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Immuno-fluorescence Assay of Leptospiral Surface-exposed Proteins
Published on: July 1, 2011
Identification of myelin basic proteins in circulating immune complexes associated with lepromatous leprosy
B Córsico1, M V Croce, R Mukherjee
1Centro de Investigaciones Immunológicas Básicas y Aplicadas (CINIBA), Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina.
Insights
Circulating immune complexes (CIC) in lepromatous leprosy patients contain myelin basic proteins (MBP). This finding suggests a role for MBP in leprosy nerve damage and demyelination.
Area of Science:
- Immunology
- Neurology
- Infectious Diseases
Background:
- Lepromatous leprosy (LL) is associated with nerve damage.
- Circulating immune complexes (CIC) are implicated in autoimmune and infectious diseases.
Purpose of the Study:
- To investigate the presence of neural antigens within CIC from LL patients.
- To explore the potential role of CIC-associated antigens in leprosy pathogenesis.
Main Methods:
- Measurement of CIC using 125I-C1q binding assay and PEG precipitation.
- Isolation and characterization of CIC using affinity chromatography (Protein A-Sepharose).
- Analysis of CIC components by SDS-PAGE and Western blotting with neural antigen antibodies.
Main Results:
- High levels of CIC detected in LL patients (95% by 125I-C1q, 90% by PEG).
- LL-CIC precipitates and eluates showed significant reactivity with anti-myelin basic protein (MBP) antibodies (76% and 71%, respectively).
- No reactivity was observed with antibodies against glial fibrillary acidic proteins, S-100, or neurofilaments.
Conclusions:
- Lepromatous leprosy CIC contain myelin basic protein (MBP) as a significant antigen.
- MBP in LL-CIC may contribute to leprosy pathogenesis through autoimmune responses to nerve damage.
- This mechanism could be crucial in the demyelination and nerve destruction observed in leprosy.
Abstract:
Circulating immune complexes (CIC) were first measured in lepromatous patients (LL) by the 125I-C1q binding assay and the polyethylene glycol (PEG) precipitation test. High levels were found by both methods (95 and 90% of positives, respectively). LL-CIC were investigated for the presence of neural antigens. CIC were precipitated in 3.5% PEG, filtered through protein A-Sepharose affinity chromatography, eluted with glycine-HCl, pH 2.8, and washed with PBS; fractions after CIC dissociation were studied by SDS-PAGE and Western blotting. The LL-CIC PEG precipitates and the glycine-HCl eluates were positive in 76 and 71% respectively against anti-myelin basic proteins (MBP) monoclonal antibody, showing a single band at 15-25 kDa similar to the one obtained incubating MBP with anti-MBP. No reaction was detected with CIC-PBS fractions; strips were incubated with other anti-neural antibodies such as anti-glial fibrillary acidic proteins, anti-S-100, and anti-neurofilaments, without any reactivity. Our results demonstrate that LL-CIC contain MBP as an antigen; its significance could be related to the pathogenesis of leprosy since the liberation of MBP after Mycobacterium leprae nerve damage may elicit anti-MBP autoantibodies to myelin breakdown, which reacts with peripheral nerve MBP inducing CIC formation. This mechanism may be important in demyelination and destruction of nerve in leprosy.
