Strange phenomenon: Dropping the live SARS-CoV-2 virus into the nose, still not getting Covid-19

A strange phenomenon occurs during the Covid-19 pandemic: some people, despite being in close contact with a positive case, are not infected. Experts hope studying these cases will help them develop drugs to prevent outbreaks.

Phoebe Garrett went to school directly at university lecture halls but did not contract Covid-19. She even organized a party, after which all participants tested positive except for her, according to the Guardian.

"I think I was intentionally exposed to the positive case about four times," said the 22-year-old girl from the town of High Wycombe (England).

In March 2021, she participated in a world-first experiment: scientists injected a live SARS-CoV-2 virus into her nose and sealed it for several hours, in a deliberate attempt to infect her. infected with Covid-19. However, her body still successfully resisted the invasion of the virus.

Scientists find a way to solve the mystery: Why are some people not infected with Covid-19?

Ms. Phoebe Garret has been exposed to many F0 but still not infected with Covid-19 - (Image: THE OBSERVER)

Prevent infection in the first place

Ms. Garrett is not the only one taking part in the trial. Of the 34 people tested for exposure to the SARS-CoV-2 virus, 16 were not infected. About half of them tested positive for low levels of the virus, usually a few days after exposure.

It is possible that this is a reflection of the immune system quickly stopping the infection from entering in the first place. Professor Christopher Chiu at Imperial College London, who led the study, said: "In previous studies with other viruses, we have seen if the SARS-CoV-2 virus is destroyed in the mucosa. nasal mucosa, they will be disabled for pathogenicity".

Other studies have also shown that it is possible to eliminate the SARS-CoV-2 virus in the early stages of entering the body, before it finds a suitable place to stay.

During the first wave of the pandemic, for example, Dr Leo Swadling at University College London and colleagues closely monitored a group of healthcare workers who had frequent contact with infected patients. They found that only about 15% of employees had T cells that responded to the SARS-CoV-2 virus, plus other signs of viral infection.

It is possible that memory T cells from previous coronavirus infections - the cells that cause the common cold - cross-react with the new coronavirus and protect them from Covid-19.

Seasonal flu corona virus forms a buffer

Seasonal coronaviruses may not be the only source of cross-protective immune responses.

Professor Cecilia Söderberg-Nauclér, an immunologist at the Karolinska Institutet in Stockholm, began investigating this possibility, after Sweden avoided a massive Covid-19 infection.

Her team searched databases of protein sequences from existing viruses. When they identified a 6-amino acid peptide in an H1N1 flu protein that matched a key part of the coronavirus spike protein, "I almost fell out of my chair," says Söderberg-Nauclér. Peptides are short chains of amino acids linked together.

Since then, they have detected antibodies to this peptide in 68% of blood donors from Stockholm. Research may suggest that the immune responses caused by H1N1 flu - the cause of the 2009-2010 swine flu pandemic - may be related to subsequent strains of the virus. It is this response that partially protects humans, though incomplete, against Covid-19.

"It provides a cushion, but it won't protect you if an infected person coughs in your face," says Ms. Söderberg-Nauclér.

Resistance to Covid-19 thanks to genetics

A small number of people may even be genetically resistant to Covid-19.

In October last year, an international team of researchers launched a global hunt to find some people with this resistance gene, in the hope of identifying protective genes.

"We are looking for very rare gene variants that are able to completely protect a person against infection," said Professor András Spaan at Rockefeller University in New York.

They are especially concerned about people who live in the same house and sleep in the same bed as someone who is infected and not infected.

"For example, one day I was talking to an elderly woman from the Netherlands who was taking care of her husband who was infected in the first wave and was not wearing a mask. We could not explain why. She's not infected."

Such resistance is known to exist to other diseases, including HIV, malaria and norovirus (common and highly contagious viruses that cause diarrhea and vomiting). In these cases, the genetic defect means that some people lack the receptors used by the pathogen to enter cells, so they cannot become infected.

The identification of such genes could lead to the development of new treatments for Covid-19, in the same way that identification of CCR5 receptor defects in HIV-resistant individuals has led to HIV treatments. new.