Rapid, Novel, Specific, High-Throughput Assay for Diagnosis of Loa loa Infection

Abstract

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. stercoralisinfected 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 ϳ 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.The development of rapid diagnostic assays for onchocerciasis (22) and lymphatic filariasis (20) has not only simplified the care of individual patients with these filarial infections but also allowed accurate and cost-effective geographic mapping for the purpose of mass chemotherapy in areas of endemicity (21) and for use in the certification process of elimination (15). Nevertheless, the coendemicity of loiasis with these and other filarial infections of humans remains an issue because of species-specific differences in the responses to available antifilarial therapies. This has been of particular concern in the setting of both the African Program for Onchocerciasis Control (APOC) and the Global Program for the Elimination of Lymphatic Filariasis (GPELF), where mass drug administration has ground to a halt in certain areas of Africa because of deaths related to ivermectin administered as part of mass treatment programs for onchocerciasis control (3,12).Although the definitive diagnosis of Loa loa infection can be made morphologically by identifying microfilariae in the blood or, rarely, after surgical removal of the adult worm (typically from its subconjunctival location), a proportion of infected individuals are amicrofilaremic (9, 13). PC...

Improved Diagnosis of Strongyloides stercoralis Using Recombinant Antigen-Based Serologies in a Community-Wide Study in Northern Argentina

“…In this study, we confirmed the results of previous studies that the recombinant-antigen-based LIPS assay accurately differentiates between sera from patients with parasitologically proven S. stercoralis infection and healthy, uninfected controls, compared to the current best available serologic test (21). LIPS assays have been successfully applied to the characterization of antibody responses to multiple infections, including Pneumocystis jirovecii, HIV, hepatitis virus, and Loa loa and, more recently, to the diagnosis of infections due to S. stercoralis (4,6,21). As has been shown previously, the LIPS format was additionally found to be superior to an ELISAbased format using the same NIE recombinant antigen (21).…”

Serological Diagnosis of Human Herpes Simplex Virus Type 1 and 2 Infections by Luciferase Immunoprecipitation System Assay

“…While the HSV-1 and HSV-2 ICP8 antigens used in the LIPS assay are highly conserved (89% amino acid identity), there were marked quantitative differences to these antigens in the plasma samples tested. This strain specificity is reminiscent of the reduced LIPS serologic responses to related filarial antigens in subjects infected with related worms (12,28).…”

“…Recently, we showed that luciferase immunoprecipitation system (LIPS) assays can quantitatively measure antibody responses to cancer-associated autoantigens (8), autoantigens associated with autoimmune diseases (9,10), and a variety of infectious agents, including hepatitis C virus, human immunodeficiency virus (HIV) (7), human T-cell leukemia virus type 1 (11), and filaria (12,28). These assays measure antibody levels in immunoprecipitations by using fusion proteins consisting of Renilla luciferase (Ruc)-antigen produced in Cos1 cells.…”

Anti-cytokine autoantibodies are associated with opportunistic infection in patients with thymic neoplasia

“…A method known as luciferase immunoprecipitation systems (LIPS) quantitatively measures antibodies to a wide range of infectious agents, [16][17][18][19] as well as to a variety of human autoantigens. [20][21][22] LIPS is a liquid phase immunoassay that uses antigens directly tagged with Renilla luciferase, which can sensitively and quantitatively detect antibodies.…”