Migration of CD8+ T Cells into the Central Nervous System Gives Rise to Highly Potent Anti-HIV CD4dimCD8bright T Cells in a Wnt Signaling-Dependent Manner

Neurological impact of HIV/AIDS and substance use alters brain function and structure

Human immunodeficiency virus (HIV) infection is the cause of acquired immunodeficiency syndrome (AIDS). Combination antiretroviral therapy (cART) has successfully controlled AIDS, but HIV-associated neurocognitive disorders (HANDs) remain prevalent among people with HIV. HIV infection is often associated with substance use, which promotes HIV transmission and viral replication and exacerbates HANDs even in the era of cART. Thus, the comorbid effects of substance use exacerbate the neuropathogenesis of HANDs. Unraveling the mechanism(s) of this comorbid exacerbation at the molecular, cell-type, and brain region levels may provide a better understanding of HAND persistence. This review aims to highlight the comorbid effects of HIV and substance use in specific brain regions and cell types involved in the persistence of HANDs. This review includes an overview of post-translational modifications, alterations in microglia-specific biomarkers, and possible mechanistic pathways that may link epigenomic modifications to functional protein alterations in microglia. The impairment of the microglial proteins that are involved in neural circuit function appears to contribute to the breakdown of cellular communication and neurodegeneration in HANDs. The epigenetic modification of N-terminal acetylation is currently understudied, which is discussed in brief to demonstrate the important role of this epigenetic modification in infected microglia within specific brain regions. The discussion also explores whether combined antiretroviral therapy is effective in preventing HIV infection or substance-use-mediated post-translational modifications and protein alterations in the persistence of neuropathogenesis in HANDs.

Unravelling the triad of neuroinvasion, neurodissemination, and neuroinflammation of human immunodeficiency virus type 1 in the central nervous system

Since the identification of human immunodeficiency virus type 1 (HIV-1) in 1983, many improvements have been made to control viral replication in the peripheral blood and to treat opportunistic infections. This has increased life expectancy but also the incidence of age-related central nervous system (CNS) disorders and HIV-associated neurodegeneration/neurocognitive impairment and depression collectively referred to as HIV-associated neurocognitive disorders (HAND). HAND encompasses a spectrum of different clinical presentations ranging from milder forms such as asymptomatic neurocognitive impairment or mild neurocognitive disorder to a severe HIV-associated dementia (HAD). Although control of viral replication and suppression of plasma viral load with combination antiretroviral therapy has reduced the incidence of HAD, it has not reversed milder forms of HAND. The objective of this review, is to describe the mechanisms by which HIV-1 invades and disseminates in the CNS, a crucial event leading to HAND. The review will present the evidence that underlies the relationship between HIV infection and HAND. Additionally, recent findings explaining the role of neuroinflammation in the pathogenesis of HAND will be discussed, along with prospects for treatment and control.

Wnt10b knockdown regulates the relative balance of adipose tissue-resident T cells and inhibits white fat deposition

BACKGROUND

Wnt10b is one of critical Wnt family members that being involved in networks controlling stemness, pluripotency and cell fate decisions. However, its role in adipose-resident T lymphocytes and further in fat metabolism yet remains largely unknown.

METHODS AND RESULTS

In the present study, we demonstrated a distinctive effect for Wnt10b on the relative balance of T lymphocytes in adipose tissue by using a Wnt10b knockdown mouse model. Wnt10b knockdown led to a reduction of adipose-resident CD4+ T cells and an elevation of Foxp3+/CD4+ Treg cells. Wnt10b-knockdown mice fed with standard diet showed less white fat deposition owing to the suppressed adipogenic process. Moreover, under high fat diet conditions, Wnt10b knockdown resulted in an alleviated obesity symptoms, as well as an improvement of glucose homeostasis and hepatic steatosis.

CONCLUSIONS

Collectively, we reveal an unexpected and novel function for Wnt10b in mediating the frequency of adipose-resident T cell subsets, that when knockdown skewing toward a Treg-dominated phenotype and further improving fat metabolism.

