Engineered biomarkers for leprosy diagnosis using labeled and label-free analysis

Area of Science:

• Biotechnology and Immunology
• Infectious Disease Diagnostics
• Biosensor Technology

Background:

• Early leprosy diagnosis remains challenging, especially in paucibacillary cases, hindering timely intervention and disease control.
• Current antigen-antibody detection methods lack the sensitivity needed to identify leprosy before symptom onset, leading to potential disabilities.
• Innovative diagnostic approaches are crucial to improve sensitivity, enable early detection, prevent disabilities, and reduce leprosy transmission.

Purpose of the Study:

• To develop a highly sensitive assay for early leprosy diagnosis using a synthetic peptide mimotope.
• To engineer and optimize a mimotope derived from Mycobacterium leprae Ag85B for enhanced antibody detection.
• To validate the diagnostic potential of a novel label-free immunosensor for detecting anti-M. leprae antibodies in human serum.

Main Methods:

• A phage-displayed mimotope mimicking M. leprae Ag85B was engineered with a flexible spacer and conjugated to a carrier protein.
• Enzyme-Linked Immunosorbent Assay (ELISA) was employed with a biotin-streptavidin system for signal amplification.
• A Quartz Crystal Microbalance (QCM) sensor was coated with the optimized mimotope for label-free biosensing.
• Comparative modeling using M. tuberculosis Ag85B was used to assess mimotope specificity.

Main Results:

• The optimized mimotope-based ELISA achieved a sensitivity of 91.7% across 132 patients, regardless of their immunological profile.
• A sensitive QCM-based immunosensor successfully detected anti-M. leprae antibodies in human serum for the first time.
• Crucially, M. leprae antibodies were detectable in the sera of paucibacillary patients, demonstrating improved diagnostic capability.

Conclusions:

• A mimotope-derived synthetic peptide offers a promising tool for early leprosy diagnosis.
• The developed label-free QCM immunosensor represents a novel and sensitive immunoassay for detecting leprosy.
• This approach has significant potential for early leprosy detection, particularly in challenging paucibacillary cases, aiding in disability prevention and transmission reduction.