The neurology of HIV infection

Metagenomic Next-Generation Sequencing for Accurate Diagnosis of Acute HIV Infection with Aseptic Meningitis: A Case Report

Background

Although individuals infected with HIV for the first time manifest a series of acute syndromes, most patients show mild or no symptoms, which complicates the initial clinical diagnosis. Early diagnosis is important for effective prevention and management of patients. Metagenomic next-generation sequencing technology (mNGS) can rapidly detect a wide range of pathogenic microorganisms, even in atypical cases. However, to date, few studies have reported the application of mNGS to diagnose acute HIV infection with aseptic meningitis.

Case Presentation

A 38-year-old man was admitted to the Department of Infectious Diseases due to repeated fever, headache, and scattered rashes on his limbs. Routine blood analysis revealed elevated absolute lymphocytes and monocytes. Moreover, monocytes were found to be significantly increased following a lumbar puncture and cerebrospinal fluid detection. mNGS results revealed the presence of the human immunodeficiency virus (HIV-1), with HIV RNA of 910 copies/mL in his cerebrospinal fluid. The HIV antigen/antibody test was negative. According to a study by Fie Big et al, a clear diagnosis of acute HIV infection at Fiebig stage I. The patient’s condition improved after treatment, and he was prescribed antiretroviral therapy (ART) after discharge.

Conclusion

Aseptic meningitis is easily misdiagnosed during the initial stages of acute HIV infection. mNGS can be used to identify the pathogen early, rapidly, and accurately, thereby improving the treatment of acute HIV infections.

Molecular neuroimaging of inflammation in HIV

People with HIV now have near-normal life expectancies due to the success of effective combination antiretroviral therapy (cART). Following cART initiation, immune recovery occurs, and opportunistic diseases become rare. Despite this, high rates of non-infectious comorbidities persist in treated people with HIV, hypothesized to be related to persistent immuno-activation. One such comorbidity is cognitive impairment, which may partly be driven by ongoing neuro-inflammation in otherwise effectively treated people with HIV. In order to develop therapeutic interventions to address neuro-inflammation in effectively treated people with HIV, a deeper understanding of the pathogenic mechanisms driving persistent neuro-inflammatory responses and the ability to better characterize and measure neuro-inflammation in the central nervous system is required. This review highlights recent advances in molecular neuroimaging techniques which have the potential to assess neuro-inflammatory responses within the central nervous system in HIV disease. Proton magnetic resonance spectroscopy (1H-MRS) has been utilized to assess neuro-inflammatory responses since early in the HIV pandemic and shows promise in recent studies assessing different antiretroviral regimens. 1H-MRS is widely available in both resource-rich and some resource-constrained settings and is relatively inexpensive. Brain positron emission tomography (PET) imaging using Translocator Protein (TSPO) radioligands is a rapidly evolving field; newer TSPO-radioligands have lower signal-to-noise ratio and have the potential to localize neuro-inflammation within the brain in people with HIV. As HIV therapeutics evolve, people with HIV continue to age and develop age-related comorbidities including cognitive disorders. The use of novel neuroimaging modalities in the field is likely to advance in order to rapidly assess novel therapeutic interventions and may play a role in future clinical assessments.

A Review on the Mechanism Between Different Factors and the Occurrence of Autism and ADHD

The incidence of neurodevelopmental disorders especially in children has been on the rise in recent decades, which is possibly caused by many different factors. In order to further explain this situation and arouse enough attention, this review will specifically elaborate genetic aspects and pathogenic hypothesis of these two kinds of neurodevelopmental diseases in children, autism and attention deficit hyperactivity disorder (ADHD) while analyzing the relationship between different environmental toxins and these two disorders. The effects of these pathogenic factors such as heavy metal lead, mercury, polyvinyl chloride (PVC) and polychlorinated biphenyls (PCBs) and their strong pathogenicity will be explained in detail through literature data retrieval and analysis. In addition, other neurotransmitter such as norepinephrine (NE) and serotonin (5-HT) signaling factors coming down to these two neurodevelopmental disorders and how their abnormal concentration present in the blood as well as the completely opposite results among experimental groups and control group will be elaborated. Furthermore, other high-risk and high-exposure factors may contribute to both diseases, such as alcohol and smoking abuse among parents, air pollutants PM2.5 and PM10 in the environment will also be discussed in the review. Since these environmental toxins and other harmful substances discussed in the paper have been linked to an increasing number of children with autism and ADHD in recent decades, from the medical perspective, this review will put forward certain succinct points to the aspects of minimizing relevant exposure or risks in clinical and daily life, as well as feasible suggestions in public health area for children, parents and prospective parents, to curb the growth of these two diseases in part by raising awareness in the population and reducing unnecessary exposure.

