Identification and partial characterisation of a new protective antigen ofBrucella abortus

Two novel Brucella abortus proteins were isolated from B. abortus strain RB 51 and their immunological properties were determined, These proteins preci pitated in the 40-60% saturated concentration range of ammonium sulphate an d had a molecular mass of 32.2 kDa and 22.9 kDa, respectively, Both were ab le tea induce a strong in-vitro blast transformation in lymphoid cells obta ined from mice previously sensitised with a crude brucella protein extract. The protection studies showed that the 22.9-kDa protein used as a protecti ve immunogen was as effective as the live B abortus RB51 vaccine but the 32 .2-kDa protein had a poor protective effect under similar conditions, The a minoterminal sequence of the 22.9-kDa and 32.2-kDa proteins was determined and analysed in a database. The lack of homology with other known B, abortu s proteins indicated that both proteins were novel antigens.