Infectious agents and Alzheimer's disease.

Alzheimer's disease (AD) is the leading cause of dementia worldwide. Individuals affected by the disease gradually lose their capacity for abstract thinking, understanding, communication and memory. As populations age, declining cognitive abilities will represent an increasing global health concern. While AD was first described over a century ago, its pathogenesis remains to be fully elucidated. It is believed that cognitive decline in AD is caused by a progressive loss of neurons and synapses that lead to reduced neural plasticity. AD is a multifactorial disease affected by genetic and environmental factors. The molecular hallmarks of AD include formation of extracellular ß amyloid (Aß) aggregates, neurofibrillary tangles of hyperphosphorylated tau protein, excessive oxidative damage, an imbalance of biothiols, dysregulated methylation, and a disproportionate inflammatory response. Recent reports have shown that viruses (e.g., Herpes simplex type 1, 2, 6A/B; human cytomegalovirus, Epstein-Barr virus, hepatitis C virus, influenza virus, and severe acute respiratory syndrome coronavirus 2, SARS-CoV-2), bacteria (e.g., Treponema pallidum, Borrelia burgdorferi, Chlamydia pneumoniae, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Fusobacterium nucleatum, Aggregatibacter actinomycetemcmitans, Eikenella corrodens, Treponema denticola, and Helicobacter pylori), as well as eukaryotic unicellular parasites (e.g., Toxoplasma gondii) may factor into cognitive decline within the context of AD. Microorganisms may trigger pathological changes in the brain that resemble and/or induce accumulation of Aß peptides and promote tau hyperphosphorylation. Further, the mere presence of infectious agents is suspected to induce both local and systemic inflammatory responses promoting cellular damage and neuronal loss. Here we review the influence of infectious agents on the development of AD to inspire new research in dementia based on these pathogens.

Acute disseminated encephalomyelitis in a patient vaccinated against SARS-CoV-2.

Acute disseminated encephalomyelitis (ADEM) is a demyelinating disease, and there are some data that link this event with various vaccinations. We report a young female admitted to the hospital with headache, fever, back pain, nausea, vomiting, and urinary retention. Two weeks prior, she received the first dose of SARS-CoV-2 mRNA vaccine. Brain and spinal cord magnetic resonance imaging (MRI) showed distinctive for ADEM widespread demyelinating lesions. The patient was successfully treated with methylprednisolone.