EbolaCheck

What did the study set out to achieve?

Symptomatic patients arriving at Ebola treatment centres in West Africa were triaged by a combination of reviewing their symptoms, assessing Ebola epidemiology in their community, and confirming infection through molecular diagnosis. Beyond acute high fever, symptoms that raise suspicion of Ebola Virus Disease (EVD) include vomiting, diarrhoea and uncontrolled haemorrhage. Importantly, these coincide with high levels of viremia and contagiousness through contact with bodily fluids, and are also symptomatic of other diseases prevalent in West Africa, such as malaria.

It is thus necessary to quickly identify and isolate EVD patients to prevent further transmission. However, until that crucial negative molecular result is returned, patients that might be Ebola-free are cared for side-by-side with confirmed positive cases, at risk of acquiring the disease and death. Minimising the time to molecular diagnosis would therefore greatly improve the chances of controlling Ebola outbreaks.

This project presented an innovative solution: ‘EbolaCheck’. Ebola-check is a point-of-need diagnostic device suitable for simple, rapid and safe patient triage at treatment centres anywhere in West Africa. The approach is based on a combination of a validated, proprietary technology for rapid, direct polymerase chain reaction (PCR) on whole blood samples [ExSyte (EBVK8), based on WO2011157989] and the standard of care RTKPCR laboratory diagnostic assays used worldwide to confirm Ebola infection. The development of this diagnostic device has helped enhance patient triage and improve healthcare worker safety.

What were the key finding?

A key finding was that reverse transcription, the process of converting RNA molecules such as the Ebola genome into DNA, is possible in crude blood, serum and cerebrospinal fluid samples. The study also demonstrated that quantification of genetic material in such crude samples is possible to the extent that the biomarker being assessed is found in concentrations ranging from a few copies to a few billion copies. The capacity to detect <10 copies of virus up to 6 billion, whether the virus has or does not have a lipid envelope, suggests that a wide variety of viruses can be reliably detected and quantified using this technology.

The solution achieved through EbolaCheck can reliably discriminate between log-range differences in viraemia as simulated by spiking mock patient sample (fresh blood and serum) with surrogate viruses or ebolavirus obtained from cell culture preps. Thus, whilst many alternatives were put forward during the Ebola outbreak, from pregnancy test-styled dip sticks to table top lab automation systems or manually and technically demanding ‘lab in a suitcase’ approaches, few combine the laboratory-free portability, simplicity and quantifiable data nature of EbolaCheck. The level of discrimination offered on viraemia, coupled to the data on mortality risk suggests future utility in reliably predicting the risk to the patient on arrival at triage or during treatment.

Outputs included:

• Single well, triplex testing instrumentation that is compatible at least with crude blood and cerebrospinal fluid at a final, pre-scale up cost per patient of US$12.
• Capability to quantify, not just detect Ebolavirus.
• ‘Gold standard’ assay migration onto EbolaCheck to achieve better performance than published assay capability.
• Migration of one more Ebola and one control assay in addition to the minimal assay in EZ1.
• Proof of principle that the platform may discriminate vaccinated from infected individuals and confirm system operational reliably.
• Validation of ‘gold standard’ reagent mix utility on the instrument (refrigerated consumables) with live Ebola.
• Evidence of utility for capsid viruses, lipid envelop viruses, gram positive and gram negative bacteria.
• Cold chain free reagent mix development compatible with EbolaCheck technology and with minimal impact on quantitative capability has been developed but not validated with live Ebola.
• Demonstration of rapid (<3 weeks) transfer of existing clinical assays onto the EbolaCheck platform to meet emerging need.
• Instrument fully compatible with chemical sterilisation and rapid redeployment-reuse.

Following this study, the team planned to field test EbolaCheck with over 400 patients in rural areas in Brazil with over 400 patients to test potential challenges like humidity and temperature, and the simplicity of the operating procedure.