Pu Wang

Document Type

Thesis - University Access Only

Award Date

2000

Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology

Abstract

Bovine herpesvirus 1 (BHV-1) is a major cattle pathogen causing bovine respiratory and reproductive tract diseases. BHV-1 establishes a latent infection that generally lasts for the lifetime of the infected animals. Acute BHV -1 infection is often associated with severe secondary bacterial infections, causing death in individuals whose immune systems are depressed. The specific cellular and molecular mechanisms of this effect are not completely defined. Many viral infections affect immune function and deplete immune cells. The objective of this study was to determine infection and replication ofBHV-1 in peripheral blood mononuclear cells (PBMC). BHV-1 infection in PBMC of latently infected calves was detected by polymerase chain reaction for viral DNA and indirect immunofluorescence staining for viral antigen. BHV-1 DNA and viral antigen were demonstrated in PBMC of calves up to month 8 post infection but no infectious virus was recovered from the PBMC. These results raise the possibility that lymphoid tissues may function as sites for BHV -1 persistence or latency. Susceptibility of PBMC to BHV-1 infection was further analyzed in vitro. Lymphocytes and monocytes were infected with BHV -1 and the expression of BHV-1 early glycoprotein D (gD) and late glycoprotein C (gC) was analyzed by flow cytometry. Lymphocytes and monocytes expressed BHV-1 glycoproteins. BHV-1-infected lymphocytes and monocytes expressed gD at a higher extent than gC. Replication of BHV-1 in monocytes and lymphocytes was abortive compared with MDBK cells. Concanavalin A (Con A) treatment oflymphocytes increased the efficiency of viral protein expression and virus production as compared with resting lymphocytes. The phenotypic analysis demonstrated that BHV -1 infection was not limited to one lymphocyte subpopulation. These observations suggest that lymphocytes and monocytes in vitro can support BHV-1 replication but the replication of BHV -1 in these cells is restricted. To study infection ofBHV-1 in macrophages, a method for the generation of a functional bovine macrophages from monocytes was established by stimulating peripheral monocytes with macrophage colony-stimulating factor (M-CSF) for 5-7 days in vitro. Monocyte-derived macrophages (MDM) are homogenous in morphology and their ability to phagocytize bacteria and latex beads, kill bacteria and express CD 14, CD 11 b and MHC class II surface molecules. This culture system provides a convenient method to obtain large number of homogenous macrophages. MDM were susceptible to BHV-1 infection. MDM supported viral protein expression and initial replication. Although virus replication is abortive, BHV-1 triggered cytopathic effects (CPE), detachment and death in infected MDM. BHV-1 infection also reduced the bactericidal ability ofMDM. UV-inactivated BHV-1 failed to induce CPE and to reduce bactericidal ability. These results indicate that replication of BHV -1 in macrophages is a determinant of BHV-1 pathogenesis.

Library of Congress Subject Headings

Cattle -- Virus diseases
Herpesvirus diseases in animals
Blood cells
Cell interaction

Format

application/pdf

Number of Pages

156

Publisher

South Dakota State University

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