Characterization of human immunodeficiency virus (HIV)-infected cells in infiltrates associated with CNS opportunistic infections in patients with HIV clade C infection

The choroid plexus: a missing link in our understanding of brain development and function

Studies of the choroid plexus lag behind those of the more widely known blood-brain barrier, despite a much longer history. This review has two overall aims. The first is to outline long-standing areas of research where there are unanswered questions, such as control of cerebrospinal fluid (CSF) secretion and blood flow. The second aim is to review research over the past 10 years where the focus has shifted to the idea that there are choroid plexuses located in each of the brain's ventricles that make specific contributions to brain development and function through molecules they generate for delivery via the CSF. These factors appear to be particularly important for aspects of normal brain growth. Most research carried out during the twentieth century dealt with the choroid plexus, a brain barrier interface making critical contributions to the composition and stability of the brain's internal environment throughout life. More recent research in the twenty-first century has shown the importance of choroid plexus-generated CSF in neurogenesis, influence of sex and other hormones on choroid plexus function, and choroid plexus involvement in circadian rhythms and sleep. The advancement of technologies to facilitate delivery of brain-specific therapies via the CSF to treat neurological disorders is a rapidly growing area of research. Conversely, understanding the basic mechanisms and implications of how maternal drug exposure during pregnancy impacts the developing brain represents another key area of research.

Worldwide Occurrence of HIV-Associated Neurocognitive Disorders and Its Associated Factors: A Systematic Review and Meta-Analysis

BACKGROUND

HIV-associated neurocognitive disorders are common in people living with HIV/AIDS and affect the adherence of patients to prescriptions, activities of daily living, and quality of life of patients. However, there is a lack of summative evidence in the area. The present meta-analysis was therefore addressing this gap.

METHODS

We did our electronic search in Psych-Info, EMBASE, Scopus, and PubMed. The retrieved articles were stored with the endnote reference manager and data was extracted using Meta-XL version 5.3. The quality of studies was evaluated with the modified Newcastle-Ottawa Scale (NOS). A random-effect model and STATA-16 were used to compute the average estimate of HAND. Heterogeneity was weighed with I² statistics. A sensitivity analysis and subgroup analysis were employed. The existence/nonexistence of a publication bias was checked with the Eggers test of publication bias.

RESULTS

The average prevalence of HAND was 50.41% (95% CI: 45.56, 55.26). The average estimate of HAND in Europe was found to be 50.015% whereas in Africa, Asia, and the United States of America (USA) it was 49.566, 52.032, and 50.407% respectively. The prevalence of HAND in studies that used the HIV Dementia Scale (IHDS) was 36.883% and 59.956% at cutoff points of IHDS <9.5 and IHDS <10 respectively. Besides, the estimated average of HAND with the global dementia scale (GDS) was 40.766%. The prevalence of HAND in cross-sectional, cohort, and case-control studies was 49.52, 54.087, and 44.45% in that order. Socio-demographic variables; low level of education and older age, clinical and HIV related variables; the advanced stage of the illness and CD4 count of 500 cells/dl or less and psychological variables such as comorbidity of depression increases the risk of HAND.

CONCLUSION

The prevalence of HIV-associated neurocognitive disorders was about 50.41%. Low level of education and older age, clinical and HIV related variables such as the advanced stage of the illness and CD4 count of 500 cells/dl or less, and comorbidity of depression were associated with HIV associated neurocognitive disorders. Public health interventions for HIV patients should target these essential problems.

Health system challenges affecting falls prevention in persons living with HIV: perspectives from physiotherapists in four sub-Saharan regions

Aim:

The aim of this study was to explore the perspectives of physiotherapists in four selected regions of sub-Saharan Africa regarding health system challenges impacting the integration of physiotherapy-led falls prevention services in the primary care of persons living with HIV (PLWH).

