Characterization of monoclonal antibodies reactive with Schistosoma haematobium-soluble egg and infected human urinary antigens

Minimising invasiveness in diagnostics: developing a rapid urine-based monoclonal antibody dipstick test for malaria

OBJECTIVE

To generate monoclonal antibodies (MAbs) for developing a rapid malaria diagnostic urine-based assay (RUBDA), using Plasmodium-infected human urinary antigens.

METHODS

Plasmodium-infected human urinary (PAgHU) and cultured parasite (CPfAg) antigens were used to generate mouse MAbs. The reactivity and accuracy of the MAbs produced were then evaluated using microplate ELISA, SDS-PAGE, Western blotting assay, microscopy and immunochromatographic tests.

RESULTS

Ninety-six MAb clones were generated, of which 68.8% reacted to both PAgHU and CPfAg, 31.3% reacted to PAgHU only, and none reacted to CPfAg only. One promising MAb (UCP4W7) reacted in WBA, to both PAgHU and CPfAg, but not to Plasmodium-negative human urine and blood, Schistosoma haematobium and S. mansoni antigens nor measles and poliomyelitis vaccines.

CONCLUSION

MAb UCP4W7 seems promising for diagnosing Plasmodium infection. Urine is a reliable biomarker source for developing non-invasive malaria diagnostic tests. SDS-PAGE and MAb-based WBA appear explorable in assays for detecting different levels of Plasmodium parasitaemia.

Immunolocalization of the 29 kDa Schistosoma haematobium species-specific antigen: a potential diagnostic marker for urinary schistosomiasis

BACKGROUND

The 29 kDa Schistosoma haematobium species-specific antigen (ShSSA) is of remarkable interest in the diagnosis of urinary schistosomiasis although it had not been fully characterized.

METHOD

To determine the biological importance of ShSSA in S. haematobium and pathogenesis of the disease, we immunolocalized ShSSA in schistosome eggshells, miracidia and adult worm sections using indirect fluorescent antibody test (IFAT).

RESULTS

ShSSA was strongly immunolocalized in the schistosome eggshells, selective regions of the miracidia body and walls of internal organs such as oviduct, ovary, vitelline duct and gut of the adult worm.

CONCLUSION

The strong immunolocalization of ShSSA in schistosome eggshells and adult worm internal organs suggests that the antigens involved in the pathogenesis of urinary schistosomiasis could have originated from the eggs and adult worms of the parasite. The findings also indicate that ShSSA may play a mechanical protective role in the survival of the parasite.

Mouse monoclonal antibodies against human urinary protein Sm-UP(2)IP of Schistosoma mansoni

There are innumerable clinical and pathological problems associated with schistosomiasis that have necessitated various control programs. Successful control would naturally depend on effective rapid diagnosis in the field. However, the overlapping distribution of urinary and intestinal schistosomiasis in hyperendemic areas calls for differential diagnosis. This study was aimed at producing anti-Schistosoma mansoni monoclonal antibodies (MAbs) for possible utilization in assays to detect antigens in the urine of infected persons. In order to raise antibodies to less immunogenic urinary parasite antigens, BALB/c mice were immunized with Schistosoma mansoni soluble worm antigens (Sm-SWA) while urinary proteins (Sm-UP(2)IP), isolated from infected human urine samples, was used as a final booster before cell fusion. Hybridoma cells were obtained by the fusion of mouse myeloma and spleen cells from the immunized mice, which were screened by microplate ELISA and then studied further to obtain anti-S. mansoni specific MAbs. The MAbs analyzed presented IgM isotypes. The reactivity of anti-S. mansoni MAbs with Sm-UP(2)IP, 13/43 (30.2%), MAbs showed stronger reactivity. It was observed that one of the MAbs cross-reacted with antigen associated with S. haematobium urinary antigen (Sh-UP(2)IP). Nine (9/13, 69.2%) MAbs recognized glycoprotein antigenic epitopes of Sm-UP(2)IP and Sm-SWA. On the other hand, 4/13 (30.8%) MAbs recognized carbohydrate antigenic epitopes. Band size of 8.9 kDa associated with Sm-UP(2)IP was detected by the 13 MAbs. With Sm-SWA, all the MAbs detected band sizes of 177.8 and 158.5 kDa. In addition, three MAbs recognized a 38.9 kDa band. The generation of anti-S. mansoni species-specific MAbs offers opportunities to develop a specific MAb-based diagnostic tool for use in the field to detect Schistosoma mansoni infection in Ghana.

