Antibody-based in vitro diagnostic (IVD) methods are powerful and popular tools for the diagnosis of infectious diseases. As a leading company in the IVD industry, Creative Biolabs helps develop high-affinity and high-specificity antibodies for diagnostic uses. We offer high-quality IVD antibody development services targeting surface-expressed antigens (e.g., polysaccharides or proteins) and serological markers. Here, we focus on the development of Legionella pneumophila-specific antibodies.
Introduction of Legionella pneumophila
Legionella pneumophila (L. pneumophila) is a thin, aerobic, pleomorphic, flagellated, non-spore-forming, Gram-negative bacterium of the genus Legionella. Legionella species are consistently recognized as one of the common causes of pneumonia. Current diagnostic tests for Legionella infection mainly include culture, direct fluorescent antibody (DFA) staining, urinary antigen detection, serological testing, and nucleic acid amplification. Commonly used specimens include respiratory secretions (sputum, bronchial aspirate or washings), as well as pleural fluid, lung biopsy, and autopsy material. Macrolides (azithromycin or clarithromycin) or fluoroquinolones (levofloxacin or moxifloxacin) are the standard treatment for Legionella pneumonia in humans.
Fig.1 Intracellular life cycle of L. pneumophila. (Franco, I. S., 2009)
Direct Fluorescent Antibody (DFA) Staining
DFA staining can detect legionella in respiratory secretions and tissue samples, in which fluorescein-labeled monoclonal or polyclonal antibodies directed against Legionella species are used. Commercial DFA tests contain fluorescently labeled antibodies that specifically target antigens present in the Legionella species. This technique has the advantage of providing results within 2-4 h but the sensitivities are dependent on the quality and specificity of the antibodies used. Moreover, it is technically demanding and should be performed by experienced laboratory personnel. False-positive may occur due to cross-reactivity but if monoclonal antibodies are used cross-reactions may be less of a problem.
Fig.2 The principle of DFA staining.
Urinary Antigen Detection
Detection of soluble Legionella antigen in urine specimens is a rapid method that provides an early diagnosis of Legionella infection and has been a useful tool for the investigation of outbreaks of Legionnaires disease. Commercial kits for diagnosis such as enzyme immunoassay (EIA), radioimmunoassay (RIA), immunochromatography, and ELISA have been developed. For the detection of L. pneumophila serogroup 1, urinary antigen tests have sensitivities in the range of 70%-100% and specificities approaching 100%. But tests that can reliably detect legionellae other than L. pneumophila serogroup 1 are in lack.
Serological Testing
Antibodies produced in response to infection take at least 8 days to develop after the onset of infection, which makes the serological testing method less useful for clinical decision making. Of the various antibody detection methods that are available, indirect immunofluorescence is the standard reference test. Generally, a 4-fold or greater increase in reciprocal antibody titer to ≥128 is considered diagnostic.
Antibody-based diagnostic tools are of great value for detection of Legionella infection. However, antibodies and commercial in vitro diagnostic (IVD) kits that are capable of detecting a wider range of pathogenic legionellae are in great need. To support the development of improved IVD antibodies and tests that will help better characterize the epidemiology of Legionnaires disease, Creative Biolabs offers first-class customizable IVD antibody development services to clients globally. Contact our scientists to discuss your project in detail and experience our expert services.
Reference
For Research Use Only.
