Bacterial lipoprotein based expression vectors as tools for the characterisation of African swine fever virus (ASFV) antigens

African swine fever virus (ASFV) is the causative agent of an important pig disease for which protective mechanisms are still poorly understood. The p resent work was aimed at the characterisation of ASFV antigens using previo usly reported vectors that allow their expression as fusion proteins with t he bacterial lipoprotein OprI. Several recombinant clones induced SLA-restr icted, ASFV-specific lymphoproliferation and one (A2) was demonstrated to s timulate ASFV-specific CTL activity in vitro, in opposition to the effect o f UV inactivated virus. The nucleotide sequence of the fragment cloned in A 2 showed 99% identity with a portion of the G1340L ORF of the BA71V isolate , and the expressed fusion lipoprotein induced specific antibodies in vivo. Blood mononuclear leukocytes from a pig immunised with outer membrane prep arations from A2 showed to reduce strongly (99.6%) the ASFV yield in cultur es of autologous macrophages. However, after inoculation with virulent viru s the pig developed acute fatal ASE Overall our results show that OprI base d expression vectors are valuable tools to screen viral antigens in terms o f their capacity to trigger immune competent cells.