Altered mental status in "Guillain-Barré syndrome" -a noteworthy clinical clue

Guillain‐Barré syndrome (GBS) is widely regarded as a “pure” peripheral nervous system disorder. However, this simplistic interpretation belies the fact that central nervous system involvement, often manifesting as derangements in mental status can occur as a complication of the “pure” form of the disorder, as part of GBS variants, as well as in a number of mimic disorders. Despite being common in clinical practice, there is no guidance in the literature as to how to approach such scenarios. Herein, we detail our approach to these cases.

Neurologic Complications of Acute HIV Infection

Purpose of Review

This review focuses on the pathophysiology of acute HIV infection (AHI) and related central nervous system (CNS) pathology, the clinical characteristics of neurologic complications of AHI, and the implications of the CNS reservoir and viral escape for HIV treatment and cure strategies.

Recent Findings

Recent studies in newly seroconverted populations show a high prevalence of peripheral neuropathy and cognitive dysfunction in AHI, even though these findings have been classically associated with chronic HIV infection. HIV cure strategies such as the "shock and kill" strategy are currently being studied in vitro and even in small clinical trials, though the CNS as a reservoir for latent HIV poses unique barriers to these treatment strategies.

Summary

Limited point of care diagnostic testing for AHI and delayed recognition of infection continue to lead to under-recognition and under-reporting of neurologic manifestations of AHI. AHI should be on the differential for a broad range of neurological conditions, from Bell's palsy, peripheral neuropathy, and aseptic meningitis, to more rare manifestations such as ADEM, AIDP, meningo-radiculitis, transverse myelitis, and brachial neuritis. Treatment for these conditions involves early initiation of antiretroviral therapy (ART) and then standard presentation-specific treatments. Current HIV cure strategies under investigation include bone marrow transplant, viral reservoir re-activation and eradication, and genome and epigenetic viral targeting. However, CNS penetration by HIV-1 occurs early on in the disease course with the establishment of the CNS viral reservoir and is an important limiting factor for these therapies.

The role of brain biopsy in the clinical management of HIV-related focal brain lesions

OBJECTIVES

Up to 20% of HIV-related focal brain lesion (FBL) diagnoses cannot be determined without invasive procedures. In such cases, brain biopsy is an important step in the evaluation algorithm. The aims of this study were to describe the clinical outcomes of patients with FBL, the proportion of diagnoses confirmed by brain biopsies and their aetiologies, and to analyse the proportion of patients in whom the biopsy motivated a change in therapeutic management.

METHODS

A retrospective cohort study was performed. The data from clinical records of patients with HIV-related FBL admitted between January 2005 and December 2015 were reviewed.

RESULTS

A total of 137 patients were included in the study. The median age was 39 years [interquartile range (IQR) 33-44.5 years]. The median CD4 count was 54 cells/μL (IQR 21-124 cells/μL). Cerebral brain biopsy was performed in 21.16% of patients (29 of 137); 68.9% of these individuals (20 of 29) were diagnosed by histology, with results of central nervous system (CNS) lymphoma in 20.6% (six of 29), progressive multifocal leucoencephalopathy in 6.8% (two of 29), toxoplasmosis in 6.8% (two of 29), tuberculoma in 6.8% (two of 29), and other diagnoses in 27.6% (eight of 29). In nine patients, the histology was nonspecific. In 75.8% of patients (22 of 29), the result of the biopsy led to a change in the therapeutic management. We did not observe higher rates of mortality related to the procedure. Overall mortality at 30 and 90 days was similar in patients who were and were not biopsied.

CONCLUSIONS

In this retrospective cohort study, cerebral biopsy was associated with significant adjustments in therapeutic management for a high percentage of patients.

