Search

CD8+ T cells are the primary mediators of antigen-specific immune responses, with their functional states finely regulated by molecular mechanisms, playing a crucial role in tumor immunity. In recent years, CD8+ T-cell-based cellular therapies (e.g., TCR-T and CAR-T cell therapy) and immune checkpoint therapies that block PD-1 signaling pathway have achieved unprecedented success in clinical cancer treatments. However, the therapeutic effects of these immunotherapies are still limited, mainly due to immune resistance, with a significant factor being the functional exhaustion of tumor antigen-specific CD8+ T cells. Consequently, a major focus and challenge in immunotherapy research is to understand the regulatory mechanisms behind this functional exhaustion and to develop intervention strategies and targets to enhance CD8+ T cell effector functions. This article reviews the research progress in antitumor immune responses of CD8+ T cells from three perspectives: The heterogeneity of exhausted CD8+ T cells, their response to PD-1 immune checkpoint blockade (ICB), and their epigenetic characteristics.

Author(s): Ran He [1]; Shiyue Hou [2]; Cheng Liu [1]; Anli Zhang [3]; Qiang Bai [1]; Miao Han [4]; Yu Yang [3]; Gang Wei [4]; Ting Shen [4]; Xinxin Yang [...]

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs), especially the Delta and Omicron variants, have been reported to show significant resistance to approved neutralizing monoclonal antibodies (mAbs) and vaccines. We previously identified a mAb named 35B5 that harbors broad neutralization to SARS-CoV-2 VOCs. Herein, we explored the protection efficacy of a 35B5-based nasal spray against SARS-CoV-2 VOCs in a small-scale clinical trial. Methods We enrolled 30 healthy volunteers who were nasally administered the modified 35B5 formulation. At 12, 24, 48, and 72 hours after nasal spray, the neutralization efficacy of nasal mucosal samples was assayed with pseudoviruses coated with SARS-CoV-2 spike protein of the wild-type strain or the Alpha, Beta, Delta, or Omicron variants. Results The nasal mucosal samples collected within 24 hours after nasal spray effectively neutralized SARS-CoV-2 VOCs (including Delta and Omicron). Meanwhile, the protection efficacy was 60% effective and 20% effective at 48 and 72 hours after nasal spray, respectively. Conclusions A single nasal spray of 35B5 formation conveys 24-hour effective protection against SARS-CoV-2 VOCs, including the Alpha, Beta, Delta, or Omicron variants. Thus, 35B5 nasal spray might be potential in strengthening SARS-CoV-2 prevention, especially in high-risk populations. Clinical Trials Registration 2022-005-02-KY. [ABSTRACT FROM AUTHOR]

Cytotoxic CD8+ T cells are the main focus of efforts to understand anti-tumor immunity and immunotherapy. The adoptive transfer of tumor-reactive cytotoxic CD8+ T lymphocytes expanded and differentiated in vitro has long been considered the primary strategy in adaptive anti-tumor immunity, however, the majority of the transferred tumor antigen-specific CD8+ T cells differentiated into CD39+CD69+ exhausted progenies, limiting its effects in repressing tumor growth. Contrarily, less attention has been addressed to the role of CD4+ T cells during tumorigenesis. Using a mouse model of metastatic melanoma, we found that transferring tumor-specific CD4+ T cells into recipients induces substantial regression of the established metastatic tumors. Notably, in vitro activated CD4+ T cells developed into cytotoxic CD4- T cells in vivo and get exhausted gradually. The blockade of PD-L1 signaling resulted in an expansion of tumor specific CD4+ T cells, which could better control the established metastatic melanoma. Moreover, the tumor-specific memory CD4+ T cell can prevent mice from tumor metastasis, and the tumor-specific effector CD4+ T cells can also mitigate the established metastatic tumor. Overall, our findings suggest a novel mechanism of CD4+ T cells in curtailing tumor metastasis and confirm their therapeutic role in combination with PD-L1 blockade in cancer immunotherapy. Hence, a better understanding of cytotoxic CD4- T cell-mediated tumor regression could provide an alternative choice for patients exhibiting suboptimal or no response to CD8+ T cell-based immunotherapies. [ABSTRACT FROM AUTHOR]

Author(s): Ran He; Shiyue Hou; Cheng Liu; Anli Zhang; Qiang Bai; Miao Han; Yu Yang; Gang Wei; Ting Shen; Xinxin Yang; Lifan Xu; Xiangyu Chen; Yaxing Hao; Pengcheng Wang; Chuhong [...]

Exhausted CD8+ T (Tex) cells are caused by persistent antigenic stimulation during chronic viral infection or tumorigenesis. Tex cells upregulate and sustain the expressions of multiple immune inhibitory receptors (IRs). Blocking IRs of Tex cells, exemplified by PD‐1, can partially restore their effector functions and thus lead to viral suppression or tumor remission. Tex cells derived from chronic viral infections share the expression spectrum of IRs with Tex cells derived from tumors; however, whether any IRs are selectively expressed by tumor‐derived Tex cells or virus‐derived Tex cells remains to be learnt. In the study, we found that Tex cells upregulate IR natural killer cell lectin‐like receptor isoform A (NKG2A) specifically in the context of tumor but not chronic viral infection. Moreover, the NKG2A expression is attributed to tumor antigen recognition and thus bias expressed by tumor‐specific Tex cells in the tumor microenvironment instead of their counterparts in the periphery. Such dichotomous NKG2A expression further dictates the differential responsiveness of Tex cells to NKG2A immune checkpoint blockade. Therefore, our study highlighted NKG2A as a disease‐dependent IR and provided novel insights into the distinct regulatory mechanisms underlying T cell exhaustion between tumor and chronic viral infection. [ABSTRACT FROM AUTHOR]