Abundance of Nef and p-Tau217 in Brains of Individuals Diagnosed with HIV-Associated Neurocognitive Disorders Correlate with Disease Severance

Nef mediates neuroimmune response, myelin impairment, and neuronal injury in EcoHIV-infected mice

The introduction of antiretroviral therapy has markedly improved the management of HIV-associated neurocognitive disorders (HAND). However, HAND still affects nearly half of HIV-infected individuals, presenting significant challenges to their well-being. This highlights the critical need for a deeper understanding of HAND mechanisms. Among HIV viral proteins, Nef is notable for its multifaceted role in HIV pathogenesis, though its specific involvement in HAND remains unclear. To investigate this, we used a murine model infected with Nef-expressing (EcoHIV) and Nef-deficient (EcoHIVΔNef) murine HIV. Comparative analyses revealed increased neuroinflammation and reduced myelin and neuronal integrity in EcoHIV-infected brains compared with those with EcoHIVΔNef. Both viruses induced astrogliosis, with stronger GFAP activation in Nef-deficient infections. These findings suggest that Nef contributes to neuroinflammation, primarily through microglial targeting and demyelination, although other factors may regulate astrogliosis. Our results indicate that Nef may significantly contribute to neuronal injury in EcoHIV-infected mice, offering insights into Nef-induced neuropathology in HAND and guiding future research.

HIV-1 Nef is carried on the surface of extracellular vesicles

Extracellular vesicles (EVs) serve as pivotal mediators of intercellular communication in both health and disease, delivering biologically active molecules from vesicle-producing cells to recipient cells. In the context of HIV infection, EVs have been shown to carry the viral protein Nef, a key pathogenic factor associated with HIV-related co-morbidities. Despite this recognition, the specific localisation of Nef within the vesicles has remained elusive. This study addresses this critical knowledge gap by investigating Nef-containing EVs. Less than 1% of the total released Nef was associated with EVs; most Nef existed as free protein released by damaged cells. Nevertheless, activity of EV-associated Nef in downregulating the major cholesterol transporter ABCA1, a critical aspect linked to the pathogenic effects of Nef, was comparable to that of free Nef present in the supernatant. Through a series of biochemical and microscopic assays, we demonstrate that the majority of EV-associated Nef molecules are localised on the external surface of the vesicles. This distinctive distribution prompts the consideration of Nef-containing EVs as potential targets for immunotherapeutic interventions aimed at preventing or treating HIV-associated co-morbidities. In conclusion, our results shed light on the localisation and functional activity of Nef within EVs, providing valuable insights for the development of targeted immunotherapies to mitigate the impact of HIV-associated co-morbidities.

Extracellular vesicles produced by HIV-1 Nef-expressing cells induce myelin impairment and oligodendrocyte damage in the mouse central nervous system

HIV-associated neurocognitive disorders (HAND) are a spectrum of cognitive impairments that continue to affect approximately half of all HIV-positive individuals despite effective viral suppression through antiretroviral therapy (ART). White matter pathologies have persisted in the ART era, and the degree of white matter damage correlates with the degree of neurocognitive impairment in patients with HAND. The HIV protein Nef has been implicated in HAND pathogenesis, but its effect on white matter damage has not been well characterized. Here, utilizing in vivo, ex vivo, and in vitro methods, we demonstrate that Nef-containing extracellular vesicles (Nef EVs) disrupt myelin sheaths and inflict damage upon oligodendrocytes within the murine central nervous system. Intracranial injection of Nef EVs leads to reduced myelin basic protein (MBP) staining and a decreased number of CC1 + oligodendrocytes in the corpus callosum. Moreover, cerebellar slice cultures treated with Nef EVs exhibit diminished MBP expression and increased presence of unmyelinated axons. Primary mixed brain cultures and enriched oligodendrocyte precursor cell cultures exposed to Nef EVs display a decreased number of O4 + cells, indicative of oligodendrocyte impairment. These findings underscore the potential contribution of Nef EV-mediated damage to oligodendrocytes and myelin maintenance in the pathogenesis of HAND.