Background:

Falls may pose a significant problem among younger PLWH in low- and middle-income countries. Physiotherapists’ role in optimising function and quality of life can do much in the prevention of falls in PLWH and reducing the harm that results. However, falls prevention strategies have not been implemented effectively especially in primary health care settings in sub-Saharan Africa. Physiotherapists’ account of the health system challenges they encounter may provide insights into potential strategies that may be considered in optimising fall prevention for PLWH in poorly resourced settings.

Methods:

A descriptive qualitative study was conducted in selected urban districts in the capital cities of four sub-Saharan African countries. In-depth interviews were conducted with 21 purposively selected physiotherapists involved in the primary care of PLWH. Audio recordings of interviews were transcribed verbatim and analysed using deductive thematic content analysis.

Findings:

The main results are presented in the theme ‘Health care system challenges’ and in nine categories informed by the WHO health system framework: lack of policies and clinical practice guidelines, shortage/Inaccessible falls prevention services, inadequate human resource, physiotherapists not adequately equipped in falls prevention, inaccessible/No facilities for BMD measurement, inefficient data capturing systems, lack of evidence regarding falls among PLWH, unclear physiotherapy role descriptions, inefficient referral system. Physiotherapists highlighted the need for more information and research regarding fall prevention for PLWH, promote their role in the primary care of PLWH and adopt a patient-centred approach to fall prevention.

Mechanisms of viral persistence in the brain and therapeutic approaches

There is growing recognition of the diversity of viruses that can infect the cells of the central nervous system (CNS). While the majority of CNS infections are successfully cleared by the immune response, some viral infections persist in the CNS. As opposed to resolved infections, persistent viruses can contribute to ongoing tissue damage and neuroinflammatory processes. In this manuscript, we provide an overview of the current understanding of factors that lead to viral persistence in the CNS including how viruses enter the brain, how these pathogens evade antiviral immune system responses, and how viruses survive and transmit within the CNS. Further, as the CNS may serve as a unique viral reservoir, we examine the ways in which persistent viruses in the CNS are being targeted therapeutically.

Effects of a four-week aerobic exercise programme on depression, anxiety and general self-efficacy in people living with HIV on highly active anti-retroviral therapy

The Human Immunodeficiency Virus (HIV) remains a major public health concern. Depression, anxiety and reduced self-efficacy are common psychological problems experienced by people living with HIV. We investigated the effects of a four-week, supervised aerobic exercise programme on depression, anxiety and self-efficacy of people living with HIV on HAART in Ibadan, Nigeria. A quasi-experimental design was used. Fifty-three eligible participants completed the study and only their data were analysed. The experimental subjects received aerobic exercise training for thirty minutes, three times per week for four weeks, alongside HAART, while control subjects were only on HAART. Depression, anxiety and self-efficacy scores were assessed at baseline and after the fourth week. Descriptive statistics of mean and standard deviation were used to summarise data, and inferential statistics of independent t-test was used to compare data between groups. At the end of the aerobic exercise programme, there was significant improvement in depression (p < 0.001), anxiety (p < 0.001) and self-efficacy scores (p = 0.042) in the experimental group, compared to the control group. More attention should be given to the prevention and management of psychological problems in people living with HIV through the use of aerobic exercise.

Falls in people living with HIV: a scoping review

OBJECTIVES

Recent research has indicated seemingly increased propensity for falls and accelerated bone demineralisation in people living with HIV (PLWH). We aim to map out the extent and nature of existing research relating to falls in PLWH and describe the relationship between bone demineralisation and falls in PLWH.

METHODS

A scoping review was done following Arksey & O'Malley's methodological framework and recommendations from Joanna Briggs Institute. Four databases were searched until October 2019 for peer-reviewed studies available in English reporting on the definition, prevalence, assessment, risk factors and interventions for falls in PLWH as well as information on bone demineralisation linked to falls in PLWH. Narrative reviews were excluded. Two reviewers independently performed the extraction using a predesigned Excel sheet. A descriptive analysis of extracted information was done.

