# Immune checkpoint changes correlate with the progression and prognosis of amyotrophic lateral sclerosis

## TL;DR

This study explores immune checkpoint molecules in ALS patients, finding that increased PD-1 and other checkpoints correlate with disease progression and worse outcomes.

## Contribution

The study identifies immune checkpoint molecules as potential biomarkers for ALS diagnosis and prognosis.

## Key findings

- Elevated PD-1 expression in CD4+ T cells correlates with faster functional decline in ALS patients.
- Serum levels of sPD-1, sBTLA, sCTLA-4, and sCD27 are higher in ALS compared to controls and mimics.
- sTIM-3 inversely correlates with ALSFRS-R scores, indicating disease severity.

## Abstract

Amyotrophic lateral sclerosis (ALS) urgently requires robust biomarkers for early diagnosis and prognostic stratification. This study aims to investigate the diagnostic and prognostic potential of membrane-bound and soluble immune checkpoint molecules in ALS pathogenesis.

In the present study at Fujian Medical Union Hospital, 72 participants (46 ALS and 26 healthy controls [HC]) underwent flow cytometry analysis of PD-1 expression in CD4+ T cells and its subsets. A second cohort (n = 93, 44 ALS, 30 HC and 19 ALS mimics [Mimics]) was evaluated using Luminex technology for 14 serum immune checkpoint molecules. A single-molecule array was used to screen the neurofilament light chain (NFL) in serum.

Flow cytometry revealed elevated PD1 expression in CD4+ T cells, particularly in Th9 and Th17 subsets (p < 0.05). ALS patients exhibiting a greater percentage of PD-1 in CD4+ T cells showed accelerated functional decline. Serum analyses identified four elevated soluble checkpoints in ALS versus both HCs and Mimics (sPD-1/sBTLA/sCTLA-4/sCD27, p < 0.05), with sCD28/TIM-3 showing higher in ALS than in Mimics, and sGITR/sCD137/sIDO/sCD80/sLAG3/sPD-L2 elevating in ALS compared to HCs. Soluble TIM-3 correlated inversely with ALSFRS-R, while sPD-L1 demonstrated dual associations: negative with ALSFRS-R and positive with NFL (all p < 0.05).

Our research demonstrated a considerable increase in membrane-bound and soluble PD-1 in ALS patients, correlating with disease progression and worse prognosis. Furthermore, we explored 13 other immune checkpoint molecules. Collectively, these molecules may be implicated in peripheral immune mechanisms underlying ALS pathogenesis. While baseline PD-1 levels show some association with prognosis, their elevation potentially indicates an unfavorable course.