Austrian study warns that COVID-19 causes depletion of key innate and adaptive immune cells

Immunology Updates: A recent study conducted by researchers from Medical University of Vienna-Austria has unveiled alarming findings regarding the long-term effects of COVID-19 on the human immune system. The research, which was conducted at the Center for Pathophysiology, Infectiology, and Immunology, demonstrates that COVID-19 not only triggers immediate immune responses but also leads to significant depletion of critical innate and adaptive immune cells over time. This discovery highlights the potential long-term consequences of even mild cases of SARS-CoV-2 infections.


Austrian study warns that COVID-19 causes depletion of key innate and adaptive immune cells

Understanding the Long-Term Impact of COVID-19
The study, led by Dr Bernhard Kratzer and Dr Pia Gattinger under the guidance of principal investigators Dr Rudolf Valenta and Dr Winfried Pickl, involved an in-depth analysis of immune parameters in 133 individuals who had recovered from COVID-19. These subjects were compared to 98 individuals who had not contracted the virus. The research aimed to investigate the number and composition of various immune cells, cytokines, and growth factors in the blood, which play a crucial role in regulating cell growth and immune responses. This Immunology Updates news report will delve into the study’s findings and their implications for the long-term health of COVID-19 survivors.
 
The participants were monitored at two critical time points: ten weeks and ten months after their initial infection. Importantly, the study took place in 2020, a time when COVID-19 vaccines were not yet available. This allowed the researchers to observe the long-term effects of SARS-CoV-2 infection without the influence of vaccination.
 
Depletion of Immune Cells: A Concerning Discovery
As expected, the researchers found signs of immune activation in both T and B cells ten weeks after infection. These immune responses were typical of the body's attempt to fight off the virus. However, what surprised the team was the significant depletion of immune cells observed ten months after recovery. Even individuals who had experienced only mild symptoms showed a marked reduction in the number of immune cells in their blood. This included a decrease in key cells responsible for maintaining immunity against new infections.
 
The study also noted a notable decline in SARS-CoV-2-specific antibodies, along with a shift in the patterns of growth factors in the blood. These changes suggest that the immune system of COVID-19 survivors may be less capable of responding effectively to new threats. This depletion of immune cells could help explain the persistence of symptoms seen in Long COVID patients, where individuals experience a range of health issues long after their initial recovery.
 
The key immune cells of the innate and adaptive immune systems that are significantly depleted following a SARS-CoV-2 infection, as identified in the study, include granulocytes, monocytes, and lymphocytes, which encompass T cells (both CD4+ helper T cells an d CD8+ cytotoxic T cells), B cells (including non-class-switched memory B cells and plasmablasts), and natural killer (NK) cells. Particularly, the study observed a marked reduction in recent thymic emigrant (RTE) T cells and non-class-switched memory B cells, alongside a decrease in overall neutrophil, monocyte, and NK cell counts.
 
The Role of Bone Marrow and Immune Cell Production
The researchers hypothesize that the long-term effects of COVID-19 might be linked to damage to the bone marrow, the primary site for the production of immune cells. According to Dr Rudolf Valenta and Dr Winfried Pickl, "Our results provide a possible explanation that certain long-term consequences of COVID-19 could be related to the damage to the cellular immune system caused by SARS-CoV-2 and the apparently reduced maturation and/or emigration of immune cells from the bone marrow."
 
This finding suggests that SARS-CoV-2 may have a more profound and lasting impact on the body's ability to produce immune cells than previously understood. The study's authors believe that this damage to the immune system could underlie many of the long-term health issues observed in COVID-19 survivors, including fatigue, neurological symptoms, and increased susceptibility to other infections.
 
A Shift in Immune Response: From Th1 to Th2 Dominance
One of the most striking findings of the study was the shift in the immune system's response from a Th1 (inflammatory) to a Th2 (anti-inflammatory) dominance over time. Th1 responses are typically associated with the body's defense against viruses and other pathogens, while Th2 responses are more involved in allergic reactions and the regulation of immune responses.
 
Ten months after infection, the researchers observed that the immune system of COVID-19 survivors had shifted towards a Th2-dominated response. This was evidenced by increased levels of Th2-associated cytokines such as IL-4 and IL-10, along with a significant decrease in Th1-associated cytokines like IFN-γ. This shift could potentially lead to a weakened ability to combat new infections and might contribute to the persistence of symptoms in Long COVID patients.
 
Implications for Long COVID and Future Research
The findings of this study have significant implications for our understanding of Long COVID. The depletion of key immune cells and the shift in immune response suggest that COVID-19 survivors may be at a higher risk of developing long-term health issues. These could include chronic fatigue, cognitive problems, and a reduced ability to fight off new infections.
 
The study's authors emphasize the need for further research to explore the mechanisms behind these long-term effects and to develop strategies for mitigating them. They propose that the damage to the immune system caused by SARS-CoV-2 could be a key factor in the development of Long COVID, and understanding this process is crucial for improving patient outcomes.
 
Conclusion: A Call for Continued Vigilance
The study conducted by MedUni Vienna underscores the importance of understanding the long-term effects of COVID-19 on the immune system. Even mild cases of the virus can lead to significant depletion of immune cells, potentially compromising the body's ability to respond to new infections. The shift from a Th1 to a Th2-dominated immune response further complicates the picture, suggesting that COVID-19 survivors may face ongoing health challenges.
These findings highlight the need for continued vigilance in monitoring and supporting the health of COVID-19 survivors. As the world continues to grapple with the pandemic, understanding and addressing the long-term consequences of the virus will be crucial in managing its impact on global health.
 
The study findings were published in the peer-reviewed journal: Allergy (A European Journal of Allergy and Clinical Immunology).
https://onlinelibrary.wiley.com/doi/10.1111/all.16210
 
For the latest Immunology Updates, keep on logging to Thailand Medical News.
 
Read Also:
https://www.thailandmedical.news/news/autopsy-study-validates-that-sars-cov-2-causes-immune-dysregulation

https://www.thailandmedical.news/news/american-researchers-claim-that-immune-downmodulation-contributes-to-long-covid-and-that-treatment-with-leronlimab-helps