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Last Updated: August 2025

Hadermann A, Jada SR, Lubbers C, Amaral LJ, Biamonte M, de Souza DK, Bol YY, Siewe Fodjo JN, Colebunders R. A Novel Biplex Onchocerca volvulus Rapid Diagnostic Test Evaluated Among 3- to 9-Year-Old Children in Maridi, South Sudan. Diagnostics (Basel). 2025 Feb 26;15(5):563. doi: 10.3390/diagnostics15050563

Background: Point-of-care diagnostic tests are essential for confirming Onchocerca volvulus transmission in remote, resource-limited, onchocerciasis-endemic communities. In Maridi, South Sudan, we field-tested a novel "biplex A" rapid diagnostic test (RDT) developed by Drugs & Diagnostics for Tropical Diseases (DDTD), San Diego, California. Methods: In February 2023, children aged 3-9 years were recruited from study sites at different distances from the Maridi Dam, a known blackfly breeding site. O. volvulus antibodies were detected using the DDTD biplex A RDT, which detects antibodies to Ov16 and OvOC3261 at test line 1 and to Ov33.3 and OvOC10469 at test line 2, along with the commercially available Ov16 SD Bioline RDT. Both tests were performed on whole blood obtained via finger prick. The feasibility and acceptability of the DDTD biplex A RDT were assessed, and its results were compared with those of the Ov16 SD Bioline RDT. Results: A total of 239 children participated in the study. The anti-Ov16 seroprevalence detected by the Ov16 SD Bioline RDT was 30.2% (72/239), with the highest prevalence observed in children living closest to the Maridi Dam (p < 0.001). Testing with the DDTD biplex A RDT was determined to be feasible, acceptable, and easy to use in a field setting. The DDTD biplex A RDT test line 1 (anti-Ov16 and anti-OvOC3261) was positive in 35.1% (84/239) of children, while test line 2 (anti-Ov33.3 and anti-OvOC10469) was positive in 18.4% (44/239). Both lines were simultaneously visible in 15.5% (37/239). Conclusions: The DDTD biplex A RDT prototype was user-friendly and practical for field deployment. However, additional research is needed to evaluate its performance relative to the commercially available Ov16 SD Bioline RDT. The high anti-Ov16 seroprevalence that was observed underscores the ongoing O. volvulus transmission near the Maridi Dam. Strengthening the onchocerciasis elimination program in Maridi should be prioritized as a critical public health intervention.

Marco Biamonte, Sam Marton, Lauren Boone, Justin Nueve, Rhea Perez, Lily A. Sullins,  Jean Saunders, Matthias Schwarz, Adina Gerson-Gurwitz, Eric S. Elder, Sasisekhar Bennuru, Yaya I. Coulibaly, Patrick N. Kpanyen, Kerstin Fischer, Peter U. Fischer, Yvonne Ashong, Dziedzom K. de Souza. Next Generation Ov16-based Rapid Tests for Onchocerciasis: Field Data. ASTMH 2024 Annual Meeting, Abstract/Presentation #6848.

