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Updated: May 17, 2026
Adapting Gastrointestinal Organoids for Pathogen Infection and Single Cell Sequencing under Biosafety Level 3 (BSL-3) Conditions
Published on: September 10, 2021
Characterization of Mucosal BPI fold-containing family A member 1-High-Expressing Neutrophils and their Immune
Xue Bai1, Shixing Chen1, Shengxia Yin1
1Department of Infectious Diseases, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, Jiangsu, China.
Background:
With the viral variants and waning of vaccine-induced immunity over time, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) breakthrough infections have become the next challenge following the coronavirus disease 2019 pandemic, highlighting the need for broader and sustained immune responses. As the first defense against viral invasion, mucosal immunity is inducible by SARS-CoV-2 infection. Previous studies focused on serum antibodies and cellular immunity in those with acquired immunity, but the specific role of mucosal immunity in breakthrough infection remains to be elucidated.
Methods:
We performed single-cell RNA sequencing (scRNA-seq) on nasal swabs and peripheral blood mononuclear cells from a prospective cohort of breakthrough-infected individuals. Findings were validated with flow cytometry and enzyme-linked immunosorbent assay in a separate multicenter cohort. In vitro experiments using recombinant protein were conducted on the human monocytic leukemia cell line THP-1, as effector cells, to investigate underlying mechanisms.
Results:
Mucosal neutrophils showed the most significant dynamic changes in after infection. A unique subpopulation of high-BPI fold-containing family A member 1 (BPIFA1)-expressing (BPI+) neutrophils was identified and found to be positively correlated with neutralizing antibody and immunoglobulin G levels in the breakthrough patient (Pt) group. With scRNA-seq, cell communication analysis revealed enhanced interactions between BPI+ neutrophils and macrophages. In vitro, BPIFA1 stimulation activated the nuclear factor (NF)-κB pathway in THP-1 cells.
Conclusions:
BPI+ neutrophils in the respiratory mucosa are pivotal in driving immune responses during breakthrough infection in those with acquired immunity by modulating macrophage activity via the NF-κB pathway line. It may trigger the production of interleukin 6, the immunostimulatory phenotype necessary for B-cell engagement, to complete the innate-to-adaptive immunity relay, which highlights their potential as a target for novel mucosal vaccine strategies.
