Protein Microarray Detects Antibodies in Melioidosis Patients

Direct pathogen detection can be difficult, and therefore an indirect serological test, which might aid early diagnosis is desirable.

The current tests for antibodies against B. pseudomallei, including the reference indirect hemagglutination assay (IHA), lack sensitivity, specificity and standardization and consequently, serological tests currently do not play a role in the diagnosis of melioidosis in endemic areas. A standardized, easy-to-perform clinical laboratory test for sensitive multiplex detection of antibodies against B. pseudomallei is still lacking.

An international team of scientists led by those at the Medical University of Graz (Austria) analyzed 196 sera and plasmas from melioidosis patients from northeast Thailand and 210 negative controls from melioidosis-endemic and non-endemic regions. They developed and validated a protein microarray, which can be used in a standard 96-well format. The array contains 20 recombinant and purified B. pseudomallei proteins, previously identified as serodiagnostic candidates in melioidosis.

Antibody detection using the B.pseudom.01-Array was performed and after processing the protein arrays were read out by the ArrayMate (Alere Technologies, Jena, Germany) and the data were analyzed. Spot intensities of at least 0.3 were defined as a specific antibody response to the respective antigens. The recognition of at least two different antigens per serum or plasma with signal intensities above 0.3 was considered melioidosis positive.

The protein array clearly discriminated between sera from melioidosis patients and controls with a specificity of 97%. Importantly, the array showed a higher sensitivity than did the indirect hemagglutination assay (IHA) in melioidosis patients upon admission (cut-off IHA titer equal to or greater than 1:160: IHA 57.3%, protein array: 86.7%). Testing of sera from single patients at 0, 12 and 52 weeks post-admission revealed that protein antigens induce either a short- or long-term antibody response.

The authors concluded that their protein array provides a standardized, rapid, easy-to-perform test for the detection of B. pseudomallei-specific antibody patterns. Thus, this system has the potential to improve the serodiagnosis of melioidosis in clinical settings. Moreover, the high-throughput assay might be useful for the detection of anti-B. pseudomallei antibodies in epidemiological studies. Further studies are needed to elucidate the clinical and diagnostic significance of the different antibody kinetics observed during melioidosis. The study was published on July 18, 2016, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
Medical University of Graz
Alere Technologies