Cape company looks to tobacco plant's cousin in search for Covid-19 antigen

Serology tests could become more important once it's known if you're immune to Covid-19 after acquiring the infection and recovering.
Serology tests could become more important once it's known if you're immune to Covid-19 after acquiring the infection and recovering.
Image: Sowetan / Thulani Mbele

The cigarette war might be raging but a distant cousin of the tobacco plant, it is hoped, will quietly join the war against Covid-19.

A Cape Town company has partnered others overseas to produce a plant-based antigen that could possibly be used in rapid- diagnostic test kits for the virus.

These tests differ from the polymerase chain reaction (PCR) tests being done at scale in SA. PCR tests for Covid-19 involve a nasal swab that is sent to a laboratory for testing. There, technicians search for the active presence of the virus, which will show if the patient is still infectious.

Rapid diagnostic tests (or serology tests), on the other hand, check for the presence of antibodies in your blood or sputum to see if you’ve had an immune response to the virus, but they do not show if you’re still infectious.

Cape Bio Pharms, a spin-off company of the biopharming research unit at the University of Cape Town, partnered international biotech companies in the Plants Against Corona initiative.

 “We are working towards developing antigens and antibodies for late-stage serology tests that detect antibodies in a patient’s blood,” said Cape Bio Pharms co-founder Tamlyn Shaw.

The company sourced the gene sequences for SARS-CoV-2 to develop antigen constructs that could speed up production of antigens, globally.

As PCR tests tell us if someone is still actively infectious, antibody tests (or serology tests) may become important once we know whether a person who has had Covid-19 is immune from getting it again.

Shaw said serology testing could be done alongside PCR testing to see if a person is producing antibodies.

“Once a person is producing antibodies, we know they’ve recovered, but not necessarily developed immunity to the virus. However, serology testing allows for continuous assessment of those who have resumed work and social care duties,” she said.

“The speed and accessibility of these test kits will allow public health authorities to consistently test for SARS-CoV-2 in their communities.”

According to Prof Wolfgang Preiser, a virology expert at the University of Stellenbosch, “antibody tests will have a role to play” in the future. But not all of them were reputable.

“We know that many of the tests being marketed overseas are not good, so before one launches into using them it will be important to assess their performance,” he said.

Preiser said the use of antibody tests to declare someone “safe” was premature. “Neither do we know a lot about immunity ... but the good news is that so much is going on in this field that we should learn more pretty soon,” he said.

Once more research is done on the body’s ability to become immune to Covid-19 after infection, the plant-based antigens could prove useful in many countries.

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