EcoHIV Infection of Primary Murine Brain Cell Cultures to Model HIV Replication and Neuropathogenesis

BACKGROUND

EcoHIV is a chimeric HIV that replicates in mice in CD4+ T cells, macrophages, and microglia (but not in neurons), causing lasting neurocognitive impairment resembling neurocognitive disease in people living with HIV. The present study was designed to develop EcoHIV-susceptible primary mouse brain cultures to investigate the indirect effects of HIV infection on neuronal integrity.

RESULTS

We used two EcoHIV clones encoding EGFP and mouse bone marrow-derived macrophages (BMM), mixed mouse brain cells, or enriched mouse glial cells from two wild-type mouse strains to test EcoHIV replication efficiency, the identity of productively infected cells, and neuronal apoptosis and integrity. EcoHIV replicated efficiently in BMM. In mixed brain cell cultures, EcoHIV targeted microglia but did not cause neuronal apoptosis. Instead, the productive infection of the microglia activated them and impaired synaptophysin expression, dendritic density, and axonal structure in the neurons. EcoHIV replication in the microglia and neuronal structural changes during infection were prevented by culture with an antiretroviral.

CONCLUSIONS

In murine brain cell cultures, EcoHIV replication in the microglia is largely responsible for the aspects of neuronal dysfunction relevant to cognitive disease in infected mice and people living with HIV. These cultures provide a tool for further study of HIV neuropathogenesis and its control.

Neuro-HIV-New insights into pathogenesis and emerging therapeutic targets

HIV-associated neurocognitive disorders (HAND) is a term describing a complex set of cognitive impairments accompanying HIV infection. Successful antiretroviral therapy (ART) reduces the most severe forms of HAND, but milder forms affect over 50% of people living with HIV (PLWH). Pathogenesis of HAND in the ART era remains unknown. A variety of pathogenic factors, such as persistent HIV replication in the brain reservoir, HIV proteins released from infected brain cells, HIV-induced neuroinflammation, and some components of ART, have been implicated in driving HAND pathogenesis in ART-treated individuals. Here, we propose another factor-impairment of cholesterol homeostasis and lipid rafts by HIV-1 protein Nef-as a possible contributor to HAND pathogenesis. These effects of Nef on cholesterol may also underlie the effects of other pathogenic factors that constitute the multifactorial nature of HAND pathogenesis. The proposed Nef- and cholesterol-focused mechanism may provide a long-sought unified explanation of HAND pathogenesis that takes into account all contributing factors. Evidence for the impairment by Nef of cellular cholesterol balance, potential effects of this impairment on brain cells, and opportunities to therapeutically target this element of HAND pathogenesis are discussed.

Accelerated brain aging with opioid misuse and HIV: New insights on the role of glially derived pro-inflammation mediators and neuronal chloride homeostasis

Opioid use disorder (OUD) has become a national crisis and contributes to the spread of human immunodeficiency virus (HIV) infection. Emerging evidence and advances in experimental models, methodology, and our understanding of disease processes at the molecular and cellular levels reveal that opioids per se can directly exacerbate the pathophysiology of neuroHIV. Despite substantial inroads, the impact of OUD on the severity, development, and prognosis of neuroHIV and HIV-associated neurocognitive disorders is not fully understood. In this review, we explore current evidence that OUD and neuroHIV interact to accelerate cognitive deficits and enhance the neurodegenerative changes typically seen with aging, through their effects on neuroinflammation. We suggest new thoughts on the processes that may underlie accelerated brain aging, including dysregulation of neuronal inhibition, and highlight findings suggesting that opioids, through actions at the μ-opioid receptor, interact with HIV in the central nervous system to promote unique structural and functional comorbid deficits not seen in either OUD or neuroHIV alone.

