Rapid, novel, specific, high-throughput assay for diagnosis of Loa loa infection.
The ability to diagnose Loa loa infection readily and accurately remains a demanding task. Among the available diagnostic methods, many are impractical for point-of-care field testing. To investigate whether luciferase immunoprecipitation systems (LIPS) can be used for rapid and specific diagnosis of L. loa infection, a LIPS assay was developed based on immunoglobulin G (IgG) and IgG4 subclass antibodies to a recombinant L. loa SXP-1 (designated LlSXP-1) antigen and tested with sera from healthy controls or patients with proven infection with L. loa, Mansonella perstans, Onchocerca volvulus, Strongyloides stercoralis, or Wuchereria bancrofti. A LIPS test measuring IgG antibody against LlSXP-1 readily differentiated L. loa-infected from uninfected patients and demonstrated markedly improved sensitivity and specificity compared with an LlSXP-1 IgG4-based enzyme-linked immunosorbent assay (67% sensitivity and 99% specificity). No significant immunoreactivity was observed with S. stercoralis-infected sera, but a small number of patients infected with O. volvulus, M. perstans, or W. bancrofti showed positive immunoreactivity. Measuring anti-IgG4-specific antibodies to LlSXP-1 showed a significant correlation (r approximately 0.85; P < 0.00001) with the anti-IgG results but showed no advantage over measuring the total IgG response alone. In contrast, a rapid LIPS format (called QLIPS) in which the tests are performed in less than 15 minutes under nonequilibrium conditions significantly improved the specificity for cross-reactive O. volvulus patient sera (100% sensitivity and 100% specificity). These results suggest that LIPS (and the even more rapid test QLIPS) represents a major advance in the ability to diagnose L. loa infection and may have future applications for point-of-care diagnostics.
Burbelo
Peter D
PD
Neurobiology and Pain Therapeutics Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, 4 Center Drive, Bethesda, Maryland 20892, USA.
Ramanathan
Roshan
R
Klion
Amy D
AD
Iadarola
Michael J
MJ
Nutman
Thomas B
TB
D000595:Amino Acid Sequence; D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood*; D000947:Antigens, Helminth; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D047468:Immunoprecipitation / Q000379:methods*; D008117:Loa / Q000235:genetics / Q000302:isolation & purification*; D008118:Loiasis / Q000175:diagnosis*; D008366:Mansonella / Q000276:immunology; D017181:Onchocerca volvulus / Q000276:immunology; D019095:Point-of-Care Systems; D012680:Sensitivity and Specificity; D016415:Sequence Alignment; D014958:Wuchereria bancrofti / Q000276:immunology
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D007074:Immunoglobulin G