Lateral-Flow Assay Rapidly Detects Plague Bacteria

Plague caused by Yersinia pestis is a known flea-borne disease that can trigger large epizootics among the rodent population. Humans that live in environments close to these rodents can contract the bubonic plague either through direct contact with infected animals or through transmission by infective flea bites.

Over the last decade, thousands of cases of plague have been reported annually, indicating that the plague has not been eliminated. This is especially true in places where public health and living conditions are poor. Several well-established assays have been applied to detect Y. pestis/F1 protein, such as the indirect hemagglutination assay (IHA), which is the current gold standard for Y. pestis detection.

Scientists at the National Defense Medical Center (Taipei, Taiwan) developed a rapid, cheap, sensitive, and specific technique, the lateral flow assay (LFA -F1 strips), to detect this pathogen, by using paired monoclonal antibodies (MAbs) against Y. pestis capsule like fraction 1 (F1) protein. Compared with the polyclonal antibody (PAb) based F1 strips, the MAb-based F1 strips have a remarkable increased detection limitation (10 to 100 fold). Furthermore, besides the limitation and specificity evaluation, the application of this F1 strip on simulated clinical samples indicate the LFA can be a good candidate to detect plague.

Recombinant F1 antigen was expressed and purified from a series of studies. The various anti-F1 monoclonal antibodies (MAbs) generated from hybridoma cells were screened with the enzyme-linked immunosorbent assay (ELISA) technique. To evaluate the feasibility of this Y. pestis F1 test strip, the F1 protein/Y. pestis was spiked into simulated clinical samples such as human serum, mouse bronchoalveolar lavage fluids, and mouse blood to mimic natural infection status. Additionally, this technique was applied to detect the Y. pestis in the environment-captured rats, to evaluate the practical usefulness of the strips.

The scientists reported that by using this MAb-based-LFA technique, 4 ng/mL of recombinant F1-protein and 103 CFU/mL of Y. pestis could be detected in less than 10 minutes, which is at least 10-folds than that of the polyclonal antibody (PAb) format. On the other hand, although various Yersinia strains were applied to the strips, only Y. pestis strain showed a positive result; all other Yersinia species did not produce a positive signal, indicating the high efficiency and specificity of the MAb-based F1-strips.

The authors concluded that the MAb-format-LFA will be valuable as a diagnostic tool for the detection of Y. pestis. This report shows that the F1 strip is sufficient to support not only the detection of plague in simulated clinical samples, but also it may be a good candidate to meet the epidemiological surveillance during an outbreak of the biological warfare. The study was published on August 14, 2018, in the journal BMC Infectious Diseases.

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