RESULTS

Fourteen studies on falls in older PLWH were identified, with all but one study conducted in high-income countries. Prevalence of falls in PLWH ranged from 12% to 41%. Variable assessment tools/tests were used to assess potential risk factors, but it remains to be determined which are more predictive and appropriate for use among PLWH. Considerable agreement existed for risk factors regarding use of medications while evidence regarding functional and cognitive impairments were variable. Few studies compared risk factors for falls in PLWH with those in age-matched and sex-matched seronegative population. There is currently no evidence for interventions to prevent or reduce falls risk in PLWH.

CONCLUSION

More research is needed on falls in younger cohorts of PLWH and in sub-Saharan Africa where HIV is most prevalent and more robust clades exist. More studies need to report on data in seronegative controls to determine risk factors unique to PLWH. More intervention studies targeted at falls prevention and promotion of bone health are required. Quality clinical practice guidelines highlighting validated assessment tools and outcome measures need to be developed.

High prevalence of neurocognitive disorders observed among adult people living with HIV/AIDS in Southern Ethiopia: A cross-sectional study

BACKGROUND

Comprehensive care given to people living with HIV/AIDS is improving over time; however, their concurrent cognitive illness is still ignored, under screened and treated particularly in developing countries. And this problem is also striking in Ethiopia. Therefore, the objective of this study was to assess HIV-associated neurocognitive disorders and associated factors among adult people living with HIV/AIDS.

METHODS

An institution based cross sectional study was conducted from April to May, 2017 at Gamo Gofa zone public Hospitals. International HIV Dementia Scale was used to screen HIV associated neurocognitive disorders. Logistic regression analysis was used to assess predictors of neurocognitive disorders.

RESULT

A total of 684 study participants were included in this study with a response rate of 98%. Among them, 56% were females while 44% were males. The mean (±SD) age of the participants was 38.8±8.8years. The screening prevalence of HIV-associated neurocognitive disorder was 67.1% (95% CI; 63.6, 70.5). Body mass index 16 kg/m2 (AOR 4.389 (1.603-12.016)), being married (AOR 0.377 (0.213-0.666), unemployment status (AOR 3.181 (1.752-5.777) and being in WHO clinical stage T3 category/advancing stages of the disease (AOR 3.558 (1.406-9.006) were the key predictors of HIV-associated neurocognitive disorders among people living with HIV/AIDS.

CONCLUSION

In this study the screening prevalence of HIV-associated neurocognitive disorder is higher than the earlier reports in Ethiopia and Africa. This indicates that early screening strategies and policies for cognitive health in people living with HIV/AIDS should be given a top priority.

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.

Neuroinvasion and Inflammation in Viral Central Nervous System Infections

Neurotropic viruses can cause devastating central nervous system (CNS) infections, especially in young children and the elderly. The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) have been described as relevant sites of entry for specific viruses as well as for leukocytes, which are recruited during the proinflammatory response in the course of CNS infection. In this review, we illustrate examples of established brain barrier models, in which the specific reaction patterns of different viral families can be analyzed. Furthermore, we highlight the pathogen specific array of cytokines and chemokines involved in immunological responses in viral CNS infections. We discuss in detail the link between specific cytokines and chemokines and leukocyte migration profiles. The thorough understanding of the complex and interrelated inflammatory mechanisms as well as identifying universal mediators promoting CNS inflammation is essential for the development of new diagnostic and treatment strategies.

