PROTECTION OF SWINE BY LIVE AND INACTIVATED VACCINES PREPARED FROM A LEADER PROTEINASE-DEFICIENT SEROTYPE A12 FOOT-AND-MOUTH-DISEASE VIRUS

Previously, we demonstrated that a genetically engineered variant of f oot-and-mouth disease virus (FMDV) serotype A12 lacking the leader pro teinase-coding region (A12-LLV2) was attenuated and induced an immune response that partially protected cattle from FMD. In this study A12-L LV2 was tested in swine as a live or chemically inactivated vaccine. A nimals vaccinated with chemically inactivated A12-LLV2 or wild-type (W T) virus in oil adjuvant developed high levels of neutralizing antibod ies and were protected from FMD upon challenge. Animals vaccinated wit h live A12-LLV2 did not exhibit signs of FMD, did not spread virus to other animals, developed a neutralizing antibody response and antibodi es to nonstructural protein 3D, and were partially protected from FMD. Animals given a similar dose of chemically inactivated A12-LLV2 in th e absence of adjuvant developed a poor immune response and were not pr otected from FMD, indicating that limited replication was responsible for the improved immune response found in animals vaccinated with live A12-LLV2. The results demonstrate the potential of A12-LLV2 as a live -attenuated vaccine as well as a safe source of antigen for chemically inactivated vaccines. (C) 1998 Elsevier Science Ltd. All rights reser ved.