Pituitary abscess in an HIV-1-infected patient

OBJECTIVES

Pituitary abscess is a rare occurrence among pituitary conditions, but one which carries life-threatening potential. An immunocompromised status is a risk factor for the development of a pituitary abscess; however, literature describes only one case among HIV-infected patients.

METHODS AND RESULTS

We present here a case of pituitary abscess in an HIV-1-positive patient, who demonstrated a shock status, disturbance of consciousness and generalized skin rash with laboratory findings of hypovolemia, acute inflammatory reaction and blood electrolyte abnormality. We first diagnosed the dermal manifestation as atypical generalized zoster, however, the other clinical findings could not be explained by VZV infection only. Combination with anamnesis, head magnetic resonance imaging scan and endocrine function test helped us to diagnose pituitary abscess. Although the etiology of the pituitary abscess could not be detected, the patient was successfully treated with antibiotics but followed by panhypopituitarism as sequela.

CONCLUSION

A pituitary abscess should be considered in HIV-infected patients with endocrinological abnormalities, visual field defects, and central nervous system infection signs or symptoms, regardless of CD4 T-cell counts.

Current diagnostic methods for HIV

Detection of HIV infection is essential for diagnosis and monitoring of the infection. There are different types of diagnostic tools available that are based on detection of HIV-specific antibodies, viral antigen or nucleic acid. Sensitivities and specificities of assays utilized for HIV detection have improved. Newer HIV testing technologies such as third-generation enzyme immunoassay which detect HIV-specific IgG and IgM antibodies, fourth-generation enzyme immunoassay which detect both anti-HIV antibodies and HIV p24 antigen and nucleic acid based tests for HIV RNA have significantly decreased the window period. This review provides an overview of current technologies for the detection and monitoring of HIV infection and recent advances in the field of HIV diagnosis.

A High Prevalence Rate of a Positive Screen for Cognitive Impairment in Patients With Human Immunodeficiency Virus Attending an Irish Clinic

Background

Human immunodeficiency virus (HIV)-associated neurocognitive disorders occurs in 20%–50% of HIV-positive patients. We undertook this study to assess the prevalence of a positive screen for cognitive impairment in the clinic population at our institution and to demonstrate the feasibility of implementing a screening program in routine clinical encounters.

Methods

This was a cross-sectional study, and patients were recruited prospectively between December 2010 and February 2013. Inclusion criteria were as follows: patients were HIV positive, over the age of 18, capable of giving informed consent, and had sufficient ability to communicate in English. Patients were screened for cognitive impairment using the Brief Neurocognitive Screen.

Results

A total of 604 patients were recruited, and 51.5% had a positive screen for cognitive impairment. The majority of the study cohort were male (78.8%), mean age was 40.9 (standard deviation, 10.2) years, 70.9% were Irish, the most common mode of transmission was men who have sex with men (49.3%), 83% were on antiretroviral therapy, and 88.7% were virally suppressed. Logistic regression showed that the main factors predictive of a positive screen for cognitive impairment were the endorsement of cognitive symptoms (P = .024), being born in Africa (P < .000001), the use of benzodiazepines (P = .00341), being unemployed (P = .008), and consumption of more than 40 units of alcohol weekly (P = .035). There was a positive screen for depression in 9.1% and a positive screen for anxiety in 24.5%.

Conclusions

The study highlights the necessity for a structured, prospective, large-scale screening program for cognitive impairment across countries with limited resources and demonstrates the feasibility of easily implementing this with minimal training.

Clinicopathological case: progressive cognitive decline with gait disturbance in a steel worker

A 57-year-old male steel plant worker presented with fatigue and altered liver function tests. Over the next two years, he developed cognitive decline, parkinsonism and seizures. This paper reports the clinicopathological conference at the 37th Edinburgh Advanced Neurology Course 2015 and outlines what we can learn from this case.