CD4 dim CD8 bright T cells are inversely associated with neuro-inflammatory markers among people with HIV

OBJECTIVE

HIV-associated neuroinflammation persists in the brain despite suppressive combination antiretroviral therapy (cART). We evaluated associations between a subset of CD8 + T cells, termed CD4 dim CD8 bright T cells, and soluble markers of immune activation and/or neuroinflammation in the cerebrospinal fluid (CSF) and plasma of people with HIV (PWH).

DESIGN

Fifteen cART-naive PWH were enrolled and underwent blood draw, lumbar puncture for CSF collection, and neuropsychological tests at week 0 (pre-cART) and 24 weeks after cART initiation.

METHODS

CSF and peripheral blood T cells were evaluated with flow cytometry and soluble markers of immune activation were measured by multiplex and singleplex assays. Spearman bootstrap correlation coefficients with 10 000 resamples were computed and reported with corresponding 95% confidence intervals (CIs) for each marker of interest and T-cell type.

RESULTS

The frequency of CSF CD4 dim CD8 bright T cells at week 0 was inversely related with CSF neopterin. In contrast, at week 24, CSF CD4 - CD8 + T cells were positively correlated with CSF s100β, a marker of brain injury. In the blood, at week 0, CD4 dim CD8 bright T cells were inversely correlated with MCP-1, IP-10, IL-8, IL-6, G-CSF, and APRIL and positively correlated with plasma RANTES and MMP1. At week 0, the frequency of blood CD4 - CD8 + were positively correlated with CRP and BAFF.

CONCLUSION

CD4 dim CD8 bright T cells are associated with some anti-inflammatory properties, whereas CD4 - CD8 + T cells may contribute to inflammation and injury. Assessing the contrast between these two cell populations in neuroHIV may inform targeted therapeutic intervention to reduce neuroinflammation and associated neurocognitive impairment.

An Efficient Humanized Mouse Model for Oral Anti-Retroviral Administration

HIV anti-retrovirals (ARVs) have vastly improved the life expectancy of people living with HIV (PLWH). However, toxic effects attributed to long-term ARV use also contribute to HIV-related co-morbidities such as heart disease, bone loss and HIV-associated neurocognitive disorders (HAND). Unfortunately, mouse models used to study the effects of ARVs on viral suppression, toxicity and HIV latency/tissue reservoirs have not been widely established. Here, we demonstrate an effective mouse model utilizing immune-compromised mice, reconstituted with infected human peripheral blood mononuclear cell (PBMCs). ARVs areincorporated into mouse chow and administered daily with combination ARV regimens includingAtripla (efavirenz, tenofovir disoproxil fumarate, and emtricitabine) and Triumeq (abacavir, dolutegravir and lamivudine). This model measures HIV-infected human cell trafficking, and ARV penetration throughout most relevant HIV organs and plasma, with a large amount of trafficking to the secondary lymphoid organs. Furthermore, the HIV viral load within each organ and the plasma was reduced in ARV treated vs. untreated control. Overall, we have demonstrated a mouse model that is relatively easy and affordable to establish and utilize to study ARVs' effect on various tissues, including the co-morbid conditions associated with PLWH, such as HAND, and other toxic effects.

HIV infection of non-classical cells in the brain

HIV-associated neurological disorders (HAND) affect up to 50% of people living with HIV (PLWH), even in the era of combination antiretroviral therapy (cART). HIV-DNA can be detected in the cerebral spinal fluid (CSF) of approximately half of aviremic ART-suppressed PLWH and its presence is associated with poorer neurocognitive performance. HIV DNA + and HIV RNA + cells have also been observed in postmortem brain tissue of individuals with sustained cART suppression. In this review, we provide an overview of how HIV invades the brain and HIV infection of resident brain glial cells (astrocytes and microglia). We also discuss the role of resident glial cells in persistent neuroinflammation and HAND in PLWH and their potential contribution to the HIV reservoir. HIV eradication strategies that target persistently infected glia cells will likely be needed to achieve HIV cure.

