Research on calpain of Schistosoma japonicum as a vaccine candidate.

Vaccine development by the use of calpain of Schistosoma japonicum has been tried in our laboratory. We cloned cDNA encoding the heavy chain of S. japonicum calpain, and prepared recombinant molecule of a possible vaccine region of the heavy chain. When BALB/c mice were immunized with our recombinant calpain of S. japonicum with Freund's complete adjuvant, we observed significant reduction in worm burden (41.2% reduction, P<0.05), and also significant anti-fecundity effects. In this sense, calpain of S. japonicum seems to have infection control as well as anti-disease effects. Mechanisms of vaccine effects of calpain remain to be clarified, however, several effector mechanisms are suspected. In immunized mice, raised level of iNos expression was observed, while adhesion of peritoneal exudates cells were also observed in the presence of calpain-immunized sera, suggesting the possibilities of both cellular and humoral protective mechanisms. We examined tissue distribution of calpain in various developmental stages of S. japonicum. Strong signal was observed around excretory grand of cercariae, and they secreted calpain during their migratory movement tested in vitro. Together with the findings, calpain seems to induce larvicidal effects in the immunized mice. We observed time-course kinetics of antibody production against vaccine candidates in experimental S. japonicum infection in pigs. Although significant levels of antibody production were observed for paramyosin and GST, no significant antibody production was observed for calpain. This suggests that calpain is less immunogenic, and route of immunization and/or choice of adjuvant are important in future trials of calpain vaccine.

The efficacy of ascofuranone in a consecutive treatment on Trypanosoma brucei brucei in mice.

Consecutive administration of ascofuranone without glycerol was found to have therapeutic efficacy against Trypanosoma brucei brucei infection in mice. A suspension of ascofuranone (25-100 mg/kg) was administrated intraperitoneally every 24 h for 1-4 consecutive days to trypanosome-infected mice and efficacy was compared with oral treatment. With intraperitoneal administration, all mice treated with 100 mg/kg ascofuranone for 4 consecutive days were cured. On contrary, with oral treatment a higher dose of ascofuranone (400 mg/kg) was needed for 8 consecutive days to cure the mice. With intraperitoneal treatment, parasitemia was strongly suppressed, with almost all long slender bloodstream forms of the parasite changed to short stumpy forms by day 3 and the parasites have been eliminated 4 days after the start of treatment. These ascofuranone-induced short stumpy forms were morphologically analogous to the stumpy forms 2 days after peak parasitemia of pleomorphic clone of T. b. brucei GUTat 3.1. However, the properties of ubiquinol oxidase activity, which is the target of ascofuranone, in mitochondria isolated from before and after treatment, were almost same. The enzymatic activities of ubiquinol oxidase were only decreased to approximately 30% within a day after treatment, and then kept at nearly the same level. In the present study, we have improved regimen for administration of ascofuranone without glycerol, and demonstrated that consecutively administrated ascofuranone showed trypanocidal effects in T. b. brucei infected mice. Our present results strongly suggest that consecutive administration of ascofuranone may be an effective chemotherapy for African trypanosomiasis.