Discovery: Lingering COVID-19 in Lungs Beyond Initial Recovery

Recent research has uncovered that the SARS-CoV-2 virus, responsible for COVID-19, can persist in the lungs for as long as 18 months after initial infection. This contradicts the common belief that the virus becomes undetectable following initial recovery. The study, which draws parallels to HIV’s viral reservoirs, underlines a compromised innate immune system’s role in this prolonged presence. Particularly, the study points to the significance of NK cells in managing these reservoirs. This finding is pivotal in comprehending the phenomena of long COVID and viral persistence mechanisms.

Groundbreaking Research on SARS-CoV-2 Longevity in Lungs

Typically, SARS-CoV-2 becomes undetectable in the upper respiratory tract within a week or two post-infection. However, this does not necessarily imply its complete absence from the body. Researchers from the Institut Pasteur, experts in HIV, and the CEA, a French public research institute, undertook a study using lung cells in an animal model. Published in Nature Immunology, their findings indicate that SARS-CoV-2 can remain in the lungs for up to 18 months post-infection due to innate immunity failure.

Unveiling Viral Reservoirs in COVID-19

Many viruses can persist in the body in an undetectable, latent state post-infection, forming ‘viral reservoirs,’ as seen in HIV. The 2021 hypothesis from the Institut Pasteur’s team about SARS-CoV-2 forming similar reservoirs has now been confirmed in a preclinical non-human primate model.

Michaela Müller-Trutwin, the Head of the HIV, Inflammation, and Persistence Unit at the Institut Pasteur, observed prolonged inflammation in primates infected with SARS-CoV-2, suggesting the virus’s continued presence.

Key Findings of the Study

The Institut Pasteur and the CEA’s IDMIT center analyzed samples from animal models infected with the virus. They found SARS-CoV-2 in the lungs of some subjects 6 to 18 months after infection, even when undetectable in the upper respiratory tract or blood. Notably, the Omicron variant showed lower lung persistence than the original strain.

Nicolas Huot, the study’s lead author, expressed surprise at finding the virus in alveolar macrophages long after infection, despite negative PCR tests. They also discovered that these viruses could still replicate.

The Role of Innate Immunity

The study then focused on NK cells, a crucial element of innate immunity, largely unexplored in SARS-CoV-2 infections. They found that macrophages infected with SARS-CoV-2 in some animals resisted destruction by NK cells, while in others, NK cells adapted and eliminated the resistant macrophages.

This research illuminates a potential mechanism for viral reservoirs: individuals with minimal or no long-term virus exhibited adaptive NK cell production, whereas those with higher virus levels showed reduced NK cell activity and no adaptive NK cells. This suggests a significant role for innate immunity in controlling persistent SARS-CoV-2.

Future Research Prospects

The team plans to study a cohort infected with SARS-CoV-2 at the pandemic’s onset to investigate the connection between identified viral reservoirs and long COVID cases. This research represents a significant step in understanding viral reservoirs and the regulatory mechanisms of viral persistence.

Reference: Nature Immunology, 2 November 2023, DOI: 10.1038/s41590-023-01661-4. The study was mainly funded by a family of major donors under the COVID Research Program.

Frequently Asked Questions (FAQs) about COVID-19 Persistence

More about COVID-19 Persistence

• Nature Immunology Study on SARS-CoV-2 Persistence
• Institut Pasteur’s Research on COVID-19
• Understanding Long COVID: Insights from Recent Studies
• Role of Innate Immunity in Viral Infections
• NK Cells and Viral Control: A Deep Dive
• Exploring Viral Reservoirs: From HIV to COVID-19
• COVID-19 Research Funding and Contributions