Yoshiyuki Shiroma

Involvement of IL-2/IL-2R system activation by parasite antigen in polyclonal expansion of CD4(+)25(+) HTLV-1-infected T-cells in human carriers of both HTLV-1 and S. stercoralis.

The intermediate state of HTLV-1 infection, often found in individuals dually infected with Strongyloides stercoralis (S. stercoralis) and HTLV-1, is assumed to be a preleukemic state of adult T-cell leukemia (ATL). To investigate the effects of S. stercoralis superinfection on the natural history of HTLV-1 infection, we characterized peripheral blood samples of these individuals in Okinawa, Japan, an endemic area for both HTLV-1 and S. stercoralis and we studied effects of the parasite antigen on T-cells. The dually infected individuals showed a significantly higher provirus load and an increase in CD4+25+ T cell population, with a significant, positive correlation. This increase was attributable to polyclonal expansion of HTLV-1-infected cells, as demonstrated by inverse-long PCR analysis of the integration sites. S. stercoralis antigen activated the IL-2 promoter in reporter gene assays, induced production of IL-2 by PBMC in vitro, and supported growth of IL-2 dependent cell lines immortalized by HTLV-1 infection or the transduction of Tax. Taken collectively, these results indicate that S. stercoralis infection induces polyclonal expansion of HTLV-1-infected cells by activating the IL-2/IL-2R system in dually infected carriers, an event which may be a precipitating factor for ATL and inflammatory diseases.

Application of enzyme immunoassay for postchemotherapy evaluation of human strongyloidiasis

Posttherapy evaluation of strongyloidiasis is frequently difficult because coprologic examination is not sensitive enough for diagnosis of chronic infection. In the present study, anti-Strongyloides enzyme-linked immunosorbent assay antibodies were monitored before and after treatment with thiabendazole and pyrvinium pamoate in 199 patients with chronic strongyloidiasis in Okinawa, Japan. A significant decrease in antibody levels was observed in patients who became negative for fecal larvae after the treatment, whereas the antibody levels did not show a significant change after the treatment in patients who were still harboring the parasite. In the group coprologically negative in the follow-up examination, however, many individuals did not show a significant fall in antibody titers after treatment, which suggests that these cases were equivocal for complete cure. By the subsequent fecal reexamination performed on the equivocal cases, approximately 20% were additionally found to be still harboring the parasite. These results indicate that serologic testing is useful to check whether a real cure has been achieved among the patients in whose fecal samples the presence of larvae has not been demonstrated after treatment.

Serodiagnosis of strongyloidiasis. The application and significance

Parasitological diagnosis based on the faecal examination is frequently difficult in cases of chronic, low-level S. stercoralis infection. Even when a newly developed sensitive method (an agar plate culture) is applied, it is essential to examine faecal samples repeatedly to achieve a correct diagnosis. Additionally, it is important to note that a negative result does not necessarily indicate the unequivocal absence of the infection. On the other hand, several serological tests which have recently been developed for strongyloidiasis have proven reliable when used to complement parasitological examination. We have developed two serological tests, ELISA and GPAT, to demonstrate Strongyloides infection and possible applications of the serological tests for diagnosis, mass-screening, epidemiological study and postchemotherapy evaluation of strongyloidiasis were reviewed based on our recent studies.

Concurrent infections with Strongyloides and T-cell leukemia virus and their possible effect on immune responses of host

Sera from 91 patients with strongyloidiasis in Okinawa prefecture, Japan, were examined for the presence of the concurrent infection with adult T-cell leukemia (ATL) virus by detecting the antibody to ATL-associated virus antigen (anti-ATLA). As high as 73.6% of the patients were found to be positive for the anti-ATLA antibody, whereas in 38 Strongyloides-negative controls, the positive rate was only 18.4% A significant increase of OKT 4+ cells and a decrease of OKT 8+ cells were noted among the patients positive for anti-ATLA antibody. A considerable rise of spontaneous proliferation of peripheral lymphocytes and a depression of mitogen-induced proliferative responses were also found in the patients. The increase of background mitogenesis was considered to be due to the concurrent infection with the ATL virus, but the depressed responses to mitogenic stimuli seemed to have no relation with the presence of the viral infection. The possible contribution of strongyloidiasis as a cofactor predisposing to ATL viral infection or leading the virus carriers to ATL patients was discussed.

Application of enzyme-linked immunosorbent assay for mass examination of strongyloidiasis in okinawa, Japan

The enzyme-linked immunosorbent assay was tested to evaluate whether it could be applicable in screening for mass examination of strongyloidiasis. A total of 2906 inhabitants in three areas (858 in Gushikawa Village, 849 in Nakazato Village and 1199 in Sashiki Town) were screened by the enzymatic assay and approximately 11-30% (11.8% in Gushikawa, 17.0% in Nakazato and 27.7% in Sashiki) were considered to be antibody positive. In the parasitological follow-up examinations of those who were antibody positive, actual infection was found in more than half (51%) the subjects. The overall infection rates estimated from the results reached 5.8% in Gushikawa, 9.1% in Nakazato and 14.0% in Sashiki (mean = 10.4%). The infection rates were significantly higher than those in previous surveys conducted in the same areas. The ELISA technique was found to be useful for strongyloidiasis screening and for seroepidemiological purposes in Okinawa.

Gelatin particle indirect agglutination test for mass examination for strongyloidiasis

An indirect agglutination test using recently developed gelatin particles was assessed to determine its applicability as a screening test for mass examination for strongyloidiasis. 1199 individuals in Sashiki Town, Okinawa Island, were screened by the test and 34.7% were determined to be antibody positive. Follow-up examination of the persons whose sera showed positive antibody responses demonstrated the presence of faecal larvae in 41.7%. The calculated infection rate (14.5%) was similar (14.1%) to that indicated by another survey using the micro-enzyme-linked immunosorbent assay (micro-ELISA), conducted simultaneously among the inhabitants. The indirect agglutination test was simple to perform in a short time and without specialized equipment. Additionally, the gelatin particles have many advantages as an antigen carrier, e.g. in handling, reading of the resulting pattern, and stable, long-term preservation. The test was considered to be more convenient than the micro-ELISA for mass screening for strongyloidiasis.

Peripheral lymphocyte subsets and their responsiveness in human strongyloidiasis

Surface phenotypes and proliferative responses of peripheral lymphocytes were investigated in a total of 64 patients with strongyloidiasis. A significant increase of CD4+ and OKIa1+ cells and a relative decrease of CD8+ cells were observed among the patients. A considerable rise of spontaneous mitogenesis and an enhanced ability to produce interleukin 2 of peripheral lymphocytes were also found in many patients. On the other hand, lymphoproliferative responses to mitogens were found to be significantly lower in the strongyloidiasis patients than in the controls. The possible relationships among these observations were discussed.