Safety and diagnostic value of brain biopsy in HIV patients: a case series and meta-analysis of 1209 patients

Early brain biopsy may be indicated in HIV patients with focal brain lesion. This study aimed to evaluate and compare the safety and diagnostic value of brain biopsy in HIV patients in the pre-highly active antiretroviral therapy (HAART) versus post-HAART era via meta-analysis. Appropriate studies were identified per search criteria. The local database was retrospectively reviewed to select a similar patient cohort. Patient demographics, brain biopsy technique, histopathology and patient outcomes were extracted from each study. Study-specific outcomes were combined per random-effects model. Outcomes were compared between the pre-HAART and post-HAART era. Correlations between outcomes and baseline characteristics were assessed via meta-regression analysis. The proportions of histopathological diagnosis were tabulated and compared between the pre- and post-HAART era. Survival analysis was performed for patients in the post-HAART era. A total of 26 studies (including the local database) with 1209 patients were included in this meta-analysis. The most common indications for brain biopsy were diagnosis unlikely to be toxoplasmosis (n=8, 42.1%), focal brain lesion (n=5, 26.3%) or both (n=3, 15.8%). The weighted proportions for diagnostic success were 92% (95% CI 90.0% to 93.8%), change in management 57.7% (45.9% to 69.1%) and clinical improvement 36.6% (26.3% to 47.5%). Morbidity and mortality were 5.7% (3.6% to 8.3%) and 0.9% (0.3% to 1.9%), respectively. Diagnostic success rate was significantly higher in the post-HAART than the pre-HAART era (97.5% vs 91.9%, p=0.047). The odds ratio (OR) for diagnostic success in patients with contrast-enhanced lesions was 2.54 ((1.25 to 5.15), p<0.01). The median survival for HIV patients who underwent biopsy in the post-HAART era was 225 days (90-2446). Brain biopsy in HIV patients is safe with high diagnostic yield. Early brain biopsy should be considered in patients without classic presentation of toxoplasmosis encephalitis.

Neurosurgery and human immunodeficiency virus in the era of combination antiretroviral therapy: a review

Human immunodeficiency virus (HIV) is a global health problem. It renders the central nervous system susceptible to infectious and noninfectious diseases. HIV-positive individuals may present to neurosurgical services with brain lesions of unknown etiology. The differential diagnosis in these cases is broad, including opportunistic infections and malignancies, and investigation should be tailored accordingly. Opportunistic infections of the central nervous system can be complicated by hydrocephalus, and the management is pathogen dependent. Patients may also present to a neurosurgical service with conditions unrelated to their HIV status. This review outlines important conditions that cause brain lesions and hydrocephalus. It addresses the issues of diagnosis and intervention in HIV-positive patients in the era of combination antiretroviral therapy, while not ignoring the potential for opportunistic central nervous system infection in undiagnosed patients. The care of HIV-positive patients presenting to neurosurgical services requires a multidisciplinary approach, which is reflected in the authorship of this review, as well as in the guidance given.

Polymorphism of Kynurenine Pathway-Related Genes, Kynurenic Acid, and Psychopathological Symptoms in HIV

HIV-infection is associated with neuroinflammation and greater psychopathological symptoms, which may be mediated by imbalances in the kynurenic pathway (KP). Two key KP enzymes that catabolize kynurenine include kynurenine-aminotransferase II (KATII), which yields antioxidative kynurenine acid [KYNA] in astrocytes, and kynurenine-3-monooxygenase (KMO), which produces neurotoxic metabolites in microglia. The relationships between polymorphisms in KMO and KATII, psychopathological symptoms, and cerebrospinal fluid (CSF) [KYNA] were evaluated in subjects with and without HIV-infection. Seventy-two HIV-positive and 72-seronegative (SN) participants were genotyped for KATII-rs1480544 and KMO-rs1053230. Although our participants were not currently diagnosed with depression or anxiety, they were assessed for psychopathological distress with Center for Epidemiologic Studies-Depression scale and Symptom Checklist-90-Revised. CSF-[KYNA] was also measured in 100 subjects (49 HIV/51 SN). HIV-participants had more psychopathological distress than SN, especially for anxiety. KATII-by-HIV interactions were found on anxiety, interpersonal sensitivity and obsessive compulsivity; KATII-C-carriers had lower scores than TT-carriers in SN but not in HIV. In contrast, the KMO-polymorphism had no influence on psychopathological symptoms in both groups. Overall, CSF-[KYNA] increased with age independently of HIV-serostatus, except KATII-TT-carriers tended to show no age-dependent variations. Therefore, the C-allele in KATII-rs1480544 appears to be protective against psychopathological distress in SN but not in HIV individuals, who had more psychopathological symptoms and likely greater neuroinflammation. The age-dependent increase in CSF-[KYNA] may reflect a compensatory response to age-related inflammation, which may be deficient in KATII-TT-carriers. Targeted treatments that decrease neuroinflammation and increase KYNA in at risk KATII-TT-carriers may reduce psychopathological symptoms in HIV.

