A comparison of several in vitro methods to assess the immune response to bovine viral diarrhea virus (BVDV) containing vaccines in cattle
Tanner, Michael Edward
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Various methods of measuring immune re sponses to vaccination are available, but there is little consensus among researchers as to which method best characterizes the response and predicts the outcome following infection of vaccinated individuals. Most studies of immune responses employ a limi ted number of in vitro assays, usually dictated by the individual lab’s expertise that provide a narrow view of the global immune response in each experimental context. The objectives of this thesis were to: 1) employ an array of assays to measure cytoki ne and lymphocyte proliferative responses to vaccination of cattle with modified live (MLV) and inactivated (killed) BVDV containing vaccines, and 2) assess the degree of correlation of the assays results. Thirty (30) seronegative calves were vaccinated (day 0) and boosted at day 14 with either MLV/MLV, MLV/killed, killed/killed, vaccines not containing BVDV, or left unvaccinated as sentinels. At days 0, 7, 14, 21, 28, and 49 blood was drawn, peripheral blood mononuclear cells (PBMC) isolated and serum co llected. Following in vitro stimulation of the PBMCs with different BVDV strains and Staphylococcal enterotoxin B (SEB), proliferation, and cytokine mRNA and protein were assayed. Serum neutralizing titers to the BVDV strains were determined. Whereas neutralizing antibody titers to the vaccinal biotype (type 1) were higher in calves primed with MLV vaccine than those raised to the type 2 or primed with the killed vaccine, no antigen-specific cytokine responses were observed. Proliferative responses to recall antigen were only observed when the NADL strain (type 1) was used to stimulate PBMCs. The discrimination of responses was best for the day 49 samples, which were collected following a period of naturally occurring respiratory disease and treatment. The results emphasize the potential disparity of results generated in parallel from different assays of the same samples. Caution should be used when interpreting the results of any one of the individual assays in qualitatively and quantitatively assessing the immune response and its correlation to protection from disease.