Viral and bacterial causes for Alzheimer’s disease: increasing evidence for a major role of infectious agents

The growing experimental data points to chronic viral and bacterial infections are possible risk factors for AD disease. Virus and bacteria are normally latent in elderly brains but reactivates under certain conditions cause persistent CNS infections by continuous pathogen replication. In depth viral and microbial agents have been reported to produce molecular hallmark of neurodegeneration, such as production and deposit of misfold protein aggregates, synaptopathies and neuronal death. HSV1 DNA plays a major evidence in viral AD. Chlamydia pneumonia antibodies present in brain tangles are major evidence in bacterial AD. The infections may be synergy with recognized risk factors such as aging, concomitant metabolic diseases and host specific genetic signature. This review will focus on the contribution given to neurodegeneration by Herpes simplex type-1 and Chlamydia pneumonia.