Heavy metals in locus ceruleus and motor neurons in motor neuron disease

Background

The causes of sporadic amyotrophic lateral sclerosis (SALS) and other types of motor neuron disease (MND) remain largely unknown. Heavy metals have long been implicated in MND, and it has recently been shown that inorganic mercury selectively enters human locus ceruleus (LC) and motor neurons. We therefore used silver nitrate autometallography (AMG) to look for AMG-stainable heavy metals (inorganic mercury and bismuth) in LC and motor neurons of 24 patients with MND (18 with SALS and 6 with familial MND) and in the LC of 24 controls.

Results

Heavy metals in neurons were found in significantly more MND patients than in controls when comparing: (1) the presence of any versus no heavy metal-containing LC neurons (MND 88%, controls 42%), (2) the median percentage of heavy metal-containing LC neurons (MND 9.5%, control 0.0%), and (3) numbers of individuals with heavy metal-containing LC neurons in the upper half of the percentage range (MND 75%, controls 25%). In MND patients, 67% of remaining spinal motor neurons contained heavy metals; smaller percentages were found in hypoglossal, nucleus ambiguus and oculomotor neurons, but none in cortical motor neurons. The majority of MND patients had heavy metals in both LC and spinal motor neurons. No glia or other neurons, including neuromelanin-containing neurons of the substantia nigra, contained stainable heavy metals.

Conclusions

Uptake of heavy metals by LC and lower motor neurons appears to be fairly common in humans, though heavy metal staining in the LC, most likely due to inorganic mercury, was seen significantly more often in MND patients than in controls. The LC innervates many cell types that are affected in MND, and it is possible that MND is triggered by toxicant-induced interactions between LC and motor neurons.

Widening the differential for brain masses in human immunodeficiency virus-positive patients: syphilitic cerebral gummata

A 39-year-old man with newly diagnosed human immunodeficiency virus (HIV) infection was admitted with right-sided weakness, right-sided vision loss and slurred speech, which worsened over several weeks. Brain imaging revealed bilateral intraparenchymal ring-enhancing lesions and enhancement of the right optic nerve. Serological findings were positive for venereal disease research laboratory test, whereas the cerebrospinal fluid venereal disease research laboratory test was nonreactive. Brain biopsy suggested a diagnosis of syphilitic cerebral gummata, and the patient's improvement with penicillin and dexamethasone further supported this etiology. Syphilitic cerebral gummata have rarely been reported in patients with HIV infection. This patient demonstrates that cerebral gummata should be considered in the differential diagnosis in immunocompromised patients with characteristic brain masses, that HIV and syphilis often coexist with early neurosyphilis appearing more frequently in this patient population and that normal cerebrospinal fluid studies may not represent a true lack of syphilitic activity in HIV patients.

Usefulness of stereotactic biopsy and neuroimaging in management of HIV-1 Clade C associated focal brain lesions with special focus on cerebral toxoplasmosis

BACKGROUND

Focal brain lesions (FBL) in HIV/AIDS frequently pose a diagnostic dilemma as the etiology varies from infective (tuberculoma, toxoplasmosis and tuberculous abscesses) to neoplastic lesions like lymphoma. For determining etiology, advanced neuroimaging techniques, serological and molecular biological tests have been evolved with varying sensitivities/specificities. Stereotactic biopsy (STB) of the lesions is reserved for lesions unresponsive to appropriate therapy.

OBJECTIVE AND METHODS

In this study, the diagnostic yield of neuroimaging [cranial CT (n=25), MRI (n=24), and Th201/99Tc SPECT scan (n=18)] is compared with histopathological diagnosis obtained by STB (n=21) or autopsy (n=4) in 25 HIV-1 subtype C seropositive individuals with FBL identified by neuroimaging with special reference to cerebral toxoplasmosis in an eighteen month study period (2006-2007).

