Serum antibody responses in opisthorchiasis.

We evaluated an enzyme-linked immunosorbent assay using crude parasite homogenates as a diagnostic test for Opisthorchis viverrini infection in humans. Serum antibody (Ab) responses to O. viverrini adult worm homogenate (AWH) and metacercaria homogenate (MH) were studied in 83 infected residents of an opisthorchiasis-endemic area in Thailand. Elevated levels of Ab persisted for over 1 year following curative treatment with praziquantel, and cross-reactivity to O. viverrini AWH and MH antigens was observed in sera from individuals with other parasitic infections. Serum Ab to crude AWH and MH are therefore unsuitable for immunodiagnosis since they may be non-specific and would not differentiate between ongoing and past infection.

Hepatitis E in a Canadian traveller.

Hepatitis E is clinically indistinguishable from hepatitis A and is caused by an enterically transmitted rna virus that is endemic in developing countries of Asia, Africa, the Middle East and North America. This report describes a Canadian traveller to Nepal, Thailand and India with one of the first confirmed cases of hepatitis E reported in Canada. Although this disease is usually self-limited with no known sequelae, it may produce fulminant hepatitis with a high case fatality rate in pregnancy. Diagnosis can be confirmed by serological tests. Apart from strict food and beverage hygiene, there are presently no prophylactic measures against this disease, and pregnant women in the third trimester should avoid travel to endemic areas.

Serum antibody response to Opisthorchis viverrini antigen as a marker for opisthorchiasis-associated cholangiocarcinoma.

The liver flukes Opisthorchis viverrini and Clonorchis sinensis chronically infect over 30 million people in south-eastern Asia, resulting in significant morbidity and a predisposition to cholangiocarcinoma (CCA). Liver fluke-associated CCA carries a poor prognosis, partly because it is often detected at a late and advanced stage. The development of improved diagnostic methods, particularly for early CCA, may improve chances of survival and cure. Accordingly, we explored the use of immunological responses to liver fluke antigens as a potential means of identifying individuals at high risk for liver fluke-associated CCA. Serum antibody responses to O. viverrini adult worm homogenate and metacercaria homogenate (MH) were studied using enzyme-linked immunosorbent and immunoblot assays in 65 infected residents of an opisthorchiasis-endemic area in Thailand. Antibody levels correlated with liver ultrasonography (U/S) findings, and immunoblot analysis revealed a 91/93 kDa MH doublet recognized only by sera of individuals with severe liver U/S findings, including CCA. These results suggest that serum antibody responses to liver fluke antigens may be useful in the identification of infected individuals who are at high risk for liver fluke-associated CCA.

Possible protective immunity in human opisthorchiasis.

Chronic infections with the liver flukes Opisthorchis viverrini and Clonorchis sinensis affect over 30 million people in southeastern Asia. With ongoing exposure, reinfection readily occurs following curative treatment and cumulative infections result in significant morbidity and a predisposition to cholangiocarcinoma. Though protective immunity has never been described in human opisthorchiasis, heterogeneity in worm burden occurs and a small number of exposed residents of endemic areas remain apparently uninfected. To explore the nature of this heterogeneity, we compared levels of serum antibody (Ab) to O. viverrini measured by an enzyme-linked immunosorbent assay in 83 stool egg-positive and 49 stool egg-negative residents of an O. viverrini-endemic area in Thailand. Compared to the egg-positive residents, the egg-negative group had significantly higher levels of immunoglobulin (Ig)G, IgA and IgM to adult worm homogenate (AWH) and total Ab to metacercaria homogenate (MH). Furthermore, immunoblot analyses revealed that a significantly higher proportion of sera from the egg-negative residents had IgA reactivity against a 38-kDa AWH antigen and IgM reactivity against carbohydrate epitopes of a 42-kDa AWH glycoprotein antigen. These findings support a hypothesis that the egg-negative group includes individuals who may be immunologically resistant to this usually chronic infection.

