Proceedings of the schistosome genome project

"The host-parasite relationship" is a vast and diverse research field which, despite huge human and financial input over many years, remains largely shrouded in mystery. Clearly, the adaptation of parasites to their different host species, and to the different environomental stresses that they represent, depends on interactions with, and responses to, various molecules of host and/or parasite origin. The schistosome genome project is a primary strategy to reach the goal; this systematic research project has successfully developed novel technologies for qualitative and quantitative characterization of schistosome genes and genome organization by extensive international collaboration between top quality laboratories. Schistosomes are a family of parasitic blood flukes (Phylum Platyhelminthes), which have seven pairs of autosomal chromosomes and one pair of sex chromosomes (ZZ for a male worm an ZW for a female), of a haploid genome size of 2.7X10 8 base pairs (Simpson et al. 1982). Schistosomes are ideal model organisms for the development of genome mapping strategies since they have a small genome size comparable to that of well-characterized model organisms such as Caenorhabditis elegans (100 Mb) and Drosophila (165Mb), and contain functional genes with a high level of homology to the host mammalian genes. Here we summarize the current progress in the schistosome genome project, the information of 3.047 transcribed genes (Expresses Sequence Tags; EST), complete sets of cDNA and genomic DNA libraries (including YAC and cosmid libraries) with a mapping technique to the well defined schistosome chromosomes. The schistosome genome project will further identify and charaterize the key molecules that are responsable for host-parasite adaptation, i.e., successful growth developement, maturation and reproduction of the parasite within its host in the near future.

The serodiagnosis of amoebiasis by enzyme-linked immunosorbent assay

We attempt to detect antibodies against Entamoeba histolytica in sera obtained from both healthy individuals and hospitalized patients by an enzyme-linked immunosorbent assay (ELISA). The limiting value for ELISA-positive was established on the basis of serologic results of 1869 healthy persons living in a non-endemic area (Japan)> The ELISA then was applied to 61 patients in 5 hospitals in Myanmar who were suspected of having amoebiasis. The ELISA results were compared with those of stool examinations, and evaluated for sensitivity. Using the llimiting value for the ELISA, there was an 83 Percent agreement of positivity between the ELISA tests and microscopic examinations. Specific anti-E-histolytica IgM was observed in the sera of 44 patients; IgG in all of the 61 patients. Since high titers of specific IgM were not observed in both stool-positive and stool-negative patients, we judged that patients with early stages of amoebic infections were not included in this population. In our ELISA, the sera of the patients did not exhibit crosss-reactions betweeen antigens prepared from the HK-9 strain of E. histolytica and antigens prepared from Trichomonas vaginalis and Giardia lamblia. On the basis of these results, we suggest that it is necessary to do two or more different examinations in order to make a definite diagnosis of amoebic infection.

Detection of Entamoeba histolytica antigen in stool samples by enzyme-linked immunosorbent assay using monoclonal antibodies

An enzyme-linked immunosorbent assay (ELISA), using monoclonal antibodies, was applied for the detection of Entamoeba histolytica antigen in stool samples obtained from 148 patients with gastrointestinal symptoms, and the results are compared with microscopic findings. Ninety nine positives by microscopy generally had high ELISA OD values. Ninety one stool samples of asymptomatic cyst passers were also investigated by ELISA, and most were found to be positive. Although false positives were observed in both symptomatic and asymptomatic cases, the ELISA appears to be useful for the detection of amoebic antigen(s). However, our results suggest that both immunological methods and microscopic examination are needed for an accurate diagnosis of intestinal amoebiasis.