HIV-1 clade-specific differences in the induction of neuropathogenesis

Limited HIV-associated neuropathologies and lack of immune activation in sub-saharan African individuals with late-stage subtype C HIV-1 infection

Although previous studies have suggested that subtype B HIV-1 proviruses in the brain are associated with physiological changes and immune activation accompanied with microgliosis and astrogliosis, and indicated that both HIV-1 subtype variation and geographical location might influence the neuropathogenicity of HIV-1 in the brain. The natural course of neuropathogenesis of the most widespread subtype C HIV-1 has not been adequately investigated, especially for people living with HIV (PLWH) in sub-Saharan Africa. To characterize the natural neuropathology of subtype C HIV-1, postmortem frontal lobe and basal ganglia tissues were collected from nine ART-naïve individuals who died of late-stage AIDS with subtype C HIV-1 infection, and eight uninfected deceased individuals as controls. Histological staining was performed on all brain tissues to assess brain pathologies. Immunohistochemistry (IHC) against CD4, p24, Iba-1, GFAP, and CD8 in all brain tissues was conducted to evaluate potential viral production and immune activation. Histological results showed mild perivascular cuffs of lymphocytes only in a minority of the infected individuals. Viral capsid p24 protein was only detected in circulating immune cells of one infected individual, suggesting a lack of productive HIV-1 infection of the brain even at the late-stage of AIDS. Notably, similar levels of Iba-1 or GFAP between HIV + and HIV- brain tissues indicated a lack of microgliosis and astrogliosis, respectively. Similar levels of CD8 + cytotoxic T lymphocyte (CTL) infiltration between HIV + and HIV- brain tissues indicated CTL were not likely to be involved within subtype C HIV-1 infected participants of this cohort. Results from this subtype C HIV-1 study suggest that there is a lack of productive infection and limited neuropathogenesis by subtype C HIV-1 even at late-stage disease, which is in contrast to what was reported for subtype B HIV-1 by other investigators.

Subtype C HIV-1 reservoirs throughout the body in ART-suppressed individuals

Subtype B HIV-1 reservoirs have been intensively investigated, but reservoirs in other subtypes and how they respond to antiretroviral therapy (ART) is substantially less established. To characterize subtype C HIV-1 reservoirs, we implemented postmortem frozen, as well as formalin fixed paraffin embedded (FFPE) tissue sampling of central nervous system (CNS) and peripheral tissues. HIV-1 LTR, gag, envelope (env) DNA and RNA was quantified using genomic DNA and RNA extracted from frozen tissues. RNAscope was used to localize subtype C HIV-1 DNA and RNA in FFPE tissue. Despite uniform viral load suppression in our cohort, PCR results showed that subtype C HIV-1 proviral copies vary both in magnitude and tissue distribution, with detection primarily in secondary lymphoid tissues. Interestingly, the appendix harbored proviruses in all subjects. Unlike subtype B, subtype C provirus was rarely detectable in the CNS, and there was no detectable HIV-1 RNA. HIV-1 RNA was detected in peripheral lymphoid tissues of 6 out of 8 ART-suppressed cases. In addition to active HIV-1 expression in lymphoid tissues, RNAscope revealed HIV RNA detection in CD4-expressing cells in the appendix, suggesting that this tissue was a previously unreported potential treatment-resistant reservoir for subtype C HIV-1.

Neuropathogenesis of HIV-1: insights from across the spectrum of acute through long-term treated infection

This review outlines the neuropathogenesis of HIV, from initial HIV entry into the central nervous system (CNS) to chronic infection, focusing on key advancements in the last 5 years. Discoveries regarding acute HIV infection reveal timing and mechanisms of early HIV entry and replication in the CNS, early inflammatory responses, and establishment of genetically distinct viral reservoirs in the brain. Recent studies additionally explore how chronic HIV infection is maintained in the CNS, examining how the virus remains in a latent "hidden" state in diverse cells in the brain, and how this leads to sustained pathological inflammatory responses. Despite viral suppression with antiretroviral therapy, HIV can persist and even replicate in the CNS, and associate with ongoing neuropathology including CD8 + T-lymphocyte mediated encephalitis. Crucial investigation to advance our understanding of the immune mechanisms that both control viral infection and lead to pathological consequences in the brain is necessary to develop treatments to optimize long-term neurologic health in people living with HIV.

Molecular Modeling of Subtype-Specific Tat Protein Signatures to Predict Tat-TAR Interactions That May Be Involved in HIV-Associated Neurocognitive Disorders

HIV-1 is responsible for a spectrum of neurocognitive deficits defined as HIV-associated neurocognitive disorders (HAND). The HIV transactivator of transcription (Tat) protein plays a key role in the neuropathophysiology of HAND. The Tat protein functions by transactivation of viral genes through its interaction with the transactivation response (TAR) RNA element. Subtype-specific Tat protein signatures including C31S, R57S and Q63E present in Tat subtype C has previously been linked to a lowered neuropathophysiology compared to Tat subtype B. In this study, we attempted to understand the molecular mechanism by which Tat subtype-specific variation, particularly, C31S, R57S, and Q63E influence the Tat-TAR interaction. We performed molecular modeling to generate accurate three-dimensional protein structures of the HIV-1 Tat subtypes C and B using the Swiss model webserver. Thereafter, we performed a molecular docking of the TAR RNA element to each of the Tat subtypes B and C protein structures using the HDOCK webserver. Our findings indicate that Tat subtype B had a higher affinity for the TAR RNA element compared to Tat subtype C based on a higher docking score of −187.37, a higher binding free energy value of −9834.63 ± 216.17 kJ/mol, and a higher number of protein–nucleotide interactions of 26. Furthermore, Tat subtype B displayed more flexible regions when bound to the TAR element and this flexibility could account for the stronger affinity of Tat subtype B to TAR. From the Tat signatures linked to neuropathogenesis, only R57/R57S are involved in Tat-TAR interaction. Due to the lack of electrostatic interactions observed between Tat subtype C and TAR, weaker affinity is observed, and this may contribute to a lower level of neuropathophysiology observed in subtype C infection.

[Analysis of Tat protein characteristics in human immunodeficiency virus type 1 sub-subtype A6 (Retroviridae: Orthoretrovirinae: Lentivirus: Human immunodeficiency virus-1)]

INTRODUCTION

Tat protein is a major factor of HIV (human immunodeficiency virus) transcription regulation and has other activities. Tat is characterized by high variability, with some amino acid substitutions, including subtypespecific ones, being able to influence on its functionality. HIV type 1 (HIV-1) sub-subtype A6 is the most widespread in Russia. Previous studies of the polymorphisms in structural regions of the A6 variant have shown numerous characteristic features; however, Tat polymorphism in A6 has not been studied.Goals and tasks. The main goal of the work was to analyze the characteristics of Tat protein in HIV-1 A6 variant, that is, to identify substitutions characteristic for A6 and A1 variants, as well as to compare the frequency of mutations in functionally significant domains in sub-subtype A6 and subtype B.

MATERIAL AND METHODS

The nucleotide sequences of HIV-1 sub-subtypes A6, A1, A2, A3, A4, subtype B and the reference nucleotide sequence were obtained from the Los Alamos international database.

RESULTS AND DISCUSSION

Q54H and Q60H were identified as characteristic substitutions. Essential differences in natural polymorphisms between sub-subtypes A6 and A1 have been demonstrated. In the CPP-region, there were detected mutations (R53K, Q54H, Q54P, R57G) which were more common in sub-subtype A6 than in subtype B.

CONCLUSION

Tat protein of sub-subtype A6 have some characteristics that make it possible to reliably distinguish it from other HIV-1 variants. Mutations identified in the CPP region could potentially alter the activity of Tat. The data obtained could form the basis for the drugs and vaccines development.

Functional impact of HIV-1 Tat on cells of the CNS and its role in HAND

Human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (Tat) is a potent mediator involved in the development of HIV-1-associated neurocognitive disorders (HAND). Tat is expressed even in the presence of antiretroviral therapy (ART) and is able to enter the central nervous system (CNS) through a variety of ways, where Tat can interact with microglia, astrocytes, brain microvascular endothelial cells, and neurons. The presence of low concentrations of extracellular Tat alone has been shown to lead to dysregulated gene expression, chronic cell activation, inflammation, neurotoxicity, and structural damage in the brain. The reported effects of Tat are dependent in part on the specific HIV-1 subtype and amino acid length of Tat used. HIV-1 subtype B Tat is the most common subtype in North American and therefore, most studies have been focused on subtype B Tat; however, studies have shown many genetic, biologic, and pathologic differences between HIV subtype B and subtype C Tat. This review will focus primarily on subtype B Tat where the full-length protein is 101 amino acids, but will also consider variants of Tat, such as Tat 72 and Tat 86, that have been reported to exhibit a number of distinctive activities with respect to mediating CNS damage and neurotoxicity.

