Issue |
Vet. Res.
Volume 31, Number 1, January-February 2000
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|
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Page(s) | 132 - 132 | |
DOI | https://doi.org/10.1051/vetres:2000076 | |
How to cite this article | Vet. Res. (2000) 132-132 |
Mechanisms of protective immunity against Aujeszky's disease virus
F.A. Zuckermann, S. Martin and R. HusmannDepartment of Veterinary Pathobiology, University of Illinois, 2001 South Lincoln Ave., Urbana, Illinois 61801, USA
Abstract -
An
understanding of the role that different types of immune effector mechanisms have in
mediating protective immunity against virus diseases of swine is key to the development of
effective vaccines for this species. The abundant literature available on the efficacy of
vaccines against Aujeszky's disease virus (ADV) has provided evidence that inactivated ADV
vaccines are not as effective as modified live virus (MLV) vaccines at
stimulating protective
immunity. The fact that similar titers of virus-neutralizing antibodies are present in pigs
receiving either type of vaccine has fueled the speculation that cell-mediated immunity must
therefore be responsible for mediating protection from disease. Certainly, the lesser ability
of inactivated ADV vaccines to provide protective immunity must reflect the inability of this
type of vaccine to induce sufficient levels of immune effector mechanism(s) important for
protection. However, the exact nature of this deficit is unknown. We have
examined this issue
by measuring the serum titer of virus-neutralizing antibodies and the frequency of
ADV-specific interferon-gamma (IFN-
)-producing cells in the peripheral blood mononuclear
cells of pigs after immunization with either inactivated or MLV ADV vaccines. We found that
while both MLV and inactivated vaccines are able to induce similar levels of neutralizing
antibodies, an inactivated vaccine is not as effective as a MLV vaccine at stimulating
ADV-specific IFN-
-producing cells. Indeed we found a correlation between the intensity of
this response and the level of protective immunity. This correlation was further
confirmed by
the observation that pigs immunized with inactivated virus in combination with either human
recombinant IL-12 or an oil-in-water adjuvant, develop an enhanced IFN-
response and level
of protective immunity, as compared to pigs receiving the inactivated virus alone. In
contrast, the titer of virus neutralizing antibodies produced in response to
the inactivated
vaccine was mildly affected by either of these adjuvants. The data obtained clearly show that
there are differences in the quality and quantity of the immunity induced by a live versus an
inactivated ADV vaccine. While inactivated commercial vaccines are equally efficient as a MLV
vaccine at inducing humoral immunity, they only induce a weak and transient virus-specific
IFN-
response. In contrast, a MLV vaccine induces a robust virus-specific
IFN-
response. In
all of the different ADV vaccine formulations tested in our experiments, a high
level of protective immunity correlated with the presence of a strong IFN-
response, while
the titer of virus-neutralizing antibodies did not. Although the results from this
study do not rule out a role for humoral immunity in protection, they do suggest that
cell-mediated immunity participate in providing a high degree of protective immunity.
The data presented argue in favor of the notion that the level of cell-mediated
immunity is a
major factor in determining the level of protection from ADV-induced disease. At
the very minimum, a strong IFN-
response in a pig is a good predictor that the animal has
developed a strong protective immune response against this virus.
Corresponding author: F.A. Zuckermann Tel.: (1) 217 333 7767; fax: (1) 217 244 7421;
e-mail: fazaaa@uiuc.edu
© INRA, EDP Sciences 2000