Groundbreaking research, published in Nature in April 2023, reveals why certain individuals remain COVID-19-proof despite exposure, attributing it to subdued and rapid immunological responses observed in asymptomatic cases.
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Researchers now know why some individuals never get infected with COVID-19, even after being exposed to it in their nasal cavities.
These individuals have more subdued and quicker immunological responses than those who experience symptoms of COVID-19, per a recent study.
“These findings shed new light on the crucial early events that either allow the virus to take hold or rapidly clear it before symptoms develop,” stated in the press release Dr. Marko Nikolić, senior author of the research and honorary consultant in respiratory medicine at University College London.
Researchers from the UK and the Netherlands conducted a human challenge study that was published in Nature on Wednesday. It is the first of its kind in which the virus that causes COVID-19, SARS-CoV-2, was purposefully exposed to participants.
For the study, 16 young, healthy volunteers under 30 were gathered by the researchers. None of them had comorbid conditions, nor had they ever received a COVID-19 vaccination or infection.
April 2023 saw the release of an online preprint of the paper before peer assessment.
3 Different Immune Responses
The 16 people were grouped based on how each of them reacted to the viral exposure.
There were six symptomatic individuals in the first group. They were classified as having infections by the study’s authors.
Despite not having any symptoms, the individuals in the second group had positive COVID-19 PCR results. It was determined that these individuals had only temporary infections.
The third group of individuals consistently had negative COVID-19 PCR test findings and showed no symptoms. Although the illnesses were identified as “abortive,” the authors attested to the fact that these individuals were infected and quickly recovered from them.
The authors report that the immune responses were either faster or more subtle in the second and third groups of people with asymptomatic COVID-19.
In the asymptomatic groups, the scientists observed immune cells migrating to the nose—the site of infection—on Day 1.
Nonetheless, the COVID-19-positive group recruited all immune cell types, whereas those who tested negative for the virus recruited fewer immune cell types.
Individuals who experienced long-term COVID-19 infections exhibited slower and more organized immune reactions. Rather than on Day 1, these individuals had all kinds of immune cells entering their noses on Day 5.
Genetic Factors
According to the scientists, those who express particular genes, including HLA-DQA2, highly “are better at preventing the onset of a sustained viral infection.”
Studies have demonstrated a correlation between milder COVID-19 development and elevated blood levels of HLA-DQA2.
Among the many human leukocyte antigen (HLA) genes is HLA-DQA2. Proteins that are seen on the cell surface are made by HLA genes. HLA proteins alert immune cells to the presence of pathogen infection in cells.
According to the scientists, their data validate that HLA-DQA2 activation inhibits the spread of the SARS-CoV-2 virus in infected cells.
Symptomatic People Had Systematic Responses
Individuals with COVID-19 symptoms were the only ones who showed consistent interferon responses. immunological system messengers called interferons can either increase or decrease inflammatory and immunological responses.
The discovery that interferons in the blood activated before those at the infection site shocked the authors. Day 3 of the infection marked the peak of interferon activity in the blood, while Day 5 of the infection showed no evidence of interferon activity at the infection site, which is the nose.
According to the authors’ news release, the virus may have spread swiftly because of the nose’s sluggish immune responses.
Asymptomatic people hardly ever had infected cells and did not experience systemic interferon reactions.
The scientists noted that “infected cells were almost exclusively found” in the nasal cavities of those who had symptoms, which is not surprising. The SARS-CoV-2 virus is produced by the cells lining the nasal canals of participants, which increases the viral burden.
“We now have a much greater understanding of the full range of immune responses, which could provide a basis for developing potential treatments and vaccines that mimic these natural protective responses,” stated Dr. Nikolić.
Recently, GreatGameIndia reported that according to a new study published in PLOS ONE, which analyzed survey data from the UK Office for National Statistics, masks were found to be ineffective after the first Omicron wave.
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