Improved diagnostics are required to map onchocerciasis in low endemicity areas. In 2021 WHO issued a Target Product Profile (TPP) that calls for a sensitivity ≥ 60% and specificity ≥ 99.8%. To reach this stringent specificity requirement, we developed a prototype rapid diagnostic test that detects IgG4 antibodies to different recombinant O. volvulus proteins arranged as two different test lines. Both test lines must be visible to count the test positive. In the latest iteration, called “Biplex D”, the first test line (TL1) is made of Ov16 and the second test line (TL2) contains a mixture of OvOC3261 and Ov33.3. When evaluated in the laboratory against a panel of cryopreserved sera containing 86 microfilariae (Mf) positives and 234 other infections, the sensitivity of Biplex D was 79% (95%CI 69-86%) and its specificity 100% (99.95-100). An earlier test version, called “Biplex C” contains only OvOC3261 and no Ov33.3 at TL2. These two versions are being validated in the field using fingerstick blood. In Bong, Liberia, a preliminary dataset on 19 patients with onchocerciasis (all Mf and nodule positive before ivermectin 18 month ago) gave a sensitivity for Biplex D of 17/19 = 89% (69-97). Combining this with the specificity data obtained in the lab, we conclude that Biplex D meets the TPP sensitivity and specificity specifications, even at the lower bound of the 95% CI. The sensitivity of Biplex C was in Liberia 16/19 = 84% (62-94%), and in Nkwanta, Ghana 11/13 = 85% (57-97%). Combining the two data sets gives a mean sensitivity of 27/32 = 84 % (68-93%), above the 60% sensitivity threshold at the lower bound of the 95% CI. Antibody prevalence data were collected in Ghana with Biplex C. In Adaklu, which is not endemic for onchocerciasis and where no skin snip were Mf positive by microscopy, the seroprevalence in adult males was 3% (1.1-7.4), suggesting that at that level no MDA should be initiated. In adult males in Nkwanta, the Mf prevalence was 4% (1.9-7.9) and the seroprevalence 44% (37-51). Despite proven transmission, both the Mf prevalence and seroprevalence was 0% in children under the age of 10, suggesting that children would be an inadequate sentinel group post-MDA.

Campillo JT, Biamonte MA, Hemilembolo MC, Missamou F, Boussinesq M, Pion SDS, Chesnais CB. Evaluation of a novel biplex rapid diagnostic test for antibody responses to Loa loa and Onchocerca volvulus infections. PLoS Negl Trop Dis. 2024 Oct 10;18(10):e0012567. doi: 10.1371/journal.pntd.0012567

Background: Endemic to Central Africa, loiasis, caused by the vector-borne worm Loa loa, affects approximately 10 million individuals. Clinical manifestations include transient angioedema (Calabar swellings), migration of the adult worm under the eye conjunctiva (eye worm) and less specific general symptoms. Loiasis presents a significant public health challenge because L. loa-infected individuals can develop serious adverse events after taking ivermectin, the drug used to combat onchocerciasis. In this context, alternative interventions and rigorous diagnostic approaches are needed. Diagnosing loiasis is challenging because its main clinical manifestations are sporadic and non-specific. The definitive diagnosis relies on identifying adult worms migrating beneath the conjunctiva, or microfilariae (pre-larvae) in blood smears. However, "occult loiasis" (infection without blood microfilariae) is frequent. Serological rapid antibody diagnostic tests (ARTs) can provide an alternative diagnostic method. We compared a novel ART simultaneously targeting onchocerciasis (IgG4 to Ov-16 and OvOC3261, test line 1) and loiasis (IgG4 to L1-SXP-1, test line 2), called IgG4-SXP-1 biplex test) to the already established Loa-ART (all IgG isotypes to Ll-SXP-1, called pan-IgG-SXP-1 test). Methodology: Blood samples underwent both ARTs, read qualitatively and semi-quantitatively. Additionally, blood smears, skin snips, Kato-Katz method for soil-transmitted helminthiases identification and eosinophilia measurements were performed. Questionnaires gathered demographic details and loiasis-related signs. ARTs performance was compared using specific loiasis-related signs and microfilaremia as references. Discordances between the two ARTs were investigated using logistic regression models. Principal findings: Out of 971 participants, 35.4% had L. loa microfilaremia, 71.9% had already experienced loiasis-related signs, 85.1% were positive in the pan-IgG-SXP-1 test and 79.4% were positive in the IgG4-SXP-1 biplex test. In the microfilariae-positive population, the sensitivity of the rapid tests was 87.4% for the pan-IgG-SXP-1 test and 88.6% for the prototype IgG4-SXP-1 biplex test. Sensitivity was similar for both ARTs when using eye worm or Calabar swelling as references, but diagnostic performance varied based on microfilaremia levels and occult loiasis. Overall, IgG4-SXP-1 biplex test demonstrated a sensitivity of 84.1% and specificity of 47.6% for loiasis compared to the pan-IgG-SXP-1 test, leading to a Kappa coefficient estimated at 0.27 ± 0.03 for the qualitative results of the 2 ARTs. In the group that tested positive with the Pan-IgG test but negative with the IgG4-specific test, there was a lower prevalence of STH infection (p = 0.008) and elevated eosinophilia (p<0.001) compared to the general tested population. Conclusion/significance: The sensitivity of each test was good (84-85%) but the diagnostic agreement between the two ARTs was poor, suggesting that IgG and IgG4 antibody responses should be interpreted differently. The assessment of the innovative rapid diagnostic IgG4-SXP-1 biplex test, designed for onchocerciasis and loiasis, shows encouraging sensitivity but underlines the necessity for further in vitro assessment.

