Introduction and Background of the Project

Introduction
Trachoma is the world’s leading infectious cause of blindness. Although global control efforts have achieved major progress, transmission persists in remote and underserved communities, and countries approaching elimination need better ways to determine whether infection has truly been interrupted. Traditional surveillance relies heavily on examining children for visible eye inflammation. As prevalence falls, however, these clinical signs become less specific, surveys become increasingly difficult and costly, and low-level transmission or resurgence can be missed. This project advances a new generation of serological tests that detect antibodies to Pgp3, a well-established marker of exposure to Chlamydia trachomatis, the bacterium that causes trachoma. The core product is a rapid dipstick test for high-throughput analysis of dried blood spot samples in laboratories. A cassette version, using the same test strip with a blood filter, may also be advanced for fingerstick testing closer to communities if trachoma programs confirm a need for it. The work builds directly on a successful earlier GHIT Fund project (G2024-108) that produced a dipstick test meeting the WHO target product profile (TPP) requirements and demonstrated that it can be manufactured at scale. This new award will move the technology from an advanced candidate into formal verification, field validation, regulatory review, and programmatic launch. In parallel, this new project will progress ready-to-use, freeze-dried Pgp3-coated beads for multiplex bead assay (MBA) testing in the laboratory from proof-of-concept delivered in G2024-108 to the stage of pilot lot production.

Project Objective
The primary objective is to bring the new trachoma dipstick rapid test from an advanced, manufacturable candidate to regulatory acceptance and programmatic launch in 2028. The test is designed for high-throughput laboratory testing of dried blood spots and serum and has already demonstrated the performance, usability, heat stability, and affordability expected by trachoma programs. During this project, the consortium will establish a verification and validation (V&V) plan in consultation with relevant WHO and technical experts, conduct the required V&V studies both in the laboratory and in the field using production-quality pilot lots, compile a complete regulatory dossier, and support a launch decision by global trachoma stakeholders. A second objective is conditional on programmatic demand: the consortium is also evaluating a cassette version that uses the same assay strip but adds a blood filter, enabling testing with fingerstick blood at or near the point of care. Evidence on performance, cost, operational feasibility, and user and community acceptance will guide whether this format should also proceed through verification, validation, regulatory review, and launch. A third, objective is to advance pre-conjugated, freeze-dried Pgp3 multiplex bead assay (MBA) beads which have been shown in the precursor project, G2024-108, to maintain the same diagnostic performance as freshly prepared beads – yet with proven thermal stability for at least two weeks at room temperature. This project will optimize and scale the process, assess reproducibility and thermal stability, obtain independent laboratory validation, and produce pilot lots. Together, these objectives aim to provide trachoma programs with practical diagnostic options spanning centralized laboratories, field settings, and integrated multiplex surveillance. Finally, this project will also continue manufacturing the new Pgp3 dipstick to cover immediate and pressing programmatic needs while waiting for regulatory approval to be secured.

Project Design
The project is organized as a staged development program with clear decision points. First, the consortium will prepare a detailed verification and validation plan for the dipstick test in consultation with relevant WHO scientific and diagnostic experts. The plan will define the laboratory studies and, if required, field studies needed to demonstrate that independently manufactured lots perform consistently under realistic operating, transport, storage, and use conditions. A separate plan will be prepared for the cassette version only if trachoma programs decide that this format is needed. Second, Medical & Biological Laboratories will supply production-grade Pgp3 antigens, while Big Eye Diagnostics will manufacture tests under an ISO-13485:2016 certified quality system to cover immediate and urgent programmatic needs. The three pilot lots will undergo laboratory verification studies covering performance, repeatability, reproducibility, specimen-related variables, stability, and other parameters. The Carter Center will coordinate any additional field validation studies required by, and included in the V&V plan, in trachoma-endemic countries. Results will be reviewed with stakeholders and incorporated into the manufacturer’s quality records. Once all results from the V&V studies are available, the consortium will assemble and submit the regulatory dossier to the appropriate WHO-supported review mechanism, respond to questions, and work with stakeholders on programmatic introduction. The multiplex bead work follows its own go/no-go pathway, whereby the team will optimize conjugation and freeze-drying, demonstrate scale-up and inter-laboratory reproducibility, assess thermal stability, obtain independent validation, and manufacture three pilot lots to lay the ground for future development.

