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.

Manman Dai,Sufang Zhu,Li Zhao,Bowen You,Xiaobo Li,Ziwei Li,Ming Liao

doi:10.3389/fcimb.2021.747094

Abstract

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 CD8high+, CD8high αα+, CD8high αβ+, CD8medium+, and CD4+CD8low+ 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 CD8high αα+ T cell population, especially T cell activation or response-related genes including CD40LG, IL2RA, IL2RB, IL17A, IL1R1, TNFRSF25, and TNFRSF11, suggesting that CD8high αα+ 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+CD8low+ (CD8low+) T cell population and the function of CD4+CD8low+ 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+CD8low+ 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.

Highlights

Avian leukosis virus subgroup J (ALV‐J) can cause neoplastic disease, immunosuppression, and other production problems, resulting in huge economic losses for poultry industries
We found that the CD8+ T cell response was a potential key factor defending against ALV‐J infection, and a marked increase in the percentage of CD8+ T cells was detected at 21 days post-infection (DPI) in the avian leukosis virus subgroup J (ALV-J) infection group compared with the control group (Dai et al, 2020)
Given that the majority of the CD8high+ populations were of the CD8ab phenotype, the CD8high ab+ T cells was assumed to be more important for clearing viruses in our previous study (Dai et al, 2020)

Summary

Introduction

Avian leukosis virus subgroup J (ALV‐J) can cause neoplastic disease, immunosuppression, and other production problems, resulting in huge economic losses for poultry industries. We found that a CD8high+ population increased in peripheral blood mononuclear cells (PBMCs) from ALV-J infected chickens compared to control chickens at 21 days post-infection (DPI), which formed three stable populations of CD8+ T lymphocytes in the infected chickens, including CD8 high+, CD8medium+, and CD4+CD8low+cells (Dai et al, 2020). Chicken CD4+CD8low+ T cells co-express CD4 and CD8alpha, but not CD8beta, and account for a large cell proportion in PBMCs (Luhtala et al, 1997), but its function was not understood. CD8 high+ and CD8medium+ T cells co-express CD8alpha and CD8beta, but not CD4, and occupy a small proportion in PBMCs (Dai et al, 2020). The difference in avian CD4+CD8+ double-positive T cell and CD8+ T cell remains uninvestigated, which greatly limited our understanding of the heterogeneity and biology of chicken T cells

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Conclusion