GLIA-NEURON CROSSTALK DURING HSV-1 INFECTION AND ITS ROLE IN NEURONAL DAMAGE

Introduction. Herpes Simplex Virus type 1 (HSV-1) establishes a lifelong infection in the peripheral ganglia and, following periodic reactivation, may reach the Central Nervous System (CNS) where its replication has been associated to induction of neurodegenerative processes typical of Alzheimer’s Disease (AD). Previous data show that in vitro HSV-1 infection enhances neuronal appearance of AD hallmarks: production/accumulation of neurotoxic fragments of Amyloid Precursor Proteins (APP) and hyperphosphorylation of Tau protein; this data were recently confirmed in an in vivo recurrent HSV-1 infection model. It is known that CNS is populated not only by neurons, but also by glia and microglia and it is possible to hypothesize that, during HSV-1 infection, these cells surrounding neurons may undergo activation and expression of proinflammatory genes, enhancing neuronal damage. Aim. To investigate the glia-neuron crosstalk during HSV-1 infection and its role in neuronal damage. Methods. Primary cultures of neuronal and glial cells were obtained by E17 rat or mouse embryo brains. Human and mouse neuroblastoma (SH-SY5Y and Neuro2A, respectively), human glioblastoma (A172) and mouse microglia (BV2) cells were grown in Dulbecco’s modified Eagle’s medium containing 10% heat-inactivated FBS and antibiotics (glutamine 0.3 mg/ml, penicillin 100 units/ml, streptomycin 100 μg/ml). Confluent cellular monolayers were infected with HSV-1 (strain F) at m.o.i. 1 for 18 hours and analyzed by Western Blot to detect tau phosphorylation and APP fragmentation. HSV-1 titers were measured in conditioned media by standard plaque assay. Cytokines and chemokines production were evaluated by ELISA. Amyloid beta peptides production was investigated by confocal Microscopy assay. Results. We have set up four HSV-1-infected neurons–glia co-culture models: human neuroblastoma/glioblastoma, mouse neuroblastoma/microglia, primary rat neurons/astrocytes/microglia, primary mouse neurons/astrocytes/microglia. In these models we found that the presence of glial cells increases Tau phosphorylation (particularly at Thr 205 residue), beta - amyloidogenic APP cleavage, pro-inflammatory cytokine (IL- 6) and chemokines (CCL5 and CCL2) production in HSV-1 infected neurons–glia co- cultures compared to infection of single cultures. Further studies are in progress to clarify the mechanisms underlying the influence of glial cells on Alzheimer’s disease hallmarks appearance during HSV-1 infection.