June 13, 2024

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SARS-CoV-2 can persist in the lungs for up to 18 months after infection

Research reveals SARS-CoV-2 can persist in the lungs for up to 18 months after infection

Research reveals SARS-CoV-2 can persist in the lungs for up to 18 months after infection

A study has found that the SARS-CoV-2 virus can linger in the lungs for as long as 18 months after infection, raising questions about the assertion that the virus is undetectable after initial recovery. This prolonged presence is linked to the dysfunction of the innate immune system.

The research confirms the existence of a “viral reservoir” similar to the HIV virus and underscores the role of NK cells in controlling these viral reservoirs. This discovery is crucial for understanding Long-COVID and the mechanisms behind the continued presence of the virus.


Research reveals SARS-CoV-2 can persist in the lungs for up to 18 months after infection


A groundbreaking study reveals that due to the failure of the innate immune system, SARS-CoV-2 can lurk in the lungs for months, remaining undetected and potentially leading to Long-COVID.

Typically, two weeks after a COVID infection, the SARS-CoV-2 virus is no longer detectable in the upper respiratory tract. But does this mean the virus is no longer present in the body? To address this question, the Pasteur Institute’s HIV specialist group collaborated with the French public research institution, the Alternative Energies and Atomic Energy Commission (CEA), to study lung cells in animal models. The results, published in the journal “Nature Immunology,” indicate that SARS-CoV-2 not only persists in the lungs of some individuals for up to 18 months but also that this continued presence seems to be associated with the failure of the innate immune system.


Discovering Viral Reservoirs in COVID-19

Certain viruses can remain hidden and difficult to detect in the body after causing an infection, known as “viral reservoirs.” HIV is an example, remaining dormant in certain immune cells and capable of reactivation at any time. The virus responsible for COVID-19, SARS-CoV-2, may also exhibit this behavior. At least, this was a hypothesis proposed by a scientific team at the Pasteur Institute in 2021, and it has now been confirmed in preclinical models of non-human primates.

“We observed prolonged inflammation in non-human primates infected with SARS-CoV-2, leading us to suspect the presence of the virus in the body,” explained Michaela Müller-Trutwin, head of the HIV, Inflammation, and Persistence Research Group at the Pasteur Institute.


Study Findings on SARS-CoV-2 Persistence

To investigate the persistence of the SARS-CoV-2 virus, scientists at the Pasteur Institute collaborated with the CEA’s IDMIT (Infectious Disease Models for Innovative Therapies) center to analyze biological samples from animal models infected with the virus. Preliminary results of the study suggest that, despite the virus being undetectable in the upper respiratory tract or blood, some individuals had the virus in their lungs six to eighteen months after infection. Another notable finding is that the viral load of the Omicron variant, in individuals with persistent lung infection, is lower than that of the original SARS-CoV-2 strain.

Nicolas Huot, the lead author of the study and a researcher in the HIV, Inflammation, and Persistence Research Group at the Pasteur Institute, remarked, “We were surprised to find the virus in immune cells—alveolar macrophages—in some individuals after such a long period, while conventional PCR tests were negative. More importantly, we cultured these viruses and observed that they could still replicate using the tools we developed to study HIV.”

To understand the role of the innate immune system in controlling these viral reservoirs, scientists then turned their attention to NK (Natural Killer) cells. Michaela Müller-Trutwin stated, “Cellular responses of the innate immune system are the body’s first line of defense, but until now, there has been limited research on SARS-CoV-2 infection. However, it has long been known that NK cells play a crucial role in controlling viral infections. This study suggests that in some animal models with SARS-CoV-2 infection, alveolar macrophages show resistance to NK cell destruction, while in others, NK cells can adapt to the infection (known as adaptive NK cells) and destroy resistant cells, in this case, macrophages.”

Therefore, this study reveals a potential explanation for the existence of “viral reservoirs”: individuals with long-term or minimal virus infections may develop adaptive NK cells, while those with more extensive virus infections not only lack adaptive NK cells but also experience reduced NK cell activity. Thus, the innate immune system appears to play a role in controlling the persistent SARS-CoV-2 virus.

“We will begin studying individuals who were infected with SARS-CoV-2 at the beginning of the pandemic to determine whether the discovered viral reservoirs and mechanisms are related to long-term COVID cases,” said Michaela Müller-Trutwin. “But these results represent a significant step in understanding the nature of viral reservoirs and the mechanisms regulating the continued presence of the virus.”

Research reveals SARS-CoV-2 can persist in the lungs for up to 18 months after infection


“SARS-CoV-2 virus persistence in alveolar macrophages is controlled by IFN-γ and NK cells” by Nicolas Huot, Cyril Planchais, Pierre Rosenbaum, Vanessa Contreras, Beatrice Jacquelin, Caroline Petitdemange, Marie Lazzerini, Emma Beaumont, Aurelio Orta-Resendiz, Félix A. Rey, R. Keith Rey, Félix A. Rosenbaum. Rey, R. Keith Reeves, Roger Le Grand, Hugo Mouquet, and Michaela Müller-Trutwin, 2 November 2023, Nature Immunology.

DOI: 10.1038/s41590-023-01661-4

(source:internet, reference only)

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