Expansion of SARS-CoV-2-specific Antibody-secreting Cells and Generation of Neutralizing Antibodies in Hospitalized COVID-19 Patients

Authors: Renata Varnaitė et al.

Link to paper: https://www.biorxiv.org/content/10.1101/2020.05.28.118729v1.full.pdf

Journal/ Pre-Print: bioRxiv

Tags: Clinical, Immunology/Immunity

Research Highlights

1. IgA, IgG, and IgM ASCs are increased in Covid-19 PBMCs relative to healthy controls.

2. Spike-specific IgA and IgG titres correlate with neutralisation capacity.

3. Increased frequency of activated CD8+ T cells in Covid-19 patients relative to healthy controls.

Summary 

The study investigates the isotype and neutralising capacity of ASCs isolated from 20 Covid19 patients. They found a significant increase in the number of IgA+, IgG+ and IgM+ ASCs in patients compared to healthy controls. Antibody neutralising titres correlated significantly with S1-specific IgA and IgG titres, while there was only a mild correlation with N-specific IgM+ titres. Patients also had significantly increased frequencies of activated CD8+ T cells and CD4+ T cells. 

Impact for SARS-CoV2/COVID19 research

Understand the immune response to SARS-CoV2/COVID19: the findings contribute towards our understanding of a humoral response mounted against SARS-CoV-2.

Study Type

· In vitro study

· Patient Case study

Strengths and limitations of the paper

Novelty: Very limited novelty. They demonstrate increase in the frequency of activated CD8+ T cells suggesting they might be relevant for the antiviral response to SARS-CoV-2.

Standing in the field: The findings are not controversial.

Appropriate statistics: Yes.

Viral model used: Live virus (SARS-CoV-2/human/SWE/01/2020)

Translatability: Limited translatability. 

Main limitations:

- They looked only at total rather than SARS-CoV-2-specific CD8+ T cells.

- Their data regarding the severity of the symptoms, duration of hospitalisation, and time from symptom onset to discharge indicate variable disease severity between patients. It would have been useful if it was also correlated with their antibody titre and cell data.

- The control group was very small (7 people) and the median age – 31, compared to 53 years for the patients.

- The authors suggest that IgG is the dominant ASC isotype during response to SARS-CoV-2 infection based on total ASC data, however the relevance of this finding is not clear, as the N-specific response had similar frequencies of IgA, IgM and IgG (Figure 1.I).