Metagonimus yokogawai: a 100-kDa Somatic Antigen Commonly Reacting with Other Trematodes

This study was undertaken to characterize the properties of a 100 kDa somatic antigen from Metagonimus yokogawai. Monoclonal antibodies (mAbs) were produced against this 100 kDa antigen, and their immunoreactivity was assessed by western blot analysis with patients' sera. The mAbs against the 100 kDa antigen commonly reacted with various kinds of trematode antigens, including intestinal (Gymnophalloides seoi), lung (Paragonimus westermani), and liver flukes (Clonorchis sinensis and Fasciola hepatica). However, this mAb showed no cross-reactions with other helminth parasites, including nematodes and cestodes. To determine the topographic distribution of the 100 kDa antigen in worm sections, indirect immunoperoxidase staining was performed. A strong positive reaction was observed in the tegumental and subtegumental layers of adult M. yokogawai and C. sinensis. The results showed that the 100 kDa somatic protein of M. yokogawai is a common antigen which recognizes a target epitope present over the tegumental layer of different trematode species.

Mucosal Immune Responses of Mice Experimentally Infected with Pygidiopsis summa (Trematoda: Heterophyidae)

Mucosal immune responses against Pygidiopsis summa (Trematoda: Heterophyidae) infection were studied in ICR mice. Experimental groups consisted of group 1 (uninfected controls), group 2 (infection with 200 metacercariae), and group 3 (immunosuppression with Depo-Medrol and infection with 200 metacercariae). Worms were recovered in the small intestine at days 1, 3, 5, and 7 post-infection (PI). Intestinal intraepithelial lymphocytes (IEL), mast cells, and goblet cells were counted in intestinal tissue sections stained with Giemsa, astra-blue, and periodic acid-Schiff, respectively. Mucosal IgA levels were measured by ELISA. Expulsion of P. summa from the mouse intestine began to occur from days 3-5 PI which sustained until day 7 PI. The worm expulsion was positively correlated with proliferation of IEL, mast cells, goblet cells, and increase of IgA, although in the case of mast cells significant increase was seen only at day 7 PI. Immunosuppression suppressed all these immune effectors and inhibited worm reduction in the intestine until day 7 PI. The results suggested that various immune effectors which include IEL, goblet cells, mast cells, and IgA play roles in regulating the intestinal mucosal immunity of ICR mice against P. summa infection.

Serological differentiation of human small fluke infections using Opisthorchis viverrini and Haplorchis taichui antigens.

Sera from 642 inhabitants of Vientiane Province (Laos) were examined by enzyme-linked immunosorbent assay (ELISA) using cytoplasmic and membranous antigens prepared from adult worms. Worms of Opisthorchis viverrini originated from liver of dissected cats, Haplorchis taichui were obtained from a stool specimen of a Laotian patient after praziquantel treatment. The sera were divided into five groups according to the intensity of infection expressed as egg count per gram of patients stool (EPG). Correlation between intensity of infection and the level of antibodies in serum was recorded. Reactions obtained using the cytoplasmic antigens were more sensitive and more specific compared to those with membranous antigens. Cross-reactions between antigens of both helminth species were found. Highly positive sera were examined using electroimmunotransfer blots (EITB) with cytoplasmic antigens of both species, which enabled the species differentiation. Antigens of both species yielded several shared fractions; however, differences between them were found: homologous sera reacted specifically with O. viverrini antigen in the area of 70 kDa and with H. taichui antigen in the area of 10 kDa. Thirty-one of 122 tested sera had specific antibodies against O. viverrini, 77 sera against H. taichui and 14 sera against both species. The results confirmed our assumption about predominant occurrence of heterophyid flukes in the human population living in studied area, compared with the occurrence of opisthorchid flukes. Hence, serology seems to be helpful tool for correct diagnosis of small fluke infections.