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Authors:Zeng et al.  

Journal/ Pre-Print:Medxriv 

Tags: Immunology/Immunity, Senescence 

Research Highlights

  1. Increasing age correlates with a decrease in T cell lymphocyte subsets but expansion of NK cells, as seen in other senescence studies.  

  1. Loss of expansion of CD8 T cells correlates with fatality in COVID-19 patients. 

  1. The loss of the capacity to expand can be recovered in vitro. 

Summary  

Zeng et al. correlate senescence of the immune system with fatality in COVID-19 patients in a retrospective study. As previously described, different lymphocyte subsets decline with age except for NK cells which appear to increase in healthy individuals. In fatal COVID-19 cases, there was a loss of expansion of SARS-CoV-2-specific immunity. However, that capacity could be restored in vitro. The results also suggest that IFNγ+CD8+ T cell expansion capacity as well as humoral immune responses correlate with patient survival time.   

Impact for SARS-CoV2/COVID19 research efforts  

Understand the immune response to SARS-CoV2/COVID19 correlated with senescence of the immune system.  

Study Type  

  • In vitro and ex vivo study 

Strengths and limitations of the paper 

Novelty: The authors correlate key factors during senescence to fatality in SARS-CoV-2 

Standing in the field:The results are in line with literature from immune senescence 

Appropriate statistics: Yes although correlations are very poor 

Viral model used:Samples from patients 

Translatability:Although the paper does not aim for translatability, an ex vivo expansion of the SARS-CoV-2-specific T cells could be derived from this study in older patients 

Main limitations:  

  • Many correlations are very poor (R values near 0) yet are described as being strong correlations. Therefore many conclusions are not valid.  

  • The authors base their results on the survival time of the patients, but not on other specific parameters of the severity of the disease. To evaluate and compare the response based on different degrees of severity of the disease would be more informative than just taking fatal cases.  

  • The results describe what it is known for senescence of the immune system and correlate it with disease severity, that it is also described to be correlated with fatality. However, there is not a comprehensive analysis to compare non-fatal cases with fatal cases in their immune senescence. 

  • The graphs for T cell expansion are mixed for the different weeks after symptoms onset, it would be clearer to have them separately.  

  • The authors could explore if NK cells that are found expanded with age in healthy individuals are also expanding in fatal COVID patients.  

  • The paper is poorly written.