Opioid and neuroHIV Comorbidity - Current and Future Perspectives

With the current national opioid crisis, it is critical to examine the mechanisms underlying pathophysiologic interactions between human immunodeficiency virus (HIV) and opioids in the central nervous system (CNS). Recent advances in experimental models, methodology, and our understanding of disease processes at the molecular and cellular levels reveal opioid-HIV interactions with increasing clarity. However, despite the substantial new insight, the unique impact of opioids on the severity, progression, and prognosis of neuroHIV and HIV-associated neurocognitive disorders (HAND) are not fully understood. In this review, we explore, in detail, what is currently known about mechanisms underlying opioid interactions with HIV, with emphasis on individual HIV-1-expressed gene products at the molecular, cellular and systems levels. Furthermore, we review preclinical and clinical studies with a focus on key considerations when addressing questions of whether opioid-HIV interactive pathogenesis results in unique structural or functional deficits not seen with either disease alone. These considerations include, understanding the combined consequences of HIV-1 genetic variants, host variants, and μ-opioid receptor (MOR) and HIV chemokine co-receptor interactions on the comorbidity. Lastly, we present topics that need to be considered in the future to better understand the unique contributions of opioids to the pathophysiology of neuroHIV. Graphical Abstract Blood-brain barrier and the neurovascular unit. With HIV and opiate co-exposure (represented below the dotted line), there is breakdown of tight junction proteins and increased leakage of paracellular compounds into the brain. Despite this, opiate exposure selectively increases the expression of some efflux transporters, thereby restricting brain penetration of specific drugs.

The Signature Amino Acid Residue Serine 31 of HIV-1C Tat Potentiates an Activated Phenotype in Endothelial Cells

The natural cysteine to serine variation at position 31 of Tat in HIV-1C disrupts the dicysteine motif attenuating the chemokine function of Tat. We ask if there exists a trade-off in terms of a gain of function for HIV-1C Tat due to this natural variation. We constructed two Tat-expression vectors encoding Tat proteins discordant for the serine 31 residue (CS-Tat vs. CC-Tat), expressed the proteins in Jurkat cells under doxycycline control, and performed the whole transcriptome analysis to compare the early events of Tat-induced host gene expression. Our analysis delineated a significant enrichment of pathways and gene ontologies associated with the angiogenic signaling events in CS-Tat stable cells. Subsequently, we validated and compared angiogenic signaling events induced by CS- vs. CC-Tat using human umbilical vein endothelial cells (HUVEC) and the human cerebral microvascular endothelial cell line (hCMEC/D3). CS-Tat significantly enhanced the production of CCL2 from HUVEC and induced an activated phenotype in endothelial cells conferring on them enhanced migration, invasion, and in vitro morphogenesis potential. The ability of CS-Tat to induce the activated phenotype in endothelial cells could be of significance, especially in the context of HIV-associated cardiovascular and neuronal disorders. The findings from the present study are likely to help appreciate the functional significance of the SAR (signature amino acid residues) influencing the unique biological properties.

HIV X4 Variants Increase Arachidonate 5-Lipoxygenase in the Pulmonary Microenvironment and are associated with Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is overrepresented in People Living with Human Immunodeficiency Virus (PLWH). HIV protein gp120 plays a key role in the pathogenesis of HIV-PAH. Genetic changes in HIV gp120 determine viral interactions with chemokine receptors; specifically, HIV-X4 viruses interact with CXCR4 while HIV-R5 interact with CCR5 co-receptors. Herein, we leveraged banked samples from patients enrolled in the NIH Lung HIV studies and used bioinformatic analyses to investigate whether signature sequences in HIV-gp120 that predict tropism also predict PAH. Further biological assays were conducted in pulmonary endothelial cells in vitro and in HIV-transgenic rats. We found that significantly more persons living with HIV-PAH harbor HIV-X4 variants. Multiple HIV models showed that recombinant gp120-X4 as well as infectious HIV-X4 remarkably increase arachidonate 5-lipoxygenase (ALOX5) expression. ALOX5 is essential for the production of leukotrienes; we confirmed that leukotriene levels are increased in bronchoalveolar lavage fluid of HIV-infected patients. This is the first report associating HIV-gp120 genotype to a pulmonary disease phenotype, as we uncovered X4 viruses as potential agents in the pathophysiology of HIV-PAH. Altogether, our results allude to the supplementation of antiretroviral therapy with ALOX5 antagonists to rescue patients with HIV-X4 variants from fatal PAH.

Attention/Working Memory, Learning and Memory in Adult Cameroonians: Normative Data, Effects of HIV Infection and Viral Genotype

OBJECTIVE

There is lack of Cameroonian adult neuropsychological (NP) norms, limited knowledge concerning HIV-associated neurocognitive disorders in Sub-Saharan Africa, and evidence of differential inflammation and disease progression based on viral subtypes. In this study, we developed demographically corrected norms and assessed HIV and viral genotypes effects on attention/working memory (WM), learning, and memory.

METHOD

We administered two tests of attention/WM [Paced Auditory Serial Addition Test (PASAT)-50, Wechsler Memory Scale (WMS)-III Spatial Span] and two tests of learning and memory [Brief Visuospatial Memory Test-Revised (BVMT-R), Hopkins Verbal Learning Test-Revised (HVLT-R)] to 347 HIV+ and 395 seronegative adult Cameroonians. We assessed the effects of viral factors on neurocognitive performance.

RESULTS

Compared to controls, people living with HIV (PLWH) had significantly lower T-scores on PASAT-50 and attention/WM summary scores, on HVLT-R total learning and learning summary scores, on HVLT-R delayed recall, BVMT-R delayed recall and memory summary scores. More PLWH had impairment in attention/WM, learning, and memory. Antiretroviral therapy (ART) and current immune status had no effect on T-scores. Compared to untreated cases with detectable viremia, untreated cases with undetectable viremia had significantly lower (worse) T-scores on BVMT-R total learning, BVMT-R delayed recall, and memory composite scores. Compared to PLWH infected with other subtypes (41.83%), those infected with HIV-1 CRF02_AG (58.17%) had higher (better) attention/WM T-scores.

CONCLUSIONS

PLWH in Cameroon have impaired attention/WM, learning, and memory and those infected with CRF02_AG viruses showed reduced deficits in attention/WM. The first adult normative standards for assessing attention/WM, learning, and memory described, with equations for computing demographically adjusted T-scores, will facilitate future studies of diseases affecting cognitive function in Cameroonians.

Clinico-Immunological Status and Neurocognitive Function of Perinatally Acquired HIV-Positive Children on cART: A Cross-Sectional Correlational Study in South Africa

Despite the undisputed benefits of combination antiretroviral therapy (cART), perinatally acquired human immunodeficiency virus (PHIV) children on treatment often present with a spectrum of neurological deficits known as HIV-associated neurocognitive impairment. Even higher CD4 cell count does not seem to prevent the development of neurocognitive impairment in children with PHIV. While CD4 cell count has shown to have the greatest prognostic value, its association with neurocognitive abilities remains to be clarified. This study aimed at determining the correlation between plasma CD4+ lymphocyte and neurocognitive function in children with PHIV on cART. In total, 152 purposively recruited hospital-based sample of children with PHIV on cART, aged 3 years to 7 years 6 months (mean age, 63.13 months), underwent neurocognitive assessment using the Wechsler Preschool and Primary Scale of Intelligence, Third Edition. Immunological status of each child was based on the plasma CD4+ lymphocyte levels. The mean CD4+ lymphocyte cell count at the time of neurocognitive assessment was 1,259.85 cells/mm3 (mean range, 139-2,717 cells/mm3), with significant age difference on CD4+ lymphocyte count levels [F (2, 149) = 13.58, p = 0.000]. CD4+ lymphocyte counts was significantly correlated with subdomains of neurocognitive function scores of task that measures working memory, processing speed, and perceptual reasoning. Global cognitive ability (Full Scale Intellectual Quotient) had no significant association with immunological status of the children. The findings support an association between immunological status of PHIV infection and executive function task. These neurocognitive faculties are critical for learning, school readiness and success in early childhood, and ultimately treatment adherence in adolescence. The need for early identification of neurodevelopment deficits in children, even when on cART, is crucial because early psychosocial and neurorehabilitative interventions can lead to better outcome for children with PHIV.

HIV-1 Tat: Role in Bystander Toxicity

HIV Tat protein is a critical protein that plays multiple roles in HIV pathogenesis. While its role as the transactivator of HIV transcription is well-established, other non-viral replication-associated functions have been described in several HIV-comorbidities even in the current antiretroviral therapy (ART) era. HIV Tat protein is produced and released into the extracellular space from cells with active HIV replication or from latently HIV-infected cells into neighboring uninfected cells even in the absence of active HIV replication and viral production due to effective ART. Neighboring uninfected and HIV-infected cells can take up the released Tat resulting in the upregulation of inflammatory genes and activation of pathways that leads to cytotoxicity observed in several comorbidities such as HIV associated neurocognitive disorder (HAND), HIV associated cardiovascular impairment, and accelerated aging. Thus, understanding how Tat modulates host and viral response is important in designing novel therapeutic approaches to target the chronic inflammatory effects of soluble viral proteins in HIV infection.

