Can persistent microbial antigens or chronic infection sustain central sensitization?

Chronic infection and persisting microbial antigens serve as potent triggers for sustained neuro-immune signaling, creating a biological environment that maintains central sensitization.

Mechanistic pathways of immune-neural crosstalk

The persistence of microbial fragments or viral proteins acts as a chronic stimulus for the innate immune system.

• Pathogen Persistence: Pathogens such as Borrelia burgdorferi shed peptidoglycan fragments that persist in tissues, while latent viruses like EBV and HHV-6 produce proteins (e.g., dUTPases) that act as pathogen-associated molecular patterns (PAMPs).
• Innate Activation: These PAMPs chronically ligate Toll-like receptors (TLR2), activating the NF-κB signaling pathway. This leads to the sustained systemic production of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α.
• Central Reinforcement: Peripheral cytokines signal across the blood-brain barrier to "prime" or activate central microglia. Activated microglia release further cytokines that directly modulate neuronal excitability.

Impact on central sensitization

The transition from systemic inflammation to central sensitization occurs through the direct alteration of synaptic plasticity.

• NMDA Receptor Modulation: Pro-inflammatory cytokines like IL-1β and TNF-α increase the expression and phosphorylation of the NR2B subunit of NMDA receptors in the spinal cord dorsal horn. This molecular shift lowers the threshold for pain signaling and enhances synaptic strength, a hallmark of central sensitization.
• Self-Reinforcing Loops: This neuro-immune crosstalk creates a feedback loop where microglial-mediated neuroinflammation sustains neuronal hyperexcitability, even if the original infectious threat is low-grade or sequestered.

Bottom line

Persistent microbial antigens and chronic viral reactivation sustain a state of innate immune activation that reinforces central sensitization by driving microglial-mediated neuroinflammation and increasing NMDA receptor-dependent neuronal hyperexcitability. This mechanism is increasingly recognized as a core driver in complex conditions like ME/CFS and Long COVID.