Chlamydia pneumoniae infection may be a trigger for the pathology observed in sporadic lateonset Alzheimer’s disease as a function of initiating neuroinflammation following entry of the organism into the brain. We have hypothesized that one entry mechanism may be by bloodborne infected monocytes trafficking the infection into the brain. This study focuses on infection of monocytes in vitro followed by analysis using immunofluorescence labeling and RT-PCR-microarray techniques. The microarrays utilized consisted of an Alzheimer’s disease pathway array and an innate and adaptive immunity array from SAbiosciences. Analysis by real time PCR for both gene arrays was performed on uninfected and C. pneumoniae-infected THP1 monocytes at 48 hr post-infection. In addition, we analyzed innate and adaptive immunity gene regulation changes following treatment of infected cells with a unique peptide, acALY18, derived from the endogenously expressed endoplasmic reticulum protein TRPC1. The peptide appears to stimulate the innate immune system through activation of the inflammasome. C. pneumoniae prominently infected THP1 monocytes at 24-48hr. Numerous large inclusions were identified using specific chlamydial monoclonal antibodies. Monocyte gene expression changes induced by infection with C. pneumoniae revealed significant up-regulation of 45 genes in the Alzheimer’s disease pathway. These included genes involved in: b-amyloid processing and clearance, apoptosis, proteases and protein kinases, and lipid metabolism. In contrast, infection resulted in significant changes in 30 genes governing innate and adaptive immunity including those for: the inflammatory response, host defense against bacteria, cytokines, chemokines, and an antibacterial humoral response. Intriguingly, following incubation of C. pneumoniae-infected cells with the acALY18 peptide (25-50nM) at 24hr post-infection, there was significant clearance of the organism from the monocytes as well as up-regulation of 38 genes. Our data suggest that C. pneumoniae infection of monocytes has a profound effect on gene regulation for both innate and adaptive immunity and for Alzheimer’s disease. Stimulating the innate immune response using the novel peptide, acALY18, promotes clearance of C. pneumoniae from infected monocytes; thereby implicating the inflammasome as a key component in eradicating this infection.
Available at: http://works.bepress.com/susan_hingley/11/