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Front Immunol
. 2026 Mar 10:17:1794103.
doi: 10.3389/fimmu.2026.1794103. eCollection 2026.
Imbalanced immune cell network and suboptimal cell activation: signatures associated with disease severity in vaccine-naïve COVID-19 patients
Ranferi Ocaña-Guzman 1 , Elvira Piten-Isidro 2 , Julio Flores-Gonzalez 1 , Lucero A Ramon-Luing 1 , Perla M Del Rio-Estrada 2 3 , Ramcés Falfán-Valencia 4 , Gloria Pérez-Rubio 1 , Ivette Buendia-Roldan 5 , Moisés Selman 6 , Leslie Chavez-Galan 1
Affiliations
Background: COVID-19 vaccination has significantly reduced mortality and morbidity. Recent studies in unvaccinated people indicate a more complex immune response beyond just the cytokine storm. Understanding changes in the immune cell network is crucial for identifying vaccine-independent immune imbalances, especially in vaccine-naïve patients needing invasive mechanical ventilation (IMV). This knowledge could help improve vaccine development and find biomarkers linked to severe COVID-19.
Methods: Peripheral blood immune cells from vaccine-naïve COVID-19 patients from the first pandemic wave were classified into those who required IMV and those who did not (No-IMV). High-dimensional immune phenotyping was performed using multiparametric flow cytometry combined with FlowSOM clustering and UMAP for dimensionality reduction. Additionally, T-cell activation efficiency after polyclonal stimulation was evaluated in vitro.
Results: IMV patients, but not No-IMV, exhibited a marked disruption of immune cell networks, characterized by a loss of immune checkpoint (IC)-expressing T-cell subsets, particularly PD-1- and LAG-3-expressing T cells. Conversely, there was an increase in the frequency of T cells co-expressing molecules linked to inflammatory pathways (TNF/TNFR) and cell death (CD95L). These changes were also associated with reduced CD8+ T-cell activation capacity and the rise of non-conventional cytotoxic CD4+ T-cell subsets. In the B-cell compartment, IMV patients displayed depletion of CCR7+ subsets and decreased PD-1 expression. Additionally, higher frequencies of NK and NKT cells expressing TNF pathway-related molecules were observed. While classical monocyte subsets expressing ICs such as PD-L1, PD-L2, and TIM-3 remained stable, non-classical monocyte subsets showed altered IC expression. In contrast, No-IMV patients maintained a relatively balanced immune architecture.
Conclusions: Vaccine-naïve COVID-19 patients requiring IMV display an immune landscape distinct from that of No-IMV patients. IMV exhibits a profound imbalance in innate and adaptive immune cell networks, characterized by inflammatory skewing, loss of regulatory subsets, and impaired cytotoxic T-cell functionality, features not observed in No-IMV. These findings reveal coordinated immune alterations beyond cytokine hyperinflammation and identify cellular immune signatures associated with severe COVID-19.
Keywords: COVID-19; cell activation; immune cells; severity; vaccine-naïve.
. 2026 Mar 10:17:1794103.
doi: 10.3389/fimmu.2026.1794103. eCollection 2026.
Imbalanced immune cell network and suboptimal cell activation: signatures associated with disease severity in vaccine-naïve COVID-19 patients
Ranferi Ocaña-Guzman 1 , Elvira Piten-Isidro 2 , Julio Flores-Gonzalez 1 , Lucero A Ramon-Luing 1 , Perla M Del Rio-Estrada 2 3 , Ramcés Falfán-Valencia 4 , Gloria Pérez-Rubio 1 , Ivette Buendia-Roldan 5 , Moisés Selman 6 , Leslie Chavez-Galan 1
Affiliations
- PMID: 41884833
- PMCID: PMC13008623
- DOI: 10.3389/fimmu.2026.1794103
Background: COVID-19 vaccination has significantly reduced mortality and morbidity. Recent studies in unvaccinated people indicate a more complex immune response beyond just the cytokine storm. Understanding changes in the immune cell network is crucial for identifying vaccine-independent immune imbalances, especially in vaccine-naïve patients needing invasive mechanical ventilation (IMV). This knowledge could help improve vaccine development and find biomarkers linked to severe COVID-19.
Methods: Peripheral blood immune cells from vaccine-naïve COVID-19 patients from the first pandemic wave were classified into those who required IMV and those who did not (No-IMV). High-dimensional immune phenotyping was performed using multiparametric flow cytometry combined with FlowSOM clustering and UMAP for dimensionality reduction. Additionally, T-cell activation efficiency after polyclonal stimulation was evaluated in vitro.
Results: IMV patients, but not No-IMV, exhibited a marked disruption of immune cell networks, characterized by a loss of immune checkpoint (IC)-expressing T-cell subsets, particularly PD-1- and LAG-3-expressing T cells. Conversely, there was an increase in the frequency of T cells co-expressing molecules linked to inflammatory pathways (TNF/TNFR) and cell death (CD95L). These changes were also associated with reduced CD8+ T-cell activation capacity and the rise of non-conventional cytotoxic CD4+ T-cell subsets. In the B-cell compartment, IMV patients displayed depletion of CCR7+ subsets and decreased PD-1 expression. Additionally, higher frequencies of NK and NKT cells expressing TNF pathway-related molecules were observed. While classical monocyte subsets expressing ICs such as PD-L1, PD-L2, and TIM-3 remained stable, non-classical monocyte subsets showed altered IC expression. In contrast, No-IMV patients maintained a relatively balanced immune architecture.
Conclusions: Vaccine-naïve COVID-19 patients requiring IMV display an immune landscape distinct from that of No-IMV patients. IMV exhibits a profound imbalance in innate and adaptive immune cell networks, characterized by inflammatory skewing, loss of regulatory subsets, and impaired cytotoxic T-cell functionality, features not observed in No-IMV. These findings reveal coordinated immune alterations beyond cytokine hyperinflammation and identify cellular immune signatures associated with severe COVID-19.
Keywords: COVID-19; cell activation; immune cells; severity; vaccine-naïve.