Antibodies to myelin oligodendrocyte glycoprotein in HIV-1 associated neurocognitive disorder: a cross-sectional cohort study

SIV-specific antibodies protect against inflammasome-driven encephalitis in untreated macaques

Viral encephalitis is a growing public health threat with limited diagnostic and treatment options. Simian immunodeficiency virus (SIV)-infected macaques are an established model for human immunodeficiency virus (HIV), and approximately 60% of untreated pigtail macaques rapidly progress to characteristic SIV encephalitis (SIVE). The immune responses of SIV-infected macaques are investigated in plasma, cerebrospinal fluid (CSF), and brain tissue to determine correlates with SIVE pathology. Macaques with SIVE show myeloid-dominant brain lesions with inflammasome activation in infected and bystander cells, as assessed by interleukin (IL)-1β, IL-18, and apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), and elevations in monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1α, and tumor necrosis factor alpha (TNF-α). SIV-specific immunoglobulin (Ig)G in plasma and CSF is predictive of SIVE as early as 21 days post-inoculation; animals with SIVE continue to show negligible seroconversion 3 months after infection. This dichotomy in immune responses, wherein some macaques fail to initiate robust IgG responses and subsequently develop SIVE, provides insight into the pathogenesis and heterogeneous outcomes in viral encephalitis.

HLA-C*07 is associated with symptomatic HIV-1-associated neurocognitive disorders (HAND) and immune dysregulation

BACKGROUND

HIV-1-associated neurocognitive disorders (HAND) in stable patients undergoing antiretroviral therapy (ART) may result from ongoing immune dysregulation and chronic inflammation. A contributing factor may result from the unstable HLA class I allele, HLA-C*07.

OBJECTIVE

To assess the genetic profile of killer-cell immunoglobulin-like receptors (KIR), human leukocyte antigens (HLA), and immune activation or senescence markers and their association with HAND in stable HIV-1 patients receiving ART.

METHODS

An observational cross-sectional study was carried out with 96 patients with asymptomatic or symptomatic HAND. HLA and KIR as well as immune activation/senescence biomarkers in peripheral blood cells were assessed by SSO-Luminex typing and flow cytometry, respectively.

RESULTS

HLA-C*07 is associated with symptomatic HAND. The frequency of two copies of HLA-C*07 was higher in patients with symptomatic than with asymptomatic HAND (12.0 vs. 2.2%, ρ < 0.001). The percentage of senescent CD8+CD28- T-cells was higher in patients with two copies of HLA-C*07 (ρ < 0.05). In patients with symptomatic HAND, the percentages of non-senescent CD8+CD28+ T cells were inversely proportional to the number of copies of the HLA-C*07 (ρ < 0.05).

CONCLUSION

Patients with symptomatic HAND showed a higher frequency of the homozygotic unstable HLA-C*07 allotype, which could be associated with neurocognitive complications. Two copies of HLA-C*07 were associated with immune senescent T lymphocyte profiles characterized by the loss of CD28 expression.

Prevalence of anti-myelin oligodendrocyte glycoprotein antibodies across neuroinflammatory and neurodegenerative diseases

Inflammatory central nervous system (CNS) diseases, such as multiple sclerosis (MS) and myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD), are characterized by humoral immune abnormalities. Anti-MOG antibodies are not specific to MOGAD, with their presence described in MS. Autoantibodies may also be present and play a role in various neurodegenerative diseases. Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease driven by motor neuron dysfunction. While immune involvement in ALS has been recognized, the presence of antibodies targeting CNS myelin antigens has not been established. We aimed to establish a live cell-based assay for quantification of serum anti-MOG IgG1 in patients with CNS diseases, including MS and ALS. In total, 771 serum samples from the John L. Trotter MS Center and the Northeast ALS Consortium were examined using a live cell-based assay for detection of anti-MOG IgG1. Samples from three cohorts were tested in blinded fashion: healthy control (HC) subjects, patients with clinically diagnosed MOGAD, and an experimental group of ALS and MS patients. All samples from established MOGAD cases were positive for anti-MOG antibodies, while all HC samples were negative. Anti-MOG IgG1 was detected in 65 of 658 samples (9.9%) from MS subjects and 4 of 108 (3.7%) samples from ALS subjects. The presence of serum anti-MOG IgG1 in MS and ALS patients raises questions about the contribution of these antibodies to disease pathophysiology as well as accuracy of diagnostic approaches for CNS inflammatory diseases.