Sakakibara Y, Konishi M, Ueno T, Murase C, Miyamoto Y, Ato M, de Souza DK, Biamonte M, Pluschke G, Yotsu RR. Pilot use of a mycolactone-specific lateral flow assay for Buruli ulcer: A case report from Japan. J Clin Tuberc Other Mycobact Dis. 2024 Jul 26;36:100469. doi: 10.1016/j.jctube.2024.100469

Buruli ulcer, caused by Mycobacterium (M.) ulcerans, is a neglected tropical disease (NTD) characterized by necrosis of the cutaneous tissue, predominantly affecting the limbs. The pathogenesis of this disease is mainly attributed to mycolactone, a lipid toxin produced by M. ulcerans. Here, we report the case of a 7-year-old Japanese girl who presented with worsening ulceration on her left forearm, extending to the elbow, following antimicrobial treatment. To evaluate disease progression, we used a mycolactone-specific lateral flow assay. The test yielded positive results in the advancing necrotic area, aiding in determining the extent of necessary debridement. After undergoing two debridement surgeries and receiving 38 weeks of antimicrobial treatment followed by skin grafting, the patient achieved cure. Timely diagnosis is imperative in avoiding prolonged treatment, highlighting the importance of readily available diagnostic point-of-care tests for Buruli ulcer. Moreover, detection of mycolactone not only can serve as a diagnostic tool for Buruli ulcer but also enables prediction of lesion spread and assessment of cure.

Eric S. Elder, Marco Biamonte, Lily Sullins, Pete Augostini, William E. Secor, Kimberly Y. Won. Laboratory Evaluation of Onchocerciasis Rapid Diagnostic Tests (RDTs). ASTMH 2023 Annual Meeting, Abstract/Presentation #6421.

Reliable diagnostic tests are needed to support onchocerciasis programs, especially in low prevalence settings. Recently two target product profiles (TPPs), one for disease mapping and one for stopping mass drug administration (MDA) were developed. The TPPs outline performance characteristics required for new tests, including clinical sensitivity (F60% for mapping and ≥89% for stopping) and specificity (≥99.8% for both). Two antibody detection rapid diagnostic tests (RDTs) developed by DDTD were independently evaluated at CDC. Test A, previously described in 2022, contained Ov16 in one band. Test B included four antigens in two bands: Ov16 and Ov33.3 (band 1) and OvOC10469 and OvOC3261 (band 2); both bands must be visible for a positive result. Tests were performed according to manufacturer instructions using two independent readers. A panel of serum samples (n=146) from persons who were skin snip positive for Onchocerca volvulus by microscopy or PCR was used to evaluate sensitivity. A specificity panel included subpanels of Mansonella perstans and/or Loa loa (n=26), Wuchereria bancrofti (n=50), Plasmodium falciparum and/or P. vivax (n=16), Schistosoma mansoni (n=40), Strongyloides stercoralis (n=9), Rheumatoid factor/Type 1 diabetes (n=20) and North Americans with no history of international travel (n=50). Sensitivity and specificity of Test B were 90.4% and 94.3%, respectively. The two tests were then directly compared on a subset of 20 positive and 150 negative samples, Test A was 90% sensitive and 97% specific, and Test B was 85% sensitive and 92% specific. Both tests met the TPP sensitivity requirements for mapping or stopping MDA but not the specificity requirements. While the specificity issues may arise in part from the choice of biomarkers, it should be noted that nearly all problematic samples were M. perstans+/O. volvulus− but from an O. volvulus endemic country. Based on these data, development of an improved version of Test B is underway. In addition, the results show that to validate any new test for onchocerciasis, there is a need for M. perstans and L. loa samples from areas where O. volvulus exposure can be rigorously ruled out.

