaccine. This was true even in animals that had the same level of antibodies. These results demonstrate that measuring the level of antibodies in serum is a not a reliable method for measuring the success of a vaccination program. Based on these results we need to develop new ways to measure the effectiveness of vaccination programs.
Technical Abstract: Subclinical illness associated with infection is thought to reduce performance and increase production costs in feedlot cattle, but underlying components remain largely unidentified. Vaccination is frequently used in feedlot settings but producers lack metrics that evaluate the effectiveness of vaccination programs. The goal of this study was to determine if levels of serum neutralizing antibody titers were predictive of levels of vaccine protection in a commercial setting. In each of the four years of this study, Angus-Nellore steers housed in a production feedlot setting were assigned to 1 of 3 vaccine treatments: killed vaccine (KV), modified live virus (MLV) vaccine, or no vaccine (control), and were challenged with a noncytopathic 1b field strain of bovine viral diarrhea virus. Rectal temperature and levels of circulating lymphocytes and platelets were monitored following challenge. While no animals were diagnosed as clinically ill with respiratory disease, indicators of disease (pyrexia, lymphopenia, and thrombocytopenia) were observed. The MLV treatment elicited higher antibody titers to the vaccination than the KV, and calves in the MLV treatment had higher mean titers at challenge. The year that elicited the highest antibody response to the vaccination and the year with the lowest frequency of phenotypic responses to the challenge were not concurrent. The MLV treatment had the highest proportion, 34.68%, of animals that were protected against the challenge regardless of the pre-challenge antibody titer and had the fewest number of lymphopenia cases in response to the challenge. Both vaccine treatments mitigated thrombocytopenia when compared to the control treatment, and the MLV treatment reduced lymphopenia; however, these symptoms were not completely eliminated in vaccinated animals. Pyrexia was present in 40.11% of the animals, but no difference in the frequency of cases between treatments was observed. Pre-challenge vaccination response was not indicative of the level of protection nor was anamnestic antibody response correlated with healthy or sick status.