Study on the virulence and cross-neutralization capabil ity of recent porcine parvovirus field isolates and vaccine viruses in experimentally infected pregnant gilts

The pathogenicity of two recent German field ISolates of Porcine parvovirus (PPV-27a and PPV 143a) and two vaccine viruses [PPV-NADL-2 and PPV-IDT (MSV)], which are used for the production of inactivated vaccines, was mvestigated by maculation of pregnant sows at day 40 of gestation. Post-infect1on sera of these sows as well as antisera prepared in rabbits by 1mmun1zation with the four above-mentioned PPV isolates and with the virulent strain PPVChallenge (Engl.) were tested for their homologous and heterologous neutralization activities All ant1sera had h1gh neutralization activities against the vaccme wuses, the PPV-Challenge (Engl ) and PPV-143a, but much lower activity against PPV-27a These results suggest that PPV-27a represents a new antigenic variant or type of PPV and vacc1nes based on the established vaccine viruses may not be fully protective against th1s field ISolate. PPV-27a has been charactenzed based on the ammo ac1d sequences of the capsid protem as a member of a new and distmct PPV cluster. lnterestmgly, the homologous neutralizing antibody titres of the sera of all three p1gs and both rabbits maculated or Immunized with PPV-27a were 100to 1 000-fold lower than the heterologous titres aga1nst any of the other viruses. The low homologous neutrahz1ng ant1body t1tres suggest a possible, yet undefined, immune escape mechanism of this PPV isolate.