Single-cell sequencing of PBMC characterizes a distinct inflammatory monocyte subset in Lyme disease patients with Post-Treatment Lyme Disease Syndrome (PTLD)

Abstract

Abstract Lyme disease (LD) is the most common tick-borne disease in the United States. Most LD patients can return to healthy (RTH) status after antibiotic treatment. Still, 20% of LD patients develop Post-Treatment Lyme Disease Syndrome (PTLD), including fatigue and musculoskeletal pain that persist for a long time. Previous RNA-seq studies showed that most individuals with PTLD had an inflammatory gene expression compared to RTH, but the specific immune components that contribute to PTLD are not well understood. Here, we performed the single-cell sequencing analysis of PBMCs from 6 RTH and 4 PTLD patients collected during multiple clinic visits after antibiotic treatment over two years. We identified a CD14+ monocyte cluster significantly enriched in 4/4 PTLD patients and 2/6 RTH patients from the beginning to 6 months post-treatment. This monocyte cluster displayed distinct inflammatory gene signatures such as CCL3, CCL4, IL1B, CXCL2, CXCL8, and others. RTH patients with such inflammatory monocytes showed low expression of CXCR2 compared to PTLD, suggesting that higher CXCR2 signaling in inflammatory monocytes may contribute to the development of PTLD. In addition, pathway analysis of upregulated genes in PTLD inflammatory monocytes indicated that this subset was induced by molecules of bacterial origin and involved in the regulation of lymphocyte activation. In conclusion, our single-cell study identified a distinct inflammatory monocyte that was enriched and may contribute to PTLD. Tracking this inflammatory monocyte subset could lead to a more accurate prediction of PTLD and identify molecular biomarkers and pathways for therapeutic intervention.