Abstract
BackgroundOnchocerciasis, an infection caused by the filarial nematode Onchocerca volvulus, is a major public health concern. Given the debilitating symptoms associated with onchocerciasis and concerns about recrudescence in areas of previous onchocerciasis control, more efficient tools are needed for diagnosis and monitoring of control measures. We investigated whether luciferase immunoprecipitation systems (LIPS) may be used as a more rapid, specific, and standardized diagnostic assay for Onchocerca volvulus infection.MethodsFour recombinantly produced Onchocerca volvulus antigens (Ov-FAR-1, Ov-API-1, Ov-MSA-1 and Ov-CPI-1) were tested by LIPS on a large cohort of blinded sera comprised of both uninfected controls and patients with a proven parasitic infection including Onchocerca volvulus (Ov), Wuchereria bancrofti (Wb), Loa loa (Ll), Strongyloides stercoralis (Ss), and with other potentially cross-reactive infections. In addition to testing all four Ov antigens separately, a mixture that tested all four antigens simultaneously was evaluated in the standard 2-hour incubation format as well as in a 15-minute rapid LIPS format.FindingsAntibody responses to the four different Ov antigens allowed for unequivocal differentiation between Ov-infected and uninfected control sera with 100% sensitivity and 100% specificity. Analysis of the antibody titers to each of these four antigens in individual Ov-infected sera revealed that they were markedly different and did not correlate (rS = –0.11 to 0.58; P = 0.001 to 0.89) to each other. Compared to Ov-infected sera, patients infected with Wb, Ll, Ss, and other conditions had markedly lower geometric mean antibody titers to each of the Ov 4 antigens (P<0.0002 for each antigen). The simplified method of using a mixture of the 4 Ov antigens simultaneously in the standard format or a quick 15-minute format (QLIPS) showed 100% sensitivity and 100% specificity in distinguishing the Ov-infected sera from the uninfected control sera. Finally, the QLIPS format had the best performance with 100% sensitivity and specificity values of 76%, 84% and 93% for distinguishing Ov from Wb, Ll and Ss-infected sera.ConclusionsThe multi-antigen LIPS assay can be used as a rapid, high throughput, and specific tool to not only to diagnose individual Ov infections but also as a sensitive and potentially point-of-care method for early detection of recrudescent infections in areas under control and for mapping new areas of transmission of Ov infection.
Highlights
As one of the neglected tropical diseases (NTDs), onchocerciasis, caused by the filarial parasite Onchocerca volvulus (Ov), can lead to blindness and disabling dermatitis
The multi-antigen luciferase immunoprecipitation systems (LIPS) assay can be used as a rapid, high throughput, and specific tool to to diagnose individual Ov infections and as a sensitive and potentially point-of-care method for early detection of recrudescent infections in areas under control and for mapping new areas of transmission of Ov infection
This study suggests that this rapid LIPS test (QLIPS) has the potential to be used in point-of-care detection of onchocerciasis and thereby may provide a new tool for diagnosis and the monitoring of transmission control measures
Summary
As one of the neglected tropical diseases (NTDs), onchocerciasis (or ‘river blindness’), caused by the filarial parasite Onchocerca volvulus (Ov), can lead to blindness and disabling dermatitis. Past and ongoing control measures, aimed at interrupting transmission by vector control (Onchocerciasis Control Programme in West Africa, OCP), reducing the burden of morbidity to tolerable levels (African Programme for Onchocerciasis Control, APOC), and eliminating the reservoir of infection wherever possible (Onchocerciasis Elimination Program for the Americas, OEPA), have led to substantial decreases in the prevalence of infection and the risk of blindness [1] Despite these measures, which currently rely almost exclusively on ivermectin distribution, estimates suggest that 37 million people remain infected with Ov with an additional 90 million people being at risk in Africa [2]. We investigated whether luciferase immunoprecipitation systems (LIPS) may be used as a more rapid, specific, and standardized diagnostic assay for Onchocerca volvulus infection
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