A recent study from researchers at the University of Cambridge and the California Institute of Technology (Caltech) found that the genes thought to be responsible for SARS-CoV-2 virus entry to cells are present in embryos as early as 13 days post-fertilisation.
Researchers found that cultured embryos that were allowed to develop in vitro expressed the cell membrane protein, ACE2, and the enzyme, TMPRSS2. The entry of SARS-CoV-2 relies on proteins on the virus surface binding to human ACE2. The binding of the virus protein and ACE2 on human cells then initiates the cleavage of these proteins by TMPRSS2. This process allows the transfer of genetic material from the virus to the host cell and therefore viral infection.
Professor Magdalena Zernicka-Goetz of both Cambridge and Caltech, to whom the development of the human embryo model is atttributed, said 'Our work suggests that the human embryo could be susceptible to COVID-19 as early as the second week of pregnancy if the mother gets sick. To know whether this really could happen, it now becomes very important to know whether the ACE2 and TMPRSS2 proteins are made and become correctly positioned at cell surfaces. If these next steps are also taking place, it is possible that the virus could be transmitted from the mother and infect the embryo's cells.'
The researchers have expressed that these findings require further research, including work on stem cells and non-human primates, before the risk is fully known.
Bailey Weatherbee, a PhD student at the University of Cambridge, emphasises 'We don't want women to be unduly worried by these findings, but they do reinforce the importance of doing everything they can to minimise their risk of infection'
This research was published in Open Biology.