Researchers detected Chlamydia pneumoniae and evidence of NLRP3 inflammasome activation in the retinas of patients with Alzheimer’s disease, according to a study published in Nature Communications. The findings indicate that retinal tissue may reflect inflammatory and infectious processes associated with neurodegeneration and could have diagnostic relevance.
The team examined postmortem retinal samples from patients with neuropathologically confirmed Alzheimer’s disease and age-matched control donors. Investigators used polymerase chain reaction (PCR), immunohistochemistry, in situ hybridization, and electron microscopy to assess the presence of C pneumoniae, amyloid-beta deposition, and inflammasome-related proteins.
Retinal tissue from patients with Alzheimer’s disease more frequently demonstrated C pneumoniae DNA and antigen compared with controls. The organism was localized to multiple retinal layers, including the ganglion cell layer and inner nuclear layer. Electron microscopy identified structures consistent with intracellular bacterial inclusions.
In addition to microbial detection, the researchers evaluated markers of inflammasome activation. Retinas from patients with Alzheimer’s disease showed increased expression of NLRP3, ASC, and cleaved caspase-1 relative to controls, supporting activation of the NLRP3 inflammasome pathway. These signals were observed in areas that also demonstrated amyloid-beta accumulation and microglial activation.
Colocalization of bacterial markers with amyloid-beta deposits was also reported. Although the study design does not establish causality, the findings support further investigation into potential links between infection, innate immune activation, and retinal pathology in Alzheimer’s disease.
The findings expand the understanding of inflammatory and infectious signatures in Alzheimer’s disease and support continued evaluation of retinal tissue as a potential diagnostic substrate.
However, the study was limited by sample size and its cross-sectional design. Detection of C pneumoniae does not clarify whether infection precedes or follows neurodegenerative changes. Additional studies will be needed to confirm these findings and to determine whether retinal microbial or inflammasome markers have a role in clinical diagnostics.
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