South African and Brazilian variants ‘may allow virus to escape immune response’

Some of the mutations seen in coronavirus variants from Brazil and South Africa appear to allow the virus to escape some of people’s immune responses, a leading virologist has said.

Professor Wendy Barclay, who is advising the Government’s Covid-19 response, said that as natural immunity becomes dense in certain parts of the world, some variants have got a “fitness advantage” and are therefore more likely to spread.

She explained that the mutations themselves are not becoming more concerning, but are slightly less controlled by previous immune responses so are going to be the fitter variants.

Prof Barclay, G2P-UK lead and head of the department of infectious disease and chairwoman in influenza virology at Imperial College London, said: “It’s not that the mutations themselves become more concerning.

“It’s likely that the viruses which have some mutations – which mean that they’re slightly less well controlled by our previous immune responses – are going to be the more fitter viruses, the ones that can spread to more people.

“We know for example in the two places where some concerning variants have arisen – in South Africa and Brazil – that in those parts of the world, there was already quite a high level of antibody response from people who’ve been infected and recovered from the virus.

“It wasn’t herd immunity but there was an increasing level of seroprevalence, as we say – people with antibodies.

“And so the fact that those variants have emerged there, in that sort of background, in that environment, shows us that the virus will respond to changes in humans it’s infecting by the fitter mutants being the ones which grow out and predominate.”

She added that in some parts of the world where immunity is already quite high, the virus is now spreading very rapidly, and more and more people are developing antibodies.

“Eventually it (the virus) will have mutations which help it be less well controlled and the fitter viruses will emerge – that’s just the way viruses will evolve,” Prof Barclay explained.

Research is ongoing to assess whether the new variants are resistant to vaccines and treatments.

Asked why these variants were emerging now, she added: “I think that we have reached a point one year on, and in certain parts of the world, where the density of natural immunity is sufficient that the variants have gotten fitness advantage and therefore more likely to emerge and spread in those parts of the world.

“In the UK it’s a little bit different – we’ve seen the UK variant derived from an immunocompromised individual who was infected for a very long time.”

Prof Barclay said there are some “key similarities” between the South African variant and the Brazilian variant which are causing some concern.

She continued: “Those mutations appear to be able to allow the virus to escape some of the immune responses that some people make.

“So I think it’s – you know it’s – logical that we take some measures. But as I said with this – what we’re doing is the science to try and underpin and firm up those changes so that other people can make decisions about when to close borders.”

The virologist explained there are two new variants in Brazil, the more concerning of which has been picked up in travellers going to Japan but has not been detected in the UK, while the other has.

Prof Barclay was speaking as a new national research project to study the effects of emerging coronavirus mutations was announced.

Funded by UK Research and Innovation (UKRI), the G2P-UK National Virology Consortium will look at how mutations in the virus affect key outcomes such as how transmissible it is, the severity of Covid-19 it causes, and the effectiveness of vaccines and treatments.

The consortium will bring together leading virologists from 10 research institutions who will work alongside the Covid-19 Genomics UK (COG-UK) consortium.

It will also work with Public Health England to boost the UK’s capacity to study newly identified virus variants and rapidly inform Government policy.

Mutations in the virus’s genome occur naturally and while some of these will have no effect, others will change how it functions.

As new virus variants arise the consortium will flag the riskiest variants, such as those associated with fast spreading virus clusters, to study.

It will also create standardised versions of the virus with and without each mutation, so they can study the effects of each change individually.

Other members of the consortium will then study how these new variants alter the virus proteins, particularly the key spike protein on the surface.

Changes to the spike protein can affect transmissibility and could potentially alter the effectiveness of vaccines and antibodies that target the protein, so this analysis plays an important role.

Scientists will then use cell cultures and animal models to study if the mutations alter the immune response, virus transmissibility, the severity of the disease it causes, or the effectiveness of vaccines and treatments.