Human schistosomiasis haematobium: effective diagnosis of active infection using a pair of monoclonal antibodies against soluble egg antigen

The present study was designed to prepare monoclonal antibodies (MAbs) against Schistosoma haematobium soluble egg antigen (SEA) with immunodiagnostic potential for urinary schistosomiasis. From a panel of MAbs, a pair of IgG1 MAbs (2D/11C and 10B/2C) specific for S. haematobium SEA was selected. Both MAbs recognized one band with a 42-kDa molecular weight by western blots. The pair of MAbs was employed in sandwich ELISA for the detection of circulating schistosome antigen (CSA), one as antigen-capturing antibody and the other as peroxidase-conjugated antigen-detecting antibody. The lower detection limit of the assay was 1 ng/ml of S. haematobium SEA. The assay was performed on sera of 65 S. haematobium-infected patients, 25 patients infected with other parasites (Fasciola hepatica, Echinococcus granulosus), and 20 noninfected individuals. CSA was demonstrated in 89% of the S. haematobium-infected group. However, CSA was negative in the sera of healthy individuals and patients infected with other parasites, giving an overall specificity of 100% for the CSA assay. A positive correlation (r=0.37, p<0.01) was detected between the number of S. haematobium eggs excreted in 10 ml urine and the CSA level detected in the sera of S. haematobium-infected patients. Our data show that the use of anti-S. haematobium MAbs for the detection of CSA provides a sensitive and specific method for the immunodiagnosis of active S. haematobium-infected patients. Moreover, CSA assay using this anti-S. haematobium MAb/ELISA system was proven to correlate with intensity of infection and hence morbidity assessment.

Applicability of a monoclonal antibody-based dipstick in diagnosis of urinary schistosomiasis in the Central Region of Ghana

Summary We tested a rapid visually read monoclonal antibody (MoAb) based dipstick assay for specific diagnosis of urinary schistosomiasis against microscopy and the use of haematuria and proteinuria in a schistosomiasis haematobia endemic area in the Central Region of Ghana. The study group consisted of 141 school children (83 males, 58 females) aged 8-19 years. A total of 129 of 141 (91.5%) submitted stool samples, and 7.8% had Schistosoma mansoni, 55% had hookworms and 6.2% had tapeworms. The presence of S. mansoni and intestinal parasites did not appear to influence the results of the MoAb-dipstick assay. The urinary schistosomiasis prevalence by MoAb-dipstick (78%) was higher (P < 0.05) than the estimate by microscopy (60.3%), microhaematuria (27%) and proteinuria (30.5%). The MoAb-dipstick correctly identified 98.8% of microscopically confirmed cases and missed one (1.3%). The dipstick was also positive for 26 of 56 (46.4%) egg-negative individuals, thereby giving a sensitivity of 98.8% and a specificity of 53.6%. On the other hand, microhaematuria and proteinuria were 38.8% and 30.6% sensitive, and 91.1% and 69.6% specific, respectively. Microhaematuria and proteinuria were less sensitive (P < 0.05) than both microscopy and MoAb-dipstick.

Infant schistosomiasis in Ghana: a survey in an irrigation community

We used a rapid, visually read, field applicable monoclonal antibody (MoAb)-dipstick assay for specific diagnosis of urinary schistosomiasis together with microscopy to determine the prevalence of infant schistosomiasis in a community in the Awutu-Efutu Senya District in the Central Region of Ghana. The study group consisted of 97 infants (51 males and 46 females) aged 2 months to 5 years. A total of 75 of 97 (77.3%) subjects submitted stool samples; none had Schistosoma mansoni. Three individuals (3.1%) had hookworms but there were no other intestinal helminths. The urinary schistosomiasis prevalence by MoAb-dipstick (30%) was higher (P < 0.05) than that estimated by microscopy (11.2%). However, three of nine (33.3%) microscopically confirmed cases tested MoAb-dipstick positive after pre-treatment of the urine specimen with heat. The youngest infant to be found infected with S. haematobium microscopically was 4 months old. Fifteen of 71 S. haematobium egg negative individuals tested dipstick positive, giving a dipstick specificity of 78.9% as compared with microscopy as gold standard test. The relative sensitivity of the dipstick was 100%.

