Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Grace F. Amborski

Abstract

Bovine Leukemia Virus (BLV) is an exogenous type-C retrovirus which can induce an aleukemic (AL) stage, a persistent lymphocytotic (PL) stage, or a lymphosarcomatous (LS) stage in infected animals. After experimental infection with BLV, whole blood and serum samples were obtained from 12 holstein heifers for 103 weeks and used to correlate clinical signs (visual observation and white blood cell counts) with changes in humoral immune response (Agar gel immunodiffusion using envelope gp50 as primary antigen, and ELISA and Western immunoblots using whole BLV as antigen). Monoclonal antibodies against BLV envelope gp50 and gag p24 were produced to confirm reactivity to specific proteins for the various assays. To confirm reactivity of monoclonals and produce large amounts of selected proteins for later studies of BLV, the genes for env, gag, and pX were cloned into eucaryotic expression vectors. After transfection of appropriate plasmids, correct expression of cloned genes was confirmed using monoclonals and indirect immunofluorescence for gp50 and p24 and CAT assay for px. Total lymphocyte counts indicated 6 cattle reached the PL stage during the 103 weeks post infection (PI). Cows progressed through three transient disease stages in the first 3 months PI: transient eosinophilia, lymph node enlargement and lymphocytosis. Of the 6 cattle demonstrating early transient lymph node enlargement, 5/6 were AL. Changes in the humoral immune response to BLV were best detected using Western immunoassays. AL cattle were more likely to have an increased antibody response to the gag protein p24 early PI as compared to PL cattle. PL animals usually reached their highest p24 antibody responses after conversion to the PL stage. Antibody response to env gp50 increased as a function of time PI regardless of disease stage. PL cattle tended to recognize a greater number of the lesser gag proteins, p15, p12 and p10 in the first year PI than AL cattle. All cattle decreased markedly in their reactivity to any of these lesser proteins after 51 weeks PI.

Pages

184

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