Infection with the Omicron variant of the coronavirus could protect against the flu

Infection with the Omicron variant of the coronavirus could protect against the flu

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A new study by researchers at the University of Kent in the UK suggests that infection with the Omicron variant (or BA.1) of SARS-CoV-2 may offer some form of protection against seasonal flu. This variant would lead to sustained production of interferons that would protect cells from superinfection by influenza A viruses.

The first case of the Omicron variant was detected on 9 November 2021 in Botswana; On November 26, 2021, the World Health Organization classified it as a variant of concern. The mutation it carries makes it more contagious and resistant to immunity from vaccines; on the other hand, it is less likely to cause severe forms of COVID-19. It quickly gave rise to several sub-variants (designated BA.2 to BA.5) and currently in France we observe a significant increase in cases associated with sub-variants BA.4 and BA.5, a form of BA. to be dominant.

Disease severity has been shown to be largely dependent on virus-induced interferon signaling. However, recent results obtained in cell lines indicate that the BA.1 variant induces a stronger production of interferons than the Delta variant that preceded it. The team of researchers therefore decided to examine the replication of Delta, BA.1 and BA.5 viruses, comparing interferon signaling in each case and observing the impact of infection with one of its variants on the replication of another. the H1N1 virus.

More durable interferon response

Interferons are proteins produced naturally by cells of the immune system in response to the presence of a pathogenic agent in the body; they cause the formation of proteins with an antiviral (or antibacterial) effect. Their name comes from the fact that they interfere with virus replication. There are three types of interferons: two come from virus-infected cells, which release interferon molecules in small amounts to “warn” neighboring cells and thus prevent the virus from multiplying; the third type is produced by lymphocytes.

In their study, the researchers first infected primary human bronchial epithelial cells and primary human monocytes with Delta and BA.1 viruses. Cells treated with simple saline without any virus served as a control sample. As expected, BA.1 showed faster replication kinetics than Delta in cell cultures. Similarly, BA.1 elicited a stronger interferon response than Delta. ” Interferon-α/β peaked at 24 h post-infection followed by a return to baseline levels, while interferon-λ remained elevated up to 120 h post-infection ”, the researchers specify in their preprint article.

Short-term responses to type I interferon (α/β) elicit a protective antiviral response, whereas long-term activity of this interferon is associated with potentially harmful inflammation. In contrast, sustained responses to type III interferon (λ) inhibit respiratory virus replication at airway epithelial barriers and prevent excessive inflammation, the team explains. The type I and III interferon responses observed here therefore explain why Omicron was found to be less pathogenic than other SARS-CoV-2 variants.

A variant that prevents the influenza virus from replicating

The researchers then performed another experiment with the same cells; after two days, they were infected with the H1N1 virus — a subtype of the influenza A virus found in most cases of seasonal flu. The aim was to verify whether the interferon response induced by BA.1 can induce an antiviral state that interferes with H1N1 replication.

Levels of genomic RNA (left) or mRNA (right) of H1N1 influenza virus (IAV), 24 h after H1N1 infection. © D. Bojková et al.

A day later, they measured the H1N1 burden in all cell groups. They then found that cells previously infected with the Delta variant, like control cells, had very high viral loads (almost 10,000 times higher), indicating that the H1N1 virus replicated very rapidly. In contrast, they observed no increase in viral load in BA.1-infected cells. ” These results indicate that only BA.1, but not Delta, induces an interferon-mediated antiviral state in cultures [cellulaires] which protects them from H1N1 infection ” the scientists conclude.

A similar experiment performed with cells infected with the BA.5 variant showed similar interferon responses, producing the same effect: both Omicron subvariants suppressed the replication of the H1N1 virus.

These results fully reflect the infection rates observed during the pandemic. ” In England, Delta infection and influenza-like illness increased after all restrictions were lifted on 19 July 2021. However, when the BA.1 variant became the dominant variant, the number of ILIs dropped sharply and has not increased since. », the researchers underline in their article. Note that these patterns may also be due to people being more cautious today and protecting themselves from winter infections.

A better understanding of how different variants of SARS-CoV-2 trigger different immune responses can help researchers more quickly determine the impact of potential new variants. But be careful, as the authors of the study point out, these results in no way mean that it is useful to intentionally contract COVID-19 to protect yourself from the flu!

source: D. Bojková et al., bioRxiv

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