RESULTS AND CONCLUSION

Cerebral toxoplasmosis was the most frequent cause of FBL (21/25, 84%), followed by one case each of tuberculoma, progressive multifocal leukoencephalopathy (PML), primary central nervous system lymphoma (PCNSL) and measles inclusion body encephalitis (MIBE), the last two diagnosed at autopsy. Of the 21 cases of cerebral toxoplasmosis, definitive diagnosis with histopathological confirmation was available in 14/21 (66.6%), with indirect evidence suggesting probable toxoplasmosis in seven, all of whom responded to antitoxoplasma therapy. CT and MRI had comparable specificities (75%), while MRI had marginally higher sensitivity (85% versus 80.9%) in detecting multiple lesions. The positive predictive value of both CT and MRI was identical (94.4%), suggesting that CT maybe a cost effective screening tool in resource restricted settings, for evaluating FBL. Sensitivity of 99Tc SPECT scan for diagnosing inflammatory lesions was 75% but failed to differentiate PCNSL from toxoplasmosis. This study is the first of its kind from India analyzing FBL with specific focus on cerebral toxoplasmosis in the setting of HIV-1 subtype C.

A comparison of computed tomography and magnetic resonance brain imaging in HIV-positive patients with neurological symptoms

We reviewed our practice in order to determine the optimum neuroimaging strategy for HIV-infected patients with acute neurological presentations between April 2007 and August 2008. Overall magnetic resonance imaging (MRI) detected cranial abnormalities in more than twice as many patients as did computed tomography (CT) (74% and 32%, n = 54 and 38, respectively). Replacement of CT by first-line MRI for all patients would have required an additional 16 MRI scans, although at a saving of 38 CT scans. Our study highlights the importance of first-line MRI brain imaging in HIV patients with neurological symptoms and reinforces the need for early transfer of patients from centres that do not have rapid access to (or expert interpretation of) MRI scanning, to an appropriate HIV specialist centre.

Estudo dos transtornos cognitivos decorrentes da infecção pelo HIV-1

A infecção pelo vírus da imunodeficiência humana atinge o Sistema Nervoso Central nos estágios iniciais, causando manifestações neuropsicológicas. Com o objetivo de estudar o desempenho de indivíduos infectados por este vírus em relação às funções cognitivas, foram avaliados 20 pacientes com contagem de linfócitos CD4+ acima de 200 células/mm³, utilizando-se a Escala de Inteligência Wechsler para Adultos. Destes, cinco (25%) eram do sexo masculino e 15 (75%) do sexo feminino, com média de idade de 39,65 desvio-padrão de 10,15 anos. A contagem média de linfócitos CD4+ foi 467,20 desvio-padrão de 215,45 células/mm?. Dentre quatorze pacientes que fizeram uso de terapia antirretroviral de alta atividade foi observado um caso com desempenho das funções cognitivas atenção e aprendizagem muito abaixo da média; os demais (n=13) tiveram desempenho dentro da média. Por meio da Escala de Inteligência Wechsler para Adultos foi possível detectar desempenho abaixo do nível médio do funcionamento cognitivo em indivíduos com resultado positivo para vírus da imunodeficiência humana, mesmo em vigência de terapia antirretroviral de alta atividade.

Attenuated neurotoxicity of the transactivation-defective HIV-1 Tat protein in hippocampal cell cultures

This study reports that the cysteine 22-->glycine 22 substitution in the HIV-1 Tat 1-86 B significantly attenuates its neurotoxicity. Consistent with previous studies, direct interactions of rat hippocampal cells with Tat 1-86 B were shown to cause dose-dependent and time-dependent neurotoxicity associated with activation of caspases from the mitochondrial apoptotic pathway. Despite the similar binding/uptake properties, Cys22 Tat 1-86 B failed to induce significant neurotoxicity and activation of caspases 9 and 3/7 in hippocampal primary cultures. Results of the study underscore the important role of cysteine-rich domain in mechanism of Tat-mediated neurotoxicity.