NF-κB Duplications in the Promoter-Variant HIV-1C LTR Impact Inflammation Without Altering Viral Replication in the Context of Simian Human Immunodeficiency Viruses and Opioid-Exposure

Recent spread of the promoter variant (4-κB) Human immunodeficiency virus-1 clade C (HIV-1C) strain is attributed to duplication of the Nuclear Factor Kappa B (NF-κB) binding sites and potential increased heroin consumption in India. To study the underlying biology of 4-κB HIV-1C in rhesus macaques, we engineered a promoter-chimera variant (4NF-κB) Simian Human Immunodeficiency Virus (SHIV) by substituting the HIV-1C Long Terminal Repeat (LTR) region consisting of 4 NF-κB and 3 Sp-1 sites with the corresponding segment in the LTR of SHIV AD8EO. The wild-type (3NF-κB) promoter-chimera SHIV was generated by inactivating the 5' proximal NF-κB binding site in SHIV 4NF-κB. CD8-depleted rhesus macaque PBMCs (RM-PBMCs) were infected with the promoter-chimera and AD8EO SHIVs to determine the effects of opioid-exposure on inflammation, NF-κB activation, neurotoxicity in neuronal cells and viral replication. Morphine-exposure of RM-PBMCs infected with SHIVs 4NF-κB, 3NF-κB, and AD8EO altered cellular transcript levels of monocyte chemoattractant protein 1, interleukin 6, interleukin 1β, and Tumor Necrosis Factor α. Of note, divergent alteration of the cytokine transcript levels was observed with these promoter-chimera wild-type and variant SHIVs. NF-κB activation was observed during infection of all three SHIVs with morphine-exposure. Finally, we observed that SHIV AD8EO infection and exposure to both morphine and naloxone had the greatest impact on the neurotoxicity. The promoter-chimera SHIV 4NF-κB and SHIV 3NF-κB did not have a similar effect on neurotoxicity as compared to SHIV AD8EO. All SHIVs replicated efficiently at comparable levels in RM-PBMCs and morphine-exposure did not alter viral replication kinetics. Future in vivo studies in rhesus macaques will provide greater understanding of 4-κB HIV-1C viral immunopathogenesis and onset of disease in the central nervous system during morphine-exposure.

Signatures of HIV-1 subtype B and C Tat proteins and their effects in the neuropathogenesis of HIV-associated neurocognitive impairments

HIV-associated neurocognitive impairments (HANI) are a spectrum of neurological disorders due to the effects of HIV-1 on the central nervous system (CNS). The HIV-1 subtypes; HIV-1 subtype B (HIV-1B) and HIV-1 subtype C (HIV-1C) are responsible for the highest prevalence of HANI and HIV infections respectively. The HIV transactivator of transcription (Tat) protein is a major contributor to the neuropathogenesis of HIV. The effects of the Tat protein on cells of the CNS is determined by the subtype-associated amino acid sequence variations. The extent to which the sequence variation between Tat-subtypes contribute to underlying mechanisms and neurological outcomes are not clear. In this review of the literature, we discuss how amino acid variations between HIV-1B Tat (TatB) and HIV-1C Tat (TatC) proteins contribute to the potential underlying neurobiological mechanisms of HANI. Tat-C is considered to be a more effective transactivator, whereas Tat-B may exert increased neurovirulence, including neuronal apoptosis, monocyte infiltration into the brain, (neuro)inflammation, oxidative stress and blood-brain barrier damage. These findings support the premise that Tat variants from different HIV-1 subtypes may direct neurovirulence and neurological outcomes in HANI.

Differential Contribution of HIV-1 Subtypes B and C to Neurological Disorders: Mechanisms and Possible Treatments

With the introduction of combinatory antiretroviral therapy, patients infected with human immunodeficiency virus type 1 (HIV-1) can live much longer than before. However, the identification of HIV-associated neurocognitive disorder (HAND), especially HIV-associated dementia in 15-20% of patients infected with HIV-1, indicates additional complexity. These disorders turn out to be subtype dependent. Recently, many studies are ongoing trying to understand how the virus induces neuronal injury which could lead to neurological dysfunction. Most of these studies are focusing on the HIV-1 release of proteins such as Tat. However, the exact role of these proteins and their involvement in neuronal degeneration remains unidentified; this is especially true since viral proteins from different HIV-1 subtypes differ in their ability to cause neuronal damage. This review describes the role of different HIV-1 subtypes, identifies probable pathways involved in neuronal damage, the contribution of different HIV-1 subtypes to the progression of HAND, and potential treatments for HAND.

CCL2 mobilizes ALIX to facilitate Gag-p6 mediated HIV-1 virion release

Cellular ESCRT machinery plays pivotal role in HIV-1 budding and release. Extracellular stimuli that modulate HIV-1 egress are currently unknown. We found that CCL2 induced by HIV-1 clade B (HIV-1B) infection of macrophages enhanced virus production, while CCL2 immuno-depletion reversed this effect. Additionally, HIV-1 clade C (HIV-1C) was refractory to CCL2 levels. We show that CCL2-mediated increase in virus production requires Gag late motif LYPX present in HIV-1B, but absent in HIV-1C, and ALIX protein that recruits ESCRT III complex. CCL2 immuno-depletion sequestered ALIX to F-actin structures, while CCL2 addition mobilized it to cytoplasm facilitating Gag-ALIX binding. The LYPX motif improves virus replication and its absence renders the virus less fit. Interestingly, novel variants of HIV-1C with PYRE/PYKE tetrapeptide insertions in Gag-p6 conferred ALIX binding, CCL2-responsiveness and enhanced virus replication. These results, for the first time, indicate that CCL2 mediates ALIX mobilization from F-actin and enhances HIV-1 release and fitness.

A Naturally Occurring Polymorphism in the HIV-1 Tat Basic Domain Inhibits Uptake by Bystander Cells and Leads to Reduced Neuroinflammation

HIV-1 Tat protein contributes to HIV-neuropathogenesis in several ways including its ability to be taken up by uninfected bystander CNS cells and to activate inflammatory host genes causing synaptic injury. Here, we report that in the globally dominant HIV-1 clade C, Tat displays a naturally occurring polymorphism, R57S, in its basic domain, which mediates cellular uptake. We examined the effect of this polymorphism on Tat uptake and its consequences for cellular gene transactivation. In decapeptides corresponding to the basic domain, a R57S substitution caused up to a 70% reduction in uptake. We also used a transcellular Tat transactivation assay, where we expressed Tat proteins of HIV-1 clade B (Tat-B) or C (Tat-C) or their position 57 variants in HeLa cells. We quantified the secreted Tat proteins and measured their uptake by TZM-bl cells, which provide readout via an HIV-1 Tat-responsive luciferase gene. Transactivation by Tat-B was significantly reduced by R57S substitution, while that of Tat-C was enhanced by the reciprocal S57R substitution. Finally, we exposed microglia to Tat variants and found that R57 is required for maximal neuroinflammation. The R57S substitution dampened this response. Thus, genetic variations can modulate the ability of HIV-1 Tat to systemically disseminate neuroinflammation.

Risk Factors and Pathogenesis of HIV-Associated Neurocognitive Disorder: The Role of Host Genetics

Neurocognitive impairments associated with human immunodeficiency virus (HIV) infection remain a considerable health issue for almost half the people living with HIV, despite progress in HIV treatment through combination antiretroviral therapy (cART). The pathogenesis and risk factors of HIV-associated neurocognitive disorder (HAND) are still incompletely understood. This is partly due to the complexity of HAND diagnostics, as phenotypes present with high variability and change over time. Our current understanding is that HIV enters the central nervous system (CNS) during infection, persisting and replicating in resident immune and supporting cells, with the subsequent host immune response and inflammation likely adding to the development of HAND. Differences in host (human) genetics determine, in part, the effectiveness of the immune response and other factors that increase the vulnerability to HAND. This review describes findings from studies investigating the role of human host genetics in the pathogenesis of HAND, including potential risk factors for developing HAND. The similarities and differences between HAND and Alzheimer's disease are also discussed. While some specific variations in host genes regulating immune responses and neurotransmission have been associated with protection or risk of HAND development, the effects are generally small and findings poorly replicated. Nevertheless, a few specific gene variants appear to affect the risk for developing HAND and aid our understanding of HAND pathogenesis.