Chemokines and relapses in childhood acute lymphoblastic leukemia: A role in migration and in resistance to antileukemic drugs

We studied whether chemokines may have a role in relapses in childhood acute lymphoblastic leukemia (ALL). We compared the levels of chemokine receptors in marrow samples from 82 children with ALL at diagnosis versus 15 at relapses, and quantified the levels of chemokines in central system fluid (CSF) samples. The functional role of specific chemokines was studied in vitro and in vivo. The expression of some chemokine receptors was upregulated upon leukemic relapse, both in B- and in T-ALL, and in cases of medullary and extramedullary involvement. CXCL10 induced chemotaxis in leukemic cell lines and in primary leukemic cells, depending upon the levels of CXCR3 expression. CXCL10 specifically diminished chemotherapy-induced apoptosis on ALL cells expressing CXCR3, partially inhibiting caspase activation and maintaining the levels of the antiapoptotic protein Bcl-2. Finally, immunodeficient mice engrafted with CXCR3-expressing human leukemic cells showed decreased infiltration of marrow, spleen, and CNS after receiving a CXCR3-antagonist molecule. CXCR3 signaling in ALL may have a dual function: chemotactic for the localisation of leukemic blasts in specific niches, and it may also confer resistance to chemotherapy, enhancing the chances for relapses.

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.

Gene expression and functional annotation of the human and mouse choroid plexus epithelium

BACKGROUND

The choroid plexus epithelium (CPE) is a lobed neuro-epithelial structure that forms the outer blood-brain barrier. The CPE protrudes into the brain ventricles and produces the cerebrospinal fluid (CSF), which is crucial for brain homeostasis. Malfunction of the CPE is possibly implicated in disorders like Alzheimer disease, hydrocephalus or glaucoma. To study human genetic diseases and potential new therapies, mouse models are widely used. This requires a detailed knowledge of similarities and differences in gene expression and functional annotation between the species. The aim of this study is to analyze and compare gene expression and functional annotation of healthy human and mouse CPE.

METHODS

We performed 44k Agilent microarray hybridizations with RNA derived from laser dissected healthy human and mouse CPE cells. We functionally annotated and compared the gene expression data of human and mouse CPE using the knowledge database Ingenuity. We searched for common and species specific gene expression patterns and function between human and mouse CPE. We also made a comparison with previously published CPE human and mouse gene expression data.

RESULTS

Overall, the human and mouse CPE transcriptomes are very similar. Their major functionalities included epithelial junctions, transport, energy production, neuro-endocrine signaling, as well as immunological, neurological and hematological functions and disorders. The mouse CPE presented two additional functions not found in the human CPE: carbohydrate metabolism and a more extensive list of (neural) developmental functions. We found three genes specifically expressed in the mouse CPE compared to human CPE, being ACE, PON1 and TRIM3 and no human specifically expressed CPE genes compared to mouse CPE.

CONCLUSION

Human and mouse CPE transcriptomes are very similar, and display many common functionalities. Nonetheless, we also identified a few genes and pathways which suggest that the CPE between mouse and man differ with respect to transport and metabolic functions.

Generation of lineage-related, mucosally transmissible subtype C R5 simian-human immunodeficiency viruses capable of AIDS development, induction of neurological disease, and coreceptor switching in rhesus macaques

Most human immunodeficiency virus (HIV) transmissions are initiated with CCR5 (R5)-using viruses across mucosal surfaces, with the majority in regions where HIV type 1 (HIV-1) clade C predominates. Mucosally transmissible, highly replication competent, pathogenic R5 simian-human immunodeficiency viruses (SHIVs) encoding biologically relevant clade C envelopes are therefore needed as challenge viruses in vaccine efficacy studies with nonhuman primates. Here we describe the generation of three lineage-related subtype C SHIVs through four successive rapid transfers in rhesus macaques of SHIVC109F.PB4, a molecular clone expressing the soluble-CD4 (sCD4)-sensitive CCR5-tropic clade C envelope of a recently infected subject in Zambia. The viruses differed in their monkey passage histories and neutralization sensitivities but remained R5 tropic. SHIVC109P3 and SHIVC109P3N were recovered from a passage-3 rapid-progressor animal during chronic infection (24 weeks postinfection [wpi]) and at end-stage disease (34 wpi), respectively, and are classified as tier 1B strains, whereas SHIVC109P4 was recovered from a passage-4 normal-progressor macaque at 22 wpi and is a tier 2 virus, more difficult to neutralize. All three viruses were transmitted efficiently via intrarectal inoculation, reaching peak viral loads of 10(7) to 10(9) RNA copies/ml plasma and establishing viremia at various set points. Notably, one of seven (GC98) and two of six (CL31, FI08) SHIVC109P3- and SHIVC109P3N-infected macaques, respectively, progressed to AIDS, with neuropathologies observed in GC98 and FI08, as well as coreceptor switching in the latter. These findings support the use of these new SHIVC109F.PB4-derived viruses to study the immunopathology of HIV-1 clade C infection and to evaluate envelope-based AIDS vaccines in nonhuman primates.

