| Summary: | Alveolar echinococcosis (AE) is a severe parasitic zoonosis caused by the larval stage of <i>Echinococcus multilocularis</i>. The identification of the antigens eliciting acquired immunity during infection is important for vaccine development against <i>Echinococcus</i> infection. Here, we identified that <i>E. multilocularis</i> calreticulin (<i>Em</i>CRT), a ubiquitous protein with a Ca<sup>2+</sup>-binding ability, could be recognized by the sera of mice infected with <i>E. multilocularis</i>. The native <i>Em</i>CRT was expressed on the surface of <i>E. multilocularis</i> larvae as well as in the secreted products of metacestode vesicles and protoscoleces (PSCs). The coding DNA for <i>Em</i>CRT was cloned from the mRNA of the <i>E. multilocularis</i> metacestode vesicles and a recombinant <i>Em</i>CRT protein (r<i>Em</i>CRT) was expressed in <i>E. coli</i>. Mice immunized with soluble r<i>Em</i>CRT formulated with Freund’s adjuvant (FA) produced a 43.16% larval vesicle weight reduction against the challenge of <i>E. multilocularis</i> PSCs compared to those that received the PBS control associated with a high titer of IgG, IgG1 and IgG2a antibody responses as well as high levels of Th1 cytokines (IFN-γ and IL-2) and Th2 cytokines (IL-4, IL-5 and IL-10), produced by splenocytes. Our results suggest that <i>Em</i>CRT is an immunodominant protein secreted by <i>E. multilocularis</i> larvae and a vaccine candidate that induces partial protective immunity in vaccinated mice against <i>Echinococcus</i> infection.
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