Molecular pathology of neuro-AIDS (CNS-HIV)

The cognitive deficits in patients with HIV profoundly affect the quality of life of people living with this disease and have often been linked to the neuro-inflammatory condition known as HIV encephalitis (HIVE). With the advent of more effective anti-retroviral therapies, HIVE has shifted from a sub-acute to a chronic condition. The neurodegenerative process in patients with HIVE is characterized by synaptic and dendritic damage to pyramidal neurons, loss of calbindin-immunoreactive interneurons and myelin loss. The mechanisms leading to neurodegeneration in HIVE might involve a variety of pathways, and several lines of investigation have found that interference with signaling factors mediating neuroprotection might play an important role. These signaling pathways include, among others, the GSK3beta, CDK5, ERK, Pyk2, p38 and JNK cascades. Of these, GSK3beta has been a primary focus of many previous studies showing that in infected patients, HIV proteins and neurotoxins secreted by immune-activated cells in the brain abnormally activate this pathway, which is otherwise regulated by growth factors such as FGF. Interestingly, modulation of the GSK3beta signaling pathway by FGF1 or GSK3beta inhibitors (lithium, valproic acid) is protective against HIV neurotoxicity, and several pilot clinical trials have demonstrated cognitive improvements in HIV patients treated with GSK3beta inhibitors. In addition to the GSK3beta pathway, the CDK5 pathway has recently been implicated as a mediator of neurotoxicity in HIV, and HIV proteins might activate this pathway and subsequently disrupt the diverse processes that CDK5 regulates, including synapse formation and plasticity and neurogenesis. Taken together, the GSK3beta and CDK5 signaling pathways are important regulators of neurotoxicity in HIV, and modulation of these factors might have therapeutic potential in the treatment of patients suffering from HIVE. In this context, the subsequent sections will focus on reviewing the involvement of the GSK3beta and CDK5 pathways in neurodegeneration in HIV.

Different effects of selective dopamine uptake inhibitors, GBR 12909 and WIN 35428, on HIV-1 Tat toxicity in rat fetal midbrain neurons

Drug abuse is a risk factor for neurological complications in HIV infection. Cocaine has been shown to exacerbate HIV-associated brain pathology and enhance neurotoxicity of HIV-1 Tat and gp120 proteins. In this study, we found that the selective inhibitor of dopamine transporter (DAT) function, 1-[2-[bis(4-fluorophenyl) methoxy]ethyl]-4-(3-phenylpropyl) piperazine (GBR 12909, vanoxerine), but not the selective inhibitors of serotonin and norepinephrine (SERT and NET) transporters, sertraline and nizoxetine, emulated cocaine-mediated enhancement of Tat neurotoxicity in rat fetal midbrain primary cell cultures. Similar to cocaine, the significant increase of Tat toxicity in midbrain cell cultures was observed at micromolar dose (5microM) of GBR 12909. However, different doses of another selective dopamine uptake inhibitor, WIN 35428 did not affect Tat neurotoxicity. The study supports the hypothesis that changes in control of dopamine (DA) homeostasis are important for the cocaine-mediated enhancement of HIV-1 Tat neurotoxicity. Our results also demonstrate that inhibitors of DA uptake, which can bind to different domains of DAT, differ in their ability to mimic synergistic toxicity of cocaine and HIV-1 Tat in the midbrain cell culture.

The Risk of Developing Peripheral Neuropathy Induced by Nucleoside Reverse Transcriptase Inhibitors Decreases over Time: Evidence from the Delta Trial

Background

Peripheral neuropathy (PN) in HIV-infected individuals is thought be due to a toxic effect on mitochondria induced by some nucleoside reverse transcriptase inhibitors (NRTI).

Methods

A time-to-event analysis was performed using data from the Delta trial to study the incidence of PN in HIV-infected individuals receiving zidovudine (AZT) alone or in combination with didanosine (ddI) or zalcitabine (ddC). In an on-treatment analysis, changes in the incidence of PN by duration of treatment were directly estimated using a flexible parametric survival model.

