Download Interference of passive and active immunity after vaccination of pigs

Interference of passive and active immunity after vaccination of pigs against
pseudorabies*
Małgorzata Pomorska-Mól
In this study the influence of maternal immunity against pseudorabies virus (PRV) on
the development of humoral and T-cell mediated immune (CMI) responses was investigated.
Pigs (n=82) born to immune sows were vaccinated with gE deleted vaccine according
to five different schedules. The lymphocyte proliferation assay (LPA) was used to estimate
the antigen specific proliferation of lymphocytes. In addition, we investigated the nature of
protective immunity induced by systemic delivery of glycoprotein E (gE)-deleted attenuated
vaccine (the Th1–Th2 polarization of immune response) by examining the profile of Th1 and
Th2 cytokines produced by PBMC stimulated in vitro with the live PRV. Moreover, the CD25
expression on CD2+ and CD8+ T lymphocytes was evaluated. Antibodies to the gB and gE of
PRV in serum were determined using ELISA kits.
Maternally derived antibodies (MDA) in the serum of unvaccinated piglets born to
immune sows were above the level considered to be positive until about 10–11 weeks of life.
High values of stimulation index were noted in groups vaccinated at 8 or 12 weeks of
age (in 60% and 100% animals, respectively). In weaners vaccinated at 10 and 14 weeks of
age, as well as in those vaccinated at 7 days and revaccinated at 8 or 12 weeks of age, 100%
of animals positively responded in the lymphocyte proliferation assay after booster. At 20
weeks of life, only animals vaccinated at 12 weeks of age, 7 days and 12 weeks of age, and 10
and 14 weeks of age showed antigen-specific proliferation. Similar results were observed with
IFN-γ secretion after exposure to live PRV. Following exposure to the PRV a higher number
of cells from vaccinated animals expressed the CD25 marker, than those from unvaccinated
ones.
Summarizing, MDA may affect maturation of both cellular and humoral immunity
against PRV in piglets, but in the case of cellular immunity, almost all early vaccinated piglets
responded specifically at least 2 weeks after vaccination. We have demonstrated that early
vaccination (at 7 days of life) with a live gE-deleted PRV vaccine, in the presence of high
levels of MDA could be effective, but that the intensity and duration of the recall proliferative
T-cell response depended on the moment of the second vaccination. The active humoral as
well as CMI responses were the highest in group vaccinated at 10 and 14 weeks of age.
* Paper prepared within Project No NN 308 275934 funded by Ministry of Science and Higher Education