HIV-1-related central nervous system disease: current issues in pathogenesis, diagnosis, and treatment

HIV-associated central nervous system (CNS) injury continues to be clinically significant in the modern era of HIV infection and therapy. A substantial proportion of patients with suppressed HIV infection on optimal antiretroviral therapy have impaired performance on neuropsychological testing, suggesting persistence of neurological abnormalities despite treatment and projected long-term survival. In the underresourced setting, limited accessibility to antiretroviral medications means that CNS complications of later-stage HIV infection continue to be a major concern. This article reviews key recent advances in our understanding of the neuropathogenesis of HIV, focusing on basic and clinical studies that reveal viral and host features associated with viral neuroinvasion, persistence, and immunopathogenesis in the CNS, as well as issues related to monitoring and treatment of HIV-associated CNS injury in the current era.

Differential induction of rat neuronal excitotoxic cell death by human immunodeficiency virus type 1 clade B and C tat proteins

In the absence of effective antiretroviral therapy, infection with clade B human immunodeficiency virus (HIV-1) infection commonly progresses to AIDS dementia. However, in India, where clade C infection is most prevalent, severe cognitive impairment due to HIV-1 is reported to be less prevalent. The Tat protein of HIV-1, which is released from HIV-1-infected macrophages, is thought to play a major role in the disruption of neuronal function as well as in the infiltration of macrophages associated with advanced neuropathogenesis. Clade B Tat is excitotoxic to hippocampal neurons by potentiating N-methyl-d-aspartate-induced currents of the zinc-sensitive NR1/NR2A N-methyl-d-aspartate receptor in a zinc-binding-dependent mechanism. This study characterizes the zinc-binding properties of clade C Tat protein. Using ultraviolet spectroscopy and the Ellman reaction, we show that clade C Tat protein binds just one zinc ion per monomer. We then investigated the ability of clade C Tat to block the inhibition of N-methyl-d-aspartate receptors from zinc antagonism through ion chelation. Although clade C Tat enhanced N-methyl-d-aspartate-mediated rat hippocampus neuronal toxicity in the presence of zinc, the increase was significantly less than that observed with clade B Tat. These findings suggest that the observed differences in neuropathogenesis found with HIV-1 clade C infection compared to clade B may, in part, be due to a decrease in Tat-mediated neurotoxicity.

HIV-1 clade B and C isolates exhibit differential replication: relevance to macrophage-mediated neurotoxicity

HIV-associated neurocognitive disorders (HAND) continue to be a consequence of HIV-1 infection among clade B-infected individuals. In contrast, the incidence of severe neurological impairment is lower among clade C-infected patients in regions of Sub-Saharan Africa and India. Biological aspects such as replication, cytopathicity, inflammatory response, and neurotoxicity unique to each clade influence neuropathogenicity and ultimately affect the clinical outcome of the disease. We hypothesize that productive infection by clade C isolates leads to macrophage-mediated neurotoxicity, although to a lesser extent than clade B isolates. Using a panel of primary isolates of clades B and C we demonstrated that clade B has higher replication efficiency in monocyte-derived macrophages (MDM) through reverse transcriptase activity assay and HIV-1 p24 antigen ELISA. To test the neurotoxicity of clades B and C, we used an in vitro neurotoxicity model. Conditioned medium from clade B-infected MDM was neurotoxic to rat and human neuron cultures. In contrast, clade C isolates mediated neurotoxicity when a higher initial viral titer was used for MDM infection. Furthermore, neurotoxicity mediated by isolates of both clades correlated with virus replication in MDM. Together, these results suggest that in comparison to clade B, primary isolates of clade C have slower replication kinetics in primary MDM, leading to lower levels of macrophage-mediated neurotoxicity. Elucidating the differences in replication and macrophage-mediated neurotoxicity between isolates of HIV-1 clades B and C will provide important insights needed to clarify the disparity seen in HAND incidence.

