Memory profiles distinguish cross-reactive and virus-specific T cell immunity to mpox

Abstract

Mpox represents a persistent health concern with varying disease severity. Reinfections with mpox virus (MPXV) are rare, possibly indicating effective memory responses to MPXV or related poxviruses, notably vaccinia virus (VACV) from smallpox vaccination. We assessed cross-reactive and virus-specific CD4+ and CD8+ Tcells in healthy individuals and mpox convalescent donors. Cross-reactive Tcells were most frequently observed in healthy donors over 45 years. Notably, long-lived memory CD8+ Tcells targeting conserved VACV/MPXV epitopes were identified in older individuals more than four decades after VACV exposure and exhibited stem-like characteristics, defined by Tcell factor-1 (TCF-1) expression. In mpox convalescent donors, MPXV-reactive CD4+ and CD8+ Tcells were more prevalent than incontrols, demonstrating enhanced functionality and skewing toward effector phenotypes, which correlated with milder disease. Collectively, we report robust effector memory MPXV-specific Tcell responses in mild mpox and long-lived TCF-1+ VACV/MPXV-specific CD8+ Tcells decades after smallpox vaccination.