Study On Detection Of Circulating Antigen For Diagnosis Of Schistosomiasis By Monoclonal Antibody

Circulating antigens(CAgs) of Schistosoma japonica are excreted by worm living in host. Because of their vanishing soon after chemotherapy, the existence of CAg can reflect active infection and worm burden and thus be possible to use for accessing effect of chemotherapy. It is a challenge in diagnosis of schistosomiasis to find a way to detect CAg that satisfy not only sensitivity but also accessing effect of chemotherapy. Detection of antibody has advantage in sensitivity but its sustaining in circulation long after worm be killed by chemotherapy. This led to low efficiency in identifying active and past infection and evaluating the effect of treatment.Monoclonal antibody(McAb) in sandwich-ELISA for CAg detection and anti-SEA ELISA for CAb detection were applied in this study for the purpose of establishing unite test of CAg and CAb. It was analyzed diagnostic performance and relationship between the unite test, CAg and CAb test. The evaluation was also carried out to diagnostic efficiency in individual infection and accessing effect of chemotherapy. Two different McAbs, JPG5 and JPS6 with its targeted antigen located at gut of adult worm and egg respectively, were also applied for detection of CAg to acquire basic understanding and their potentials in diagnosis of shcistosomiasis. A trial to detect multi-epitops of CAg was done by using combination of McAbs in the way of homogeneous and heterogeneous for an intention to improve their efficiency of CAg diagnosis.The detection of CAg by JPG3 McAb and CAb by SEA ELISA showed 78.7% and 95.7% in sensitivity, 93.7% and 96.1% in specificity and Youden index 0.725 and 0.918 respectively. It indicated that JPG3 can be used as a potential probe for CAg detection. Examination to patients followed up treatment, CAg and CAb showed positive rate of 65.0% and 90.0% at 6 months post treatment, 55.0% and 82.5% at 12 months post treatment. The positive rate of CAg was lower than that of CAb. This proved that CAg detection by JPG3 is valuable in accessing the chemotherapy effect, but CAb detection is invaluable for this purpose.Parallel test and serial test of CAg and CAb showed 95.7% and 75.9% in sensitivity and 92.2% and 99.2% in specificity respectively. The parallel test can improve sensitivity while the serial test can improve the specificity. Detection to egg negative individuals from endemic area showed 89.8% and 40.7% of positive rate by parallel test and serial test respectively. This shows that higher specificity of serial test has advantage in decreasing false identification to non-infected individuals in endemic area.CAg detection by JPG5 and JPS6 showed 74.3% and 78.7% in sensitivity, 96.8% and 95.2% in specificity and Youden index 0.711 and 0.731 respectively. Both showed low cross reactivity with other diseases. The results shows that this two McAbs have similar diagnostic efficiency and can be used as candidates as the probe for CAg detection.Detection to patients followed up, CAg detection by JPG5 showed 41.4% and 65.5% negative turning rate at 6 months and 12 months post treatment, while 40.1% and 43.8% by JPS6. JPG5 and JPS6 have similar effect in accessing effect of chemotherapy after 6 months, but JPG5 shows a better effect than JPS6 after 12 months. This indicated CAg located at the gut of adult worm is more valuable than that from SEA. Of three McAbs, JPG5 shows a higher potential in accessing effect of chemotherapy.The detection of CAg by combination of homogeneous JPG5+JPG1 and heterogeneous JPS6+JPG1 showed 80.1% and 73.5% in sensitivity, 97.7% and 96.1% in specificity and Youden index 0.737 and 0.696 respectively. Both combinations showed similar efficiency. Compared with single epitop detection, no obvious improvement had been observed in effect of detection and diagnostic efficiency by multi-epitope detection.This study tried new way to detect CAg and CAb simultaneously and establish unite test as well as multi-epitops of CAg detection by different McAbs. It is expected that further research will contribute more to solve key problems in diagnosis of Schistosomiasis in the future and thus to push forward the process of schistosomiasis control in China.