Establishment and preliminary evaluation of droplet digital PCR methods for detecting Schistosoma japonicum DNA in host infection
10.3969/j.issn.1002-2694.2025.00.076
- VernacularTitle:微滴式数字PCR检测日本血吸虫核酸的方法建立及应用的初步评价
- Author:
Xian-shi TANG
1
;
Jing YANG
1
;
Guo-li QU
1
;
Yong-liang XU
1
;
De-sheng TONG
1
Author Information
1. 江苏省血吸虫病防治研究所,国家卫生健康委员会寄生虫病预防与控制技术重点实验室,江苏省寄生虫与媒介控制技术重点实验室,无锡 214064
- Publication Type:Journal Article
- Keywords:
Schistosoma japonicum;
oncomelania;
mouse;
droplet Digital PCR(ddPCR)
- From:
Chinese Journal of Zoonoses
2025;41(5):544-552
- CountryChina
- Language:Chinese
-
Abstract:
This study established a droplet digital PCR(ddPCR)EvaGreen assay and probe methods for Schistosoma japonicum detection,and evaluated their application in detecting early infections in the S.japonicum host oncomelania and mice.Primers and corresponding probes for both ddPCR methods were designed and synthesized,and plasmids containing target sequences were constructed.The sensitivity of the two methods was tested through detection of the corresponding plasmids,and infectious and mixed oncomelania genomic DNA.Their specificity was evaluated by the detection of genomic DNA of negative oncomelania,Schistosoma mansoni,Clonorchis sinensis,Spirometra mansoni,and S.japonicum(as a positive control).The ddPCR probe method was evaluated by detection of early infection of oncomelania exposed tomiracidium with various ratios and incubation times,and the early migration and distribution of cercaria or schistosomula in mouse hosts infected with 200 cercaria via abdominal skin contact.According to standard curves constructed through the detection of plasmid serial dilutions,the regression equation for the EvaGreen assay was y=-0.839 9x+7.050 9,with a correlation coefficient R2=0.988 1,and the regression equation for the probe method was y=-1.047 5x+7.255 1,with a correlation coefficient R2=0.999 8.The lowest limit of plasmid detection with the probe method was between 38.94 cp/μL and 194.74 cp/μL.Both methods successfully detected positive reactions in the genomic DNA samples of infectious oncomelania at concentrations above 0.002 ng/μL and in the genomic DNA of each group of oncomelania mixtures.No significant differences between probe methods were observed in the detection values in the control group and the genomic DNA of negative oncomelania,S.mansoni,C.sinensis,and S.mansoni.However,the detection value of genomic DNA of negative oncomelania(291 ng/μL)with the EvaGreen assay was(20.3±4.39)cp/μL,a value significantly higher than the(1.5±0.1)cp/μL observed in the control group.For detection of early infection in oncomelania,the probe method detected Schistosoma japonicum DNA after 30 s incubation at room temperature with a≥5∶1 ratio of miracidium to oncomelania;the detection value peaked after a short time(5 min),and the peak value showed a fold increase similar to the increase in the miracidium to oncomelania ratio.Detection of early stage infection in mice with the probe method revealed that the schistosomula entered the lungs on day 2 and the liver on day 4,and continually migrated within the organs with abundant blood supply(spleen,kidney,and brain)in the first 9 days;moreover,a tendency toward ectopic parasitism was observed in the heart and pancreas on day 9,and a constantly negative control level was observed in the testes.The ddPCR probe method was more accurate and specific than the EvaGreen assay in the detection of plasmids,and infectious and mixed oncomelania,and the latter showed non-specific reactions in negative oncomelania detection.In a practical application,the probe method was demonstrated to be sensitive,to effectively reflect the early infection of oncomelania,and to reveal schistosomula migration and distribution in multiple organs of infected mice.
