EFFECT OF VACCINATION ROUTE AND COMPOSITION OF DNA VACCINE ON THE INDUCTION OF PROTECTIVE IMMUNITY AGAINST PSEUDORABIES INFECTION IN PIGS

Vaccination with naked DNA may be an alternative to conventional vacci nes because it combines the efficacy of attenuated vaccines with the b iological safety of inactivated vaccines. We recently showed that the vaccination with naked DNA coding for the immunorelevant glycoprotein D (gD) of pseudorabies virus (PRV) induced both antibody and cell-medi ated immunity in pigs and provided protection against challenge infect ion. To determine whether the efficacy of the naked DNA vaccination ag ainst PRV could be improved, we compared three sets of variables. Firs t, the efficacy of the naked DNA vaccine coding only for the immunorel evant go was compared with a cocktail vaccine containing additional pl asmids coding for two other immunorelevant,glycoproteins, gB and gC. S econd, the intramuscular route of vaccination was compared with the in tradermal route. Third, the commonly used needle method of inoculation was compared with the needleless Pigjet(TM) injector method. Five gro ups of five pigs were vaccinated three times at 4-weeks intervals and challenged with the virulent NIA-3 strain of PRV 6 weeks after the las t vaccination. Results showed that although the cocktail vaccine induc ed stronger cell-mediated immune responses than the vaccine containing only go plasmid, both vaccines protected pigs equally well against ch allenge infection. Intradermal inoculation with a needle induced signi ficantly stronger antibody and cell-mediated immune responses and bett er protection against challenge infection than intramuscular inoculati on. Our data show that the route of administering DNA vaccines in pigs is important for an optimal induction of protective immunity. (C) 199 8 Elsevier Science B.V. AU rights reserved.