The protective effect of CD40 ligand-CD40 signalling is limited during the early phase of Plasmodium infection.

γδ T cells are essential for eliminating Plasmodium berghei XAT. Because administration of the agonistic anti-CD40 antibody can induce elimination of P. berghei XAT parasites in γδ T cell-deficient mice, we considered that γδ T cells might activate dendritic cells via CD40 signalling during infection. Here we report that administration of the anti-CD40 antibody to γδ T cell-deficient mice 3-10 days post-P. berghei XAT infection could eliminate the parasites. Our data suggest that dendritic cell activation via γδ T cells expressing CD40 ligand is critical during the early phase of infection.

Sexual differentiation and developmental stage identification of the Indian cockroach, Pycnoscelus indicus (Blattodea: Blaberidae).

We found that sexual differentiation of all the nymphal stages of Pycnoscelus indicus (Fabricius) was possible by observing the developmental features of their posterior abdominal segments. Using this observation, the sex of even the 1(st) stage instar nymph could be determined. The female of the 1(st) to 6(th) stage instar nymph possess a V-shaped notch at the middle of the posterior edge of the 9(th) sternite. This notch is not seen in the male nymph. In the female 7(th) stage (final stage) instar nymph, the styli were not apparent and, the 8(th) and 9(th) sternites became degenerated and were covered over by the profoundly developed 7(th) sternite. In contrast, all stages of the male nymph showed the presence of styli. Thus, it is possible to differentiate the sex of all the stages, from 1(st) to 7(th), of the nymph of P. indicus taxonomically. Moreover, it is also possible to identify the various specimens as to which stage the nymphal instar belong to, by counting the number of cercal segments from the ventral view.

Cockroach fauna in the Ogasawara Chain Islands of Japan and analysis of their habitats.

A survey of cockroach fauna was carried out on the 3 inhabited islands of the Ogasawara chain island of Japan, namely, Chichijima island, Hahajima island and Iwo island. Seven species, namely, Periplaneta americana (Linnaeus, 1758), Periplaneta australasiae (Fabricius, 1775), Blattella lituricollis (Walker, 1868), Onychostylus vilis (Brunner von Wattenwyl, 1865), Supella longipalpa (Fabricius, 1798), Pycnoscelus surinamensis (Linnaeus, 1758) and Opisthoplatia orientalis (Burmeister, 1838), were collected on Chichijima island. Four species, namely, P. americana, P. australasiae, O. vilis and P. surinamensis were collected on Hahajima island and 6 species, namely, P. americana, P. australasiae, B. lituricollis, O. vilis, P. surinamensis and Neostylopyga rhombifolia were collected on Iwo island. This is the first record of N. rhombifolia and Onychostylus orientalis on the Ogasawara chain islands. Our study increases the recorded taxon of cockroaches on the Ogasawara from 3 families, 5 genera 10 species to 4 families, 7 genera, 12 species. A list of the cockroach species on Ogasawara islands reported to date as well as a key for their identification is also presented. Periplaneta americana and P. australasiae, being the dominant species, together with S. longipalpa, were collected mostly in the indoor environment, indicating their preference for this habitat. Pycnoscelus surinamensis, which is considered as an outdoor insect has been found in semi-household environments such as greenhouse and shed, indicating their new adaptation to the changing environment.

Enhancement of dendritic cell activation via CD40 ligand-expressing γδ T cells is responsible for protective immunity to Plasmodium parasites.

Previous reports have shown that γδ T cells are important for the elimination of malaria parasites in humans and mice. However, how γδ T cells are involved in protective immunity against blood-stage malaria remains unknown. We infected γδ T-cell-deficient (TCRδ-KO) mice and control wild-type mice with Plasmodium berghei XAT, which is a nonlethal strain. Although infected red blood cells were eliminated within 30 d after infection, TCRδ-KO mice could not clear the infected red blood cells, showed high parasitemia, and eventually died. Therefore, γδ T cells are essential for clearance of the parasites. Here, we found that γδ T cells play a key role in dendritic cell activation after Plasmodium infection. On day 5 postinfection, γδ T cells produced IFN-γ and expressed CD40 ligand during dendritic cell activation. These results suggest that γδ T cells enhance dendritic cell activation via IFN-γ and CD40 ligand-CD40 signaling. This hypothesis is supported strongly by the fact that in vivo induction of CD40 signaling prevented the death of TCRδ-KO mice after infection with P. berghei XAT. This study improves our understanding of protective immunity against malaria and provides insights into γδ T-cell-mediated protective immunity against various infectious diseases.

[Possibility of invasion of Echinococcus into Honshu with pet dogs from Hokkaido and overseas].

PURPOSE: The number of pet dogs moving with their owners to Honshu, the main island of Japan, from Hokkaido, and the number of dogs imported from overseas were examined, and the possibility of invasion of Echinococcus multilocularis and E. granulosus with these dogs was discussed. METHODS: The number of pet dogs moving to Honshu-island from Hokkaido was examined with the movement notifications based on the Rabies Prevention Act in 29 prefectures during the period from 1996 to 2001. The number of pets was also examined by questionnaire targeting 3 aviation and 3 ferry companies. The number of dogs imported from overseas was examined with the Annual Reports of the Animal Quarantine Service of Japan, The sanitary conditions of hotels for pet owners were also examined with a questionnaire. RESULTS: Approximately 140 pet dogs were found to have officially moved annually from Hokkaido to Honshu during the study period. However, the actual number might be two to three times this estimate, because many dogs moved without notification. Nearly ten thousand pet dogs were transported a year to and from Honshu and Hokkaido by planes and ferries. A value of three thousand would be expected if people from Hokkaido were accompanying their pets at the rate of the registered dogs per population, one animal per 23 Hokkaido residents. Up to 30 pet dogs infested with E. multilocularis would probably be included per year, according to the infestation rate of 1% in Hokkaido. The number of imported dogs from overseas was assessed at approximately 15 thousand a year, but these dogs were not obligated to receive animal quarantine with respect to echinococcal infestation in Japan. Hotels for pet owners were considered to be managed rather sanitarily, though certain administrative guidance is necessary to prevent hydatid disease infection of travelers and hotel workers. The authors consider that dogs from Hokkaido and also from echinococcosis endemic countries should undergo fecal examination for parasite eggs to prevent invasion of the parasite into Honshu. CONCLUSION: The authors propose the fecal examination of the dogs from Hokkaido and also from overseas for preventing invasion of E. multilocularis and E. granulosus into Honshu, Japan.