Moriyasu Tsuji

Production of interleukin 10 during malaria caused by lethal and nonlethal variants of Plasmodium yoelii yoelii

We investigated the induction of T-helper cell subsets during the course of lethal or nonlethal blood-stage Plasmodium yoelii 17X infection in C57BL/6 mice, which are relatively susceptible to these intraerythrocytic parasites. C57BL/6 mice infected with the nonlethal variant (PyNL) showed a moderate level of parasitemia and resolution of primary acute infection by week 4. Mice infected with the lethal variant (PyL) developed fulminating parasitemia and ultimately died. T-helper subset function was assessed during infection by determining the kinetics of in vitro production of the Thl-derived cytokine interferon-γ (IFN-γ) and the Th2-derived cytokine interleukin 10 (IL-10) by means of bioassay and enzyme-linked immunosorbent assay (ELISA), respectively. Spleen cells obtained from mice infected with PyL within the 1st week of infection produced high levels of IL-10 and IFN-γ in response to malaria antigen. IL-10 also appeared in sera from PyL-infected mice at the same time at which the in vitro IL-10 response peaked. In contrast, spleen cells from mice infected with PyNL failed to produce IL-10 during the course of infection. CD4+ T-lymphocytes from mice infected with the lethal variant were a major source of IL-10, although non T-cells were also involved in the production of IL-10 during this malaria infection. In addition, the initial burst of IL-10 in response to malaria antigens was seen concomitantly with the production of IFN-γ within the 1st week of infection. These results indicate that both Thl and Th2 subsets of T-helper lymphocytes are activated during infection with the lethal variant of P. yoelii and support the contention of other investigators that a strong Th2 response early in infection is associated with the lethal outcome of malaria.

History of Katayama disease: schistosomiasis japonica in Katayama district, Hiroshima, Japan.

Historical account of Katayama disease is presented as a centenary record since the discovery of Schistosoma japonicum in Japan in 1904. The ever unknown endemic disease was called Katayama disease. Katayama district, Hiroshima Prefecture is one of endemic areas of schistosomiasis japonica in Japan. The causative parasite was first discovered in a human case in Katayama district. After the discovery of the parasite, life history, diagnosis, treatment, control measures and even eradication have been worked out, attempted and succeeded in Katayama district together with other endemic areas in Japan. Hiroshima Prefecture declared safety from the disease in 1980.

Attenuation of Eimeria caviae by selection for precocious development

An attenuated line of Eimeria caviae was produced by selection for early maturation of oocysts during serial passage in guinea pigs. The prepatent period of the parasite was reduced from 11 to 6 days. Parasites of the precocious line and the parent strain were found in the crypts of the epithelial cells of caecum and colon and were morphologically indistinguishable. The period of development of type I, type II and type III merozoites of the E. caviae precocious line in guinea pigs was similar to that of the parent strain until the 3rd day. The time of the transition from gametocytes to oocysts was 2 days in both the precocious line and the parent strain. The maximum number of oocysts per gram of faeces and the pathogenicity of the precocious line were less than those of the parent strain.