GENETIC IMMUNIZATION OF SERONEGATIVE ONE-DAY-OLD PIGLETS AGAINST PSEUDORABIES INDUCES NEUTRALIZING ANTIBODIES BUT NOT PROTECTION AND IS INEFFECTIVE IN PIGLETS FROM IMMUNE DAMS

Immune response inhibition by maternal antibodies is a major impedimen t to the vaccination of the young born to immune dams. This study expl ored the efficiency of genetic immunization of the neonates at bypassi ng this inhibition, by testing the muscular inoculation of the go glyc oprotein gene of pseudorabies virus (PRV) in piglets. Plasmid DNA (400 mu g) was inoculated in four groups of one-day-old piglets, from sows vaccinated or not against PRV. Half of the groups received a booster injection on day 42. All piglets were challenged on day 115. Only pigl ets from non-immune sows and which received a booster injection develo ped a medium level of neutralizing antibodies, but they were not signi ficantly protected against the challenge. Piglets from immune sows nei ther developed an antibody response nor were primed against PRV, as de monstrated by the antibodies kinetics after challenge. It can therefor e be concluded that genetic immunization was inefficient at efficientl y preventing the immune response inhibition by colostral antibodies.