Protective immune response in BALB/c mice induced by a suicidal DNA vaccine of the MIC3 gene of Toxoplasma

Vet Parasitol. 2009 Jun 21. [Epub ahead of print]

Protective immune response in BALB/c mice induced by a suicidal DNA vaccine of the MIC3 gene of Toxoplasma gondii

Fang R, Nie H, Wang Z, Tu P, Zhou D, Wang L, He L, Zhou Y, Zhao J.

State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, Hubei, PR China; College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, Hubei, PR China.

To evaluate the protective efficiency of a suicidal DNA vaccine against protozoal parasite Toxoplasma gondii, the microneme protein 3 (MIC3) gene was cloned into suicidal vector pSCA1 and conventional DNA vaccine vector pcDNA3.1+ respectively, their protection against T. gondii challenge were assessed in this study. The recombinant plasmids named pSCA/MIC3 and pcDNA/MIC3 were transfected into BHK-21 cells. The expression of MIC3 in BHK-21 cells was confirmed by RT-PCR and indirect immunofluorescence test. Then BALB/c mice were immunized with pSCA/MIC3 or pcDNA/MIC3. Anti-Tg-MIC3 antibodies were detected by indirect ELISA and the cell immune response were examined by lymphocyte proliferation assay and real time RT-PCR. The results showed that the titre of anti-Tg-MIC3 antibodies, stimulation index (SI) of lymphocyte proliferation response and IFN-gamma expression level induced by pSCA/MIC3 and pcDNA/MIC3 were significantly higher than controls (P<0.05), whereas IL-4 expression level in BALB/c mice immunized with either pSCA/MIC3 or pcDNA/MIC3 was lower than that in control group. After a lethal challenge against T. gondii, survival time of the mice immunized with this suicidal DNA vaccine pSCA/MIC3 and conventional DNA vaccine pcDNA/MIC3 were significantly prolonged in comparison with the control groups (P<0.05), but the difference of protective immune response in BALB/c mice between pSCA/MIC3 and pcDNA/MIC3 was not statistically significant (P>0.05). The findings demonstrated that like conventional DNA vaccine pcDNA/MIC3, suicidal DNA vaccine pSCA/MIC3 also provided favourable efficacy, but it could improve the biosafety of conventional vaccines. This result suggested that suicidal DNA vaccine pSCA/MIC3 is a potential candidate vaccine against toxoplasmosis.

PMID: 19592172 [PubMed - as supplied by publisher]