Trafficking of immune cells in the central nervous system

The CNS is an immune-privileged environment, yet the local control of multiple pathogens is dependent on the ability of immune cells to access and operate within this site. However, inflammation of the distinct anatomical sites (i.e., meninges, cerebrospinal fluid, and parenchyma) associated with the CNS can also be deleterious. Therefore, control of lymphocyte entry and migration within the brain is vital to regulate protective and pathological responses. In this review, several recent advances are highlighted that provide new insights into the processes that regulate leukocyte access to, and movement within, the brain.

Biomarkers of HIV-1-associated neurocognitive disorders: challenges of proteomic approaches

HIV-1 enters the brain shortly after infection, which may lead to neurological complications and in the most severe cases to encephalitis, dementia and death. The introduction of antiretroviral therapy reduced the incidence of the most severe conditions, nevertheless, approximately half of those infected with this virus will suffer to various degrees from HIV-1-associated neurocognitive disorders. Despite many years of research, there are no biomarkers that can objectively measure and, more importantly, predict the onset and the tempo of HIV-1-associated neurocognitive disorders. Here we review biomarker candidates of neurocognitive impairment due to HIV infection of the brain that have been proposed during the last two decades, and discuss perspectives and limitations of proteomic approaches in the search for new, more sensitive and specific biomarkers.

Changes in MRS neuronal markers and T cell phenotypes observed during early HIV infection

OBJECTIVE

To determine if changes in brain metabolites are observed during early HIV infection and correlate these changes with immunologic alterations.

METHODS

Eight subjects with early HIV infection, 9 HIV-seronegative controls, and 10 chronically HIV-infected subjects without neurologic impairment underwent 1H magnetic resonance spectroscopy. Subjects with early stage infection were identified near the time of HIV seroconversion and imaged within 60 days of an evolving Western blot, while still having detectable plasma virus. Subjects had blood drawn for viral RNA and T cell quantification.

RESULTS

Both N-acetylaspartate (NAA) and Glx (glutamate + glutamine) were decreased in the frontal cortical gray matter of seropositive subjects. NAA levels were found to be decreased in the centrum semiovale white matter of chronically HIV-infected subjects, but not in those with early infection. Both HIV-infected cohorts demonstrated a lower number of CD4+ T lymphocytes and a higher number of CD8+ T lymphocytes in their blood. Lower NAA levels in the frontal cortex of subjects with early infection were associated with an expansion of CD8+ T cells, especially effector CD8+ T cells.

CONCLUSIONS

These results verify metabolism changes occurring in the brain early during HIV infection. Lower NAA and Glx levels in the cortical gray matter suggests that HIV causes neuronal dysfunction soon after infection, which correlates to the expansion of CD8+ T cells, specifically to an activated phenotype. Utilizing magnetic resonance spectroscopy to track NAA levels may provide important information on brain metabolic health while allowing better understanding of the virus-host interactions involved in CNS functional deficits.

