Characterization of Nef expression in different brain regions of SIV-infected macaques.

Shadan S Yarandi,Sarah Vakili,Ilker K Sariyer,Martina Donadoni,Jake A Robinson,Tricia H Burdo,Eliseo A Eugenin

doi:10.1371/journal.pone.0241667

Abstract

ObjectiveHIV-associated CNS dysfunction is a significant problem among people with HIV (PWH), who now live longer due to viral suppression from combined anti-retroviral therapy (ART). Over the course of infection, HIV generates toxic viral proteins and induces inflammatory cytokines that have toxic effects on neurons in the CNS. Among these viral proteins, HIV Nef has been found in neurons of postmortem brain specimens from PWH. However, the source of Nef and its impact on neuronal cell homeostasis are still elusive.Methods and resultsHere, in using a simian immunodeficiency virus (SIV) infected rhesus macaque model of neuroHIV, we find SIV Nef reactivity in the frontal cortex, hippocampus and cerebellum of SIV-infected animals using immunohistochemistry (IHC). Interestingly, SIV-infected macaques treated with ART also showed frequent Nef positive cells in the cerebellum and hippocampus. Using dual quantitative RNAscope and IHC, we observed cells that were positive for Nef, but were not for SIV RNA, suggesting that Nef protein is present in cells that are not actively infected with SIV. Using cell specific markers, we observed Nef protein in microglia/macrophages and astrocytes. Importantly, we also identified a number of NeuN-positive neurons, which are not permissive to SIV infection, but contained Nef protein. Further characterization of Nef-positive neurons showed caspase 3 activation, indicating late stage apoptosis in the CNS neurons.ConclusionsOur results suggest that regardless of ART status, Nef is expressed in the brain of SIV infected macaques and may contribute to neurological complications seen in PWH.

Highlights

Human immunodeficiency virus (HIV) infection has transitioned from a rapidly-progressing, fatal disease to a chronic infection with the intervention of combined antiretroviral therapy (ART) [1, 2]
Our results suggest that regardless of ART status, Negative Regulatory Factor (Nef) is expressed in the brain of simian immunodeficiency virus (SIV) infected macaques and may contribute to neurological complications seen in people with HIV (PWH)
Due to the current clinical presentation of HIV infection where encephalitis is rare, we did not include the lesions seen in SIVE in quantitative analysis and there was no significant difference between the number of Nef+ cells in SIV+ no ART and SIV+ ART+ in three different brain regions analyzed

Summary

Introduction

Human immunodeficiency virus (HIV) infection has transitioned from a rapidly-progressing, fatal disease to a chronic infection with the intervention of combined antiretroviral therapy (ART) [1, 2]. ART successfully suppresses virus in the plasma and effectively increases the life expectancy of people with HIV (PWH) [3, 4]. ART has limited penetrance in certain organs, such as the brain, leading to the formation of viral reservoirs and development of chronic neuroinflammation and neurological disorders [5]. In the pre-ART era, HIV-associated neurocognitive disorders were severe, since the onset of ART more mild forms predominate [6]. Despite suppression of viral replication, persistent neuroinflammation continues to perturb CNS homeostasis [7]. Many studies have investigated HIVassociated neurological dysfunction, the molecular pathways where HIV viral proteins contribute to neurological impairment over the course of HIV infection are not fully understood

Methods

Results

Conclusion