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.

The potential role of HIV-1 latency in promoting neuroinflammation and HIV-1-associated neurocognitive disorder

Despite potent suppression of HIV-1 viral replication in the central nervous system (CNS) by antiretroviral therapy (ART), between 15% and 60% of HIV-1-infected patients receiving ART exhibit neuroinflammation and symptoms of HIV-1-associated neurocognitive disorder (HAND) - a significant unmet challenge. We propose that the emergence of HIV-1 from latency in microglia underlies both neuroinflammation in the CNS and the progression of HAND. Recent molecular studies of cellular silencing mechanisms of HIV-1 in microglia show that HIV-1 latency can be reversed both by proinflammatory cytokines and by signals from damaged neurons, potentially creating intermittent cycles of HIV-1 reactivation and silencing in the brain. We posit that anti-inflammatory agents that also block HIV-1 reactivation, such as nuclear receptor agonists, might provide new putative therapeutic avenues for the treatment of HAND.

Bromodomains in Human-Immunodeficiency Virus-Associated Neurocognitive Disorders: A Model of Ferroptosis-Induced Neurodegeneration

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) comprise a group of illnesses marked by memory and behavioral dysfunction that can occur in up to 50% of HIV patients despite adequate treatment with combination antiretroviral drugs. Iron dyshomeostasis exacerbates HIV-1 infection and plays a major role in Alzheimer's disease pathogenesis. In addition, persons living with HIV demonstrate a high prevalence of neurodegenerative disorders, indicating that HAND provides a unique opportunity to study ferroptosis in these conditions. Both HIV and combination antiretroviral drugs increase the risk of ferroptosis by augmenting ferritin autophagy at the lysosomal level. As many viruses and their proteins exit host cells through lysosomal exocytosis, ferroptosis-driving molecules, iron, cathepsin B and calcium may be released from these organelles. Neurons and glial cells are highly susceptible to ferroptosis and neurodegeneration that engenders white and gray matter damage. Moreover, iron-activated microglia can engage in the aberrant elimination of viable neurons and synapses, further contributing to ferroptosis-induced neurodegeneration. In this mini review, we take a closer look at the role of iron in the pathogenesis of HAND and neurodegenerative disorders. In addition, we describe an epigenetic compensatory system, comprised of bromodomain-containing protein 4 (BRD4) and microRNA-29, that may counteract ferroptosis by activating cystine/glutamate antiporter, while lowering ferritin autophagy and iron regulatory protein-2. We also discuss potential interventions for lysosomal fitness, including ferroptosis blockers, lysosomal acidification, and cathepsin B inhibitors to achieve desirable therapeutic effects of ferroptosis-induced neurodegeneration.

IgG intrathecal synthesis in HIV-associated neurocognitive disorder (HAND) according to the HIV-1 subtypes and pattern of HIV RNA in CNS and plasma compartments

We hypothesized that humoral immunity stimulation in the CNS in HIV-1C patients would be lower than that in HIV-1B due to a defective Tat chemokine dimotif (C30C31) that might influence cellular trafficking and CNS inflammation. Sixty-eight paired CSF and blood samples from people with HIV (PWH), free of CNS opportunistic infections, were included, HIV-1B (n = 27), HIV-1C (n = 26), and HIV negative (n = 25). IgG intrathecal synthesis was assayed using quantitative and qualitative methods. IgG oligoclonal bands (OCB) in CSF were observed in 51% of PWH, comparable between HIV-1B and HIV-1C, as well as the medians of IgG intrathecal synthesis formulas. The group with HIV infection aviremic in CSF and blood showed 75% of OCB. There was a poor positive correlation between the IgG quotient and GDS. The impact of HIV-1 on IgG intrathecal production was not subtype dependent. Low-grade CNS intrathecal IgG production persists in HIV CNS infection even in PWH with CSF and blood HIV RNA controlled.