[Genetic diversity of human immunodeficiency viruses and antiretroviral therapy]

The lecture is devoted to the analysis of the state-of-the-art of the impact of genetic diversity of human immunodeficiency (HIV) viruses on the pattern of infection and the efficiency of antiretroviral therapy (ART). It provides brief information on the origin and evolution of HIV and on the current classification of their genetic variants. The molecular epidemiological situation of HIV infection in Russia and nearby states and the major molecular HIV variants that are dominant in these countries, as well as their origin and prevalence trends are characterized. How the diversity of HIV can affect the efficiency of diagnosis, the transmission of the virus, and the pattern of HIV pathogenesis are briefly reviewed. The comparative data available in the world's scientific literature on these topics are given. More detailed attention is given to the possible causes of varying therapeutic effects against different HIV subtypes, as well as to the specific features of the formation and phenotyping manifestation of ART drug resistance mutations. There is evidence for the necessity of forming a unified follow-up system for treated HIV-infected patients during ART scaling, including in an effort to evaluate the impact of the specific features of the HIV genome on the efficiency of treatment regimens used in Russia.

Brain is a potential sanctuary for subtype C HIV-1 irrespective of ART treatment outcome

Subtype C HIV-1 is responsible for the largest proportion of people living with HIV-1 infection. However, there is limited information about the roles of the brain and its cell types as a potential sanctuary for this subtype and how the sanctuary may be affected by the administration of anti-retroviral therapy (ART). To address this issue, we collected postmortem brain tissues from ART treated HIV-1 infected Zambian individuals who experienced complete viral suppression and those who did not. Tissues from various brain compartments were collected from each individual as frozen and formalin-fixed paraffin embedded brain specimens, for detection and quantification of HIV-1 genomes and identification of the infected cell type. Genomic DNA and RNA were extracted from frozen brain tissues. The extracted DNA and RNA were then subjected to droplet digital PCR for HIV-1 quantification. RNA/DNAscope in situ hybridization (ISH) for HIV-1 was performed on formalin-fixed paraffin embedded brain tissues in conjugation with immunohistochemistry to identify the infected cell types. Droplet digital PCR revealed that HIV-1 gag DNA and RNA were detectable in half of the cases studied regardless of ART success or failure. The presence of HIV-1 lacked specific tissue compartmentalization since detection was random among various brain tissues. When combined with immunohistochemistry, RNA/DNAscope ISH demonstrated co-localization of HIV-1 DNA with CD68 expressing cells indicative of microglia or peripheral macrophage. Our study showed that brain is a potential sanctuary for subtype C HIV-1, as HIV-1 can be detected in the brain of infected individuals irrespective of ART treatment outcome and no compartmentalization of HIV-1 to specific brain compartments was evident.

T cells establish and maintain CNS viral infection in HIV-infected humanized mice

The human brain is an important site of HIV replication and persistence during antiretroviral therapy (ART). Direct evaluation of HIV infection in the brains of otherwise healthy individuals is not feasible; therefore, we performed a large-scale study of bone marrow/liver/thymus (BLT) humanized mice as an in vivo model to study HIV infection in the brain. Human immune cells, including CD4+ T cells and macrophages, were present throughout the BLT mouse brain. HIV DNA, HIV RNA, and/or p24+ cells were observed in the brains of HIV-infected animals, regardless of the HIV isolate used. HIV infection resulted in decreased numbers of CD4+ T cells, increased numbers of CD8+ T cells, and a decreased CD4+/CD8+ T cell ratio in the brain. Using humanized T cell-only mice (ToM), we demonstrated that T cells establish and maintain HIV infection of the brain in the complete absence of human myeloid cells. HIV infection of ToM resulted in CD4+ T cell depletion and a reduced CD4+/CD8+ T cell ratio. ART significantly reduced HIV levels in the BLT mouse brain, and the immune cell populations present were indistinguishable from those of uninfected controls, which demonstrated the effectiveness of ART in controlling HIV replication in the CNS and returning cellular homeostasis to a pre-HIV state.

HIV/neuroAIDS biomarkers

HIV infection often causes neurological symptoms including cognitive and motor dysfunction, which have been collectively termed HIV/neuroAIDS. Neuropsychological assessment and clinical symptoms have been the primary diagnostic criteria for HIV/neuroAIDS, even for the mild cognitive and motor disorder, the most prevalent form of HIV/neuroAIDS in the era of combination antiretroviral therapy. Those performance-based assessments and symptoms are generally descriptive and do not have the sensitivity and specificity to monitor the diagnosis, progression, and treatment response of the disease when compared to objective and quantitative laboratory-based biological markers, or biomarkers. In addition, effects of demographics and comorbidities such as substance abuse, psychiatric disease, nutritional deficiencies, and co-infection on HIV/neuroAIDS could be more readily determined using biomarkers than using neuropsychological assessment and clinical symptoms. Thus, there have been great efforts in identification of HIV/neuroAIDS biomarkers over the past two decades. The need for reliable biomarkers of HIV/neuroAIDS is expected to increase as the HIV-infected population ages and their vulnerability to neurodegenerative diseases, particularly Alzheimer's disease increases. Currently, three classes of HIV/neuroAIDS biomarkers are being pursued to establish objective laboratory-based definitions of HIV-associated neurologic injury: cerebrospinal fluid biomarkers, blood biomarkers, and neuroimaging biomarkers. In this review, we will focus on the current knowledge in the field of HIV/neuroAIDS biomarker discovery.

A mouse model of HIV-associated neurocognitive disorders: a brain-behavior approach to discover disease mechanisms and novel treatments

HIV-associated neurocognitive disorders (HAND) remain highly prevalent despite combined antiretroviral therapy (cART). Although the most common forms of HAND are mild and identified through neuropsychological testing, there is evidence that with aging these mild forms become more prevalent and may advance to the most severe form of HAND, HIV-associated dementia. Therefore, novel therapies must be developed that can be used adjunctively with cART to prevent deterioration or restore normal cognitive function. In order to develop innovative treatments, animal models are used for preclinical testing. Ideally, a HAND animal model should portray similar mild cognitive deficits that are found in humans. A mouse model of HAND is discussed, which demonstrates mild behavioral deficits and has been used to investigate cART and novel treatments for HAND. This model also shows correlations between abnormal mouse behavior due to HIV in the brain and pathological parameters such as gliosis and neuronal abnormalities. A recent advancement utilizes the object recognition test to monitor mouse behavior before and after treatment. It is postulated that this model is well suited for preclinical testing of novel therapies and provides correlations of mild cognitive impairment with pathological markers that can give further insight into the pathophysiology of HAND.

HIV-associated synaptic degeneration

Human immunodeficiency virus (HIV) infection induces neuronal injuries, with almost 50% of infected individuals developing HIV-associated neurocognitive disorders (HAND). Although highly activate antiretroviral therapy (HAART) has significantly reduced the incidence of severe dementia, the overall prevalence of HAND remains high. Synaptic degeneration is emerging as one of the most relevant neuropathologies associate with HAND. Previous studies have reported critical roles of viral proteins and inflammatory responses in this pathogenesis. Infected cells, including macrophages, microglia and astrocytes, may release viral proteins and other neurotoxins to stimulate neurons and cause excessive calcium influx, overproduction of free radicals and disruption of neurotransmitter hemostasis. The dysregulation of neural circuits likely leads to synaptic damage and loss. Identification of the specific mechanism of the synaptic degeneration may facilitate the development of effective therapeutic approaches to treat HAND.

Neuroimaging abnormalities in clade C HIV are independent of Tat genetic diversity

Controversy remains regarding the neurotoxicity of clade C human immunodeficiency virus (HIV-C). When examined in preclinical studies, a cysteine to serine substitution in the C31 dicysteine motif of the HIV-C Tat protein (C31S) results in less severe brain injury compared to other viral clades. By contrast, patient cohort studies identify significant neuropsychological impairment among HIV-C individuals independent of Tat variability. The present study clarified this discrepancy by examining neuroimaging markers of brain integrity among HIV-C individuals with and without the Tat substitution. Thirty-seven HIV-C individuals with the Tat C31S substitution, 109 HIV-C individuals without the Tat substitution (C31C), and 34 HIV- controls underwent 3T structural magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). Volumes were determined for the caudate, putamen, thalamus, corpus callosum, total gray matter, and total white matter. DTI metrics included fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). Tracts of interest included the anterior thalamic radiation (ATR), cingulum bundle (CING), uncinate fasciculus (UNC), and corpus callosum (CC). HIV+ individuals exhibited smaller volumes in subcortical gray matter, total gray matter and total white matter compared to HIV- controls. HIV+ individuals also exhibited DTI abnormalities across multiple tracts compared to HIV- controls. By contrast, neither volumetric nor diffusion indices differed significantly between the Tat C31S and C31C groups. Tat C31S status is not a sufficient biomarker of HIV-related brain integrity in patient populations. Clinical attention directed at brain health is warranted for all HIV+ individuals, independent of Tat C31S or clade C status.

