When venom calms the storm: Stonefish venoms suppress LPS-induced Th1 cytokine expression and secretion in human PBMCs.

Venoms are known to modulate immunological processes. In this study, we investigated the immunomodulatory properties of venoms from two stonefish species, Synanceia verrucosa (SvV) and Synanceia horrida (ShV), using immunological assays including reverse-transcription quantitative polymerase chain reaction (RT-qPCR), cytometric bead array (CBA), and enzyme-linked immunosorbent assay (ELISA). Both venoms exhibited significant immunosuppressive activity, particularly in lipopolysaccharide (LPS)-stimulated human peripheral blood mononuclear cells (PBMCs), with less pronounced effects on phorbol 12-myristate 13-acetate with ionomycin (P/I)-stimulated cells. The venoms primarily suppressed Th1-associated cytokines (TNF, IFN-γ, IL-6, and IL-12), as well as IL-10 (Th2) and MCP-1, indicating a stronger inhibition of the Th1 subset. SvV demonstrated greater activity compared to ShV, suppressing cytokines on which ShV had no effect, and having activity at concentrations as low as 1.25 μg/mL. Stability studies showed that both frozen and lyophilized venoms retained immunosuppressive activity comparable to fresh venom, while reversed-phase high-performance liquid chromatography (RP-HPLC) abolished this activity entirely. Size-exclusion chromatography (SEC) revealed the immunosuppressive activity was strongest in the early and late fractions of each venom. Our results highlight the selective immunosuppressive effects of S. verrucosa and S. horrida venoms on human PBMCs, particularly via modulation of Th1 cytokines in response to LPS. The stability and bioactivity of specific venom fractions underscore their potential as sources for novel immunotherapeutic agents.