ON THE IMMUNOLOGICAL RESPONSE TO SKIN TEST ANTIGENS FOR PSEUDORABIES IN SWINE
Abstract
Procedures were developed for the production of two effective pseudorabies virus (PrV) skin test antigens, one consisting of chemically inactivated virions, the other of viral nucleocapsids. In vivo methods used to determine the immunological basis of a cutaneous response to the virion antigen in PrV-infected swine suggested that the reaction was due to the cell-mediated immune system. The evidence was obtained through experiments to demonstrate: (1) passive transfer of immunity, which did not materialize; (2) antihistamine blocking of the PrV skin test and of the tuberculin purified protein derivative reaction, which did not eventuate in either case; and (3) through histopathological studies on biopsies of skin at test sites, which revealed a cellular response typical of delayed type hypersensitivity. The nucleocapsid antigen reaction was similar to the cutaneous response induced by the virion antigen. False positive results did not occur with either test antigen. Three vaccinal doses of the virion antigen and the nucleocapsid antigen were given intramuscularly on three separate occasions to PrV-susceptible swine. The virion antigen elicited a detectable humoral immune response after the second injection as determined by the standard serum neutralization (SN) test and an enzyme-linked immunosorbent assay (ELISA) for pseudorabies. The nucleocapsid antigen did not cause a humoral response detectable by the SN test; however, anti-PrV antibodies were measurable by the ELISA in a few of the principals. The nucleocapsid antigen principals, as a whole, did not differ significantly from the control animals. Both antigens appeared similar in their ability to induce a cutaneous cell-mediated immune response in PrV-infected swine. Either antigen provided a fast, effective, and reproducible method for the evaluation of the immune status of swine herds. Use of the nucleocapsid antigen should avoid the problem of seroconversion as determined by the SN test that is encountered with the virion antigen.
Degree
Ph.D.
Subject Area
Microbiology
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