EFFECTS OF COMBRETUM HEREROENSE AND CANTHIUMMUNDIANUM water EXTRACTS ON PRODUCTION AND EXPRESSION OF INTERLEUKIN-4

BACKGROUND

Combretum hereroense and Canthium mundianum are two plants commonly used by traditional healers in the Northern region of Limpopo, South Africa for the treatment of diarrhea and inflammation. In the present study, the effects of their water extracts on the production and expression of interleukin-4 by peripheral blood mononuclear cells (PBMC'S) from HIV positive and negative individuals was evaluated.

MATERIALS AND METHODS

Blood samples were collected from both HIV positive and HIV negative volunteers and were used for the purification of Peripheral blood mononuclear cells (PBMC). The PBMCs were cultured together with the water extracts after activation with phytohemagglutinin (PHA) for three days. Solid-phase sandwich ELISA (MABTECH) kit was used to detect IL-4 on un-stimulated and stimulated PBMC'S with phytohemaglutinin (PHA) and plant extracts, followed by the isolation of RNA using RNAesy Qiagen mini kit from the cells. Reverse transcriptase real time PCR was used to evaluate IL-4 gene expression by the cells.

RESULTS

Combretum hereroense showed higher production of IL-4 at three different concentrations and a significant expression of mRNA with 4-fold amplification increase at 300μg/ml and 2-fold amplification increase at 20μg/ml. Canthium mundianum also showed increased production of IL-4 at 300μg/ml, but inhibited its production at 20μg/ml. Both extracts showed no expression at 50μg/ml. The response of the PBMCs from HIV negative individuals was more pronounced than that of HIV positive individuals who mostly increased production of IL4 at smaller concentrations unlike their HIV negative counterparts. Although in vitro studies do not necessarily predict in vivo outcomes, the plant extracts modulated the immune system by enhancing the production and expression of IL-4 in both HIV- and HIV+ individuals at different concentrations.

CONCLUSIONS

For the first time we have shown that the immunomodulatory effect of medicinal plants may depend on the clinical status of the individual. The present study revealed that the effect of the water extracts from the two plants on IL-4 expression and production is dependent on the microbiological state of the individual and is dose dependent. Further studies are needed to identify the active components in the extracts and also characterize the patients further for a better understanding of the mechanisms of action of these extracts.

Biomarkers of chemotaxis and inflammation in cerebrospinal fluid and serum in individuals with HIV-1 subtype C versus B

A defective chemokine motif in the HIV-1 Tat protein has been hypothesized to alter central nervous system cellular trafficking and inflammation, rendering HIV-1 subtype C less neuropathogenic than B. To evaluate this hypothesis, we compared biomarkers of cellular chemotaxis and inflammation in cerebrospinal fluid (CSF) and serum in individuals infected with HIV-1 subtypes B (n = 27) and C (n = 25) from Curitiba, Brazil. None had opportunistic infections. Chemokines (MCP-1, MIP-1α, MIP-1β, RANTES, IP-10) and cytokines (TNF-α, IFN-γ, IL-1β, IL-2, IL-4, IL-6, IL-7, IL-10) were measured using the multiplex bead suspension array immunoassays or ELISA HD. CSF and serum biomarker concentrations were compared between subtype B and C groups and HIV-positive and HIV-negative subjects (N = 19) using an independent group t test (unadjusted analysis) and linear regression (adjusted analysis), controlling for nadir CD4 and CSF and plasma HIV RNA suppression. CSF levels of cytokines and chemokines were significantly (p < 0.05) elevated in HIV-positive versus HIV-negative participants for 7/13 biomarkers measured, but levels did not differ for subtypes B and C. Serum levels were significantly elevated for 4/13 markers, with no significant differences between subtypes B and C. Although pleocytosis was much more frequent in HIV-positive than in HIV-negative individuals (27 vs. 0 %), subtypes B and C did not differ (32 and 22 %; p = 0.23). We did not find molecular evidence to support the hypothesis that intrathecal chemotaxis and inflammation is less in HIV-1 subtype C than in subtype B. Biomarker changes in CSF were more robust than in serum, suggesting compartmentalization of the immunological response to HIV.

The Evolving Profile of the Signature Amino Acid Residues in HIV-1 Subtype C Tat

Using several HIV-1 tat exon 1 amino acid sequences available from public databases and additional sequences derived from a southern Indian clinical cohort, we compared the profile of the signature amino acid residues (SAR) between two different time periods, 1986-2004 and 2005-2014. The analysis identified eight positions as signature residues in subtype C Tat and demonstrated a changing pattern at four of these positions between the two periods. At three locations (histidine 29, serine 57, and proline 60), there appears to be a nonuniform negative selection against the SAR. The negative selection appears to be severe, especially against histidine 29 (p < .0001) and moderate against proline 60 (p < .0001). The negative selection against serine 57 is statistically insignificant and appears to have begun recently. At position 63, the frequency of signature residue glutamic acid increased over the past decade, although the difference was not significant. Importantly, at the three locations where the negative selection is in progress, the substitute amino acids are the generic residues present in most of the other HIV-1 subtypes. Our data demonstrate that viral evolution can subject specific amino acid residues to subtle and progressive selection pressures without affecting the prevalence of other amino acid residues.

Mortality of treated HIV-1 positive individuals according to viral subtype in Europe and Canada: collaborative cohort analysis

OBJECTIVES

To estimate prognosis by viral subtype in HIV-1-infected individuals from start of antiretroviral therapy (ART) and after viral failure.

DESIGN

Collaborative analysis of data from eight European and three Canadian cohorts.

METHODS

Adults (N>20 000) who started triple ART between 1996 and 2012 and had data on viral subtype were followed for mortality. We estimated crude and adjusted (for age, sex, regimen, CD4 cell count, and AIDS at baseline, period of starting ART, stratified by cohort, region of origin and risk group) mortality hazard ratios (MHR) by subtype. We estimated MHR subsequent to viral failure defined as two HIV-RNA measurements greater than 500 copies/ml after achieving viral suppression.

RESULTS

The most prevalent subtypes were B (15 419; 74%), C (2091; 10%), CRF02AG (1057; 5%), A (873; 4%), CRF01AE (506; 2.4%), G (359; 1.7%), and D (232; 1.1%). Subtypes were strongly patterned by region of origin and risk group. During 104 649 person-years of observation, 1172/20 784 patients died. Compared with subtype B, mortality was higher for subtype A, but similar for all other subtypes. MHR for A versus B were 1.13 (95% confidence interval 0.85,1.50) when stratified by cohort, increased to 1.78 (1.27,2.51) on stratification by region and risk, and attenuated to 1.59 (1.14,2.23) on adjustment for covariates. MHR for A versus B was 2.65 (1.64,4.28) and 0.95 (0.57,1.57) for patients who started ART with CD4 cell count below, or more than, 100 cells/μl, respectively. There was no difference in mortality between subtypes A, B and C after viral failure.

CONCLUSION

Patients with subtype A had worse prognosis, an observation which may be confounded by socio-demographic factors.

Multivariable analysis to determine if HIV-1 Tat dicysteine motif is associated with neurodevelopmental delay in HIV-infected children in Malawi

Background

HIV-1 Tat protein is implicated in HIV-neuropathogenesis. Tat C31S polymorphism (Tat^CS) has been associated with milder neuropathology in vitro and in animal models but this has not been addressed in a cohort of HIV-infected adults or children.

Methods

HIV viral load (VL) in plasma and cerebrospinal fluid (CSF) were determined and plasma HIV tat gene was sequenced. Neurodevelopmental assessment was performed using Bayley Scales of Infant Development III (BSID-III), with scores standardized to Malawian norms. The association between Tat^CS and BSID-III scores was evaluated using multivariate linear regression.

Results

Neurodevelopmental assessment and HIV tat genotyping were available for 33 children. Mean age was 19.4 (SD 7.1) months, mean log VL was 5.9 copies/mL (SD 0.1) in plasma and 3.9 copies/mL (SD 0.9) in CSF. The prevalence of Tat^CC was 27 %. Z-scores for BSID-III subtests ranged from −1.3 to −3.9. Tat^CC was not associated with higher BSID-III z-scores.

Conclusions

The hypothesis of milder neuropathology in individuals infected with HIV Tat^CS was not confirmed in this small cohort of Malawian children. Future studies of tat genotype and neurocognitive disorder should be performed using larger sample sizes and investigate if this finding is due to differences in HIV neuropathogenesis between children and adults.

Cerebral injury in perinatally HIV-infected children compared to matched healthy controls

OBJECTIVE

The current study aims to evaluate the neurologic state of perinatally HIV-infected children on combination antiretroviral therapy and to attain a better insight into the pathogenesis of their persistent neurologic and cognitive deficits.

