HCMV infection induces AD pathology in astrocytes in vitro

Abstract

AbstractBackgroundInfectious agents have long been suspected to be risk factors for Alzheimer’s disease (AD). Some studies have identified a link between neurotropic viruses and AD. While these studies demonstrated an association between AD and neuroviruses, most do not establish a causal link. However, many AD pathological hallmarks, including beta amyloid plaques (Aβ), astrogliosis, neuroinflammation, and neuronal damage, overlap with pathologies caused by neuroviruses. Approximately 80% of adults are seropositive for human cytomegalovirus (HCMV), a virus that is neuroinvasive, productively infects brain cells, and is immune‐dominant in aging populations. Using post‐mortem tissues from the Rush Alzheimer’s Disease Center we previously reported that HCMV infection is associated with AD clinical markers. In the present study, we assessed the ability of HCMV infection to induce two AD pathological hallmarks in astrocytes: Aβ production and astrocyte reactivity.MethodTo determine the impact of HCMV infection on astrocytes, we generated low‐passage clinical HCMV isolates for infection of human fetal astrocytes (HFA) and astroglioma (U251) cells. To assess the ability of HCMV to produce Aβ, we infected HFAs and U251s with HCMV for 3‐9 days then immunostained for Aβ and HCMV proteins. To test whether HCMV infection results in astrocyte reactivity, we infected HFAs with HCMV for 5 days then quantified levels of reactivity‐associated transcripts via quantitative PCR.ResultHFA and U251 infected cells showed HCMV cytopathic effects characteristic of permissive cells, including enlargement and plaque formation. HCMV infection of HFA and U251 cells induced the expression of Aβ as observed by co‐staining of Aβ and HCMV proteins. Aβ production was observed within 3 days and persisted until at least 9 days post‐infection. To assess the amyloidogenicity of HCMV, we employed the Waltz algorithm, which predicted two amyloidogenic sequences within immunodominant HCMV proteins pp65 and IE1 (average score: 98.3). Further, HCMV infection of HFAs mediated a 2‐ to 4‐ fold induction in CXCL10, CD44, and IRGM, reactivity‐associated genes also involved in immune and inflammatory pathways.ConclusionOur data demonstrate that HCMV infection can contribute to AD pathology in cultured astrocytes. These findings could ultimately inform the use of antiviral therapy to prevent and/or reduce AD severity.