Recovery of HIV encephalopathy in perinatally infected children on antiretroviral therapy

AIM

To describe the trajectory of clinical signs in children who developed human immunodeficiency virus encephalopathy (HIVE) after starting early antiretroviral therapy (ART).

METHOD

This was a retrospective case-cohort description of HIVE among Cape Town participants from the Children with HIV Early AntiRetroviral treatment (CHER) trial. Criteria for HIVE diagnosis were at least two of: (1) acquired central motor deficit, (2) impaired brain growth, and (3) failure to attain or loss of developmental milestones in the absence of an alternative aetiology.

RESULTS

Of 133 surviving participants who initiated ART at a median age of 9 weeks and who were followed until a median age of 6 years, 20 (12%) developed HIVE at a median age 31 months (interquartile range 19-37). In these, the first neurological deterioration was noticed at a median age of 19 months, when 16 were on ART and nine had undetectable HIV viral load for a median of 12 months. Signs of upper motor neurons were present in 18, of whom 12 resolved and four had persistent spastic diplegia; 19 had motor delay, of whom 14 resolved; 12 had language delay, of whom 11 resolved; and 16 had impaired brain growth, of whom only five recovered. For the 16 participants already on ART at HIVE diagnosis, regimens were not altered in response to diagnosis.

INTERPRETATION

HIVE may occur despite early ART initiation and virological suppression and then resolve on unchanged ART, most likely as intrathecal inflammation subsides.

WHAT THIS PAPER ADDS

Despite suppressive antiretroviral therapy, children can develop human immunodeficiency virus encephalopathy, The most common manifestations are motor deficits and impaired brain growth. Most experience improvement, with many resolving without additional intervention.

Myelin oligodendrocyte glycoprotein antibodies in neurological disease

Anti-myelin oligodendrocyte glycoprotein (MOG) antibodies (MOG-Abs) were first detected by immunoblot and enzyme-linked immunosorbent assay nearly 30 years ago, but their association with multiple sclerosis (MS) was not specific. Use of cell-based assays with native MOG as the substrate enabled identification of a group of MOG-Ab-positive patients with demyelinating phenotypes. Initially, MOG-Abs were reported in children with acute disseminated encephalomyelitis (ADEM). Further studies identified MOG-Abs in adults and children with ADEM, seizures, encephalitis, anti-aquaporin-4-antibody (AQP4-Ab)-seronegative neuromyelitis optica spectrum disorder (NMOSD) and related syndromes (optic neuritis, myelitis and brainstem encephalitis), but rarely in MS. This shift in our understanding of the diagnostic assays has re-invigorated the examination of MOG-Abs and their role in autoimmune and demyelinating disorders of the CNS. The clinical phenotypes, disease courses and responses to treatment that are associated with MOG-Abs are currently being defined. MOG-Ab-associated disease is different to AQP4-Ab-positive NMOSD and MS. This Review provides an overview of the current knowledge of MOG, the metrics of MOG-Ab assays and the clinical associations identified. We collate the data on antibody pathogenicity and the mechanisms that are thought to underlie this. We also highlight differences between MOG-Ab-associated disease, NMOSD and MS, and describe our current understanding on how best to treat MOG-Ab-associated disease.

Untreated Patients Dying With AIDS Have Loss of Neocortical Neurons and Glia Cells

