Studies of Low Levels of Anti-Pseudorabies Antibody in Swine
Wang, Fun-In
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Permalink
https://hdl.handle.net/2142/71352
Description
Title
Studies of Low Levels of Anti-Pseudorabies Antibody in Swine
Author(s)
Wang, Fun-In
Issue Date
1988
Doctoral Committee Chair(s)
Hahn, Edwin C.
Department of Study
Veterinary Medical Science
Discipline
Veterinary Medical Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Veterinary Science
Abstract
Traditionally, the serum-neutralization (SN) test is used for routine survey. One observation in pseudorabies (PR) diagnosis is that infected pigs develop low SN titers that only occasionally exceed 1:64. Since pseudorabies virus (PRV) is neurotropic, even lower antibody levels can be present in the cerebrospinal fluid (CSF). Study of low antibody and its causes was initiated to elucidate new features of PR pathogenesis.
A sensitive assay, the single-dilution indirect solid-phase radioimmunoassay (IRIA), was developed for detection of low levels of antibody. The IRIA was sensitive, specific, quantitative, and correlated well (R = 0.846$-$0.868) with the SN test. The IRIA was applied to study the anti-PRV IgG levels within the CSF compared to that in serum. Samples were collected from pigs after viral infection, vaccination and challenge, live-attenuated virus vaccination, killed-virus vaccination, and from piglets with maternal antibody. The CSF from infected pigs contained higher levels of anti-PRV IgG associated with an increase in total IgG and albumin, suggesting leakage through a blood-brain barrier impairment. Vaccination reduced the elevation of CSF anti-PRV IgG levels following challenge.
The reasons for low SN titers are not clear. One hypothesis is that infection of immune cells may lead to suppression of the humoral response. Flow cytometry was used as a quantitative tool to study the susceptibility of porcine peripheral blood leukocytes (PBLs) to PRV. Prior to infection, three major populations (lymphocytes, monocytes and granulocytes) of normal porcine PBLs were enriched and characterized by light-scattering. These light-scattering properties allowed placement of appropriate bitmaps for analysis of virus-infected PBLs. After in vitro infection, PBLs were analyzed for cell-surface viral antigen expression and cell viability. All types of PBLs, except granulocytes, were susceptible to PRV. Approximately 5.75% of resting lymphocytes were susceptible. The T-lymphoblasts and monocytes were highly susceptible and could be killed by the virus. Also, PRV was isolated from peripheral blood mononuclear cells (PBMCs) of approximately 50% of piglets following low dose intranasal infection. Thus, infection of immune cells is likely in vivo. My findings suggest that one reason for low SN titers may be the susceptibility of porcine lymphocytes and monocytes to PRV infection. (Abstract shortened with permission of author.)
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