[Immunogenicity and immunoprotection of a leptospiral DNA vaccine]

Leptospirosis is one of the most widespread zoonosis. Immunization of NZW rabbit with plasmid DNA constructs encoding leptospiral endoflagellin can induce specific antibody response in the animal. The vector, VR1012 consists of a pUC18 backbone with the cytomegalovirus (CMV) IE1 enhancer, promoter, and intron A transcription regulatory elements and the BGH polyadenylation sequences driving the expression of leptospiral endoflagellar gene, flaB2. In this study, a pair of oligonucleotide primers were designed to amplify the endoflagellar of L. interrogans serovar lai. An approximately 840 bp fragment was generated with PCR and inserted into expressed plasmid vector, VR1012, after the fragment of VR1012 were digested respectively with EcoRV and Sall. A recombinant plasmid (designated VR1012 + flaB2) was obtained. Plasmid encoding leptospiral endoflagellin was injected into quadriceps of NZW rabbits. This resulted in the generation of specific leptospiral antibody with very high ELISA titer. Immunoprotection was performed in guinea pigs. The group "VR1012 + flaB2" had higher survival rate, compared with the group "VR1012 only" (control) and the group "Normal Saline only" (control). The result suggests that the technique of DNA injection should have an advantage over certain previous vaccine technologies.