Bothra A, Perry ML, Wei E, Moayeri M, Ma Q, Biamonte MA, Siirin M, Leppla SH. S9.6-based hybrid capture immunoassay for pathogen detection. Sci Rep. 2023 Dec 19;13(1):22562. doi: 10.1038/s41598-023-49881-w

The detection of pathogens is critical for clinical diagnosis and public health surveillance. Detection is usually done with nucleic acid-based tests (NATs) and rapid antigen tests (e.g., lateral flow assays [LFAs]). Although NATs are more sensitive and specific, their use is often limited in resource-poor settings due to specialized requirements. To address this limitation, we developed a rapid DNA-RNA Hybrid Capture immunoassay (HC) that specifically detects RNA from pathogens. This assay utilizes a unique monoclonal antibody, S9.6, which binds DNA-RNA hybrids. Biotinylated single-stranded DNA probes are hybridized to target RNAs, followed by hybrid capture on streptavidin and detection with S9.6. The HC-ELISA assay can detect as few as 104 RNA molecules that are 2.2 kb in length. We also adapted this assay into a LFA format, where captured Bacillus anthracis rpoB RNA of 3.5 kb length was detectable from a bacterial load equivalent to 107 CFU per 100 mg of mouse tissue using either HC-ELISA or HC-LFA. Importantly, we also demonstrated the versatility of HC by detecting other pathogens, including SARS-CoV-2 and Toxoplasma gondii, showing its potential for broad pathogen detection. Notably, HC does not require amplification of the target nucleic acid and utilizes economical formats like ELISA and LFA, making it suitable for use in sentinel labs for pathogen detection or as a molecular tool in basic research laboratories. Our study highlights the potential of HC as a sensitive and versatile method for RNA-based pathogen detection.

Biamonte MA, Cantey PT, Coulibaly YI, Gass KM, Hamill LC, Hanna C, Lammie PJ, Kamgno J, Nutman TB, Oguttu DW, Sankara DP, Stolk WA, Unnasch TR. Onchocerciasis: Target product profiles of in vitro diagnostics to support onchocerciasis elimination mapping and mass drug administration stopping decisions. PLoS Negl Trop Dis. 2022 Aug 3;16(8):e0010682. doi: 10.1371/journal.pntd.0010682

In June 2021, the World Health Organization (WHO), recognizing the need for new diagnostics to support the control and elimination of onchocerciasis, published the target product profiles (TPPs) of new tests that would support the two most immediate needs: (a) mapping onchocerciasis in areas of low prevalence and (b) deciding when to stop mass drug administration programs. In both instances, the test should ideally detect an antigen specific for live, adult O. volvulus female worms. The preferred format is a field-deployable rapid test. For mapping, the test needs to be ≥ 60% sensitive and ≥ 99.8% specific, while to support stopping decisions, the test must be ≥ 89% sensitive and ≥ 99.8% specific. The requirement for extremely high specificity is dictated by the need to detect with sufficient statistical confidence the low seroprevalence threshold set by WHO. Surveys designed to detect a 1-2% prevalence of a given biomarker, as is the case here, cannot tolerate more than 0.2% of false-positives. Otherwise, the background noise would drown out the signal. It is recognized that reaching and demonstrating such a stringent specificity criterion will be challenging, but test developers can expect to be assisted by national governments and implementing partners for adequately powered field validation.

