Date of Award

1-1-1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Microbiology & Immunology

Abstract

Cattle and laboratory animals develop resistance to infestation with ixodid ticks following a sensitizing exposure. Antigenic substances introduced during feeding stimulate immune effector mechanisms that include antibody, cell-mediated immunity, complement, and other soluble mediators. Resistance is expressed by immunopathological modulation of normal tick feeding and development processes.Acquired resistance and immune responsiveness of ixodid infested Bos taurus and Bos indicus cattle has been investigated. Ixodid salivary gland antigen (SGA) specific, and cross-reactive, IgG response curves were determined by dot enzyme-linked immunosorbent assay (Dot-ELISA). Immunoglobulin titer did not necessarily correlate directly with levels of resistance, indicating the importance of other immune defense mechanisms.Guinea pig resistance to Dermacentor andersoni adult or nymph infestation was measured by biological parameters that included percent engorgement, engorgement weights, and percent molt. Longitudinal analysis of SGA specific immunoglobulin production revelaed significant increases in Dot-ELISA titer through four sequential infestations. These antibody responses were not directly proportional to resistance, since resistance expression was reasonably constant after the sensitizing exposure. Prausnitz-Kustner testing demonstrated ixodid antigen specific and cross-reactive homocytotropic immunoglobulin.A role for antibody in acquired resistance was examined by passive transfer of sera from these resistant animals to naive guinea pigs. Biological and histological evidence indicated serum recipients, challenged with D. andersoni larvae, expressed significant levels of resistance. Immunoglobulin from D. andersoni infested guinea pigs bound antigen associated with the surface of cultured embryonic cells of D. andersoni. Cross-reactive antibody from Amblyomma americanum infested calves was localized in membranes of sectioned D. andersoni salivary glands. Electrophoretically fractionated D. andersoni larvae and A. americanum ova soluble extracts were electroeluted onto nitrocellulose and subjected to indirect immunoassay for detection of polypeptides recognized by antibody from infested cattle and laboratory animals. Several proteins were immunolocalized and provide a foundation for further research in the utilization of these molecules for vaccination against tick infestation.

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