CD4dim CD8bright T Cells Home to the Brain and Mediate HIV Neuroinvasion

CD4^dim CD8^bright T cells are a mature population of CD8⁺ T cells that upon activation upregulate CD4 dimly on their surface. Expression of CD4 on these cells suggests that they can be an additional source of HIV neuroinvasion and persistence in the brain. We used HIV-infected NOD/SCID/IL-2rcγ^-/- (NSG) humanized mice to track CD4^dim CD8^bright T cell homing to the brain and define their role in HIV dissemination into the brain. We report here that CD4^dim CD8^bright T cells are found in the brain at a median frequency of 2.6% and in the spleen at median frequency of 7.6% of CD3⁺ T cells. In the brain, 10 to 20% of CD4^dim CD8^bright T cells contain integrated provirus, which is infectious as demonstrated by viral outgrowth assay. CD4^dim CD8^bright T cells in the brain exhibited significantly higher expression of the brain homing receptors CX3CR1 and CXCR3 in comparison to their single-positive CD8⁺ T cell counterpart. Blocking lymphocyte trafficking into the brain of humanized mice via anti-VLA4 and anti-LFA1 antibodies reduced CD4^dim CD8^bright T cell trafficking into the brain by 60% and diminished brain HIV proviral DNA by 72%. Collectively, our findings demonstrate that CD4^dim CD8^bright T cells can home to the brain and support productive HIV replication. These studies also reveal for the first time that CD4^dim CD8^bright T cells are capable of HIV neuroinvasion and are a reservoir for HIV. IMPORTANCE We report here a seminal finding of a novel population of T cells, termed CD4^dim CD8^bright T cells, that plays a role in HIV neuroinvasion and is a reservoir for HIV in the brain.

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

What HIV in the Brain Can Teach Us About SARS-CoV-2 Neurological Complications?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of COVID-19, a disease that as of July 10, 2020, has infected >12 million people and killed >500,000. COVID-19 infection leads to acute respiratory distress syndrome in a subset of patients and is a primary driver of acute morbidity in infected persons. However, it is becoming increasingly clear that SARS-CoV-2 infection drives dysfunction and pathology outside the lungs, including reports of renal, cardiac, and neurological complications. In this study, we summarize the known incidence and evidence of neurological complications associated with SARS-CoV-2 infection and other pathogenic coronaviruses. These studies describe a poorly understood spectrum of COVID-19 central nervous system symptoms, ranging from common and subclinical issues such as anosmia and headache to more concerning reports of stroke and encephalopathy. We discuss potential mechanisms of pathogenesis, including a discussion of how the understanding of neurological complications known to occur in HIV-1 patients may provide insight into SARS-CoV-2-associated neurological manifestations. Specifically, three hypotheses are discussed that are informed by decades of knowledge about HIV pathogenesis in the brain, which include a potential direct viral effect, an indirect viral effect, and/or a neuroimmune axis effect. Individually or in combination these potential effects may contribute to COVID-19 neurological complications.

Clonal expansion of CD4+CD8+ T cells in an adult patient with Mycoplasma pneumoniae-associated Erythema multiforme majus

Background

Erythema multiforme (EM) is an acute, immune-mediated mucocutaneous disease, most often preceded by herpes simplex virus (HSV) infection or reactivation. Mycoplasma pneumoniae (Mp) is considered the second major trigger of EM and is often associated with an atypical and more severe presentation of disease, characterized by prominent mucosal involvement. However, contrary to HSV-associated Erythema multiforme (HAEM), immunological mechanisms of Mp-associated EM remain unclear.

Case presentation

We present the case of a 50-year-old male patient presenting with community-acquired pneumonia (CAP) and erythema multiforme majus (EMM). Acute Mp infection was diagnosed by seroconversion, with no evidence of HSV infection as a cause of EMM. We performed immune phenotyping of blister fluid (BF) and peripheral blood (PB) T cells and detected a clonally expanded TCRVβ2⁺ T cell population that was double positive for CD4 and CD8, and expressed the cytotoxic markers granulysin and perforin. This CD4⁺CD8⁺ population comprised up to 50.7% of BF T cells and 24.9% of PB T cells. Two years prior to the onset of disease, the frequency of PB CD4⁺CD8⁺T cells had been within normal range and it gradually returned to baseline levels with the resolution of symptoms, suggesting an involvement of this population in EMM disease pathophysiology.

