Induction of immune responses in mice by a DNA vaccine encoding Cryptosporidium parvum Cp12 and Cp21 and its effect against homologous oocyst challenge
2010
Yu, Qinlei | Li, Jianhua | Zhang, Xichen | Gong, Pengtao | Zhang, Guocai | Li, Shuhong | Wang, Huitang
Cp12 and Cp21 surface proteins on the sporozoite of Cryptosporidium parvum have been identified as the immunodominant antigens involved in the immune response to C. parvum infection. In the present study, the efficacy of Cp12 and Cp21 antigens as vaccine candidates was investigated in BALB/c mice that were susceptible to C. parvum infection. DNA sequences of Cp12, Cp21, Cp12-Cp21, and C (CpG oligodeoxynucleotide (ODN))-Cp12-Cp21 were amplified and then cloned into pVAX1 vector to form the four recombinant plasmids pVAX1-Cp12, pVAX1-Cp21, pVAX1-Cp12-Cp21, and pVAX1-C-Cp12-Cp21. Recombinant protein expression from these four plasmids in HeLa cells were confirmed by indirect immunofluorescence staining and Western blot analysis. The in vivo efficacies of the four DNA vaccines were tested in BALB/c mice. The results indicated that the four DNA vaccines elicited significant antibody responses and specific cellular responses when compared to control mice that received vector only or PBS. Among those four plasmids, pVAX1-C-Cp12-Cp21 elicited significantly higher levels of IgG. Also, the percentages of CD4⁺ and CD8⁺ T cells were significantly higher in the group with pVAX1-C-Cp12-Cp21 nasal sprays. Their efficacy in immunoprotection against homologous challenge was also detected after administration of the four DNA vaccines. The results showed that mice in the pVAX1-C-Cp12-Cp21 nasal group had a 77.5% reduction in the level of oocyst shedding and a significant difference was detected when this group was compared with the pVAX1, PBS, pVAX1-Cp12, and pVAX1-Cp21 groups. The reduction in the level of oocysts shedding from the group of pVAX1-C-Cp12-Cp21 nasal spray was also higher than that of pVAX1-Cp12-Cp21 group. These results suggested that C-Cp12-Cp21-DNA may provide an effective means of eliciting humoral and cellular responses and generating protective immunity against C. parvum infections in BALB/c mice.
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