Can infection-triggered immune responses cross-react with neural antigens and sustain autoimmunity?

Post-infectious autoimmunity is a biologically established phenomenon in which an antimicrobial immune response can target structurally similar host neural molecules. The clearest human model is Campylobacter jejuni–associated Guillain–Barré syndrome (GBS), rather than a mechanism assumed to apply uniformly to all infections or neurologic syndromes.

Clinical and mechanistic evidence

• In C. jejuni–associated GBS, bacterial lipooligosaccharides (LOS) contain terminal carbohydrate structures resembling peripheral-nerve gangliosides, including GM1, GD1a, GM1b, GalNAc-GD1a, and GQ1b.
• Antibodies induced against LOS can bind both bacterial antigens and neural gangliosides at motor-nerve axolemma and nodes of Ranvier. Near-complete inhibition of anti-ganglioside antibody reactivity by homologous LOS in some patient sera supports recognition of a shared epitope, rather than two unrelated antibody responses.
• This cross-reactivity has a plausible pathogenic sequence: anti-LOS/ganglioside antibodies deposit at peripheral nerves, activate complement, and—together with macrophage-mediated injury—produce axonal or demyelinating motor-nerve dysfunction.

Infection may be absent when autoimmune disease emerges

• In GBS, neurological illness may become fully apparent after clearance of the enteric infection. Approximately half of patients have negative stool cultures two weeks after diarrhoea onset; thus, negative microbiologic testing during neuropathy does not exclude a preceding infectious trigger.
• A comparable clinical pattern occurs after HSV encephalitis: neuropsychiatric relapse 2–8 weeks later, negative repeat HSV PCR, and poor antiviral response should raise concern for post-infectious autoimmune encephalitis, particularly anti-NMDAR disease. Early CSF HSV PCR can nonetheless be falsely negative, warranting repeat testing after 3–7 days when clinical suspicion remains high.

Bottom line

• Molecular mimicry can cause antimicrobial immunity to cross-react with neural antigens and drive post-infectious autoimmune disease after the organism is no longer detectable. The evidence is particularly compelling for ganglioside-mediated GBS following C. jejuni infection; persistent symptoms may also reflect residual nerve injury as antibody titres decline over months.