Did he have Covid again? They find new clues about why some people are still free of infection

Four years of the pandemic, without knowing what the fever and discomfort of SARS-CoV-2 is, despite new strains appearing every year. Yes, there are some people who have ‘survived’ the new wave of Covid whose body ‘repels’ the action of the virusand then. However, at the other end of the spectrum are individuals in whom the disease is potentially fatal.

In between, the group that goes through it almost “without getting Covid”, with mild and manageable symptoms or almost without any symptoms, or even without testing positive in PCR tests. The scientific community investigates How is this seamless infection control achieved? And data from a study has recently been published that may help us understand this better.

An international team of researchers from the Wellcome Sanger Institute, University College London (UCL), Imperial College London and the Netherlands Cancer Institute, among other centres, has been in charge. The scientists analysed Molecular details

what happens in the The immune system of people who have never had Covid When the SARS-CoV-2 virus vaccine was administered.

in British studies The COVID-19 Human ChallengeThe SARS-CoV-2 virus was administered nasally by a team led by Imperial College London Healthy young adult volunteers with no history of Covid and that they were not vaccinated, nor did they have antibodies against the infection. Before the Alpha variant (the one that was prevalent in early 2021), very low doses of the original strain of SARS-CoV-2 were used.

Chronology of an ‘announced transition’

The researchers carried out detailed monitoring of blood and nasal lining throughout the infection, as well as the activity of immune cells before infection in 16 volunteers. Teams from the Wellcome Sanger Institute and UCL used single-cell sequencing to generate a data set of more than 600,000 individual cells.

Result are published in Nature and provide the most complete chronology to date of how the body responds to exposure to SARS-CoV-2, or any infectious disease. This work is part of the initiative human cell atlas For Map all cell types in the human body,

Ten of the 16 individuals cleared the virus immediately and did not show a typical generalized immune response, but instead activated subtle and previously unknown innate immune responses. The researchers suggest that a high level of activity of a gene called HLA-DQA2 before exposure also helped people avoid persistent infection.

The momentary, the meaningless and the permanent

Its Ten people did not develop persistent infectionThree developed a “transient” infection, characterized by intermittent positive viral tests in nasal swabs, and seven developed an infection the researchers call “abortive,” characterized by the absence of positive viral tests.

The other six volunteers developed persistent infections, which were associated with mild symptoms and were characterized by persistently positive viral results, evidenced by multiple tests.

It should be noted that, despite these differences in the outcomes of infection, tAll participants shared the same gene expression signature Regarding early activation of the innate immune response, including the transient loss of the activated version of monocytes and an increase in blood levels of mucosa-associated invariant T cells, which are immune cells that are also involved in innate immunity.

Marco NicoliThe lead author of the study at UCL said: “These findings shed new light on the critical early events that allow the virus to take hold or to be eliminated quickly before symptoms develop. Now We know the full range of immune responses betterThis could lay the groundwork for developing potential treatments and vaccines that mimic these natural protective responses.”

For other main authors and first signatories, Rick LindeboomFrom the Netherlands Cancer Institute, research has been done “a unique opportunity To see how immune responses are in adults without a history of COVID-19 when they encounter a new pathogen, in an environment where factors such as timing of infection and comorbidities can be controlled.

The secret of the immune response

In an article he goes hand in hand with studies in Nature, Benjamin Israel And Akiko IwasakiBoth of Yale University in New Haven, highlight that “controlled human infection models have long provided valuable information on human immunity and protection against disease-causing agents, and future plans with this model include testing intranasal vaccine candidates.”

The research now being published “represents a remarkable step forward in understanding the complexities of SARS-CoV-2 infection. By unraveling the mysteries of early immune responses, the study provides Promising avenues for future therapeutic research and development in the ongoing fight against COVID-19″.