Untreated human immunodeficiency virus (HIV) depletes its host CD4 cells, ultimately leading to acquired immunodeficiency syndrome (AIDS). In brain, the HIV confines itself to astrocytes and microglia, the resident brain macrophages, but does not infect oligodendrocytes and neurons. Nonetheless, cognitive symptoms associated with HIV and AIDS are attributed to loss of axons and white matter damage. We used design-based stereology to estimate the numbers of neocortical neurons and glial cells (astrocytes, oligodendrocytes, and microglia), in a series of 12 patients dying with AIDS before the era of retroviral treatments, and in 13 age-matched control brains. Relative to the control material, there was a 19% loss of neocortical neuron (p = 0.04) and a 29% reduction of oligodendrocytes (p = 0.003) in the patients with AIDS, whereas astrocyte and microglia numbers did not differ between patients and controls. Furthermore, we saw a 17% reduction in mean hemispheric volume in the AIDS group (p = 0.0015), which was driven by neocortical and white matter loss (p < 0.05), while the archicortex, subcortical gray matter, and ventricular volumes were within normal limits. Our results confirm previous reports of neuronal loss in AIDS. The new finding of oligodendrocyte loss supports the proposal that HIV in the brain provokes demyelination and axonal dysfunction and suggests that remyelination treatment strategies may be beneficial to patients suffering from HIV-associated neurocognitive deficits.

Symptomatic cerebrospinal fluid HIV-1 escape with no resistance-associated mutations following low-level plasma viremia

The majority of neurologically symptomatic cerebrospinal fluid HIV-1 escape cases are connected with resistance-associated mutations and potentially explained by low cerebrospinal fluid antiretroviral concentrations. However, there are still significant knowledge gaps regarding the physiopathology and long-term management of neurosymptomatic viral escape. We report a case of Parkinson-like syndrome following cerebrospinal fluid HIV-1 escape in a 40-year-old female patient with an history of persistent low-level plasma viremia under treatment. No resistance-associated mutations, high viral diversity (env deep sequencing), adequate pharmacokinetics, atypical CD3-CD14-CD4+CD5-CD2-/+CD7-/+ lymphocytes, low-level Epstein-Barr virus replication, and white matter autoimmune reactivity were observed in the cerebrospinal fluid. Antiretroviral regimen modification led to rapid clinical and radiological improvements. This case may increase the current uncertain knowledge on the origin of cerebrospinal fluid HIV-1 and illustrates the consequences of uncontrolled compartmental viral replication; it also highlights the relevance and persistence of immune activation and the possibility of various detrimental mechanisms underlying neurosymptomatic viral escape.

Lymphocyte-Dominant Encephalitis and Meningitis in Simian Immunodeficiency Virus-Infected Macaques Receiving Antiretroviral Therapy

A retrospective neuropathologic review of 30 SIV-infected pigtailed macaques receiving combination antiretroviral therapy (cART) was conducted. Seventeen animals with lymphocyte-dominant inflammation in the brain and/or meninges that clearly was morphologically distinct from prototypic SIV encephalitis and human immunodeficiency virus encephalitis were identified. Central nervous system (CNS) infiltrates in cART-treated macaques primarily comprised CD20⁺ B cells and CD3⁺ T cells with fewer CD68⁺ macrophages. Inflammation was associated with low levels of SIV RNA in the brain as shown by in situ hybridization, and generally was observed in animals with episodes of cerebrospinal fluid (CSF) viral rebound or sustained plasma and CSF viremia during treatment. Although the lymphocytic CNS inflammation in these macaques shared morphologic characteristics with uncommon immune-mediated neurologic disorders reported in treated HIV patients, including CNS immune reconstitution inflammatory syndrome and neurosymptomatic CSF escape, the high prevalence of CNS lesions in macaques suggests that persistent adaptive immune responses in the CNS also may develop in neuroasymptomatic or mildly impaired HIV patients yet remain unrecognized given the lack of access to CNS tissue for histopathologic evaluation. Continued investigation into the mechanisms and outcomes of CNS inflammation in cART-treated, SIV-infected macaques will advance our understanding of the consequences of residual CNS HIV replication in patients on cART, including the possible contribution of adaptive immune responses to HIV-associated neurocognitive disorders.

