Testing different antigen capture ELISA formats for detection of Leptospira spp. in human blood serum

Isolation of a novel DNA aptamer against LipL32 as a potential diagnostic agent for the detection of pathogenic Leptospira

Leptospirosis is a potentially life-threatening zoonosis caused by pathogenic Leptospira and for rapid diagnostics, direct detection is desirable. LipL32 protein is the most suitable biomarker for direct detection. DNA aptamers are sought to be generated against LipL32 by Systemic Evolution of Ligands via Exponential Enrichment (SELEX). LepDapt-5a is the most potent aptamer candidate among all the candidates, as determined by direct Enzyme-linked Aptasorbent Assay (ELASA). LepDapt-5a was predicted to form a G-quadruplex structure as predicted by QGRS Mapper and validated experimentally by direct ELASA. The diagnostic potential of the aptamer was further tested on a direct and sandwich ELASA platform. A LOD of 106 mL-1 and 105 mL-1 were estimated by direct and sandwich ELASA platforms, respectively, which are within the range associated with leptospiremia levels. The dot blot assay developed was able to attain a LOD of 104 CFU mL-1 against pathogenic Leptospira, which is also within the leptospiremia level. This is the first-ever DNA aptamer and hybrid-heterodimeric aptamer constructed against LipL32. The diagnostic potentiality of the LepDapt-5a DNA aptamer was proven on three major diagnostic platforms, which are direct ELASA, sandwich ELASA, and aptamer-based dot assay.

Diagnostic efficacy of lsa63 antigen for human leptospirosis

BACKGROUND

Timely diagnosis of leptospirosis is essential for early and effective treatment, for there are many differential diagnoses for it.. Leptospiral researchers have an increasing interest in developing new serological methods with recombinant antigens to improve the Leptospirosis diagnosis. Several serological tests have been developed for the proper diagnosis of leptospirosis.

OBJECTIVES

To improve the previous works we developed an enzyme linked immunosorbent assay (ELISA) with novel recombinant leptospiral surface adhesion (Lsa63) protein to offer a new test.

MATERIALS AND METHODS

In an experimental study, Recombinant Lsa63 (rLsa63) was produced in Escherishia coli (E.coli) BL21 (DE3). By using rLsa63, we generated IgM and IgG ELISA. Performance of these tests was compared to microscopic agglutination golden test (MAT). Two hundred twenty human serum samples were obtained from individuals suspicious of leptospirosis who were referred to Guilan Province Central Leptospira Laboratory for definitive diagnosis. The sensitivity, specificity and other statistical indexes of Lsa63-ELISAs were also determined.

RESULTS

Among 220 serum samples, 30% (n = 65) had positive MAT responses, and also 38% (n = 84) and 40.9% (n = 90) showed positive reaction to IgG and IgM rLsa63-ELISA, respectively. The sensitivity, specificity and accuracy were 93.8%, 81.29 % and 85.0 for IgM-Lsa63- ELISA and 83.07, 80, 64 and 81.36 for IgG-Lsa63- ELISA, respectively.

CONCLUSIONS

Our results demonstrated that the sensitivity and specificity of Lsa63-ELISAs are promising for the detection of Leptospira serovars.

Leptospirosis: current situation and trends of specific laboratory tests

Leptospirosis is re-emerging as a worldwide zoonosis and is caused by bacteria of the genus Leptospira. Human leptospirosis is associated with high temperature and humidity. Laboratory tests are indispensible for the early diagnosis and proper disease management. The demand for suitable leptospirosis point-of-care diagnostic tests grows with the awareness and number of incidences. Confirmation is achieved by the microscopic agglutination test, bacterial cultivation, PCR or histopathologic methods. However, high costs, poor standardization and/or elaborate sample preparation prevent routine use at the point of care. Cost-efficient, but insensitive serological methods dominate the diagnostic landscape and, likewise, urgently need improvement toward greater compliance with some of the point-of-care criteria. Combined application of antigen and antibody detection methods increases accuracy, but also new development or transfer of diagnostic technologies should be considered useful. Nano- and microparticle technology may play a key role in improving future antigen detection methods.