A Sensitive and Specific IgM-ELISA for the Serological Diagnosis of Human Leptospirosis Using a rLipL32/1-LipL21-OmpL1/2 Fusion Protein

Key words: 
• Leptospira /
• Outer membrane protein /
• Fusion antigen /
• Recombinant expression /
• IgM-ELISA

Abstract: Objective To construct a HpL32/1-lipL21-OmpL1/2 fusion gene and its prokaryotic expression system, and to establish an enzyme-linked immunosorbent assay (ELISA) using the rLipL32/1-LipL21-OmpL1/2 fusion antigen of Leptospira interrogans for sensitive and specific detection of IgM in the serum of patients with leptospirosis.Methods HpL32/1-lipL21-OmpL1/2 fusion genes were constructed using a primer-linking PCR. The target recombinant protein antigens, rLipL32/1, rLipL21, rOmpL1/2 and rLipL32/1-LipL21-OmpL1/2, were expressed and the purified antigens were then immobilized to the surface of microplate wells for ELISA-based detection of IgM in the sera of leptospirosis patients.Results Of 493 acute leptospirosis patients, 95.7% and 97.8% were positive by rLipL32/1-LipL21-OmpL1/2-lgM-EUSA using different serum dilutions, which was higher than the rLipL32/1-lgM-ELISA (93.1% and 90.3%), rLipL21-lgM-ELISA (90.3% and 87.0%), and rOmpL1-lgM-ELISA (85.6% and 81.1%) (P<0.01). All IgM-ELISAs tested negative against 56 non-leptospirosis patients with typhoid fever, hemorrhagic fever or dengue fever.Conclusion Trigeminal fusion antigen increases ELISA sensitivity and the rLipL32/1-LipL21-OmpL1/2-IgM-EUSA is a sensitive and specific serological diagnostic method for clinical leptospirosis.