Malaria remains a major global health burden, with repeated infections shaping host immunity in complex and incompletely understood ways1. CD4⁺ T cells play a central role in antimalarial immune responses by coordinating effector cytokine production, supporting B-cell help, and regulating inflammation2,3. During malaria reinfection, CD4⁺ T cells undergo dynamic transcriptional reprogramming, reflecting shifts among effector, regulatory, memory, proliferative, and exhausted states that influence both parasite control and immunopathology4,5. Accurately resolving this heterogeneity is essential for understanding immune protection, immune dysfunction, and the durability of naturally acquired or vaccine-induced immunity to Plasmodium infection. Here, we present a reproducible Seurat-based protocol to analyze CD4⁺ T-cell scRNA-seq data across malaria reinfection timepoints.
Single-cell RNA sequencing (scRNA-seq) enables high-resolution characterization of immune heterogeneity and has identified parasite-responsive CD4⁺ T-cell subsets, exhaustion programs, and regulatory networks in malaria6,7,8,9. However, analytical variability in quality control, normalization, clustering, and integration can limit reproducibility and complicate cross-study comparisons10,11. However, a standardized and biologically guided workflow specifically optimized for analyzing CD4⁺ T-cell dynamics during malaria reinfection is lacking.
Existing computational frameworks for scRNA-seq analysis, including Seurat and Scanpy, provide comprehensive toolsets for preprocessing, clustering, and downstream interpretation of single-cell data12,13,14. Seurat, implemented in R, offers tightly integrated workflows for normalization, data integration, and visualization, including variance-stabilizing approaches such as SCTransform that improve signal detection in heterogeneous immune datasets13. Scanpy, implemented in Python, provides scalable solutions optimized for large datasets and efficient memory usage, making it particularly suitable for high-throughput or cloud-based analyses12,14. Despite these advances, there remains a need for standardized, reproducible workflows that explicitly address biological questions in infection settings while maintaining transparency, adaptability, and consistency across datasets. The present protocol addresses this gap by combining the robustness of Seurat-based preprocessing with structured biological interpretation tailored to CD4⁺ T-cell responses during malaria reinfection. Compared to existing general-purpose workflows, this protocol emphasizes reproducibility, biologically informed parameter selection, and consistent cross-timepoint analysis tailored to infection models.
A key feature of this protocol is its emphasis on reproducibility and practical usability. Quality-control thresholds are not fixed but are derived using data-adaptive approaches based on median absolute deviation, allowing thresholds for transcript complexity, sequencing depth, and mitochondrial content to scale with dataset-specific distributions. This design makes the workflow applicable across datasets of varying sizes, typically ranging from several thousand to tens of thousands of cells, and across a wide range of sequencing depths commonly encountered in droplet-based scRNA-seq experiments. Guidance embedded within the workflow supports appropriate parameter selection for dimensionality reduction, clustering resolution, and integration, ensuring that analyses remain both biologically meaningful and technically robust. Nevertheless, the workflow depends on data quality and sequencing depth and may require adjustment for datasets with extreme sparsity or batch effects.
This protocol is designed for intermediate to advanced users with basic familiarity in R and single-cell analysis, while remaining accessible to motivated beginners through its structured, stepwise implementation and fully reproducible outputs. The workflow generates standardized tables and figures at each stage, including quality-control summaries, clustering outputs, differential expression results, and enrichment analyses, thereby facilitating transparency, validation, and reuse in collaborative or multi-study contexts. This protocol is particularly suitable for studies investigating immune heterogeneity across timepoints or conditions in infection and immunology research.
The method provides a reproducible, end-to-end Seurat-based workflow for CD4⁺ T-cell scRNA-seq analysis across malaria reinfection timepoints. It integrates adaptive quality control, variance stabilization, dimensional reduction, clustering, and multi-sample integration when appropriate13,15. To enhance biological interpretability, the workflow incorporates immune and CD4⁺ T-cell subset gene module scoring to quantify functional programs including Th1, Tfh, Tr1, Treg, central memory, effector memory, proliferation, cytotoxicity, and exhaustion16,17,18. Complementary cluster marker identification, timepoint differential expression analysis, and pathway enrichment using Gene Ontology and KEGG databases are included to support robust annotation and comparison of T-cell states19,20. Although demonstrated using publicly available Plasmodium scRNA-seq datasets, this protocol is broadly applicable to other malaria reinfection models and immunological perturbations where reproducible and interpretable single-cell analysis of CD4⁺ T cells is required. Overall, this protocol provides a reproducible and biologically interpretable framework for single-cell analysis of CD4⁺ T-cell responses, supporting robust investigation of immune dynamics in malaria and related systems.