Gliotoxin

Gliotoxin is an immunosuppressive mycotoxin of the epipolythiodioxopiperazine (ETP) class, produced principally by Aspergillus fumigatus indoors and by a subset of Aspergillus terreus strains. It is one of the few mycotoxins whose biological activity depends directly on a disulfide bridge, reduction of the bridge eliminates activity. Most regulatory attention to gliotoxin concerns clinical aspergillosis rather than environmental food-safety scenarios.

The defining structural feature is the internal disulfide bridge across a dioxopiperazine ring. Reduction or alkylation of this bridge abolishes biological activity. ETP-class mycotoxins are also produced by other genera (chetomin from Chaetomium, sirodesmin from Sirodesmium) but those compounds are not commonly relevant in dust-DNA-detected indoor mycology.

Gliotoxin's principal characterized effects are immunosuppressive: it induces apoptosis in macrophages and neutrophils, inhibits NF-κB activation, and disrupts phagocytic function^[1][2]. The disulfide bridge participates in protein binding via thiol exchange with cysteine residues; this redox-active mechanism distinguishes gliotoxin from purely receptor-binding mycotoxins. Mechanism description is cellular only; clinical interpretation is the domain of medical mycology.

Documented production at A_w ≥ 0.92 with optimum at 37 °C: notably, body temperature, which facilitates in-host production during invasive aspergillosis. Substrates include damp organic materials, decaying vegetation, and HVAC condensate. A. fumigatus's thermotolerance (growth to ~50 °C) and HVAC association make gliotoxin one of the few mycotoxins with a documented indoor air route via HVAC biofilm.

Decaying organic matter, compost, HVAC systems, damp building materials. Gliotoxin is also a clinical mycology concern in invasive aspergillosis, where in-host production by A. fumigatus contributes to immunosuppression that aids fungal persistence.

No food or environmental regulatory limits are established. The molecule is principally relevant in clinical mycology rather than dietary exposure scenarios, which is the inverse of most major mycotoxins.

Other ETPs (chetomin from Chaetomium species, sirodesmin from Sirodesmium) share the disulfide-bridge mechanism but are not commonly detected on ERMI-style panels.