Development of an immunochromatographic test with anti-LipL32-coupled gold nanoparticles for Leptospira detection.

Detection of antibody specific to Leptospira by various immunological techniques has been used for leptospirosis diagnosis. However, the sensitivity of antibody detection during the first few days after infection is low. Molecular techniques are suggested to provide earlier diagnosis than antibody detection, but a rapid and easy to perform assay for Leptospira antigen detection would provide an additional useful tool for disease diagnosis. In this study, we coupled gold nanoparticles with antibody to LipL32, a protein commonly found in pathogenic Leptospira. This coupled gold reagent was used in the immunochromatographic strip for Leptospira detection. We demonstrated that the sensitivity of Leptospira detection by this strip was 10(3) ml(-1). There was no positive result detected when strips were tested with non-pathogenic Leptospira, Staphylococcus aureus, Streptococcus group B, Acinetobacter baumannii, Escherichia coli, Salmonella typhi, Klebsiella pneumoniae, Enterococcus faecalis or Enterococcus faecium. These data suggest that gold nanoparticles coupled with antibody to LipL32 could be used for Leptospira detection by a rapid test based on an immunochromatographic technique.