Diagnostic Research
Background
NIAID is supporting various efforts to evaluate and improve existing diagnostic procedures. Approximately 20 percent of its extramural Lyme disease research portfolio is devoted to developing novel and more sensitive diagnostic procedures. New applications are submitted for review and funded on a regular basis. In addition to significant efforts in the area of diagnosis, NIAID grantees work directly with scientists from the Centers for Disease Control and Prevention (CDC) to evaluate and compare the effectiveness of currently used diagnostic methods.
In 1998, the US Food and Drug Administration granted approval to Chembio Diagnostic Systems to market the Wampole PreVue™ Borrelia burgdorferi Antibody Detection Assay. The assay is a single use, unitized immunochromatographic test that uses recombinant B. burgdorferi antigens for the qualitative presumptive (first step) detection of IgG and IgM antibodies to B. burgdorferi in human serum or whole blood. This test is to be used only in patients with history, signs, and symptoms that are consistent with Lyme disease. It is intended for use in clinical and physicians’ office laboratories.
Novel Approaches
In collaboration with CDC, NIAID also plays a major role in encouraging the development of novel approaches to improve the diagnosis of Lyme borreliosis in humans with various co-infections (e.g., ehrlichiosis or babesiosis), as well as in immunized people. For example, NIAID grantees have shown that a synthetic peptide composed of 26 amino acid residues (C6) derived from a variable surface antigen (VlsE) of B. burgdorferi can be used in a new, rapid, and extremely sensitive ELISA test (the C6 ELISA) for diagnosing Lyme disease. Because this diagnostic test for Lyme disease, which has been approved by FDA, does not detect antibodies specific for recombinant OspA, it can be used even for those who have been immunized with the licensed OspA-based LYMErix vaccine (J Clin Microbiol 40: 2591, 2002).
Of great importance is the fact that decreases in the titer of antibodies against C6 can be used as an indicator of the efficacy of antibiotic therapy for patients with localized or disseminated Lyme disease, but not for chronic Lyme disease (Eur J. Clin Microbiol Infect Dis 23: 615, 2004). This is indeed a major advance since no other laboratory test enables one to obtain such information (J Clin Microbiol 40: 2591, 2002). The results obtained with the C6 ELISA are consistent with those obtained with other diagnostic tests and may obviate the time and expense for conducting additional laboratory tests to confirm the diagnosis of Lyme disease (Clin Diag Lab Immunol 11: 924, 2004). The NIAID- supported investigators are now working closely with the CDC to determine if the C6 ELISA can eventually replace the traditional two-tiered conventional ELISA and Western blot assays. The results of other studies confirmed that a decline in the anti-C6 antibody titer coincides with the efficacy of antimicrobial therapy in patients with early localized or early disseminated Lyme borreliosis (Clin Diag Lab Immunol 12: 1069, 2005).
Although the Lyme Urinary Antigen Test (LUAT) is one of several diagnostic tests used routinely in NIAID’s clinical studies on chronic Lyme disease, the results of independent quality control assessments of tests conducted by extramural and intramural scientists showed the LUAT to be unreliable because it yields an unacceptably high percentage of false positive reactions ( Amer J Med 110: 217, 2001). A critical evaluation of urine-based PCR assays for the diagnosis of Lyme borreliosis likewise affirmed that urine is not a suitable material for the diagnosis of Lyme borreliosis (Clin. Diag. Lab. Immunol. 12, 910, 2005). By contrast, the similar assessments confirmed a high degree of reproducibility and concordance (virtually 100 percent) for the results obtained using ELISA and Western blot assays (Amer J Med 110: 217, 2001).
The Borrelia burgdorferi-specific immune complex (IC) test, in which polyethylene glycol (PEG) is used to isolate ICs from serum, has been advocated by some investigators as an approach for the early diagnosis of active borreliosis.However, recent findings indicate that it may not be more effective in detecting early and active infections than other conventional tests in which unprocessed serum specimens are used (Clin Diag Lab Immunol 12: 1036, 2005).
Future Needs
There is a great need to develop additional simple, sensitive, and rapid procedures to distinguish those who are actively infected with B. burgdorferi from those who have either recovered from a previous infection or have been immunized previously. Since the genome of B. burgdorferi has now been completely sequenced, greater advances towards this goal are anticipated as this information is used in conjunction with microarray technology and proteomics to improve diagnosis as well as provide new insights on the pathogenesis of this disease and pathogen-specific host response mechanisms.
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