Lack of serum antibodies against glycoprotein E in pseudorabies virus-immune pigs infected with wild-type virus.
OBJECTIVE
To examine whether pigs with solid immunity against pseudorabies virus (PRV) could harbor latent infection with wild-type PRV without developing antibodies against glycoprotein E (gE), which is used as a marker protein to differentiate pigs that have been vaccinated from pigs infected with wild-type PRV.


METHODS
Specific-pathogen-free pigs that were seronegative for antibodies to PRV.


METHODS
Oropharyngeal swab specimens were collected, and virus content was measured, Serum samples were obtained 1 week before and 2 and 4 weeks after challenge exposure. Four weeks after challenge exposure, pigs were slaughtered; various tissues were collected for virus isolation, and DNA was analyzed by polymerase chain reaction.


RESULTS
Of the intranasally inoculated pigs, only 1 pig shed virus (for 1 day) but none developed antibodies directed against gE. Of the inoculated IM pigs, 3 pigs shed virus (for several days) and 5 developed antibodies directed against gE. One pig did not shed virus and did not develop detectable gE antibodies. However, variable amounts of wild-type virus DNA were detected in various tissues.


CONCLUSIONS
Immunized pigs can be infected with wild-type PRV without being detected by the gE-specific ELISA, which is routinely used to discriminate between infected and vaccinated pigs. The implication for eradication programs is that these pigs might be a source of new outbreaks.
Department of Mammalian Virology, Institute for Animal Science and Health (ID-DLO) Lelystad, The Netherlands.
L
L
Jacobs
T G
TG
Kimman
A
A
Bianchi
D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D000917:Antibody Formation; D005784:Gene Amplification; D011558:Herpesvirus 1, Suid / Q000276:immunology*; D016133:Polymerase Chain Reaction; D011557:Pseudorabies / Q000276:immunology*; D013552:Swine; D014759:Viral Envelope Proteins / Q000276:immunology*
D000914:Antibodies, Viral; D014759:Viral Envelope Proteins; C089580:glycoprotein E, Suid herpesvirus 1