Separation and characterization of adult worm proteins and glycoproteins from the liver fluke Opisthorchis viverrini.

Detailed studies of liver fluke proteins and antigens are necessary to facilitate further investigation of the human immune responses to these parasites. Accordingly, Opisthorchis viverrini antigens were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. We initially encountered excessive background smearing, vertical streaking, and indistinct bands that were similar to problems previously described by investigators studying this and other trematodes including Schistosoma mansoni. These problems were especially evident with silver staining of proteins and occurred despite the extensive use of protease inhibitors. They were minimized by using mini (vs. large) SDS-PAGE and Coomassie blue protein staining. With the latter 2 techniques, adult worm somatic proteins and excretory-secretory products were separated and characterized. Immunoblots using rabbit anti-adult worm sera demonstrated that some of these proteins were antigens common to both the adult and metacercarial stages. Several of these antigens also corresponded (according to molecular weight) to glycoproteins, detected by concanavalin A blotting. These findings form a base for subsequent studies of the human immune response to liver fluke infection.

Tumour markers in the detection of opisthorchiasis-associated cholangiocarcinoma.

Opisthorchiasis is a major public health problem in north-east Thailand, where over 7 million inhabitants are reported to be infected. A significant percentage of infected individuals develops cholangiocarcinoma terminally, which is rapidly fatal. To determine whether certain tumour markers are elevated in Thai patients with cholangiocarcinoma, and thus might be useful in the diagnosis of cholangiocarcinoma associated with opisthorchiasis in Thailand, the tumour markers CA125 and CA19-9 were measured by radioimmunoassay in 94 serum samples. The subjects consisted of 52 patients admitted for non-gastroenterological diseases, 7 patients with histologically proven cholangiocarcinoma, 7 patients with clinically suspected cholangiocarcinoma, and 28 patients with uncomplicated opisthorchiasis. The mean levels (+/- standard deviation [SD]) of CA19-9 and CA125 in the controls were 12.5 +/- 10.2 and 24.7 +/- 11.1 units/ml respectively. Using the mean + 3SD as the cut-off level, 57.1% of patients with confirmed cholangiocarcinoma had elevated CA19-9 and 28.6% had elevated CA125. In patients with clinically suspected cholangiocarcinoma, 71.4% had elevated CA19-9 and 28.6% had elevated CA125. Among opisthorchiasis patients, 3.6% had elevated CA125 and none had elevated CA19-9. 1.9% of controls had elevated CA19-9 and none had elevated CA125. When positivity of either CA125 or CA19-9 was used as an indicator of malignancy, the sensitivity and specificity of the combined tests reached 85.7% and 98.1% respectively. These preliminary results suggest that the measurement of CA125 and CA19-9 may be useful in the early detection of opisthorchiasis-associated cholangiocarcinoma.

Resectable bronchogenic carcinoma presenting with hypercalcemia: tumor-associated granulomatous reaction and probable production of 1,25-dihydroxyvitamin D.

A patient with hypercalcemia, increased levels of 1,25-dihydroxyvitamin D, and a resectable squamous cell bronchogenic carcinoma surrounded by numerous non-caseating epithelioid granulomas, achieved normocalcemia, decreased levels of 1,25-dihydroxyvitamin D, and no evidence of tumor recurrence at 30 months following complete resection of his tumor. We suggest that an excess production of 1,25-dihydroxyvitamin D, through the granulomatous reaction around the tumor, was the mechanism of hypercalcemia. To our knowledge, no such mechanism of hypercalcemia has been previously reported with bronchogenic carcinoma. Furthermore, a review of the literature reveals that in cases of bronchogenic carcinoma, hypercalcemia is almost always associated with large and unresectable tumors, with a median survival after the discovery of hypercalcemia of only one month. This case, then, is unique because it describes an unusual mechanism of hypercalcemia with bronchogenic carcinoma and it emphasizes the rare occurrence of the potentially curable patient presenting with bronchogenic carcinoma complicated by hypercalcemia.