BDNF and Alzheimer disease: Aβ42 has been found to aggregate influenza virus, attract neutrophils, and enhance hydrogen peroxide release by neutrophils, suggesting it may have antiviral properties.CA/09 H1N1 may cause overactivation of microglia and lower expression levels of BDNF and GDNF, increasing the risk of AD.influenza type A virus infection can activate inositol requiring enzyme 1 (IRE1) causing X-box binding protein 1 (XBP1) splicing and inducing ER stress, which is expected to be involved in AD pathogenesis.