PREreview del Pre-Omicron Immunity Generates IgG⁺ but Not IgA⁺ Memory B Cells Reactive to Omicron Spike Protein

Summary/Abstract:

A 2025 longitudinal cohort study analyzes the presence of IgG+ and IgA after COVID injection (administration of treatment). This study analyzed 18 patients over the course of three months, dissecting their results based on the patient’s continence, their blood work data, and PCR analysis of Omicron resistance within each patient.  The study primarily collected blood samples from folks after they have received their third dose of the BNT162b2 vaccine, a specified sample of the COVID vaccine. Using flow cytometry and B cell receptor sequencing, the spike protein B cells were examined thoroughly.   Findings show that the frequency of Omicron reactive IgA+ B cells were lower than that of the Lineage A reactive cells, whereas Omicron reaction IgG+ memory B cells were more frequent.  These responses were predominantly localized in classical memory and double negative DNA subsets. Findings demonstrate that memory B cells after baseline infection and immune response from previous injection in patient’s vaccine history were primed for antigenic recognition despite Omicron’s diverse genetic makeup.   There was low measurable IgA+ antigen, which explained some patients' prolonged symptoms of COVID, proving baseline injection may not be the “end all, be all” for Omicron resistance. 

Introduction

• Establishes a clear understanding of Lineage A vs. Omicron variant genetic diversity: (pg 2 → “Omicron has 37 amino acid substitutions in the S protein, 15 of which are in the receptor binding domain (RBD), compared to Lineage A”.

• Does not clearly state the premise of the experiment, rather, explains the differences between Lineage A of COVID strain and Omicron respectively.

• Rather than establishing a connection to their ongoing measure of antigens in patients, they have proposed a treatment for Omicron resistant patients before the premise of the experiment was introduced  (pg. 2 → “Despite this reported reduction in cross-protection by serum neutralising antibodies, research has shown that two or three-dose vaccination still protected individuals infected with Omicron against severe disease and hospitalisation, although protection against infection and transmission was reduced”. 

• Introduction effectively concludes on which antibody was the most present in infected patients using serological and multi-parameter flow cytometry assays, determining IgG+ was consistent and present within patients 

Methods

• Serological and multi-parameter flow cytometry assays → Serological responses to Omicron are present, but reduced, following vaccination with or without non-Omicron infection

• Eighteen vaccinated workers were part of the study, with 12 having been previously vaccinated with 6 having not. The sample size is too small to determine consistent antigen presence in comparison to a larger population.

• Upon testing, the Lineage A vaccine did little to none in providing Omicron resistant immunity antigens, while Lineage A antigens were still present in the vaccine itself.

  • Analysis of serum antibody responses showed a general trend towards lower neutralisation potency to the Omicron variant.

• There were no explicit methods mentioned other than blood testing of each patient halfway through cohort study in order to establish a clear study metric.

• The reader can assume that PCR analysis was conducted when authors discussed this finding on pg 3 → (Having shown in the previous analysis that the frequency of Omicron spike-reactive IgA+ B cells is lower than IgG+ B-cells, we determined if there were differences in the frequency of non-classical ‘double-negative’ (DN) memory and classical (germinal centre) memory IgG+ and IgA+ B-cells reactive to Lineage A and Omicron trimeric spike)

Results

• Omicron-reactive B cells in Omicron-naive donors vaccinated against Lineage A are somatically hyper-mutated and class-switched, meaning that there is limited resistance or immune response overall with Lineage A against Omicron receptor

• Fig 4 – demonstrated that there was effective response from Lineage A to fight COVID infection, but on specified strains, there was sporadic data collected. Frequency of IgG+ B cells are consistently reactive with Lineage A vaccine while Omicron was sensitive sporadically.

• In the results, the authors clarified that they have indeed used PCR analysis to analyze the B cell receptor behavior on pg. 4 → “From the donor samples, 13-154 B cells from 5 donors were sorted by binding to Lineage A or Omicron trimerized-spikes, amplified using PCR targeting the V-genes and the constant regions for IgG and IgA, and sequenced using Illumina 2x250bp paired-end next-generation sequencing to produce a repertoire of B cell receptor (BCR) sequences”

• Overall, there was an absence of IgA, but IgG+ antigen was consistently present in all patients.

Discussion

• A clear conclusion that individuals previously vaccinated with Lineage A vaccine had an effective immune response against SARS COV-2 with the increased IgG+ antigen and memory B cell, but no increased IgA antigen or presence whatsoever

• For the study to be effective, titers for antibody detection or an effective framework for what is studied will be sufficient for the reader to understand the premise.

• PCR amplification was discussed very briefly, but never to support the antigen presence. Rather, only to add methods to create a more trustworthy study rather than measuring antigen.

• Suggestions would be to use one relevant method, and specifically center the study around antigen presence instead of an overview of Omicron resistance in patients.

Competing interests

The authors declare that they have no competing interests.

Use of Artificial Intelligence (AI)

The authors declare that they did not use generative AI to come up with new ideas for their review.