Objective: To evaluate how the efficacy of DNA inocutation affects the ability to raise protective immunity against Leptospira.
Methods: A pair of oligonucleotide primers were designed to amplify the endoflagellar gene of L. interrogans sensu stricto serovar lai. An approximately 840bp fragment was generated with PCR and inserted into VR1012, a plasmid DNA expression vector, after the fragment and VR1012 were digested respectively with EcoRV and Sal I. A recombinant plasmid designated as VR1012+flaB2 was obtained. The vector, VR1012 consits of a pUC18 backbone with the cytomegalovirus (CMV) IE1 enhancer, promoter, and intron A, transcription regulatory elements and the BGH polyadenylation sequences driving the expressing of leptospiral endoflagellar gene of L. interrogans sensu stricto serovar lui. Plasmid encoding leptospiral endoflagellin gene was injected into quadriceps of NZW rabbits.
Results: This resulted in the generation of specific leptospiral antibody with high ELISA titer (1:32768) in the rabbits. Immuno/protection was performed in guinea pigs without adjuvant. The group "VR1012 + flaB2" showed higher survival rate (90%, 9/10 animals), compared with the group "VR1012 lack flaB2" and the group "normal saline".
Conclusion: The technique of DNA vaccine has potential advantages over certain other vaccine preparation technologies. However whether DNA vaccine will be useful for vaccine development remains to be tested.