Conclusions

This report is the first to provide a phenotypic description of lesional T cells in Mp-associated EMM. Characterizing the local immune response might help to address pathophysiological questions and warrants further systematic research.

CD32 is enriched on CD4dimCD8bright T cells

CD4^dimCD8^bright T cells, a genuine population of CD8⁺ T cells, are highly activated and cytolytic. Recently, the low affinity IgG Fc fragment receptor CD32a was described as marker of HIV latency while others reported that CD32a is associated with T cell activation. Given that we have previously established that CD4^dimCD8^bright T cells are highly activated, mediate anti-HIV responses, and are infected by HIV, we assessed here CD32 expression on CD4^dimCD8^bright T cells in context of HIV. CD32 frequency on peripheral CD4^dimCD8^bright and CD4⁺ T cells was determined by flow cytometry among HIV negative and HIV positive patients. We report that among HIV^- individuals, mean CD32 percent expression was 60% on CD4^dimCD8^bright T cells and 17% on CD4⁺ T cells (p<0.01). Among HIV⁺ patients, mean CD32 percent expression was 54% on CD4^dimCD8^bright T cells and 12% on CD4⁺ T cells (p<0.001). CD32 expression on CD4^dimCD8^bright T cells did not correlate with CD4 count and viral load and was not different by HIV serostatus. CD32 was also higher on other double positive T cell populations in both HIV negative and HIV positive donors in comparison to their single positive T cell counterpart. Together, these studies indicate that CD32 is enriched on double positive T cells regardless of HIV serostatus. The functional role of CD32 on these double positive T cells remains to be elucidated.

Role of T Lymphocytes in HIV Neuropathogenesis

PURPOSE OF REVIEW

The purpose of this review is to summarize the current knowledge on the role of CD4⁺ T lymphocytes leading to HIV assault and persistence in the central nervous system (CNS) and the elimination of HIV-infected CNS resident cells by CD8⁺ T lymphocytes.

RECENT FINDINGS

HIV targets the CNS early in infection, and HIV-infected individuals suffer from mild forms of neurological impairments even under antiretroviral therapy (ART). CD4⁺ T cells and monocytes mediate HIV entry into the brain and constitute a source for HIV persistence and neuronal damage. HIV-specific CD8⁺ T cells are also massively recruited in the CNS in acute infection to control viral replication but cannot eliminate HIV-infected cells within the CNS. This review summarizes the involvement of CD4⁺ T cells in seeding and maintaining HIV infection in the brain and describes the involvement of CD8⁺ T cells in HIV neuropathogenesis, playing a role still to be deciphered, either beneficial in eliminating HIV-infected cells or deleterious in releasing inflammatory cytokines.

The impact of substance abuse on HIV-mediated neuropathogenesis in the current ART era

Approximately 37 million people worldwide are infected with human immunodeficiency virus (HIV). One highly significant complication of HIV infection is the development of HIV-associated neurocognitive disorders (HAND) in 15-55% of people living with HIV (PLWH), that persists even in the antiretroviral therapy (ART) era. The entry of HIV into the central nervous system (CNS) occurs within 4-8 days after peripheral infection. This establishes viral reservoirs that may persist even in the presence of ART. Once in the CNS, HIV infects resident macrophages, microglia, and at low levels, astrocytes. In response to chronic infection and cell activation within the CNS, viral proteins, inflammatory mediators, and host and viral neurotoxic factors produced over extended periods of time result in neuronal injury and loss, cognitive deficits and HAND. Substance abuse is a common comorbidity in PLWH and has been shown to increase neuroinflammation and cognitive disorders. Additionally, it has been associated with poor ART adherence, and increased viral load in the cerebrospinal fluid (CSF), that may also contribute to increased neuroinflammation and neuronal injury. Studies have examined mechanisms that contribute to neuroinflammation and neuronal damage in PLWH, and how substances of abuse exacerbate these effects. This review will focus on how substances of abuse, with an emphasis on methamphetamine (meth), cocaine, and opioids, impact blood brain barrier (BBB) integrity and transmigration of HIV-infected and uninfected monocytes across the BBB, as well as their effects on monocytes/macrophages, microglia, and astrocytes within the CNS. We will also address how these substances of abuse may contribute to HIV-mediated neuropathogenesis in the context of suppressive ART. Additionally, we will review the effects of extracellular dopamine, a neurotransmitter that is increased in the CNS by substances of abuse, on HIV neuropathogenesis and how this may contribute to neuroinflammation, neuronal insult, and HAND in PLWH with active substance use. Lastly, we will discuss some potential therapies to limit CNS inflammation and damage in HIV-infected substance abusers.

