がん免疫療法における免疫関連有害事象発症のメカニズム解明

2023 Fiscal Year Research-status Report

• Project/Area Number: 21K08152
• Research Institution: Nagoya University
• Principal Investigator: コーチン ビタリー 名古屋大学, 医学系研究科, 特任助教 (30648001)
• Project Period (FY): 2021-04-01 – 2025-03-31
• Keywords: GPRC5A / irAEs / ICIs / autoimmune Ab / cytotoxic T cells

Outline of Annual Research Achievements

Immune Related Adverse Events (irAEs) restrain ICIs use. The irAEs are caused by ICI-induced autoimmunity against self-tissues by auto-antibody (Ab) or self-reacting T cells. We found GPRC5A-derived peptide epitope presented by HLA-A24 specifically in human lung cells and currently investigating whether autoreactive T cells and/or Ab to GPRC5A may be responsible for the inflammation and damage in lung tissue of patients who underwent treatment with ICIs.
We use HLA-A24-transgenic mice (A24-Tg) as a model. We have confirmed that lung tissue of the A24-Tg animals express HLA-A24 and can process and present GPRC5A-derived peptide epitope identical to the one in human cells.

Current Status of Research Progress

3: Progress in research has been slightly delayed.

Reason

The objective of the third year (2023-2024) was completed by numerous attempts to induce self-reacting CTLs using immunization of homozygous A24-Tg mice with mouse self-GPRC5A peptide. We used a number of protocols that varied in immunization intervals (ranging from 10 to 20 days), different combination of ICI antibody (and-PD-1 and/or anti-CTLA-4), and age of mice (young vs. old). We observed a tendency for a higher number of immune cell infiltrates (so called LNLS, lymph node-like structures) in the H/E-stained FFPE lung tissue specimens of mice immunized and treated with and-PD-1 and -CTLA-4 Ab. However, we couldn’t isolate self-reacting CTLs using these immunization schemes.

Strategy for Future Research Activity

It seems that congenic expression of GPRC5A in mice precludes induction of self-reacting CTLs as they are removed during negative selection process in thymus. We are currently developing GPRC5A knock-out (KO) / A24-Tg mice to address this issue by using CRISPR gene editing. Such GPRC5A-KO/A24-Tg mice should have intact precursor CD8+ CTLs directed against the GPRC5A epitope. Theoretically such CTLs could be easily induced upon immunization. Upon their induction, they can be expanded and adoptively transferred to A24-Tg mice with intact (wild type) GPRC5A gene, thus turning into self-reactive CTLs. We will investigate whether these CTLs would attack HLA-A24-expressing lung tissue causing inflammation and damage similar to irAEs in patients.

Causes of Carryover

研究遂行に想定以上に時間を要したもの.
We are currently trying to develop GPRC5A-KO/A24-Tg mice line using CRISPR gene editing. When the mice are prepared, we are going to immunize them using established protocols.