METHODS

We included perinatally HIV-infected children between 8 and 18 years and healthy controls matched for age, sex, ethnicity, and socioeconomic status. All participants underwent a 3.0 T MRI with 3D-T1-weighted, 3D-fluid-attenuated inversion recovery, and diffusion-weighted series for the evaluation of cerebral volumes, white matter hyperintensities (WMH), and white matter (WM) diffusion characteristics. Associations with disease-related parameters and cognitive performance were explored using linear regression models.

RESULTS

We included 35 cases (median age 13.8 years) and 37 controls (median age 12.1 years). A lower gray matter and WM volume, more WMH, and a higher WM diffusivity were observed in the cases. Within the HIV-infected children, a poorer clinical, immunologic, and virologic state were negatively associated with volumetric, WMH, and diffusivity markers.

CONCLUSIONS

In children with HIV, even when long-term clinically and virologically controlled, we found lower brain volumes, a higher WMH load, and poorer WM integrity compared to matched controls. These differences occur in the context of a poor cognitive performance in the HIV-infected group, and larger, longitudinal studies are needed to increase our understanding of the pathogenesis of cerebral injury in perinatally HIV-infected children.

Executive Dyscontrol of Learning and Memory: Findings from a Clade C HIV-positive South African Sample

OBJECTIVE

Although pre-clinical work suggests there might be differences in neurovirulence across HIV-1 clades, few studies investigate neuropsychological deficits in the globally predominant clade C infection. The purpose of this study was to investigate verbal learning and memory performance in HIV-positive individuals in Cape Town, South Africa, where clade C is the most prevalent subtype of the virus.

METHOD

Using a case-control design, we recruited 53 isiXhosa-speaking, cART-naïve HIV-positive adults and 53 demographically matched HIV-negative controls. Participants were administered a comprehensive neuropsychological test battery. The test of interest was the Hopkins Verbal Learning Test-Revised (HVLT-R); previous studies have used that instrument to identify executive dyscontrol of verbal learning and memory processes in clade B HIV-positive participants.

RESULTS

HIV-positive participants showed only partial impairment on the HVLT-R's learning/memory components (e.g., they recalled significantly fewer words across learning trials, but displayed relatively intact performance on delayed recall trials). They also displayed little executive dyscontrol over encoding and retrieval processes (e.g., there were no significant between-group differences on measures of semantic or serial clustering).

CONCLUSIONS

Post-cART era studies suggest that verbal learning and memory performance is impaired in clade B samples, at least partially due to executive dyscontrol over encoding and retrieval processes. We found few such impairments in the current clade C sample. These preliminary findings suggest different CNS vulnerability across clades that would have implications for delineating clade-specific neuropathological and neurocognitive clinical features.

The cross-talk of HIV-1 Tat and methamphetamine in HIV-associated neurocognitive disorders

Antiretroviral therapy has dramatically improved the lives of human immunodeficiency virus 1 (HIV-1) infected individuals. Nonetheless, HIV-associated neurocognitive disorders (HAND), which range from undetectable neurocognitive impairments to severe dementia, still affect approximately 50% of the infected population, hampering their quality of life. The persistence of HAND is promoted by several factors, including longer life expectancies, the residual levels of virus in the central nervous system (CNS) and the continued presence of HIV-1 regulatory proteins such as the transactivator of transcription (Tat) in the brain. Tat is a secreted viral protein that crosses the blood–brain barrier into the CNS, where it has the ability to directly act on neurons and non-neuronal cells alike. These actions result in the release of soluble factors involved in inflammation, oxidative stress and excitotoxicity, ultimately resulting in neuronal damage. The percentage of methamphetamine (MA) abusers is high among the HIV-1-positive population compared to the general population. On the other hand, MA abuse is correlated with increased viral replication, enhanced Tat-mediated neurotoxicity and neurocognitive impairments. Although several strategies have been investigated to reduce HAND and MA use, no clinically approved treatment is currently available. Here, we review the latest findings of the effects of Tat and MA in HAND and discuss a few promising potential therapeutic developments.

Investigation of Neuropathogenesis in HIV-1 Clade B and C Infection Associated with IL-33 and ST2 Regulation

In present research work, for the first time, we demonstrate that neuropathogenesis in HIV-1 clade B and C infection is associated with IL-33 and ST2 dysregulation, that is, implication toward neuropathogenesis. It is known that neuropathogenesis of HIV infected individuals is clade dependent. Proinflammatory cytokines and related receptors play a significant role in the complex regulatory mechanisms of neuropathogenesis in HIV-1 infection. Among them, IL-33 is an inflammatory cytokine expressed in the central nervous system (CNS) and activates microglia cells and may affect neuroimmune inflammatory processes involved in HIV neuropathogenesis. Beside this, IL-33 receptor (ST2) plays a role in neuroinflammatory processes through the modulation of the biological action of IL-33. quantitative real time PCR (qRT-PCR), ELISA, Western blot (WB), and flow cytometry experiments were performed to elucidate the role of IL-33/ST2 in HIV neuropathogenesis in CNS cells. Apoptosis and mechanisms of IL-33 in neuronal cells were studied using caspase-3 assay and RT-PCR. Results of the studies suggest that the infection in CNS cells with HIV-1 clade B resulted in higher levels of IL-33/ST2L expression compared to HIV-1 clade C infection. Furthermore, higher concentrations of IL-33 were associated with a decrease in myocyte enhancer factor 2C (MEF2C) expression, a transcription factor that regulates synaptic function, and an increase in apoptosis, NOD2, and SLC11A1 in clade B infection. This led to neuroinflammation which dysregulates synaptic function and apoptosis. These parameters are common in neuroAIDS provoked by HIV infection.

Of mice and monkeys: can animal models be utilized to study neurological consequences of pediatric HIV-1 infection?

Pediatric human immunodeficiency virus (HIV-1) infection remains a global health crisis. Children are much more susceptible to HIV-1 neurological impairments than adults, which can be exacerbated by coinfections. Neurological characteristics of pediatric HIV-1 infection suggest dysfunction in the frontal cortex as well as the hippocampus; limited MRI data indicate global cerebral atrophy, and pathological data suggest accelerated neuronal apoptosis in the cortex. An obstacle to pediatric HIV-1 research is a human representative model system. Host-species specificity of HIV-1 limits the ability to model neurological consequences of pediatric HIV-1 infection in animals. Several models have been proposed including neonatal intracranial injections of HIV-1 viral proteins in rats and perinatal simian immunodeficiency virus (SIV) infection of infant macaques. Nonhuman primate models recapitulate the complexity of pediatric HIV-1 neuropathogenesis while rodent models are able to elucidate the role specific viral proteins exert on neurodevelopment. Nonhuman primate models show similar behavioral and neuropathological characteristics to pediatric HIV-1 infection and offer a stage to investigate early viral mechanisms, latency reservoirs, and therapeutic interventions. Here we review the relative strengths and limitations of pediatric HIV-1 model systems.

HIV Subtypes B and C gp120 and Methamphetamine Interaction: Dopaminergic System Implicates Differential Neuronal Toxicity

HIV subtypes or clades differentially induce HIV-associated neurocognitive disorders (HAND) and substance abuse is known to accelerate HIV disease progression. The HIV-1 envelope protein gp120 plays a major role in binding and budding in the central nervous system (CNS) and impacts dopaminergic functions. However, the mechanisms utilized by HIV-1 clades to exert differential effects and the methamphetamine (METH)-associated dopaminergic dysfunction are poorly understood. We hypothesized that clade B and C gp120 structural sequences, modeling based analysis, dopaminergic effect, and METH potentiate neuronal toxicity in astrocytes. We evaluated the effect of clade B and C gp120 and/or METH on the DRD-2, DAT, CaMKs and CREBP transcription. Both the structural sequence and modeling studies demonstrated that clade B gp120 in V1-V4, α -2 and N-glycosylated sites are distinct from clade C gp120. The distinct structure and sequence variation of clade B gp120 differentially impact DRD-2, DAT, CaMK II and CaMK IV mRNA, protein and intracellular expression compared to clade C gp120. However, CREB transcription is upregulated by both clade B and C gp120, and METH co-treatment potentiated these effects. In conclusion, distinct structural sequences of HIV-1 clade B and C gp120 differentially regulate the dopaminergic pathway and METH potentiates neurotoxicity.

Differential immune mechanism to HIV-1 Tat variants and its regulation by AEA [corrected]

In the retina, Müller glia is a dominant player of immune response. The HIV-1 transactivator viral protein (Tat) induces production of several neurotoxic cytokines in retinal cells. We show that HIV-1 clades Tat B and C act differentially on Müller glia, which is reflected in apoptosis, activation of cell death pathway components and pro-inflammatory cytokines. The harsher immune-mediated pathology of Tat B, as opposed to milder effects of Tat C, manifests at several signal transduction pathways, notably, MAPK, STAT, SOCS, the NFκB signalosome, and TTP. In activated cells, anandamide (AEA), acting as an immune-modulator, suppresses Tat B effect through MKP-1 but Tat C action via MEK-1. AEA lowers nuclear NF-κB and TAB2 for both variants while elevating IRAK1BP1 in activated Müller glia. Müller glia exposed to Tat shows enhanced PBMC attachment. Tat-induced increase in leukocyte adhesion to Müller cells can be mitigated by AEA, involving both CB receptors. This study identifies multiple signalling components that drive immune-mediated pathology and contribute to disease severity in HIV clades. We show that the protective effects of AEA occur at various stages in cytokine generation and are clade-dependant.