Johnson O, Giorgi E, Fronterrè C, Amoah B, Atsame J, Ella SN, Biamonte M, Ogoussan K, Hundley L, Gass K, Diggle PJ. Geostatistical modelling enables efficient safety assessment for mass drug administration with ivermectin in Loa loa endemic areas through a combined antibody and LoaScope testing strategy for elimination of onchocerciasis. PLoS Negl Trop Dis. 2022 Feb 9;16(2):e0010189. doi: 10.1371/journal.pntd.0010189

The elimination of onchocerciasis through community-based Mass Drug Administration (MDA) of ivermectin (Mectizan) is hampered by co-endemicity of Loa loa, as individuals who are highly co-infected with Loa loa parasites can suffer serious and occasionally fatal neurological reactions from the drug. The test-and-not-treat strategy of testing all individuals participating in MDA has some operational constraints including the cost and limited availability of LoaScope diagnostic tools. As a result, a Loa loa Antibody (Ab) Rapid Test was developed to offer a complementary way of determining the prevalence of loiasis. We develop a joint geostatistical modelling framework for the analysis of Ab and Loascope data to delineate whether an area is safe for MDA. Our results support the use of a two-stage strategy, in which Ab testing is used to identify areas that, with acceptably high probability, are safe or unsafe for MDA, followed by Loascope testing in areas whose safety status is uncertain. This work therefore contributes to the global effort towards the elimination of onchocerciasis as a public health problem by potentially reducing the time and cost required to establish whether an area is safe for MDA.

Ella SN, Ogoussan K, Gass K, Hundley L, Diggle PJ, Johnson O, Biamonte M, Atsame J. An Integrated District Mapping Strategy for Loiasis to Enable Safe Mass Treatment for Onchocerciasis in Gabon. Am J Trop Med Hyg. 2021 Nov 15;106(2):732-739. doi: 10.4269/ajtmh.21-0799

The lack of a WHO-recommended strategy for onchocerciasis treatment with ivermectin in hypo-endemic areas co-endemic with loiasis is an impediment to global onchocerciasis elimination. New loiasis diagnostics (LoaScope; Loa antibody rapid test) and risk prediction tools may enable safe mass treatment decisions in co-endemic areas. In 2017-2018, an integrated mapping strategy for onchocerciasis, lymphatic filariasis (LF), and loiasis, aimed at enabling safe ivermectin treatment decisions, was piloted in Gabon. Three ivermectin-naïve departments suspected to be hypo-endemic were selected and up to 100 adults per village across 30 villages in each of the three departments underwent testing for indicators of onchocerciasis, LF, and loiasis. An additional 67 communities in five adjoining departments were tested for loiasis to extend the prevalence and intensity predictions and possibly expand the boundaries of areas deemed safe for ivermectin treatment. Integrated testing in the three departments revealed within-department heterogeneity for all the three diseases, highlighting the value of a mapping approach that relies on cluster-based sampling rather than sentinel sites. These results suggest that safe mass treatment of onchocerciasis may be possible at the subdepartment level, even in departments where loiasis is present. Beyond valuable epidemiologic data, the study generated insight into the performance of various diagnostics and the feasibility of an integrated mapping approach utilizing new diagnostic and modeling tools. Further research should explore how programs can combine these diagnostic and risk prediction tools into a feasible programmatic strategy to enable safe treatment decisions where loiasis and onchocerciasis are co-endemic.

Won KY, Gass K, Biamonte M, Dagne DA, Ducker C, Hanna C, Hoerauf A, Lammie PJ, Njenga SM, Noordin R, Ramaiah KD, Ramzy R, Scholte RGC, Solomon AW, Souza AA, Tappero J, Toubali E, Weil GJ, Williams SA, King JD. Diagnostics to support elimination of lymphatic filariasis-Development of two target product profiles. PLoS Negl Trop Dis. 2021 Nov 15;15(11):e0009968. doi: 10.1371/journal.pntd.0009968

