The Transcriptional Differences of Avian CD4+CD8+ Double-Positive T Cells and CD8+ T Cells From Peripheral Blood of ALV-J Infected Chickens Revealed by Smart-Seq2

It is well known that chicken CD8(+) T cell response is vital to clearing viral infections. However, the differences between T cell subsets expressing CD8 receptors in chicken peripheral blood mononuclear cells (PBMCs) have not been compared. Herein, we used Smart-Seq2 scRNA-seq technology to characterize the difference of chicken CD8(high+), CD8(high) alpha alpha(+), CD8(high) alpha beta(+), CD8(medium+), and CD4(+)CD8(low+) T cell subsets from PBMCs of avian leukosis virus subgroup J (ALV-J)-infected chickens. Weighted gene co-expression network analysis (WGCNA) and Trend analysis revealed that genes enriched in the Cytokine-cytokine receptor interaction pathway were most highly expressed in the CD8(high) alpha alpha(+) T cell population, especially T cell activation or response-related genes including CD40LG, IL2RA, IL2RB, IL17A, IL1R1, TNFRSF25, and TNFRSF11, suggesting that CD8(high) alpha alpha(+) T cells rather than other CD8 subpopulations were more responsive to ALV-J infections. On the other hand, genes involved in the FoxO signaling pathway and TGF-beta signaling pathway were most highly expressed in the CD4(+)CD8(low+) (CD8(low+)) T cell population and the function of CD4(+)CD8(low+) T cells may play roles in negatively regulating the functions of T cells based on the high expression of CCND1, ROCK1, FOXO1, FOXO3, TNFRSF18, and TNFRSF21. The selected gene expressions in CD8(+) T cells and CD4(+)CD8(low+) double-positive T cells confirmed by qRT-PCR matched the Smart-Seq2 data, indicating the reliability of the smart-seq results. The high expressions of Granzyme K, Granzyme A, and CCL5 indicated the positive response of CD8(+) T cells. Conversely, CD4(+)CD8(+) T cells may have the suppressor activity based on the low expression of activation molecules but high expression of T cell activity suppressor genes. These findings verified the heterogeneity and transcriptional differences of T cells expressing CD8 receptors in chicken PBMCs.

Automated summary

This study characterized the differences in CD8 and CD4(+)CD8 low T cell subsets from chickens infected with avian leukosis virus subgroup J (ALV-J) using RNA sequencing technology, finding that CD8(high) alpha alpha(+) T cells had the highest expression of genes in the cytokine-cytokine receptor interaction pathway, suggesting they were more responsive to ALV-J infections. Conversely, CD4(+)CD8(low+) T cells may play a role in negatively regulating T cell functions.