Self-test HIV diagnostics utilizing structurally novel, shark-derived binding domains

University Of Maryland Baltimore, Baltimore MD

Investigators

Abstract

PROJECT SUMMARY Since the first serologic tests were introduced at the peak of the AIDS crisis in the 1980s, continuous improvements in diagnostic technology have enabled the earlier detection and routine monitoring of HIV positive individuals. However, there are two areas where current HIV diagnostics fall short of ideal, and which we will attempt to directly address in this proposal; the first is the need for a simple diagnostic tool that allows individuals to self‐test for acute phase HIV infections. The second challenge is the provision of a diagnostic tool that will allow patients previously diagnosed as HIV positive to monitor their viral load following ART interruption or check for loss of viral control due to the emergence of drug‐ resistance. Given these diagnostics are to be used in a patients own home (or other non‐clinical, setting), they need to be cheap, robust, and suitable for use without prior training or specialist equipment. Further, they should use a biological sample that can be obtained in a minimally invasive manner (e.g. a finger‐stick blood drop) to encourage frequent retesting in target populations. To address the above problems, we will integrate two existing technologies to generate a sensitive home‐test diagnostic for HIV. The first technology is a structurally novel binding domain, so called VNARs, that we isolate from immunized sharks. Despite their diminutive size (12kDa), the VNAR domains raised thus far have binding affinities equal to classical antibodies but are intrinsically much more chemo‐ and thermostable. VNARs interact with antigen in unique ways and can be raised against epitopes that are inaccessible to conventional antibodies; we will exploit this fact to target the HIV proteins p24 and Env, allowing us to capture and accurately quantify free proteins or whole virus in unmanipulated blood. We will integrate these VNARs with our second technology, the programmable Bio‐Nano‐Chip (p‐BNC), a microchip‐ based detection system which utilizes porous agarose microbeads as 3D diagnostic surfaces. Immunometric assays can be performed by loading the beads with biomolecules such as antibodies, or in this case VNARs, allowing the capture and quantitation of desired target(s) in biological samples. To enable use of this technology in a non‐clinical setting, we will develop credit card‐sized diagnostic cartridges that have a microbead‐based sensor array at their core, and microfluidic system for the delivery of sample, wash buffer, and detection reagent. This will be deployed and read by a battery‐ powered handheld reader system that will be developed and fabricated during our project. This system will use an imaging system derived from smartphones and enable the safe and secure uploading of data to a cloud‐based repository. Together these technologies will allow us to deliver an inexpensive, robust, sensitive, and accurate diagnostic test that can be used by an individual to assess their HIV status or closely monitor their viral load, without a clinic visit.