Mikio Kimura

Trends in malaria cases in Japan.

n Abstractn n Just after World War II, more than 10,000 malaria cases per year were reported in Japan, including indigenous, imported and induced malaria. Malaria has been successfully eradicated since 1961 in Japan and now only imported malaria cases are encountered. However, as the number of Japanese people who are going abroad and also the number of foreigners who are visiting Japan increases (about 16 and 5 millions, respectively, in 2001), so does the chance for Japanese doctors to see imported malaria or transfusion-transmitted malaria cases. In fact, the total number of the patients with acute malaria in Japan has been around 100–150 annually for the last 10 years. Of those, about 75% are Japanese and 25% are foreigners, and about 75% are male and 25% are female. The peak age is in the 20s. Recently, about 45% of patients are Plasmodium falciparum and another 45% Plasmodium vivax infections. The former species is likely to be seen in travelers coming back from African countries and the latter is mainly from Asian countries. The important issue is that patients in Japan have not been diagnosed promptly nor treated properly because doctors in Japan are no longer familiar with tropical medicine. Therefore, some patients are dying from severe malaria as a consequence. As it is, most of the effective medicines for drug-resistant malaria or severe malaria have not been registered in Japan. There is now a need for medical practitioners to focus on travel medicine in Japan.n n

Antibody responses induced by immunization with a Japanese rabies vaccine determined by neutralization test and enzyme-linked immunosorbent assay

The immunogenicity of a Japanese purified chick embryo cell culture rabies vaccine (PCECV) was examined. Serum samples were obtained from 86 subjects after pre-exposure or post-exposure prophylaxis. Rabies antibody titres were determined by neutralization test and enzyme-linked immunosorbent assay (ELISA). Titres higher than 0.5 international units (IU)/ml were demonstrated by neutralization test in all the 19 subjects after three-time pre-exposure immunization on days 0, 30 and 180. Titres higher than 0.5IU/ml were also demonstrated by neutralization test in all the 23 subjects after four-time post-exposure immunization on days 0, 3, 7 and 14. There was a correlation between neutralization and ELISA antibody titres (r=0.697); however, neutralization titers were higher than ELISA titres for most of the samples. The results suggest that current Japanese rabies vaccine induces recommended levels of neutralizing antibodies after pre- and post-exposure prophylaxes.

Travelers' risk of malaria by destination country: a study from Japan.

n Summaryn n Backgroundn Country-specific information on the incidence of malaria in travelers provides the most reliable data on which to base the pre-travel risk assessment. Some such studies have been conducted among Western travelers; however, to our knowledge, there have been no reports on Japanese travelers.n n n Methodsn Malaria cases that were diagnosed between April 1999 and December 2005 and were reported to the national infectious disease surveillance body were used as the numerators after grouped into countries of disease acquisition. The denominators, the numbers of Japanese travelers visiting individual countries were derived from the recipient countries and obtained through a Japanese organization.n n n Resultsn In addition to the well-documented high risks in sub-Saharan countries, our study showed that travelers to Papua New Guinea were exposed to a significantly high risk of malaria. In Asia, Myanmar had the highest risk. Generally, malaria incidence rates among Japanese travelers were lower than those previously reported on Western travelers. However, the rates were rather comparable to the data obtained recently.n n n Conclusionsn These malaria incidence data in travelers should be taken into consideration for pre-travel risk assessment. They need to be constantly updated, and at the same time, limitations in data interpretation that are inherent in various study methodologies should also be clarified.n n

Significant role of Fas ligand-binding but defective Fas receptor (CD95) in lymph node hyperplasia composed of abnormal double-negative T cells.

The functional differences between two mutations of the Fas (CD95) locus, Faslpr (lpr) and Faslprcg (lprcg), were investigated using bone marrow (BM) transplantation on the C3H mouse background. Both lpr/lpr and lprcg/lprcg BM transferred caused lymph node (LN) hyperplasia in lpr/+ and lprcg/+ recipients, although it was clearly smaller than that in lpr/lpr and lprcg/lprcg recipients of lpr/lpr and lprcg/lprcg BM. In addition, both BM induced significantly larger LN hyperplasia in lprcg/+ than lpr/+ recipients. Appearance of CD4− CD8−[double negative (DN)] T cells in the periphery is the most consistent phenotype of Fas mutations. Importantly, the proportion of DN T cells was higher in larger LN hyperplasia in the order of lpr/+, lprcg/+ and lpr/lpr or lprcg/lprcg recipients. On the other hand, both lpr/lpr and lprcg/lprcg BM transferred into wild‐type (+/+) mice caused marked LN atrophy. The former, but not the latter, induced wasting syndrome. Faslg1d (gld)‐homozygous lpr/lpr BM transferred into +/+ mice elicited LN hyperplasia of the same extent as that in lpr/lpr mice transferred with lpr/lpr BM, but not wasting syndrome. Taken together with the fact that DN T cells massively express Fas ligand (FasL), this study implied that FasL overexpressed on DN cells may be involved in the accumulation of DN T cells in LN, LN atrophy and wasting syndrome, and that lprcg Fas, which can bind to Fas ligand but not transduce apoptosis signal into cells, may modulate these pathological conditions by interfering with the binding of FasL to Fas.