As lymphatic filariasis (LF) programs move closer to established targets for validation elimination of LF as a public health problem, diagnostic tools capable of supporting the needs of the programs are critical for success. Known limitations of existing diagnostic tools make it challenging to have confidence that program endpoints have been achieved. In 2019, the World Health Organization (WHO) established a Diagnostic Technical Advisory Group (DTAG) for Neglected Tropical Diseases tasked with prioritizing diagnostic needs including defining use-cases and target product profiles (TPPs) for needed tools. Subsequently, disease-specific DTAG subgroups, including one focused on LF, were established to develop TPPs and use-case analyses to be used by product developers. Here, we describe the development of two priority TPPs for LF diagnostics needed for making decisions for stopping mass drug administration (MDA) of a triple drug regimen and surveillance. Utilizing the WHO core TPP development process as the framework, the LF subgroup convened to discuss and determine attributes required for each use case. TPPs considered the following parameters: product use, design, performance, product configuration and cost, and access and equity. Version 1.0 TPPs for two use cases were published by WHO on 12 March 2021 within the WHO Global Observatory on Health Research and Development. A common TPP characteristic that emerged in both use cases was the need to identify new biomarkers that would allow for greater precision in program delivery. As LF diagnostic tests are rarely used for individual clinical diagnosis, it became apparent that reliance on population-based surveys for decision making requires consideration of test performance in the context of such surveys. In low prevalence settings, the number of false positive test results may lead to unnecessary continuation or resumption of MDA, thus wasting valuable resources and time. Therefore, highly specific diagnostic tools are paramount when used to measure low thresholds. The TPP process brought to the forefront the importance of linking use case, program platform and diagnostic performance characteristics when defining required criteria for diagnostic tools.

Souza AA, Ducker C, Argaw D, King JD, Solomon AW, Biamonte MA, Coler RN, Cruz I, Lejon V, Levecke B, Marchini FK, Marks M, Millet P, Njenga SM, Noordin R, Paulussen R, Sreekumar E, Lammie PJ. Diagnostics and the neglected tropical diseases roadmap: setting the agenda for 2030. Trans R Soc Trop Med Hyg. 2021 Jan 28;115(2):129-135. doi: 10.1093/trstmh/traa118

Accurate and reliable diagnostic tools are an essential requirement for neglected tropical diseases (NTDs) programmes. However, the NTD community has historically underinvested in the development and improvement of diagnostic tools, potentially undermining the successes achieved over the last 2 decades. Recognizing this, the WHO, in its newly released draft roadmap for NTD 2021-2030, has identified diagnostics as one of four priority areas requiring concerted action to reach the 2030 targets. As a result, WHO established a Diagnostics Technical Advisory Group (DTAG) to serve as the collaborative mechanism to drive progress in this area. Here, the purpose and role of the DTAG are described in the context of the challenges facing NTD programmes.

Gobbi F, Buonfrate D, Boussinesq M, Chesnais CB, Pion SD, Silva R, Moro L, Rodari P, Tamarozzi F, Biamonte M, Bisoffi Z. Performance of two serodiagnostic tests for loiasis in a Non-Endemic area. PLoS Negl Trop Dis. 2020 May 26;14(5):e0008187. doi: 10.1371/journal.pntd.0008187

Loiasis, caused by the filarial nematode Loa loa, is endemic in Central and West Africa where about 10 million people are infected. There is a scarcity of convenient, commercial diagnostics for L. loa. Microscopy requires trained personnel and has low sensitivity, while the serodiagnosis is currently not standardized. Individual case management is also important in non-endemic countries to treat migrants, expatriates and tourists. We retrospectively compared the performance of a Loa Antibody Rapid Test (RDT) and a commercial ELISA pan-filarial test on 170 patients, 65 with loiasis [8 with eyeworm, 29 with positive microfilaremia, 28 with neither microfilaremia nor history of eyeworm but eosinophilia and history of Calabar swelling (probable loiasis)], 95 with other common parasitic infections and no previous exposure to L. loa (37 with M. perstans, 1 with Brugia sp., 18 with strongyloidiasis, 20 with schistosomiasis, 5 with hookworm, 4 with Ascaris lumbricoides infection, 10 with hyper-reactive malarial splenomegaly), and 10 uninfected controls. The sensitivity of the RDT and of the ELISA were 93.8% (61/65) and 90.8% (59/65), respectively. For the RDT, most of the cross-reactions were observed in patients with M. perstans: 7/37 (18.9%), followed by 1/10 (10%) with hyper-reactive malarial splenomegaly and 1/20 (5%) with schistosomiasis. None of the 27 subjects infected with intestinal nematodes was found positive at this test. The ELISA is meant to be a pan-filarial assay, and reacted extensively with cases of M. perstans (95%), as expected, and also in 11/18 (61.1%) patients with strongyloidiasis and in 3/5 (60%) with hookworm infection. The RDT and the ELISA are both highly sensitive for the diagnosis of loiasis. The main difference lies in the extent of cross-reactivity with other parasites. Considering that the RDT is specifically meant for Loa loa infection, and its high sensitivity, this test could be a useful tool for the diagnosis of occult loiasis.

