[Application of magnetic particle antibody immunoassay in detection of anti-Schistosoma japonicum egg antibody].

OBJECTIVE: To establish a magnetic particle antibody immunoassay (MPAIA) for the detection of specific antibody in sera of schistosomiasis patients. METHODS: Fluorescein isothiocyanate (FITC) was used to label Schistosoma japonicum soluble egg antigen (Sj-SEA). Anti-human IgG coated with alkaline phosphatase (ALP) as enzyme-labeled second antibody, and magnetic beads were coupled with sheep anti-FITC antibody as solid phase. Phenolphthale in monophosphate was used as substrate to set up MPAIA for the detection. Serum samples from cases with schistosomiasis or other helminth infections were tested. RESULTS: The positive rate of MPAIA was 96.7% (116/120) with the sera of S. japonicum-infected cases. No cross reaction was observed with sera of trichinellosis, paragonimiasis or cysticercosis cases. The positive titer with reference sample was 1: 1,600. The precision was lower than 10%. The MPAIA tips can be stored at 4 degrees C for 12 months. CONCLUSION: MPAIA shows a high sensitivity, proper specificity and long-term validity for schistosomiasis detection.

[Detection of Trichomonas vaginalis with direct immunofluorescence assay].

OBJECTIVE: To detect Trichomonas vaginalis (Tv) by direct immunofluorescence assay (DFA) and discuss its clinical significance. METHODS: The parasites at a concentration of 3 x 10(5) cells/L were fixed by acetone on slides which were then blocked by 1% BSA (bovine serum albumin) or 10% BSA or 10% NCS (newborn calf serum) respectively, incubated with different dilution of polyclonal goat anti-Tv IgG (1:20-1:2,560) for different incubation time (15, 30, 45, 60, 90, 120 min). 120 clinical vaginal specimens were examined by direct immunofluorescence assay, the wet mount method and the in vitro cultivation. RESULTS: Blocked by 1% or 10% BSA, incubated at 37 degrees C for 45 min with a titer 1:160 of polyclonal antibody were the optimal conditions for direct immunofluorescence assay. Its sensitivity and specificity were 87.9% and 98.6% respectively in comparison with the in vitro cultivation method. CONCLUSION: Direct immunofluorescence assay is a useful alternative to the wet mount method which shows a lower sensitivity.

[Screening of schistosomiasis japonica diagnostic antigen with phage 12-mer peptide library].

OBJECTIVE: To obtain the mimic epitope of specific and sensitive diagnostic antigen in schistosomiasis japonica from phage 12-mer peptide library. METHODS: Specific Ig was purified from sera of patients with acute schistosomiasis and used to immunoscreen the phage peptide library (PH. D.-12). After 3 rounds of panning, 10 positive plaques were selected and amplified. The immunoactivity of each clone was examined by ELISA. The sensitivity and specificity of immunoactive clones were confirmed by detecting the sera of patients with different parasitosis. RESULTS: Six clones could bind to the specific Ig purified from sera of patients with acute schistosomiasis. One clone with the highest A492 value showed a high sensitivity and specificity. CONCLUSION: The clone (SjA1) identified by the specific Ig from the library played a better part in the immunodiagnosis of schistosomiasis.

[Screening of mimic epitopes of Trichinella spiralis antigen from phage 12-mer peptide library].

OBJECTIVE: To screen special mimic epitopes of Trichinella spiralis antigen from peptide library for exploring new diagnostic antigens. METHODS: Ts-IgG purified from serum of trichinosis patients was used to screen the phage 12-mer peptide library for 5 rounds. 24 clones were picked out randomly to detect the immunoactivity. The sensitivity and specificity of the 6 clones (T1 - T6) whose A values were higher than others were tested by ELISA. RESULTS: The sensitivity of the clones T1 - T6 was the same with larval antigen of Trichinella spiralis (TsA) (positive rate: 100%, P > 0.05), and there was no difference in specificity between T1 - T6 and TsA (negative rate: 0 - 40%, P > 0.05); T3 and T6 did not react with sera from patients of paragonimiasis, showing higher specificity than TsA (P < 0.05); T6 did not react with sera from patients of schistosomiasis, also showing higher specificity than TsA (P < 0.05). CONCLUSION: The mimic antigenic epitopes of Trichinella spiralis have been successfully obtained by screening phage 12-mer peptide library.

[Detecting effect comparison between MPAIA, DDIA and IHA for screening advanced schistosomiasis].

OBJECTIVE: To evaluate the effects of the magnetic particle antibody immunoassay (MPAIA), dipstick dye immunoassay (DDIA) and indirect hemagglutination assay (IHA), on detecting advanced schistosomiasis. METHODS: The sera of 224 cases of advanced schistosomiasis were detected by MPAIA, DDIA, and IHA, and the positive rates were compared. RESULTS: The positive rates of MPAIA, DDIA and IHA, were 67.14%, 14.29% and 16.52%, respectively,the positive coincidence rate of MPAIA is higher than the one of IHA and DDIA. CONCLUSION: The value of MPAIA is higher than that of DDIA or IHA in screening advanced schistosomiasis.

[Detection of urine antibodies to Schistosoma japonicum by magnetic particle affinity immunoassay].

OBJECTIVE: To explore a non-invasive method for detection of urine antibodies to Schistosoma japonicum. METHODS: The urine antibodies to S. japonicum were detected by magnetic particle affinity immunoassay (MPAIA) in 158 cases of schistosomiasis japonica and 100 health persons, and their serum antibodies to S. japonicum were also detected at the same time. RESULTS: The sample of urine by MPAIA was 10 microl original urine without any special treatment. The positive rate of urine and serum were 48.10% (76/158)and 88.61% (140/158), respectively. There was difference between the performance of two methods (chi2 = 60.24, P < 0.05). However, both of their specificity were 100% (100/100). CONCLUSION: MPAIA is viable for detection of urine antibodies to S. japonicum, but its sensitivity should be improved.