Led by researchers from Vanderbilt University Medical Center in Nashville and Murdoch University in Perth, Australia, a new study uses multiomic single-cell sequencing to provide new insights into the immunopathogenesis and cellular and molecular signaling pathways driving the rare but life-threatening adverse drug reactions Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN).
Considered parts of the same disease across a spectrum of severity, SJS, SJS/TEN overlap syndrome, and TEN cause the skin to blister and peel off, like severe burns.
From 2010 to 2020, the U.S. saw 51,040 hospitalizations for the three diseases combined, or about 13 cases per every 1 million hospitalizations, with SJS accounting for 73% of cases. Mortality rates for these hospitalizations were 5.4% in the SJS group, 14.4% in the SJS-TEN overlap syndrome group, and 15.3% in the TEN group.
Reported in Nature Communications, the study analyzed cells from 15 patients with SJS/TEN — cell by cell, 109,888 cells in all, from unaffected skin, affected skin, and blister fluid at the site of tissue damage. Molecular sequencing extended to each cell’s transcriptome, cell surface proteome, and T cell receptors.
Because of the rarity of SJS/TEN, the study relied on samples collected at 12 centers in the U.S., Australia and South Africa.
“Our analysis offers new insights into how SJS/TEN develops at a cellular level and suggests several potential avenues for developing earlier approaches to diagnosis and targeted therapies for these severe conditions,” said the study’s principal investigator, Elizabeth Phillips, MD, professor of Medicine in the Division of Infectious Diseases, professor of Dermatology, holder of the John A. Oates Chair, director of the Center of Drug Safety and Immunology, and a world leader in the study of severe cutaneous adverse reactions.
The study shows that, regardless of severity or which drug caused the reaction, the damage in SJS/TEN is orchestrated by cytotoxic CD8+ tissue-resident memory T cells. Cytotoxic means these cells can directly kill other cells, CD8+ refers to a protein on their surface, and tissue-resident memory indicates they stay in the skin rather than circulate in the blood.
In the new analysis, these T cells were found in far greater numbers in SJS/TEN-affected skin and blister fluid. They interacted directly with keratinocytes, the main type of cell in the outer layer of skin, likely through a process involving nearly ubiquitous proteins called HLA class I that present fragments of other proteins to immune cells. Keratinocytes in affected skin showed changes apt to make them more vulnerable to being killed by these T cells: They increased expression of HLA class I and decreased a protein called LGALS3, which normally interacts with another protein, LAG3, on the T cells to restrain their activity.
“In this study, we’re witnessing the cytotoxic CD8+ T cells targeting and killing the very skin cells that activate them,” said Phillips. “Keratinocytes not only activate their own assassins, but they also show evidence at cellular and molecular levels of letting their guard down, making themselves more vulnerable.”
Among other cellular processes implicated in this new analysis of SJS/TEN:
• MIF signaling: MIF is a protein involved in immune responses and inflammation.
• PKM-mediated metabolic changes: PKM is an enzyme that affects how cells process energy.
• JAK-STAT signaling: This is a chain of chemical reactions that helps cells respond to outside signals and is involved in immune responses.
The study also found potential roles for other cell types, including macrophages — immune cells that engulf and digest cellular debris and pathogens and may be critical in the healing phase of disease.
“The study is a major step forward, providing a detailed map of how different cells interact in SJS/TEN and identifying potential targets for earlier diagnosis and novel treatments,” Phillips said. “In support of use of drugs like etanercept — a TNF-a, or tumor necrosis factor-alpha receptor antagonist that is being studied in SJS/TEN — TNF appeared upregulated across T cells, natural killer cells and macrophages.
“However, of great interest are a number of novel targets, including therapies that target cells with LAG3 protein, and MIF and JAK-STAT signaling.”
Others[MB1] on the study from VUMC include Rama Gangula, Eric Mukherjee, Amy Palubinsky, Chelsea Campbell, Katherine Konvinse, Celestine Wanjalla, Spyros Kalams, Silvana Gaudieri, Samuel Bailin, Abha Chopra, and Simon Mallal. The study was funded by the National Institutes of Health (grants U01AI154659, P50GM115305, R01HG010863, R21AI139021, R01AI152183, P30AI110527, D43TW010559, K42TW011178) and SJS Research in Memory of Angela Anderson.
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