Neuropsychological test performance among healthy persons in northern India: development of normative data

Accurate identification of neurocognitive impairment associated with HIV infection (and other CNS-involved conditions) is dependent upon utilization of appropriate normative neuropsychological test performance data from healthy individuals with a similar background, culture, and characteristics of the target individual or group to be tested. In India, regional differences in language, culture, and availability of resources can significantly affect performance on neuropsychological testing. This study developed age- and education-adjusted normative data for commonly used neuropsychological test scores for use in northern India.

Genetic diversity and proviral DNA load in different neural compartments of HIV-1 subtype C infection

In India, the low prevalence of HIV-associated dementia (HAD) in the Human immunodeficiency virus type 1 (HIV-1) subtype C infection is quite paradoxical given the high-rate of macrophage infiltration into the brain. Whether the direct viral burden in individual brain compartments could be associated with the variability of the neurologic manifestations is controversial. To understand this paradox, we examined the proviral DNA load in nine different brain regions and three different peripheral tissues derived from ten human subjects at autopsy. Using a highly sensitive TaqMan probe-based real-time PCR, we determined the proviral load in multiple samples processed in parallel from each site. Unlike previously published reports, the present analysis identified uniform proviral distribution among the brain compartments examined without preferential accumulation of the DNA in any one of them. The overall viral DNA burden in the brain tissues was very low, approximately 1 viral integration per 1000 cells or less. In a subset of the tissue samples tested, the HIV DNA mostly existed in a free unintegrated form. The V3-V5 envelope sequences, demonstrated a brain-specific compartmentalization in four of the ten subjects and a phylogenetic overlap between the neural and non-neural compartments in three other subjects. The envelope sequences phylogenetically belonged to subtype C and the majority of them were R5 tropic. To the best of our knowledge, the present study represents the first analysis of the proviral burden in subtype C postmortem human brain tissues. Future studies should determine the presence of the viral antigens, the viral transcripts, and the proviral DNA, in parallel, in different brain compartments to shed more light on the significance of the viral burden on neurologic consequences of HIV infection.

Association between brain volumes and HAND in cART-naïve HIV+ individuals from Thailand

This study aimed to determine the effects of human immunodeficiency virus (HIV) on brain structure in HIV-infected individuals with and without HIV-associated neurocognitive disorders (HAND). Twenty-nine HIV-uninfected controls, 37 HIV+, treatment-naïve, individuals with HAND (HIV+HAND+; 16 asymptomatic neurocognitive impairment (ANI), 12 mild neurocognitive disorder (MND), and 9 HIV-associated dementia HAD), and 37 HIV+, treatment-naïve, individuals with normal cognitive function (HIV+HAND-) underwent magnetic resonance imaging (MRI) and neuropsychological assessment. The HIV-infected participants had a mean (SD) age of 35 (7) years, mean (interquartile range (IQR)) CD4 count of 221 (83-324), and mean (IQR) log10 plasma viral load of 4.81 (4.39-5.48). Six regions of interest were selected for analyses including total and subcortical gray matter, total white matter, caudate, corpus callosum, and thalamus. The HIV+/HAND+ group exhibited significantly smaller brain volumes compared to the HIV-uninfected group in subcortical gray and total gray matter; however, there were no statistically significant differences in brain volumes between the HIV+HAND+ and HIV+HAND- groups or between HIV+/HAND- and controls. CD4 count at time of combination antiretroviral therapy (cART) initiation was associated with total and subcortical gray matter volumes but not with cognitive measures. Plasma viral load correlated with neuropsychological performance but not brain volumes. The lack of significant differences in brain volumes between HIV+HAND+ and HIV+HAND- suggests that brain atrophy is not a sensitive measure of HAND in subjects without advanced immunosuppression. Alternatively, current HAND diagnostic criteria may not sufficiently distinguish patients based on MRI measures of brain volumes.

The grafting of universal T-helper epitopes enhances immunogenicity of HIV-1 Tat concurrently improving its safety profile

Extracellular Tat (eTat) plays an important role in HIV-1 pathogenesis. The presence of anti-Tat antibodies is negatively correlated with disease progression, hence making Tat a potential vaccine candidate. The cytotoxicity and moderate immunogenicity of Tat however remain impediments for developing Tat-based vaccines. Here, we report a novel strategy to concurrently enhance the immunogenicity and safety profile of Tat. The grafting of universal helper T-lymphocyte (HTL) epitopes, Pan DR Epitope (PADRE) and Pol₇₁₁ into the cysteine rich domain (CRD) and the basic domain (BD) abolished the transactivation potential of the Tat protein. The HTL-Tat proteins elicited a significantly higher titer of antibodies as compared to the wild-type Tat in BALB/c mice. While the N-terminal epitope remained immunodominant in HTL-Tat immunizations, an additional epitope in exon-2 was recognized with comparable magnitude suggesting a broader immune recognition. Additionally, the HTL-Tat proteins induced cross-reactive antibodies of high avidity that efficiently neutralized exogenous Tat, thus blocking the activation of a Tat-defective provirus. With advantages such as presentation of multiple B-cell epitopes, enhanced antibody response and importantly, transactivation-deficient Tat protein, this approach has potential application for the generation of Tat-based HIV/AIDS vaccines.

Anti-tat Hutat2:Fc mediated protection against tat-induced neurotoxicity and HIV-1 replication in human monocyte-derived macrophages

BACKGROUND

HIV-1 Tat is essential for HIV replication and is also a well-known neurotoxic factor causing HIV-associated neurocognitive disorder (HAND). Currently, combined antiretroviral therapy targeting HIV reverse transcriptase or protease cannot prevent the production of early viral proteins, especially Tat, once HIV infection has been established. HIV-infected macrophages and glial cells in the brain still release Tat into the extracellular space where it can exert direct and indirect neurotoxicity. Therefore, stable production of anti-Tat antibodies in the brain would neutralize HIV-1 Tat and thus provide an effective approach to protect neurons.

METHODS

We constructed a humanized anti-Tat Hutat2:Fc fusion protein with the goal of antagonizing HIV-1 Tat and delivered the gene into cell lines and primary human monocyte-derived macrophages (hMDM) by an HIV-based lentiviral vector. The function of the anti-Tat Hutat2:Fc fusion protein and the potential side effects of lentiviral vector-mediated gene transfer were evaluated in vitro.

RESULTS

Our study demonstrated that HIV-1-based lentiviral vector-mediated gene transduction resulted in a high-level, stable expression of anti-HIV-1 Tat Hutat2:Fc in human neuronal and monocytic cell lines, as well as in primary hMDM. Hutat2:Fc was detectable in both cells and supernatants and continued to accumulate to high levels within the supernatant. Hutat2:Fc protected mouse cortical neurons against HIV-1 Tat86-induced neurotoxicity. In addition, both secreted Hutat2:Fc and transduced hMDM led to reducing HIV-1BaL viral replication in human macrophages. Moreover, lentiviral vector-based gene introduction did not result in any significant changes in cytomorphology and cell viability. Although the expression of IL8, STAT1, and IDO1 genes was up-regulated in transduced hMDM, such alternation in gene expression did not affect the neuroprotective effect of Hutat2:Fc.

CONCLUSIONS

Our study demonstrated that lentivirus-mediated gene transfer could efficiently deliver the Hutat2:Fc gene into primary hMDM and does not lead to any significant changes in hMDM immune-activation. The neuroprotective and HIV-1 suppressive effects produced by Hutat2:Fc were comparable to that of a full-length anti-Tat antibody. This study provides the foundation and insights for future research on the potential use of Hutat2:Fc as a novel gene therapy approach for HAND through utilizing monocytes/macrophages, which naturally cross the blood-brain barrier, for gene delivery.

Humanized mouse models for HIV-1 infection of the CNS

Since the onset of the HIV epidemic, there has been a shift from a deadly diagnosis to the management of a chronic disease. This shift is the result of the development of highly effective drugs that are able to suppress viral replication for years. The availability of these regimens has also shifted the neurocognitive pathology associated with infection from potentially devastating to a much milder phenotype. As the disease outcome has changed significantly with the availability of antiretroviral therapy, there is an opportunity to re-evaluate the currently available models to address the neurocognitive pathology seen in suppressed patients. In the following, we seek to summarize the current literature on humanized mouse models and their utility in understanding how HIV infection leads to changes in the central nervous system (CNS). Also, we identify some of the unanswered questions regarding HIV infection of the CNS as well as the opportunities and limitations of currently existing models to address those questions. Finally, our conclusions indicate that the earlier humanized models used to study HIV infection in the CNS provided an excellent foundation for the type of work currently being performed using novel humanized mouse models. We also indicate the potential of some humanized mouse models that have not been used as of this time for the analysis of HIV infection in the brain.