HIV-1-associated neurocognitive disorder: epidemiology, pathogenesis, diagnosis, and treatment

The modern antiretroviral treatment of human immunodeficiency virus (HIV-1) infection has considerably lowered the incidence of opportunistic infections. With the exception of the most severe dementia manifestations, the incidence and prevalence of HIV-associated neurocognitive disorders (HAND) have not decreased, and HAND continues to be relevant in daily clinical practice. Now, HAND occurs in earlier stages of HIV infection, and the clinical course differs from that before the widespread use of combination antiretroviral treatment (cART). The predominant clinical feature is a subcortical dementia with deficits in the domains concentration, attention, and memory. Motor signs such as gait disturbance and impaired manual dexterity have become less prominent. Prior to the advent of cART, the cerebral dysfunction could at least partially be explained by the viral load and by virus-associated histopathological findings. In subjects where cART has led to undetectable or at least very low viral load, the pathogenic virus-brain interaction is less direct, and an array of poorly understood immunological and probably toxic phenomena are discussed. This paper gives an overview of the current concepts in the field of HAND and provides suggestions for the diagnostic and therapeutic management.

Oligodendrocyte Injury and Pathogenesis of HIV-1-Associated Neurocognitive Disorders

Oligodendrocytes wrap neuronal axons to form myelin, an insulating sheath which is essential for nervous impulse conduction along axons. Axonal myelination is highly regulated by neuronal and astrocytic signals and the maintenance of myelin sheaths is a very complex process. Oligodendrocyte damage can cause axonal demyelination and neuronal injury, leading to neurological disorders. Demyelination in the cerebrum may produce cognitive impairment in a variety of neurological disorders, including human immunodeficiency virus type one (HIV-1)-associated neurocognitive disorders (HAND). Although the combined antiretroviral therapy has markedly reduced the incidence of HIV-1-associated dementia, a severe form of HAND, milder forms of HAND remain prevalent even when the peripheral viral load is well controlled. HAND manifests as a subcortical dementia with damage in the brain white matter (e.g., corpus callosum), which consists of myelinated axonal fibers. How HIV-1 brain infection causes myelin injury and resultant white matter damage is an interesting area of current HIV research. In this review, we tentatively address recent progress on oligodendrocyte dysregulation and HAND pathogenesis.

[HIV 1-associated neurocognitive disorder: current epidemiology, pathogenesis, diagnosis and management]

By restoring the immunological function the modern antiretroviral treatment of human immunodeficiency virus (HIV-1) infection has considerably lowered the incidence of opportunistic infections. As opposed to the classical manifestations of HIV-induced immunosuppression the incidence and prevalence of HIV-associated neurocognitive disorders (HAND) has not noticeably decreased and HAND continues to be relevant in daily clinical practice. At present, HAND occurs in earlier stages of HIV infection, and the clinical course differs from that before the introduction of combination antiretroviral treatment (cART). The predominant clinical manifestation is a subcortical dementia with deficits in the domains attention, concentration and memory. Signs of central motor pathway lesions have become less frequent and less prominent. Prior to the advent of cART the cerebral dysfunction could at least partially be explained by the viral load and by virus-associated histopathological findings. In patients with at least partially successfully treated infections, this relationship no longer exists, but a plethora of poorly understood immunological and probably toxic phenomena are under discussion.This consensus paper summarizes the progress made in the last 12 years in the field of HAND and provides suggestions for the diagnostic and therapeutic management.

Compartmentalized intrathecal immunoglobulin synthesis during HIV infection - a model of chronic CNS inflammation?

HIV infects the central nervous system (CNS) during primary infection and persists in resident macrophages. CNS infection initiates a strong local immune response that fails to control the virus but is responsible for by-stander lesions involved in neurocognitive disorders. Although highly active anti-retroviral therapy now offers an almost complete control of CNS viral proliferation, low-grade CNS inflammation persists. This review focuses on HIV-induced intrathecal immunoglobulin (Ig) synthesis. Intrathecal Ig synthesis early occurs in more than three-quarters of patients in response to viral infection of the CNS and persists throughout the course of the disease. Viral antigens are targeted but this specific response accounts for <5% of the whole intrathecal synthesis. Although the nature and mechanisms leading to non-specific synthesis are unknown, this prominent proportion is comparable to that observed in various CNS viral infections. Cerebrospinal fluid-floating antibody-secreting cells account for a minority of the whole synthesis, which mainly takes place in perivascular inflammatory infiltrates of the CNS parenchyma. B-cell traffic and lineage across the blood-brain-barrier have not yet been described. We review common technical pitfalls and update the pending questions in the field. Moreover, since HIV infection is associated with an intrathecal chronic oligoclonal (and mostly non-specific) Ig synthesis and associates with low-grade axonal lesions, this could be an interesting model of the chronic intrathecal synthesis occurring during multiple sclerosis.

