Effect of Plasmid Dosage and Immunization Occasions on Immune Response Induced by Gene-gun Delivered DNA Vaccine

Objective To investigate the effect of plasmid dosage and immunization occasions on the immune response induced by gene-gun delivered DNA vaccine.Methods DNA vaccine plasmid p1.0-Env carrying the Env gp145 gene of HIV-1 was constructed.BALB/c mice were inoculated with the constructed plasmid at various dosages by gene-gun for various times,using those inoculated by i.m.injection as control.The specific antibody level against Env of immunized mice was determined by ELISA.Results The antibody level induced with the DNA vaccine delivered by gene-gun was significantly higher than that by i.m.injection.At a dosage range of 0.1～2.25 μg,the specific antibody level against Env induced by gene-gun increased with the increasing dosage of DNA vaccine.However,no further enhancement of humoral immune response was observed after the dosage of DNA vaccine increased to 5 or 10 μg.The delivery of DNA vaccine by gene-gun for 1 and 2 times induced only low specific antibody responses,while that for 3 times induced high antibody response.Conclusion Delivery by gene-gun enhanced the antibody response induced with DNA vaccine.The optimal dosage of DNA vaccine for mice was about 2.25 μg.The immunization with 2.25 μg of DNA vaccine by gene-gun for 3 times induced high humoral immune response.