Canonical and Non-Canonical Wnt Signaling in Immune Cells

Cell differentiation, proliferation, and death are vital for immune homeostasis. Wnt signaling plays essential roles in processes across species. The roles of Wnt signaling proteins and Wnt ligands have been studied in the past, but the context-dependent mechanisms and functions of these pathways in immune responses remain unclear. Recent findings regarding the role of Wnt ligands and Wnt signaling in immune cells and their immunomodulatory mechanisms suggest that Wnt ligands and signaling are significant in regulating immune responses. We introduce recent key findings and future perspectives on Wnt ligands and their signaling pathways in immune cells as well as the immunological roles and functions of Wnt antagonists.

HIV and drug abuse mediate astrocyte senescence in a β-catenin-dependent manner leading to neuronal toxicity

Emerging evidence suggests that cell senescence plays an important role in aging-associated diseases including neurodegenerative diseases. HIV leads to a spectrum of neurologic diseases collectively termed HIV-associated neurocognitive disorders (HAND). Drug abuse, particularly methamphetamine (meth), is a frequently abused psychostimulant among HIV+ individuals and its abuse exacerbates HAND. The mechanism by which HIV and meth lead to brain cell dysregulation is not entirely clear. In this study, we evaluated the impact of HIV and meth on astrocyte senescence using in vitro and several animal models. Astrocytes constitute up to 50% of brain cells and play a pivotal role in marinating brain homeostasis. We show here that HIV and meth induce significant senescence of primary human fetal astrocytes, as evaluated by induction of senescence markers (β-galactosidase and p16^INK4A ), senescence-associated morphologic changes, and cell cycle arrest. HIV- and meth-mediated astrocyte senescence was also demonstrated in three small animal models (humanized mouse model of HIV/NSG-huPBMCs, HIV-transgenic rats, and in a meth administration rat model). Senescent astrocytes in turn mediated neuronal toxicity. Further, we show that β-catenin, a pro-survival/proliferation transcriptional co-activator, is downregulated by HIV and meth in human astrocytes and this downregulation promotes astrocyte senescence while induction of β-catenin blocks HIV- and meth-mediated astrocyte senescence. These studies, for the first time, demonstrate that HIV and meth induce astrocyte senescence and implicate the β-catenin pathway as potential therapeutic target to overcome astrocyte senescence.

Intradermal injection of a Tat Oyi-based therapeutic HIV vaccine reduces of 1.5 log copies/mL the HIV RNA rebound median and no HIV DNA rebound following cART interruption in a phase I/II randomized controlled clinical trial

BACKGROUND

A Tat Oyi vaccine preparation was administered with informed consent to 48 long-term HIV-1 infected volunteers whose viral loads had been suppressed by antiretroviral therapy (cART). These volunteers were randomized in double-blind method into four groups (n = 12) that were injected intradermally with 0, 11, 33, or 99 µg of synthetic Tat Oyi proteins in buffer without adjuvant at times designated by month 0 (M0), M1 and M2, respectively. The volunteers then underwent a structured treatment interruption between M5 and M7.

RESULTS

The primary outcomes of this phase I/IIa clinical trial were the safety and lowering the extent of HIV RNA rebound after cART interruption. Only one undesirable event possibly due to vaccination was observed. The 33 µg dose was most effective at lowering the extent of HIV RNA and DNA rebound (Mann and Whitney test, p = 0.07 and p = 0.001). Immune responses against Tat were increased at M5 and this correlated with a low HIV RNA rebound at M6 (p = 0.01).

CONCLUSION

This study suggests in vivo that extracellular Tat activates and protects HIV infected cells. The Tat Oyi vaccine in association with cART may provide an efficient means of controlling the HIV-infected cell reservoir.