Systems analysis of human brain gene expression: mechanisms for HIV-associated neurocognitive impairment and common pathways with Alzheimer's disease

Background

Human Immunodeficiency Virus-1 (HIV) infection frequently results in neurocognitive impairment. While the cause remains unclear, recent gene expression studies have identified genes whose transcription is dysregulated in individuals with HIV-association neurocognitive disorder (HAND). However, the methods for interpretation of such data have lagged behind the technical advances allowing the decoding genetic material. Here, we employ systems biology methods novel to the field of NeuroAIDS to further interrogate extant transcriptome data derived from brains of HIV + patients in order to further elucidate the neuropathogenesis of HAND. Additionally, we compare these data to those derived from brains of individuals with Alzheimer’s disease (AD) in order to identify common pathways of neuropathogenesis.

Methods

In Study 1, using data from three brain regions in 6 HIV-seronegative and 15 HIV + cases, we first employed weighted gene co-expression network analysis (WGCNA) to further explore transcriptome networks specific to HAND with HIV-encephalitis (HIVE) and HAND without HIVE. We then used a symptomatic approach, employing standard expression analysis and WGCNA to identify networks associated with neurocognitive impairment (NCI), regardless of HIVE or HAND diagnosis. Finally, we examined the association between the CNS penetration effectiveness (CPE) of antiretroviral regimens and brain transcriptome. In Study 2, we identified common gene networks associated with NCI in both HIV and AD by correlating gene expression with pre-mortem neurocognitive functioning.

Results

Study 1: WGCNA largely corroborated findings from standard differential gene expression analyses, but also identified possible meta-networks composed of multiple gene ontology categories and oligodendrocyte dysfunction. Differential expression analysis identified hub genes highly correlated with NCI, including genes implicated in gliosis, inflammation, and dopaminergic tone. Enrichment analysis identified gene ontology categories that varied across the three brain regions, the most notable being downregulation of genes involved in mitochondrial functioning. Finally, WGCNA identified dysregulated networks associated with NCI, including oligodendrocyte and mitochondrial functioning. Study 2: Common gene networks dysregulated in relation to NCI in AD and HIV included mitochondrial genes, whereas upregulation of various cancer-related genes was found.

Conclusions

While under-powered, this study identified possible biologically-relevant networks correlated with NCI in HIV, and common networks shared with AD, opening new avenues for inquiry in the investigation of HAND neuropathogenesis. These results suggest that further interrogation of existing transcriptome data using systems biology methods can yield important information.

Common transcriptional signatures in brain tissue from patients with HIV-associated neurocognitive disorders, Alzheimer's disease, and Multiple Sclerosis

HIV-Associated Neurocognitive Disorders (HAND) is a common manifestation of HIV infection that afflicts about 50 % of HIV-positive individuals. As people with access to antiretroviral treatments live longer, HAND can be found in increasing segments of populations at risk for other chronic, neurodegenerative conditions such as Alzheimer's disease (AD) and Multiple Sclerosis (MS). If brain diseases of diverse etiologies utilize similar biological pathways in the brain, they may coexist in a patient and possibly exacerbate neuropathogenesis and morbidity. To test this proposition, we conducted comparative meta-analysis of selected publicly available microarray datasets from brain tissues of patients with HAND, AD, and MS. In pair-wise and three-way analyses, we found a large number of dysregulated genes and biological processes common to either HAND and AD or HAND and MS, or to all three diseases. The common characteristic of all three diseases was up-regulation of broadly ranging immune responses in the brain. In addition, HAND and AD share down-modulation of processes involved, among others, in synaptic transmission and cell-cell signaling while HAND and MS share defective processes of neurogenesis and calcium/calmodulin-dependent protein kinase activity. Our approach could provide insight into the identification of common disease mechanisms and better intervention strategies for complex neurocognitive disorders.