The Persistence of HIV Diversity, Transcription, and Nef Protein in Kaposi's Sarcoma Tumors during Antiretroviral Therapy

Epidemic Kaposi's sarcoma (KS), defined by co-infection with Human Herpes Virus 8 (HHV-8) and the Human Immunodeficiency Virus (HIV), is a major cause of mortality in sub-Saharan Africa. Antiretroviral therapy (ART) significantly reduces the risk of developing KS, and for those with KS, tumors frequently resolve with ART alone. However, for unknown reasons, a significant number of KS cases do not resolve and can progress to death. To explore how HIV responds to ART in the KS tumor microenvironment, we sequenced HIV env-nef found in DNA and RNA isolated from plasma, peripheral blood mononuclear cells, and tumor biopsies, before and after ART, in four Ugandan study participants who had unresponsive or progressive KS after 180-250 days of ART. We performed immunohistochemistry experiments to detect viral proteins in matched formalin-fixed tumor biopsies. Our sequencing results showed that HIV diversity and RNA expression in KS tumors are maintained after ART, despite undetectable plasma viral loads. The presence of spliced HIV transcripts in KS tumors after ART was consistent with a transcriptionally active viral reservoir. Immunohistochemistry staining found colocalization of HIV Nef protein and tissue-resident macrophages in the KS tumors. Overall, our results demonstrated that even after ART reduced plasma HIV viral load to undetectable levels and restored immune function, HIV in KS tumors continues to be transcriptionally and translationally active, which could influence tumor maintenance and progression.

A Rationale and Approach to the Development of Specific Treatments for HIV Associated Neurocognitive Impairment

Neurocognitive impairment (NCI) associated with HIV infection of the brain impacts a large proportion of people with HIV (PWH) regardless of antiretroviral therapy (ART). While the number of PWH and severe NCI has dropped considerably with the introduction of ART, the sole use of ART is not sufficient to prevent or arrest NCI in many PWH. As the HIV field continues to investigate cure strategies, adjunctive therapies are greatly needed. HIV imaging, cerebrospinal fluid, and pathological studies point to the presence of continual inflammation, and the presence of HIV RNA, DNA, and proteins in the brain despite ART. Clinical trials exploring potential adjunctive therapeutics for the treatment of HIV NCI over the last few decades have had limited success. Ideally, future research and development of novel compounds need to address both the HIV replication and neuroinflammation associated with HIV infection in the brain. Brain mononuclear phagocytes (MPs) are the primary instigators of inflammation and HIV protein expression; therefore, adjunctive treatments that act on MPs, such as immunomodulating agents, look promising. In this review, we will highlight recent developments of innovative therapies and discuss future approaches for HIV NCI treatment.

Ectopic expression of HIV-1 Tat modifies gene expression in cultured B cells: implications for the development of B-cell lymphomas in HIV-1-infected patients

An increased frequency of B-cell lymphomas is observed in human immunodeficiency virus-1 (HIV-1)-infected patients, although HIV-1 does not infect B cells. Development of B-cell lymphomas may be potentially due to the action of the HIV-1 Tat protein, which is actively released from HIV-1-infected cells, on uninfected B cells. The exact mechanism of Tat-induced B-cell lymphomagenesis has not yet been precisely identified. Here, we ectopically expressed either Tat or its TatC22G mutant devoid of transactivation activity in the RPMI 8866 lymphoblastoid B cell line and performed a genome-wide analysis of host gene expression. Stable expression of both Tat and TatC22G led to substantial modifications of the host transcriptome, including pronounced changes in antiviral response and cell cycle pathways. We did not find any strong action of Tat on cell proliferation, but during prolonged culturing, Tat-expressing cells were displaced by non-expressing cells, indicating that Tat expression slightly inhibited cell growth. We also found an increased frequency of chromosome aberrations in cells expressing Tat. Thus, Tat can modify gene expression in cultured B cells, leading to subtle modifications in cellular growth and chromosome instability, which could promote lymphomagenesis over time.