New Zealand scientists have been growing the SARS-CoV-2 virus using a lab process called viral culture. Photo / ESR
New Zealand scientists have been growing the SARS-CoV-2 virus using a lab process called viral culture. Photo / ESR
While New Zealand is at the brink of quashing Covid-19, Kiwi scientists have been busy growing the coronavirus in some of the country's most contained labs.
Using samples from New Zealand Covid-19 patients, they've been getting a closer look at the SARS-CoV-2 using a lab technique called viral culture – and what they discover could aid efforts to make a vaccine, here and overseas.
Otago University's Professor Miguel Quinones-Mateu and colleagues succeeded at safely isolating the virus back in March, only days after New Zealand reported its first confirmed case.
His team have since repeated the process using samples taken from seven different patients - and have since received 23 requests from other labs, universities and companies to share what they'd found.
Quinones-Mateu explained inactivated viral culture material was highly sought after because it could be used as a positive control in other labs, to ensure tests were working properly.
Having the virus was also crucial to developing anti-viral strategies and vaccines, he said, and his team were now planning to use it in work using animal models.
Given the obvious care needed in handling the virus, scientists have been using what are called PC3 labs – or those isolated and secure enough to have a physical containment biosafety level of three.
These are immensely contained, built to global standards and subject to the strictest biosafety precautions – and ESR scientists have been using their Wellington-based PC3 lab to carry out their own cultures.
ESR's clinical virology team leader, Lauren Jelley, said most other types of viruses, such as influenza and enterovirus, were typically studied in PC2 labs.
The PC3 setting involved a range of other protective measures, such as specific clothing that had to be sterilised through autoclaving after use.
She described viral culture as "a bit of a challenge", but New Zealand was fortunate that other countries had the virus first and scientists here could learn from them.
"Virus culture is a bit like gardening – if you can grow plants well, then you can culture cells well, ready for virus isolation," she said.
"It is about looking at how the cells are growing and knowing what to do to keep them healthy and in good condition."
ESR routinely maintained cells for viral culture and already had VERO cells - originally isolated from the kidneys of African green monkeys - that the virus could grow in.
"We grew these cells up in flasks until they formed a layer on the side of the flask," Jelley explained.
"We then diluted the virus down and poured the diluted virus over the cells. The virus attaches to the cells and then moves into the cells.
"The virus uses the cells to make more copies of itself and then bursts out of the cells causing holes in the layer."
Next, her team monitored how well the virus was growing by observing how many dead cells had detached from the cell layer, leaving gaps.
They monitored this effect every one-to-two days, then took segments off to inactivate the virus and ran polymerase chain reaction (PCR) tests to confirm the virus had grown.
"We then store the rest of the contents of the flask in a freezer, for long-term storage," she said.
"The only samples that come out of PC3 for this virus are inactivated, meaning they are not infectious."
By growing the virus, the team was also increasing what's called its titre – or concentration.
Some of the early clinical samples they received had very low titres of the virus, which meant scientists couldn't use them to unravel their genetic make-up using the latest sequencing techniques.
"We can take the original clinical samples that we received and grow them, so that next-gen sequencing can be performed," Jelley said.
