Faster, locally produced Covid-19 tests on the cards

CSIR senior researcher Dr Lusisizwe Kwazi has been working on a one-step kit, which could be ready for “national roll-out within six months”, depending on approval from the SA Health Products Regulatory Authority.

The current two-step nasal and throat swab tests for Covid-19 test for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through polymerase chain reaction testing.

CSIR said the virus’ first genetic material – its RNA – has to be converted to DNA using an enzyme called reverse transcriptase, in a reaction called RT-PCR. PCR was then used to make thousands of copies of the DNA until there was enough of the tiny molecules to detect.

“If the test detects the targeted DNA copies, there must have been viral RNA in the sample, hence the test is positive.”

The research council said it had already established highly efficient technology to produce the enzyme, which was necessary for the second step.

“This enzyme is known as DNA Tag polymerase. Only three grams of the protein produced in E.coli bacteria in as little as three days, is enough for a billion PCR reactions,” Kwezi said.

He, however, cautioned that it did not equate to Covid-19 tests for a billion people as, among other technical reasons, diagnostic tests had to be carefully repeated several times to ensure the accuracy of the results for each patient.

“But it does mean that a high amount of this important reagent is available locally and affordably.”

Kwezi added that a 3g batch was delivered to local company, CapeBio Technologies by the CSIR.

The local company had licensed and commercialised the technology.

It would be rolled out to support the national testing effort once CapeBio got approval.

“Thanks to funding just awarded through the strategic health innovation partnership – a partnership between the South African Medical Research Council and the Department of Science and Innovation (DSI) – the CSIR and CapeBio are now working to add the reverse transcriptase enzyme to the mix as well, so that the two-step Covid-19 PCR test can be done in a single step.

“This will reduce the turnaround time of tests.”

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