Related Experiment Video
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
Single-cell RNA sequencing reveals mucosal BPIFA1-high-expressing neutrophils aid immune defense in SARS-CoV-2
Xue Bai1, Shixing Chen1, Shengxia Yin1
1Department of Infectious Diseases, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing 210008, Jiangsu, China.
Background:
With the viral variants and waning of vaccine-induced immunity over time, SARS-CoV-2 breakthrough infections have become the next challenge following the COVID-19 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 the acquired immune, 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 ELISA in a separate multicenter cohort. In vitro experiments using recombinant protein were conducted on the human monocytic leukemia cell THP-1, as effector cells, to investigate underlying mechanisms.
Results:
Mucosal neutrophils showed the most significant dynamic changes in post-infection. A unique subpopulation of high-BPIFA1-expressing (BPI+) neutrophils was identified and found to be positively correlated with neutralizing antibody and IgG levels in break-through patients (Pt) group.By scRNA-seq, cell communication analysis revealed enhanced interactions between BPI+ neutrophils and macrophages. In vitro, BPIFA1 stimulation activated the NF-κB pathway in THP-1 cells.
Conclusions:
BPI+ neutrophils in the respiratory mucosa are pivotal in driving immune responses during breakthrough infection by modulating macrophage activity via the NF-κB pathway. 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.
