New research has for the first time compared images of the protein spikes
that develop on the surface of cells exposed to the Oxford-AstraZeneca
vaccine to the protein spike of the SARS-CoV-19 coronavirus. The images show
that the spikes are highly similar to those of the virus and support the
modified adenovirus used in the vaccine as a leading platform to combat
COVID-19.
The SARS-CoV-2 virus, which causes COVID-19, has a large number of spikes
sticking out of its surface that it uses to attach to, and enter, cells in
the human body. These spikes are coated in sugars, known as glycans, which
disguise parts of the viral proteins to the human immune system.
The vaccine developed by the University of Oxford and AstraZeneca is an
adenovirus-vectored vaccine, which involves taking a safe version of a virus
and adding in the information from part of a pathogen, in this case the
SAR-CoV-2 spike, in order to generate neutralising antibodies against that
target.
In this new study, published in the journal ACS Central Science, scientists
from the University of Oxford and the University of Southampton, worked
together to characterise the SARS-CoV-2 spikes manufactured by the cells
presented with the Oxford-AstraZeneca vaccine. The Oxford work was led by
Professors Teresa Lambe, Peijun Zhang and Sarah Gilbert and Professor Max
Crispin led the work in Southampton.
The Scientists exposed a range of cells in vitro to the Oxford-AstraZeneca
vaccine. Using an imaging technique known as cryo-electron microscopy
(cryoEM) they took thousands of images which they then combined to build up
a clear picture of the resulting protein spikes on the cells. Professor
Peijun Zhang, of the University of Oxford and the Electron Bio-Imaging
Centre (eBIC) at Diamond Light Source, who led the imaging work said,
“CryoEM is an immensely powerful technique which enabled us to visualise the
dense array of spikes that had been manufactured and presented on the
surface of the cells”.
Further chemical analysis of the glycans that coat the newly developed
protein spikes revealed that they bear a high resemblance to those
surrounding the SARS-CoV-2 spikes. This is an essential feature of the
vaccine as it means that it can deliver close mimics of the coronavirus that
are important in triggering the immune response needed to protect against
COVID-19.
Professor Crispin said, “In this study we set out to see how closely the
vaccine induced spikes resembled those of the infectious virus. We were
really pleased to see a large amount of native-like spikes.”
“This study will hopefully provide further understanding for the public,
helping them see how the Oxford-AstraZeneca vaccine works. Many people may
not realise how their cells become little factories manufacturing viral
spikes that then trigger the immune response needed to fight off the
disease. This may also provide reassurance that the vaccine is doing its job
and generating the material that we need to present to our immune systems.”
Reference:
Watanabe Y, Mendonça L, Allen ER, et al. Native-like SARS-CoV-2 spike
glycoprotein expressed by ChAdOx1 nCoV-19/AZD1222 Vaccine. ACS Cent Sci.
2021. doi:
10.1021/acscentsci.1c00080
Tags:
Medical Science