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Published on: July 1, 2011
Enzyme immunoassay for Q fever: comparison with complement fixation and immunofluorescence tests and dot
R Cowley1, F Fernandez, W Freemantle
1Division of Pathology, Centre for Applied Microbiology and Research, Salisbury, Wiltshire, United Kingdom.
Insights
New enzyme-linked immunosorbent assays (ELISA) offer a rapid and sensitive method for diagnosing Q fever. These tests, alongside enhanced immunofluorescence, show high agreement and are recommended replacements for the complement fixation test.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Q fever is a significant zoonotic disease caused by Coxiella burnetii.
- Current diagnostic methods like complement fixation (CF) have limitations, including anticomplementary activity in serum samples.
Purpose of the Study:
- To develop and optimize enzyme-linked immunosorbent assays (ELISA) for detecting Coxiella burnetii specific IgG and IgM antibodies.
- To compare the diagnostic performance of ELISA and enhanced immunofluorescence (EIF) with the traditional CF test.
Main Methods:
- Purified Coxiella burnetii cells were used to develop IgG and IgM ELISAs.
- Optimization involved evaluating microtiter plates, blocking agents, incubation conditions, antigen stability, and substrates.
- Assay reliability was assessed using 600 human serum samples and compared against CF and EIF tests.
Main Results:
- ELISA and EIF tests demonstrated complete agreement in all tested samples.
- Dot immunoblotting provided rapid, qualitative results that also agreed with ELISA and EIF.
- ELISA and EIF detected positive cases missed by CF, especially those with anticomplementary activity.
Conclusions:
- ELISA and EIF are rapid, sensitive, and reliable serodiagnostic tests for Q fever.
- Dot immunoblotting serves as an effective screening tool.
- ELISA and EIF are recommended as superior replacements for the complement fixation test in Q fever diagnosis.
Abstract:
Enzyme-linked immunosorbent assays (ELISA) for the detection of specific immunoglobulin G (IgG) and IgM antibodies were developed by using purified Coxiella burnetii cells. Variables, including type of microtiter plate, blocking agent, incubation conditions, antigen stability, and substrate type, were examined to achieve optimal ELISA performance. The reliabilities of the assay systems were compared with those of complement fixation (CF) and enhanced immunofluorescence (EIF) tests with 600 human serum samples from defined clinical cases of Q fever, routine samples, and serum specimens from farmers. ELISA and EIF test results agreed in all cases. Dot immunoblotting was also used to test some of these sera and gave a rapid, qualitative result, which agreed with ELISA and EIF test results in all cases. No instances were found in which both ELISA and EIF test results were negative and the CF test results was positive. However approximately 5% of the sera were positive by ELISA and the EIF test while the CF test result was either negative or unreadable because of serum anticomplementary activity. We conclude that dot immunoblotting is a useful screening test, whereas ELISA and the EIF test are both rapid and sensitive tests when used for the serodiagnosis of Q fever and should be considered to be replacements for the CF test.
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01:33Enzyme-Linked Immunosorbent Assay
There are many different types of ELISAs, but they all involve an antibody molecule whose constant region binds an enzyme, leaving the variable region free to bind its specific antigen. Enzyme-substrate reaction allows the antigen to be visualized or quantified.
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