In addition, the immune cross reaction between rCp23 and rCp15–23 was observed. To examine the generation of the specific cellular immune responses to rCp15–23 fusion protein, rCp23 protein and crude extract of C. parvum, single spleen cell suspensions from different protein immunized or control (adjuvant-immunized) mice collected 14 days after the final immunization were prepared and used for T cell characterization analysis. The antigen-specific lymphocytes were examined by direct staining with antibodies for surface expression of cluster of differentiation CD4+ and CD8+. The results showed that the number of
CD4+ and CD8+ T cells was increased in all three immunized groups compared with adjuvant control group (P < 0·01), whereas the number of CD4+ T cells was much more than that of CD8+ T cells. In addition, the stimulation of cells from rCp15–23 fusion
protein immunized mice generated higher CD4+, see more CD8+ T cells and the ratio of CD4+/CD8+ than either Crizotinib molecular weight crude extract or rCp23 protein groups (P < 0·01) (Figure 5). ELISA was used to detect the concentrations of cytokines in the supernatants of in vitro activated lymphocytes at day 14 after the third doses of vaccine. In the spleen cells, significantly higher concentrations of IFN-γ or IL-12 were found in all antigen immunized groups, whereas no IFN-γ or IL-12 was detected in the adjuvant control group. The IFN-γ and IL-12 levels were found to be significantly higher in rCp15–23 fusion protein immunized mice compared with the
crude extract immunized mice (P < 0·05) (Figure 6). No significant difference was observed in crude extract immunized mice compared with adjuvant control group mice. Very low level of IL-4 was found in our study in all the groups and no difference was found between different groups. To examine differences in protection of C. parvum Pregnenolone infection after different protein immunization, faecal oocyst shedding was detected. The faecal oocyst shedding was noted between days 3 and 7 post-infection in both the crude extract protein immunized group and adjuvant control group, in the rCp23 protein immunized group between days 4 and 8 post-infection, in the rCp15–23 fusion protein immunized group between days 5 and 9 post-infection. The manifestations of C. parvum infection, i.e. oocyst shedding was not noted or was minimal on days 10 and thereafter. The prepatent period of oocysts shedding was longer after immunization with both rCp23 protein and rCp15–23 fusion protein. However, the increase in the prepatent period in mice immunized with rCp15–23 fusion protein was obvious compared with those in mice immunized with either crude extract or rCp23 protein (Figure 7). In addition, the oocyst shedding number was reduced in C. parvum challenged mice following immunization. In rCP15–23 recombinant protein immunized group, the oocyst shedding number was reduced 31·4% compared with the adjuvant control group (P < 0·05).