Assessment of morbidity in Schistosoma haematobium infection: current methods and future tools

Recently, new potential tools for assessment of Schistosoma haematobium related morbidity have emerged. The tools are based on detection of S. haematobium egg antigens in urine or detection of eosinophil cationic protein (ECP) in urine, which may reflect the inflammatory response in the urinary tract. So far two markers have been assessed in long-term post treatment follow-up studies, allowing for an evaluation both before treatment and during regression and reappearance of infection and urinary tract morbidity. The results from these studies and the usefulness of the markers as morbidity assessment tools are discussed.

A monoclonal antibody-based dipstick assay for diagnosis of urinary schistosomiasis

A Schistosoma haematobium species-specific mouse immunoglobulin (Ig) G1 monoclonal antibody (mab) Sh2/15.F that bound a 29 kDa peptide was utilized to develop a membrane-based dipstick enzyme-linked immunosorbent assay for specific diagnosis of urinary schistosomiasis. Strips of polyvinylidene difluoride membrane were wetted with methanol and stored in distilled water. The strips were used to capture urinary antigens which were then revealed by incubation in a mixture of specific mab and peroxidase-conjugated goat anti-mouse IgG. The assay correctly identified 26/30 (87%) of egg-negative control individuals and 53/54 (98%) of parasitologically confirmed cases including all of 6 individuals treated with praziquantel (40 mg/kg) but not cured. Also, the assay detected S. haematobium antigens in the urine of 3 individuals from whom 2 specimens had to be examined microscopically to confirm infection, thus suggesting that the mab detection method may have greater sensitivity than microscopy.

Limited field evaluation of a rapid monoclonal antibody-based dipstick assay for urinary schistosomiasis

A rapid, visually read monoclonal antibody (MoAb)-based dipstick assay for specific diagnosis of urinary schistosomiasis was field tested with microscopy and the use of hematuria and proteinuria in a schistosomiasis hematobia endemic area in Southern Ghana. The study group consisted of 229 individuals (114 males and 115 females) aged 1 to 86 years; 145/229 (63.3%) of the subjects submitted stool samples from which no S. mansoni eggs were detected. However, infections with Necator americanus (hookworms) 33.1%, Ascaris lumbricoides 2.8%, Trichuris trichiura (whipworm) 2.8%, and Strongyloides stercoralis 0.7% were detected but did not appear to influence the results of the MoAb-dipstick assay. Urinary schistosomiasis prevalence was estimated as 47.6% by microscopy, 48% by MoAb-dipstick, 39.7% by microhematuria, and 23.6% by proteinuria. The MoAb-dipstick correctly identified 108/109 (99.1%) of microscopically confirmed cases and 118/120 (98.3%) of egg-negative individuals, thereby giving a sensitivity of 99.1% and a specificity of 98.3%. On the other hand, microhematuria and proteinuria were, respectively, 76.1% and 40.4% sensitive, and 94.2% and 92.5% specific when compared to microscopy. Microhematuria and proteinuria had significantly lower sensitivity (P < 0.001) than either microscopy or dipstick.

Extraction of Schistosoma haematobium antigens from infected human urine and generation of potential diagnostic monoclonal antibodies to urinary antigens

Proteins in Schistosoma haematobium infected human urine were concentrated by precipitation with saturated ammonium sulphate 50% (v/v) and various fractions obtained at different stages of precipitation tested for presence of schistosome antigens (ShAgs) by dot-ELISA. The protein fraction (UP2S) obtained following two-times precipitation was found to contain high concentrations of ShAg. Fraction UP2S was dialysed against phosphate-buffered saline (pH 7.4) and further purified by Sephadex G-200 column chromatography. Two protein peaks were eluted of which the first peak UP2S(pkI) was found to contain high concentrations of ShAgs as determined by microplate-ELISA. The second peak UP2S(pkII) consisted of human urine proteins. Further analysis of UP2S(pkI) revealed that ShAgs were mainly in the form of immune complexes with human IgG, IgM, IgA, IgE and complement C3. The ShAgs in both UP2S and UP2S(pkI) were found to be active as they induced immune responses in mice which produced antibodies reactive with S. haematobium worm as well as soluble egg antigens (SEA). Pure ShAgs were obtained from UP2S following dissociation of immune complexes with a carbonate buffer (pH 11.42) and further purification on Sephadex G-200. Immunizations with UP2S led to the generation of MoAbs which could bind both SEA and UP2S.