A simple blood test may soon support doctors predict whether a patient with a rare and often fatal brain infection will respond to immunotherapy, according to research published this week in JAMA Neurology. The findings offer a crucial step toward personalizing treatment for progressive multifocal leukoencephalopathy (PML), a devastating condition caused by the John Cunningham (JC) virus.
PML primarily affects individuals with weakened immune systems, including those with HIV/AIDS, cancer, or autoimmune diseases treated with immunosuppressant drugs. The virus attacks cells that produce myelin, the protective sheath around nerve fibers, leading to progressive neurological damage and, frequently, death. While immunotherapy – specifically immune checkpoint inhibitors (ICIs) – has emerged as a treatment option, its success rate varies significantly, and it carries the risk of serious side effects. Determining which patients will benefit from ICIs has been a major clinical challenge.
Researchers at the Medical Center Hannover (MHH) in Germany have identified virus-specific T cells in the blood as a potential biomarker for predicting ICI response. Their study, encompassing data from 111 PML patients treated at 39 clinics worldwide between 2021 and 2024, revealed a strong correlation between the presence of these T cells before treatment and positive outcomes. Patients with detectable virus-specific T cells experienced higher response rates, improved neurological function, lower viral loads, and increased survival probabilities compared to those without them. Notably, they also experienced fewer immune-related side effects.
Predicting Immunotherapy Success with a Blood Test
The study’s findings represent a significant advancement in the management of PML. “We observed that PML patients with detectable virus-specific T cells before therapy initiation showed significantly higher response rates, better functional outcomes, lower viral loads, and a better probability of survival during and after ICI treatment,” explained Professor Dr. Thomas Skripuletz, senior physician at the Clinic for Neurology with Clinical Neurophysiology at MHH, in a press statement.
The research team’s work builds on previous breakthroughs at MHH in treating PML. In 2021, Professor Skripuletz’s team pioneered a novel approach using donor-derived, allogeneic DIAVIS-T cells – immune cells specifically targeted to fight the JC virus – to halt the virus’s spread. These cells are sourced from healthy individuals who have been exposed to the JC virus but haven’t developed PML, possessing T cells capable of recognizing and attacking infected cells. However, the effectiveness of this donor-cell therapy hinges on whether the patient already has some level of their own antiviral T-cell response.
The Role of AlloCELL and Donor T-Cells
The analysis of virus-specific T cells is conducted at the alloCELL laboratory at MHH, which maintains a unique registry of T-cell donors. “Thanks to our unique T-cell donor registry alloCELL at MHH, we always find a suitable T-cell donation when no own defense cells can be detected,” stated Professor Dr. Britta Eiz-Vesper, an immunologist at the MHH Institute for Transfusion Medicine and Transplant Engineering and a co-author of the study. The alloCELL registry not only catalogs tissue characteristics but also the number of specific T cells against various viruses, enabling rapid identification of suitable donors and the production of T-cell products within days.
The MHH team distributes these donor T-cells to treatment centers across Germany and internationally. While ICI therapy remains a significant treatment option globally, the presence of pre-existing virus-specific T cells appears to be a key determinant of its success. The researchers emphasize that the blood test for these T cells could help clinicians identify patients most likely to benefit from ICIs, minimizing unnecessary treatment and potential side effects.
Implications for PML Treatment and Future Research
The study underscores the importance of pre-existing antiviral immunity in combating PML. “Our data provide initial evidence, in a larger cohort, that a blood test for virus-specific T cells could be suitable as a biomarker,” Professor Skripuletz noted. The goal is to integrate this testing into standard clinical practice before initiating ICI therapy.
Progressive multifocal leukoencephalopathy, as described by the National Institute of Neurological Disorders and Stroke (NINDS), is a disease of the brain’s white matter caused by the JC virus. The virus is common, carried by a majority of people, but typically harmless except in those with compromised immune systems. The identification of a predictive biomarker for ICI response represents a major step forward in improving outcomes for these vulnerable patients.
Disclaimer: This article provides information for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
The researchers plan to continue investigating the role of T cells in PML and explore ways to enhance the immune response in patients who lack these protective cells. The next step will involve validating these findings in larger, multi-center studies and developing standardized protocols for T-cell testing. Further research is also needed to understand the long-term effects of both ICI therapy and donor T-cell infusions in PML patients.
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