Broad phenotypic alterations and potential dysfunctions of lymphocytes in COVID-19 recovered individuals
Authors: Yang, et al., 2020
Journal/ Pre-Print: MedRxiv
Selective lymphopenia of CD4+ T cells in COVID-19 recovered individuals compared to healthy donors.
Alterations in subset make up of both CD8+ and CD4+ T cells of COVID-19 recovered individuals compared to healthy donors.
This study examines phenotypic alterations in lymphocytes of 55 COVID-19 recovered patients compared to 55 age matched healthy donors. With respect to overall frequency, CD8+ T cells and B cells were comparable, yet there was a significant decrease in CD4+ T cells in the recovered cohort. Interestingly, there were subset variations amongst CD8+ and CD4+ cells. This study is limited in that patients only donated one sample and therefore changes over time were not observed. Furthermore, there was a lack of analysis of functional variation of the different populations across the cohorts.
Impact for SARS-CoV2/COVID19 research efforts
Understand the immune response to SARS-CoV2/COVID19
Further strengthens the argument that there is an aberrant T cell response to SARS-CoV-2 infection relative to healthy donors.
This is particularly highlighted in the reduced number of Tcm cells in recovered patients compared to healthy donors.
Clinical Cohort study
Strengths and limitations of the paper
Standing in the field:Adds weight to the growing opinion that there is an aberrant lymphocyte response, particularly that of T cells, in response to SARS-CoV-2 infection.
Appropriate statistics: T-test used throughout despite no evidence that data sets are normally distributed. Some plots, particularly those in Fig 2, clearly show a skewed data set and therefore a non-parametric test would be more appropriate.
Viral model used:Patients who had recovered from SARS-CoV-2 infection.
Co-morbidities of recovered patients not shown, therefore donors may not be matched in this regard.
This study solely examined surface markers, or the expression of cytokines in a binary way. Single-cell gene expression studies of lymphocytes are likely to be more fruitful in examining how the phenotypic changes seen in lymphocytes of COVID-19 patients pertains to aberrant function.
Very heterogeneous responses within groups indicating that larger group sizes are needed to detect true significance. Also unclear what the biological significance is of some of the differences
Only percentages of populations shown, would have been useful to see absolute cell counts