Acellular outer membrane vesicles of Brucella abortus strain 19 elicits both humoral and cell mediated immune response in mice

Outer membrane vesicles (OMVs) contain biologically active proteins, lipoolysaccharide (LPS), periplasmic and membranebound proteins and are known to perform diverse biological functions. OMVs from Brucella abortus S19 were isolated and characterized by transmission electron microscopy (TEM), SDS-PAGE and immunoreactivity was investigated by western blotting. On TEM, bilayered spherical structures of 50–200 nm were observed. SDS-PAGE of OMVs revealed approximate bands size of 82 kDa, 68 kDa, 38 kDa, 32 kDa, 29 kDa and 18 kDa. Western blot analysis of OMVs revealed a dominant immunoreactive band of 38 kDa that correspond to some major outer membrane proteins. Humoral immune response was measured by indirect ELISA which showed that OMV specific antibodies were detected from 7^th day post immunization (DPI) onwards and showed a rising trend up to 35^th DPI. Cell mediated immune (CMI) response against OMVs as evidenced by the proliferation of splenocytes have also been observed. Thus OMVs were found to possess immunogenic proteins which had potential to induce both humoral as well as cell mediated immunity. After correlating this immune response with protection it has been concluded that OMV can be used as one of the vaccine candidate against brucellosis.