NMDA receptor activation by HIV-Tat protein is clade dependent

In countries infected with HIV clade B, some patients develop a rapidly progressive dementia that if untreated results in death. In regions of the world infected with HIV clade C, only milder forms of cognitive impairment have been recognized. HIV-infected macrophages are the principal mediators of dementia. HIV clade C, however, efficiently infects macrophages and HIV-infected macrophages are found in the brains of clade C-infected patients. HIV-infected macrophages release Tat protein, which may act directly on neurons to cause toxicity. We found that Tat released from Tat-expressing cells was at least 1000-fold more toxic than recombinant Tat protein. We determined whether Tat could interact with NMDA receptors and whether these interactions are clade dependent. It is demonstrated that Tat binds directly to the NMDA receptor leading to excitotoxicity. The Cys 30-Cys 31 motif in Tat is critical for exciting the NMDA receptor and the Cys31Ser mutation found in clade C Tat has a significantly attenuated neurotoxic response. Through molecular modeling and site-directed mutagenesis, we predict that Cys 31 disrupts the disulfide bond between Cys 744 and Cys 798 on the NR1 subunit of the NMDA receptor by directly interacting with Cys 744 leading to a free thiol group on Cys 798 and subsequent persistent activation of the NMDA receptor.

Estimation of virological and immunological parameters in subjects from South India infected with human immunodeficiency virus type 1 clade C and correlation of findings with occurrence of neurological disease

Several studies carried out in Western countries have demonstrated that a number of virological and immunological markers such as viral loads, cytokines, beta(2)-microglobulin, neopterin, etc., are elevated in the serum and cerebrospinal fluid (CSF) of human immunodeficiency virus (HIV)-infected individuals with neurological disease. The neurological manifestations of HIV infection noted in Indian patients is different from those reported in Western countries. Moreover, few studies have investigated the role of virological and immunological parameters with respect to the progression of HIV-1 clade C infection in India. In this study, we measured virological (HIV-1 RNA levels) and immunological parameters (CD4 cell count and inflammatory markers) in the plasma and CSF of HIV-1-infected neurologically asymptomatic and symptomatic (with opportunistic infections and/or dementia) subjects. By using clade-specific polymerase chain reaction (PCR), we ascertained that all samples used for the study were infected with HIV-1 clade C. Among the various laboratory parameters evaluated, high viral loads in the CSF, low CD4 counts, and higher levels of interleukin (IL)-1alpha, IL-6, tumor necrosis factor alpha (TNFalpha), beta(2)-microglobulin, and neopterin were noted in HIV-infected subjects with neurological disease as compared to asymptomatic subjects. These data suggest that the markers evaluated in plasma and CSF samples correlated with occurrence of neurological disease in symptomatic individuals as compared to asymptomatic HIV infected subjects.

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

Human immunodeficiency virus (HIV)-associated dementia (HAD) is common among clade B HIV-infected individuals, but less common and less severe among individuals infected with clade C HIV-1, suggesting clade-specific differences in neuropathogenicity. Although differences in neuropathogenicity have been investigated in vitro using viral proteins responsible for HAD, to date there are no virological studies using animal models to address this issue. Therefore, we investigated neuropathogenesis induced by HIV-1 clades using the severe combined immune deficiency (SCID) mouse HIV encephalitis model, which involves intracranial injection of macrophages infected with representative clade B (HIV-1(ADA)) or clade C (HIV-1(Indie-C1)) HIV-1 isolates into SCID mice. In cognitive tests, mice exposed to similar inputs of HIV-1 clade C made fewer memory errors than those exposed to HIV-1 clade B. Histopathological analysis of mice exposed to clade B exhibited greater astrogliosis and increased loss of neuronal network integrity. In vitro experiments revealed differences in a key characteristic of HIV-1 that influences HAD, increased monocyte infiltration. HIV-1(Indie-C1)-infected macrophages recruited monocytes poorly in vitro compared with HIV-1(ADA)-infected macrophages. Monocyte recruitment was HIV-1 Tat and CCL2 dependent. This is the first demonstration, ever since HIV neuropathogenesis was first recognized, that viral genetic differences between clades can affect disease severity and that such studies help identify key players in neuropathogenesis by HIV-1.