Prion protein modulation of virus-specific T cell differentiation and function during acute viral infection

Abstract

The differentiation and functionality of virus-specific T cells during acute viral infections are crucial for establishing long-term protective immunity. While numerous molecular regulators impacting T cell responses have been uncovered, the role of cellular prion proteins (PrPc) remains underexplored. Here, we investigated the impact of PrPc deficiency on the differentiation and function of virus-specific T cells using the lymphocytic choriomeningitis virus (LCMV) Armstrong acute infection model. Our findings reveal that Prnp-/- mice exhibit a robust expansion of virus-specific CD8+ T cells, with similar activation profiles as wild-type mice during the early stages of infection. However, Prnp-/- mice had higher frequencies and numbers of virus-specific memory CD8+ T cells, along with altered differentiation profiles characterized by increased central and effector memory subsets. Despite similar proliferation rates early during infection, Prnp-/- memory CD8+ T cells had decreased proliferation compared with their wild-type counterparts. Additionally, Prnp-/- mice had higher numbers of cytokine-producing memory CD8+ T cells, indicating a more robust functional response. Furthermore, Prnp-/- mice had increased virus-specific CD4+ T cell responses, suggesting a broader impact of PrPc deficiency on T cell immunity. These results unveil a previously unrecognized role for PrPc in regulating the differentiation, proliferation, and functionality of virus-specific T cells, providing valuable insights into immune system regulation by prion proteins during viral infections.

Keywords: LCMV; T cells; memory T cells; prions; viral infection.

Figure 1.

Prnp deletion results in increased virus-specific memory CD8⁺ T cells. WT and Prnp^–/– mice were infected with LCMV Armstrong and spleens were harvested at indicated time points. (A) Frequencies of tetramer⁺ CD8⁺ T cells at 8 dpi and representative FACS plots. (B) Numbers of tetramer⁺ CD8⁺ T cells at 8 dpi. (C) Frequencies of tetramer⁺ CD8⁺ T cells at 27 dpi and representative FACS plots. (D) Numbers of tetramer⁺ CD8⁺ T cells at 27 dpi. *P < 0.05.

Figure 2.

Prnp deletion does not change PD-1 and CD127 expression levels in virus-specific CD8⁺ T cells. WT and Prnp^–/– mice were infected with LCMV Armstrong and spleens were harvested at indicated time points. (A) Mean fluorescence intensity (MFI) of PD-1 in tetramer⁺ CD8⁺ T cells at 8 dpi. (B) MFI of CD127 in tetramer⁺ CD8⁺ T cells at 8 dpi. (C) MFI of CD127 in tetramer⁺ CD8⁺ T cells at 27 dpi.

Figure 3.

Prnp deletion results in decreased proliferation of virus-specific memory CD8⁺ T cells. WT and Prnp^–/– mice were infected with LCMV Armstrong and spleens were harvested at indicated time points. (A) Frequencies of Ki67⁺ in tetramer⁺ CD8⁺ T cells at 8 dpi. (B) Frequencies and FACS plot representative of Ki67⁺ in tetramer⁺ CD8⁺ T cells at 27 dpi. *P < 0.05, **P < 0.001.

Figure 4.

Prnp deletion alters virus-specific memory CD8⁺ T cell subset differentiation. WT and Prnp^–/– mice were infected with LCMV Armstrong and spleens were harvested at 27 dpi. Frequencies and representative FACS plots of Tcm cells (CD127⁺, CD62L⁺), (Tem cells (CD127⁺, CD62L^–), and Ttem cells (CD127^–, CD62L^–) in (A) GP_33–41 tetramer⁺ and (B) GP_394–404 tetramer⁺ CD8⁺ T cells. Numbers of Tcm cells (CD127⁺, CD62L⁺), Tem cells (CD127⁺, CD62L^–), and Ttem cells (CD127^–, CD62L^–) in (C) GP_33–41 tetramer⁺ and (D) GP_394–404 tetramer⁺ CD8⁺ T cells. (E) The ratio of Tem cells to Ttem cells is shown for each tetramer. *P < 0.05, **P < 0.001, ***P < 0.005, and ****P < 0.0001.

Figure 5.

Prnp deletion does not change the effector function of virus-specific effector CD8⁺ T cells early postinfection. Spleens were isolated from WT and Prnp^–/– LCMV Armstrong–infected mice at 8 dpi and stimulated ex vivo with indicated LCMV peptides. Frequencies and representative FACS plots of IFNγ⁺ and IFNγ⁺TNFα⁺ in (A) GP_33–41 peptide–stimulated and (B) NP_396–404 peptide–stimulated CD8⁺ T cells. *P < 0.05.

Figure 6.

Prnp deletion increases the numbers of cytokine-producing virus-specific memory CD8⁺ T cells. Spleens were isolated from WT and Prnp^–/– LCMV Armstrong–infected mice at 27 dpi and stimulated ex vivo with indicated LCMV peptides. Frequencies and representative FACS plots of IFNγ⁺ and IFNγ⁺TNFα⁺ in (A) GP_33–41 peptide–stimulated and (B) NP_396–404 peptide–stimulated CD8⁺ T cells. Numbers of IFNγ⁺ and IFNγ⁺TNFα⁺ in (C) GP_33–41 peptide–stimulated and (D) NP_396–404 peptide–stimulated CD8⁺ T cells. (E) The frequencies of IFNγ⁺CD107⁺ CD8⁺ T cells stimulated with GP_33–41 and NP_396–404 peptides and representative FACS plots. *P < 0.05, **P < 0.001.

Figure 7.

Prnp deletion results in increased numbers of virus-specific CD4⁺ memory T cells. Spleens were isolated from WT and Prnp^–/– LCMV Armstrong–infected mice at and 8 and 27 dpi, and the immune response was characterized. (A) Frequencies and numbers of tetramer⁺ CD4⁺ T cells at 8 dpi. (B) Frequencies and representative FACS plots of IFNγ⁺ and IFNγ⁺TNFα⁺ in GP_66–76 peptide–stimulated ex vivo CD4⁺ T cells at 8 dpi. (C) Frequencies and FACS plot representatives of IFNγ⁺ and IFNγ⁺TNFα⁺ in GP_66–76 peptide–stimulated ex vivo CD4⁺ T cells at 27 dpi. (D) Numbers of IFNγ⁺ and IFNγ⁺TNFα⁺ in GP_66–76 peptide–stimulated ex vivo CD4⁺ T cells at 27 dpi. *P < 0.05.