Impact of the HIV Tat C30C31S dicysteine substitution on neuropsychological function in patients with clade C disease

Previous animal studies have identified a C31S residue substitution in the C30C31 dicysteine motif of the Tat protein that is associated with reduced neurovirulence in clade C human immunodeficiency virus (HIV). However, clinical studies of patients infected with clade C HIV have reported significant levels of cognitive impairment. To date, no study has specifically examined cognitive function in clade C-infected patients as a function of the presence or absence of the Tat C31 substitution. The present study investigated the impact of the Tat C30C31S genetic substitution among individuals residing in South Africa infected with clade C HIV that either exhibited the C30C31 motif (n = 128) or the C31S motif (n = 46). A control group of seronegative individuals was included to examine the overall impact of HIV on cognitive performance. All individuals completed a comprehensive neuropsychological battery consisting of tests sensitive to HIV. Results revealed that clade C-infected individuals performed significantly worse across cognitive tests compared to seronegative controls. However, there were no significant differences in cognitive performances between individuals with the C31S motif versus those without the C31S substitution. Proximal CD4 cell count and plasma viral load were unrelated to cognitive performances for either group. Results confirm that the C31S dicysteine motif substitution of the Tat protein does not appreciably moderate neuropsychological outcomes in clade C. Further, these findings highlight the importance of clinical management of cognitive symptoms among individuals infected with this viral clade worldwide.

The gp120 protein is a second determinant of decreased neurovirulence of Indian HIV-1C isolates compared to southern African HIV-1C isolates

Regional differences in neurovirulence have been documented among subtype/clade-C HIV-1 isolates in India and Southern Africa. We previously demonstrated that a C31S substitution in Clade-C Tat dicysteine motif reduces monocyte recruitment, cytokine induction and direct neurotoxicity. Therefore, this polymorphism is considered to be a causative factor for these differences in neurovirulence. We previously reported on the genotypic differences in Tat protein between clade-C and rest of the clades showing that approximately 90% of clade-C HIV-1 Tat sequences worldwide contained this C31S polymorphism, while 99% of non-clade C isolates lacked this Tat polymorphism at C31 residue (Ranga et al. (2004) J Virol 78∶2586–2590). Subsequently, we documented intra-clade-C differences in the frequency of Tat dicysteine variants between India and Southern Africa, as the basis for differential disease severity and showed the importance of the Tat dicysteine motif for neuropathogenesis using small animal models. We have now examined if determinants of neurovirulence besides Tat are different between the clade-C HIV-1 isolates from Southern Africa and India. Envelope glycoprotein gp120 is a well-documented contributor to neurotoxicity. We found that gp120 sequences of HIV-1 isolates from these two regions are genetically distinct. In order to delineate the contribution of gp120 to neurovirulence, we compared direct in vitro neurotoxicity of HIV-infected supernatants of a representative neurovirulent US clade-B isolate with two isolates each from Southern Africa and India using primary human neurons and SH-SY5Y neuroblastoma cells. Immunodepletion of gp120 of both US clade B and the Southern African clade C isolates revealed robust decreases in neurotoxicity, while that of the Indian isolates showed minimal effect on neurotoxicity. The gp120 as a cause of differential neurotoxicity was further confirmed using purified recombinant gp120 from HIV isolates from these regions. We conclude that gp120 is one of the key factors responsible for the decreased neurovirulence of Indian clade C HIV-1 isolates when compared to South African clade C HIV-1.

Phylogenetic characterization of six full-length HIV-1 subtype C molecular clones from three patients: identification of rare subtype C strains containing two NF-κB motifs in the long terminal repeat

Molecular surveillance is the backbone of HIV-1 vaccinology. Full-length HIV-1 sequences are useful tools that can provide a better understanding of the epidemiology in a given region. A limited number of full-length HIV-1 sequences are available from India, where >95% of the HIV infections are due to HIV-1 subtype C (HIV-1C), which is distinct from the prototype African HIV-1C. In this study, we sequenced six full-length clones isolated from three patients. Extensive phylogenetic analyses of the full-length viral sequences using bioinformatic tools identified a separate cluster of Indian strains, thus confirming the distinct phylogenetic identity of the Indian HIV-1C. Notably, the long terminal repeat (LTR) of two of the six molecular clones contained only two NF-κB binding sites. The sequences also displayed features characteristic of HIV-1C including a Tat dicysteine motif, a shortened Rev open reading frame, and a predicted CCR5 coreceptor tropism for gp120 of three of the proviral sequences.

Viral and cellular factors underlying neuropathogenesis in HIV associated neurocognitive disorders (HAND)

As the HIV-1 epidemic enters its fourth decade, HIV-1 associated neurological disorders (HAND) continue to be a major concern in the infected population, despite the widespread use of anti-retroviral therapy. Advancing age and increased life expectancy of the HIV-1 infected population have been shown to increase the risk of cognitive dysfunction. Over the past 10 years, there has been a significant progress in our understanding of the mechanisms and the risk factors involved in the development of HAND. Key events that lead up to neuronal damage in HIV-1 infected individuals can be categorized based on the interaction of HIV-1 with the various cell types, including but not limited to macrophages, brain endothelial cells, microglia, astrocytes and the neurons. This review attempts to decipher these interactions, beginning with HIV-1 infection of macrophages and ultimately resulting in the release of neurotoxic viral and host products. These include: interaction with endothelial cells, resulting in the impairment of the blood brain barrier; interaction with the astrocytes, leading to metabolic and neurotransmitter imbalance; interactions with resident immune cells in the brain, leading to release of toxic cytokines and chemokines. We also review the mechanisms underlying neuronal damage caused by the factors mentioned above. We have attempted to bring together recent findings in these areas to help appreciate the viral and host factors that bring about neurological dysfunction. In addition, we review host factors and viral genotypic differences that affect phenotypic pathological outcomes, as well as recent advances in treatment options to specifically address the neurotoxic mechanisms in play.

HIV clades B and C are associated with reduced brain volumetrics

The human immunodeficiency virus (HIV) has multiple genetic clades with varying prevalence throughout the world. Both HIV clade C (HIV-C) and HIV clade B (HIV-B) can cause cognitive impairment, but it is unclear if these clades are characterized by similar patterns of brain dysfunction. We examined brain volumetrics and neuropsychological performance among highly active antiretroviral therapy (HAART)-naïve HIV-B and HIV-C participants. Thirty-four HAART-naïve HIV-infected (HIV+) participants [17 HIV-B (USA); 17 HIV-C (South Africa)] and 34 age- and education-matched HIV-uninfected (HIV−) participants were evaluated. All participants underwent similar laboratory, neuropsychological, and neuroimaging studies. Brain volume measures were assessed within the caudate, putamen, amygdala, thalamus, hippocampus, corpus callosum, and cortical (gray and white matter) structures. A linear model that included HIV status, region, and their interaction assessed the effects of the virus on brain volumetrics. HIV− and HIV+ individuals were similar in age. On laboratory examination, HIV-C participants had lower CD4 cell counts and higher plasma HIV viral loads than HIV-B individuals. In general, HIV+ participants performed significantly worse on neuropsychological measures of processing speed and memory and had significantly smaller relative volumetrics within the thalamus, hippocampus, corpus callosum, and cortical gray and white matter compared to the respective HIV− controls. Both HIV-B and HIV-C are associated with similar volumetric declines when compared to matched HIV− controls. HIV-B and HIV-C were associated with significant reductions in brain volumetrics and poorer neuropsychological performance; however, no specific effect of HIV clade subtype was evident. These findings suggest that HIV-B and HIV-C both detrimentally affect brain integrity.

Perinatally acquired HIV infection: long-term neuropsychological consequences and challenges ahead

Over the past three decades, perinatal HIV infection in the United States has evolved from a fatal disease to a manageable chronic illness. As the majority of youth with perinatal HIV infection age into adolescence and adulthood, management of this stigmatizing, transmittable disease in the backdrop of a cadre of environmental stressors presents challenges beyond those of other chronic illnesses. The neurologic and neuropsychological consequences of this neurotropic virus have important implications for the successful navigation of responsibilities related to increasingly independent living of this aging population. This article will review the neurologic and neuropsychological consequences of perinatal HIV infection and concomitant factors in the era of highly active antiretroviral therapy and will provide an overview of the neuropathology, pathogenesis, neuroimaging findings, and treatment of perinatal HIV infection, as well as recommendations for service provision and future research.