Gonzalez-Moa MJ, Van Dorst B, Lagatie O, Verheyen A, Stuyver L, Biamonte MA. Proof-of-Concept Rapid Diagnostic Test for Onchocerciasis: Exploring Peptide Biomarkers and the Use of Gold Nanoshells as Reporter Nanoparticles. ACS Infect Dis. 2018 Jun 8;4(6):912-917. doi: 10.1021/acsinfecdis.8b00031

Three O. volvulus immunogenic peptide sequences recently discovered by peptide microarray were adapted to a lateral flow assay (LFA). The LFA employs gold nanoshells as novel high-contrast reporter nanoparticles and detects a serological response against the 3 peptides, found in OvOC9384, OvOC198, and OvOC5528, respectively. When tested on 118 sera from O. volvulus infected patients and 208 control sera, the LFA was 90%, 63%, and 98% sensitive for each peptide, respectively, and 99-100% specific vs samples from healthy volunteers. Samples of other filarial infections cross-reacted by 7-24%. The sensitivity, specificity, and cross-reactivity values matched those obtained by ELISA with the same sample set. While the exact choice of peptide(s) will require fine-tuning, this work establishes that O. volvulus peptides identified by peptide microarray can be translated into an antibody-based LFA and that gold nanoshells provide the same sensitivity, specificity, and cross-reactivity as the corresponding ELISA assays.

Pedram B, Pasquetto V, Drame PM, Ji Y, Gonzalez-Moa MJ, Baldwin RK, Nutman TB, Biamonte MA. A novel rapid test for detecting antibody responses to Loa loa infections. PLoS Negl Trop Dis. 2017 Jul 27;11(7):e0005741. doi: 10.1371/journal.pntd.0005741

Ivermectin-based mass drug administration (MDA) programs have achieved remarkable success towards the elimination of onchocerciasis and lymphatic filariasis. However, their full implementation has been hindered in Central Africa by the occurrence of ivermectin-related severe adverse events (SAEs) in a subset of individuals with high circulating levels of Loa loa microfilariae. Extending MDA to areas with coincident L. loa infection is problematic, and inexpensive point-of-care tests for L. loa are acutely needed. Herein, we present a lateral flow assay (LFA) to identify subjects with a serological response to Ll-SXP-1, a specific and validated marker of L. loa. The test was evaluated on serum samples from patients infected with L. loa (n = 109) and other helminths (n = 204), as well as on uninfected controls (n = 77). When read with the naked eye, the test was 94% sensitive for L. loa infection and was 100% specific when sera from healthy endemic and non-endemic controls or from those with S. stercoralis infections were used as the comparators. When sera of patients with O. volvulus, W. bancrofti, or M. perstans were used as the comparators, the specificity of the LFA was 82%, 87%, and 88%, respectively. A companion smartphone reader allowed measurement of the test line intensities and establishment of cutoff values. With a cutoff of 600 Units, the assay sensitivity decreased to 71%, but the specificity increased to 96% for O. volvulus, 100% for W. bancrofti, and 100% for M. perstans-infected individuals. The LFA may find applications in refining the current maps of L. loa prevalence, which are needed to eliminate onchocerciasis and lymphatic filariasis from the African continent.