How can your partnership (project) address global health challenges?

Trachoma elimination has entered a difficult “last mile.” When disease is common, clinical examination can guide mass antibiotic treatment. When prevalence becomes very low, visible eye signs are less reliable indicators of ongoing transmission, trained graders encounter few true cases, and large surveys become expensive and labor-intensive. Programs nevertheless need strong evidence to decide when mass drug administration can safely stop, to validate elimination, and to detect renewed transmission before blindness returns. This project addresses that gap by providing objective, standardized serological tools that measure population exposure to the bacterium causing trachoma. The dipstick test is designed for affordable, high-throughput testing of dried blood spots in regional or national laboratories and can be integrated into existing survey workflows. The potential cassette version could extend testing to lower-infrastructure settings using a small fingerstick blood sample. Both formats are instrument-free, simple to interpret, and designed to tolerate the challenging transport and temperature conditions common in endemic regions. The ready-to-use multiplex bead reagents could create an even broader benefit: by reducing the technical skill and cold-chain requirements associated with multiplex testing, they may help more laboratories in low- and middle-income countries participate in integrated serosurveillance for several neglected tropical diseases using the same samples. Together, these tools can give national programs more reliable evidence, use limited surveillance resources more efficiently, and support confident decisions on stopping treatment, confirming interruption of transmission, and protecting communities from resurgence. Affordable manufacturing and close involvement of WHO and implementing organizations strengthen the pathway to equitable access and adoption.

What sort of innovation are you bringing in your project?

The project combines several practical innovations designed around the realities of trachoma surveillance. The first is a dry-conjugate lateral-flow format. In the earlier laboratory method developed at the Centers for Disease Control and Prevention (CDC), a key Pgp3 reagent had to be prepared freshly and incubated with samples overnight. In the new test, the conjugate is built into the strip and is released when sample and buffer are added. This shortens the overall dried-blood-spot workflow to about one hour, removes a technically demanding preparation step, and reduces dependence on refrigerated reagent shipment. The test also uses an optimized dual-antigen configuration selected to combine strong performance with reliable large-scale manufacturing. This design supports consistent production and economical automated reel-to-reel manufacture. A heat-stable positive control is also planned so users can periodically confirm that the test continues to perform correctly in hot climates. The cassette concept extends the same proven assay strip with a blood filter for direct fingerstick sampling. If stakeholders choose this format, it may also be paired with a smartphone reader for standardized result capture and data transfer. Finally, the project explores pre-conjugated, freeze-dried Pgp3 beads and reagents for multiplex bead assays. Reconstitution with buffer could replace complex on-site bead preparation and reduce cold-chain needs, making advanced multiplex serosurveillance more accessible to lower-infrastructure laboratories and potentially adaptable to other neglected tropical diseases in the future.

Role and Responsibility of Each Partner

Drugs & Diagnostics for Tropical Diseases (DDTD), the Designated Development Partner, will provide overall scientific, consortium, budget, and reporting leadership. DDTD will coordinate decision-making across the partnership, lead engagement with WHO scientific advisers and other trachoma stakeholders, support verification and validation activities, and contribute its expertise in assay development, nanoparticle conjugation, and freeze-drying. If the cassette format proceeds, DDTD will also coordinate adaptation of the digital reader application. Medical & Biological Laboratories Co., Ltd. (MBL) will manufacture ISO-production-grade Pgp3 antigens needed for test production. For the multiplex bead work, MBL will co-lead process optimization, scale-up, reproducibility and thermal-stability studies, external validation, and production of pilot lots under an appropriate quality system. The Carter Center (TCC) will bring programmatic and field-validation expertise. It will help shape the verification and validation strategy, coordinate any additional studies required in trachoma-endemic countries, connect the project with implementing partners and national programs, and contribute to preparation of the final regulatory dossier and launch planning. Big Eye Diagnostics, Inc. (BEDx) will serve as the future legal manufacturer. BEDx will lead ISO 13485-compliant test manufacturing, conduct and document laboratory verification studies, support field validation, maintain the product records within its quality management system, and lead regulatory submission and responses to reviewers. The partners will govern the project jointly through regular executive and technical meetings, with clearly assigned activity leads and continuing input from global trachoma experts and end users.