Gene cloning, expression and serological evaluation of the 12-kDa antigen-B subunit from Echinococcus granulosus.

A 12-kDa subunit of antigen B from Echinococcus granulosus has recently been cloned, expressed and used in diagnostic ELISA to test human sera for evidence of cystic echinococcosis. The performance of the ELISA based on the recombinant antigen (rAgB) was compared with that of similar assays based on native antigen B (nAgB) or hydatid-cyst fluid. For the preparation of the rAgB, total RNA was extracted from Ec. granulosus protoscoleces so that antigen-B complementary DNA could be synthesised, amplified by PCR, and then cloned into the pQE30 expression vector. The recombinant plasmid was transformed in Escherichia coli and induced using isopropyl-beta-D-thiogalactopyrano-side. Bacterial samples were collected, lysed and then analysed by SDS-PAGE and western blotting. The recombinant protein was purified by affinity chromatography. Although the performance of the ELISA based on cyst fluid appeared identical to that of the assay based on the recombinant antigen (with a sensitivity, specificity, positive predictive value and negative predictive value of 96.0%, 97.0%, 97.2% and 95.5%, respectively), the corresponding results for the ELISA based on nAgB (98.6%, 100%, 100% and 98.5%) were slightly better. Despite this difference (which was not statistically significant), the comparative ease with which large quantities of the recombinant antigen could be produced make the antigen a potentially useful tool in the diagnosis of cystic echinococcosis.

Comparison of adult somatic and cysteine proteinase antigens of Fasciola gigantica in enzyme linked immunosorbent assay for serodiagnosis of human fasciolosis.

Fasciolosis caused by Fasciola hepatica and Fasciola gigantica is one of the major public health problems in the world and in Iran. Considering that stool examination for Fasciola eggs is not a sensitive method and immunodiagnosis methods are more applicable for this purpose, so the present study was conducted to compare the somatic (S) and cysteine proteinase (CP) antigens of F. gigantica in IgG-ELISA to diagnose human fasciolosis. Serum samples obtained from 100 individuals collected during the fasciolosis outbreak in 1999 in the Gilan province of Northern Iran that were coprologically positive for fasciolosis were analyzed by IgG-ELISA. Sera from healthy control individuals, not infected with any parasitic diseases (n=50) and from others with different parasitic infections including hydatidosis (n=40), toxocariosis (n=20), amoebiosis (n=10), and malaria (n=5) were examined as well. The cut-off point for (S) and CP was 0.40 and 0.35, respectively. All 100 individuals that showed clinical manifestations of fasciolosis, were also seropositive using both antigens, whereas all 50 non-infected controls were seronegative, therefore the sensitivity of the test was 100% for both antigens. The specificity of (S) and CP antigens were calculated as 96.9 and 98.4%, respectively. The positive and negative predictive values of the test regarding (S) antigen were 96 and 100%, whereas these values as for CP antigen were 98 and 100% correspondingly. Two individuals with hydatidosis and two with toxocariasis had antibodies that were reactive against (S) antigen, whereas concerning CP antigen, one individual with hydatidosis and another with toxocariasis showed cross-reactivity against it. We have demonstrated that altogether CP antigen provides a more conclusive diagnosis as possessing lower cut-off and enabling better to discriminate between seronegative and seropositive subpopulations.

Comparison of enzyme-linked immunosorbent assay and indirect immunofluorescence assay in the diagnosis of human strongyloidiasis.

BACKGROUND: An enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence assay (IFA) were evaluated for serological diagnosis of human strongyloidiasis. METHODS: Serum specimens obtained from 46 individuals infected with Strongyloides stercoralis, 37 healthy persons and 381 persons with other parasitic infections were tested using an IgG-ELISA that used crude antigen of S. stercoralis filariform larvae and an IFA. Test sera were pre-incubated with antigens from Ascaris, Toxocara and hydatid protoscolices to remove non-specific antibodies. RESULTS: The sensitivity, specificity, positive predictive value and negative predictive value for ELISA were 93.5%, 96.1%, 72.9% and 99.2%, respectively, and those for IFA were 87%, 90.1%, 49.4% and 98.4%, respectively. Both assays showed false positivity in hydatidosis, ascariasis and toxocariasis; however, this was less common with ELISA. CONCLUSION: ELISA method using filariform larval antigen may be a sensitive and specific test for human strongyloidiasis, and may be preferable to IFA.

The present status of human helminthic diseases in Iran.

Over the last few decades there have been several marked changes in the human helminthiases found in Iran. Fascioliasis is emerging as an important chronic disease of humans, especially in the northern province of Gilan (where outbreaks in 1989 and 1999 involved >7000 and >10,000 cases, respectively) and, more recently, in the western province of Kermanshah. In contrast, no cases of urinary schistosomiasis, a disease that once affected thousands of individuals in south-western Khuzestan province, have been reported in Iran in recent years, and no cases of dracunculiasis have been seen in the country since the mid-1970s. Approximately 1% of all admissions to surgical wards are attributable to cystic echinococcosis, which is still considered endemic, but only a few cases of alveolar echinococcosis have been recorded. Over the last decade, there appears to have been a generally downward trend in the incidence of intestinal helminthiases in Iran. Recent estimates of the prevalences of ascariasis and strongyloidiasis, for example, lie between just 0.1% and 0.3%, and <1% of the population now appears to be infected with hookworm. In contrast, human infection with Hymenolepis and Enterobius remains relatively common. There have been a few case reports of toxocariasis and a few sero-epidemiological investigations of this disease but problems in accurate diagnosis have prevented good estimates of the general prevalence of this nematode infection. Just nine cases of pentastomiasis (all caused by Linguatula), 12 of dirofilariasis, one of gongylonemiasis, and three of moniliformiasis have been formally recorded in Iran.

Helminth parasites of the wild boar, Sus scrofa, in Luristan province, western Iran and their public health significance.

Seven helminth species were obtained from 12 wild boars (Sus scrofa) during a survey from 2000 to 2001 in Luristan province, western Iran. These species include the cestode larvae Cysticercus tenuicollis (25%), C. cellulosae (8.3%), the nematodes Metastrongylus apri (41.6%), M. pudendotectus (16.6%), M. salmi (8.3%), Trichuris suis (8.3%) and the acanthocephalan Macracanthorhynchus hirudinaceus (41.6%). No trematodes were found. Seven wild boars (58.3%) were identified as having at least one helminth species. A single infection was detected in 16.6% of cases, but a three species infection covered the highest rank (25%). All these helminths have been reported from other areas of Iran including the north, northeast and southwest, but not in Luristan. Among seven helminths identified, at least three species are transmissible to humans. The public health significance of these helminths is discussed.