Autoinflammation with Infantile Enterocolitis (AIFEC) Cell Models for Research

Autoinflammation with Infantile Enterocolitis (AIFEC) is an ultra-rare autoinflammatory disorder caused by gain-of-function mutations in NLRC4. The exact prevalence is unknown, but fewer than 100 cases have been reported worldwide. Onset is typically in infancy, with severe enterocolitis, recurrent fever, and macrophage activation syndrome (MAS). Without treatment, mortality is high, but early diagnosis and IL-18 blockade improve outcomes. The disease is not cancer, but its hyperinflammatory nature makes it a valuable model for studying inflammasome dysregulation.

AIFEC provides a unique opportunity to study inflammasome signaling, IL-18 biology, and macrophage activation. The NLRC4 inflammasome is a key player in innate immunity, and AIFEC mutations offer a clear genetic basis for mechanistic studies. Public datasets include patient-derived iPSCs and CRISPR-edited cell lines. Open questions include the precise molecular mechanisms of NLRC4 activation and the development of targeted therapies.

• • AIFEC is driven by dysregulated inflammasome signaling. Key pathways include:
• • NLRC4 inflammasome assembly: NLRC4 mutations (e.g., T337S, V341A) promote spontaneous oligomerization with NAIP proteins, leading to caspase-1 activation.
• • Caspase-1 activation: Cleaves pro-IL-1β and pro-IL-18 into active cytokines.
• • Pyroptosis: Gasdermin D cleavage triggers inflammatory cell death.
• • IL-18 overproduction: Excessive IL-18 drives MAS and enterocolitis.

Data from ClinVar and literature.

• • Key networks involved:
• • Inflammasome signaling: NLRC4, NAIP, caspase-1, IL-1β, IL-18.
• • Cytokine signaling: IL-18 receptor, NF-κB, JAK/STAT.
• • Cell death pathways: pyroptosis, necroptosis.
• • Macrophage activation: IFN-γ, TNF-α, IL-6.

Organoids: Intestinal organoids from AIFEC patients recapitulate enterocolitis and are useful for studying epithelial barrier dysfunction.

• • Animal models for AIFEC include:
• • Knock-in mouse models: Nlrc4 gain-of-function mutations (e.g., T337S) recapitulate hyperinflammation.
• • Conditional knockout mice: For studying cell-type-specific roles.
• • Humanized mice: Engrafted with patient-derived immune cells.
• • No PDX models (not cancer).

• • CRISPR-Cas9 gene editing enables the creation of isogenic cell lines with specific NLRC4 mutations. For example:
• • NLRC4 T337S knock-in in THP-1 cells: Mimics patient mutation, leading to constitutive inflammasome activation.
• • NLRC4 knockout in THP-1 cells: Abolishes inflammasome signaling, useful as a negative control.
• • Reporter lines: e.g., IL-18 luciferase reporter to monitor pathway activity.

These models are commercially available as sequence-verified, isogenic lines, accelerating research without the need for in-house editing.

Knockout and knock-in lines are used to validate the role of NLRC4 and other inflammasome components. For example, NLRC4 knockout cells show reduced IL-18 secretion, confirming its necessity. Knock-in lines with patient mutations demonstrate gain-of-function effects.

Isogenic pairs (wild-type vs. mutant) are used to screen for inhibitors of inflammasome activation. Resistance mechanisms can be studied by exposing cells to repeated drug treatment and selecting for resistant clones.

CRISPR screens can identify synthetic lethal partners of NLRC4 mutations, revealing potential therapeutic targets. For example, a screen might identify genes whose knockout selectively kills NLRC4-mutant cells.