Objective To clone and express the Leptospira interrogans(L.interrogans)vaccine candidate gene,LB061 and to analysis the immunogenicity and conservation of the recombinant protein in different serovars of L.interrogans.Methods The characters of LB061 gene were predicted by bioinformatics software.The prokaryotic expression system of the LB061 was constructed by routine molecular biological techniques.Expression of the recombinant LB061 protein was induced by IPTG,and confirmed by Western blot.Balb/C mice were immunized with ercombinant LB061 and immune serum was used to study the immunogenicity of LB061 and the conservation of expressed LB061 in sixteen different serovars.In addition,antibodies against LB061 in rabbit serum infected with L.interrogans strain Lai(56601)were examined by Western blot.Results LB061 is a putative outer membrane protein in L.interrogans as predicted by bioinformatical analysiss.The prokaryotic expression system of LB061 was constructed successfully.Serum titers of anti-recombinant LB061 antibodies in immunized BALB/c mice were 1:32000.LB061 was detected in sixteen different serovars of L.interrogans.LB061-specific antibodies were detected in rabbit serum infected wit L.interrogans strain Lai by Western blot.Conclusion The vaccine candidate gene,LB061,of L.interrogans serogroup,icterohemorrhagic serovar,Lai strain can elicit antibody responses in rabbit during infection with Leptospira interrogans.Our studies provide a basis for further investigation on the role of LB061 as a vaccine candidate gene.