SARS-CoV-2 specific memory B-cells from individuals with diverse disease severities recognize SARS-CoV-2 variants of concern

Abstract

In this investigation we examined the magnitude, breadth, and durability of SARS-CoV-2 specific antibodies in two distinct B-cell compartments: long-lived plasma cell-derived antibodies in the plasma, and peripheral memory B-cells along with their associated antibody profiles elicited after in vitro stimulation. We found that magnitude varied amongst individuals, but was the highest in hospitalized subjects. Variants of concern (VoC) -RBD-reactive antibodies were found in the plasma of 72% of samples in this investigation, and VoC-RBD-reactive memory B-cells were found in all but 1 subject at a single time-point. This finding, that VoC-RBD-reactive MBCs are present in the peripheral blood of all subjects including those that experienced asymptomatic or mild disease, provides a reason for optimism regarding the capacity of vaccination, prior infection, and/or both, to limit disease severity and transmission of variants of concern as they continue to arise and circulate.

Figure 1:

Plasma antibody titers overtime and stratified by disease severity A) Plasma ELISA titers for pre-2020 plasma (black n=6), asymptomatic (blue n=2), non-hospitalized green (n=16), and hospitalized red (n=6). Subjects who were vaccinated between sample collection are boxed out in both panels and were excluded from all statistical and data analysis. Geometric mean titers (GMT) are listed above each group. B) Comparison between ELISA titers against RBD-WA1 and VoC-RBD. Samples from subjects who received a vaccination prior to the second draw were excluded from the data analysis. Paired t-test was performed indicating significant differences between the values (p-value 0.0004) significance denoted by ***.

Figure 2:

SARS-CoV-2 specific MBC frequency overtime and stratified by disease severity. A) MBC SARS CoV-2 specific frequency for pre-2020 plasma (black n=6), asymptomatic (blue n=2), non-hospitalized green (n=15), and hospitalized red (n=6). Subjects who were vaccinated between sample collection are boxed out in both panels and were excluded from all statistical and data analysis. Geometric mean titers (GMT) are listed above each group. B) Comparison between RBD-specific MBC frequency against WA1-RBD and VoC-RBD. T-test of log-transformed data, no statistically significant difference between WA-1 and VoC MBC Ab binding. Samples from subjects who had been vaccinated prior to blood draw were excluded from this analysis.

Figure 3:

The relationship between WA-1 RBD and VoC RBD antibody binding by ELISA, WA-1 RBD and VoC RBD MBC frequency as well as the relationship between LLPC derived antibody titers and MBC frequency for each antigen. A) Correlation between RBD-VoC specific ELISA titer and RBD-WA-1 specific ELISA titer. Dotted line indicates line of identity. Spearman correlation coefficient R²=0.877 p-value <0.0001. B) Correlation between RBD-VoC specific MBC frequency and RBD-WA-1 specific MBC frequency. Samples from subjects who received vaccination were excluded from this analysis. Dotted line indicates line of identity. Spearman correlation coefficient R²=0.885 p-value <0.0001. C) Correlation between WA-1 RBD MBC frequency and ELISA titer (R²=.346) and between VoC-RBD MBC frequency and ELISA titer (R²=.331).