Results

A total of 3,195 patients (total follow-up 4,593 person-years) were included in the analysis. AZT+ddC was associated with a higher incidence of PN (6.2 cases/100 person-years) compared with AZT monotherapy (3.0 cases/100 person-years) and AZT+ddI (2.2 cases/100 person-years). The risk of PN peaked around day 90 following randomization (at 8.9 events/100 person-years in the AZT+ddC arm). PN was also associated with age at entry (hazard ratio (HR)=2.35 for those aged 35–44 years compared with <30) and current CD4+ T-cell count (HR=2.27 for CD4+ T-cell counts <150 cell/mm3 compared with >350).

Conclusion

Our findings challenge the common supposition that PN arises from cumulative exposure to NRTIs. We found that patients who developed PN tended to do so shortly after exposure to antiretroviral therapy. Therefore, our results support the hypothesis of a susceptibility in a subgroup of patients. These results will be of direct interest to those working in resource-limited countries where potentially neurotoxic dideoxynucleosides are still widely used.

Progressive multifocal leukoencephalopathy as first manifestation of sarcoidosis

Progressive multifocal leukoencephalopathy (PML) is a demyelinating neurologic disorder caused by a polyomavirus, called JC virus. PML affects mainly immunocompromised hosts. We report a case of PML as first manifestation of sarcoidosis in a previously healthy man. Treatment with cidofovir, resulted in a neurological and radiological stabilization. To our knowledge the association of PML and sarcoidosis without previous immunosuppressive treatment has only been described in a few cases, none of them were treated with cidofovir.

HIV infection with immunodeficiency presenting with subacute cognitive decline: recent illustrative cases

We describe three recent patients in whom evaluation of subacute, progressive encephalopathy led to the initial diagnosis of human immunodeficiency virus infection. The clinical neurological picture of a predominance of abnormalities of mental function with few elementary neurological deficits, in conjunction with a paucity of systemic symptoms and lack of evidence for prior opportunistic infections preceding the encephalopathy are notable. The cognitive, behavioral, and neuropsychiatric disturbances are described in detail to illustrate the range of manifestations of disordered mental states associated with encephalopathy in individuals with HIV infection. The importance of a comprehensive and broad-minded work-up by brain magnetic resonance imaging, cerebrospinal fluid examination, and specific microbiological tests in delineating the potential multifactorial pathogenesis of the cerebral syndromes in relation to the HIV infection is emphasized. The gratifying long-term clinical improvements in parallel with resolution of neuroimaging and other laboratory abnormalities in response to antiretroviral drug treatment are reported.

Dopaminergic marker proteins in the substantia nigra of human immunodeficiency virus type 1-infected brains

With the advent of highly active antiretroviral therapy, human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) is becoming a more chronic, manageable disease; nevertheless, the prevalence of neurological complications of AIDS is increasing. In this study, protein levels of tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the substantia nigra of HIV-infected brains and -seronegative controls were determined by immunoblotting. The immunoreactivity of neuronal specific enolase (NSE) was used to assess cell loss. Although there were no changes in levels of immunoreactive DAT or NSE proteins in HIV brains, levels of immunoreactive TH were significantly reduced, relative to controls. These results suggest that decreases in TH, the rate-limiting enzyme of dopamine synthesis, may be a factor in the neurological manifestations of HIV infection.

Ion channel functional candidate genes in multigenic neuropsychiatric disease

Scores of monogenic Mendelian ion channel diseases serve to anchor the pathophysiology of the channelopathies, but there are also now clear examples of environmental, pharmacogenetic, and acquired channelopathy mechanisms. The cardinal feature of heritable ion channel disease is a periodic disturbance of rhythmic function in constitutionally hyperexcitable tissue. While the complexity of neuroanatomy obscures functional analysis of mutations causing monogenic seizure, ataxia, or migraine syndromes, extrapolation from the cardiac (Long QT [LQT]) and muscle (Periodic Paralysis) channelopathy syndromes provides a simplified predictive framework of molecular pathology: electrically stabilizing potassium ion (K(+)) and chloride ion (Cl(-)) channels, likely having lesions that diminish their current, and excitatory Na(+) channels, likely having gain-of-function lesions. The voltage-gated calcium channel gene family that contains CACNA1C, the newest LQT locus, causing Timothy Syndrome with a phenotype including autism, has proven to be particularly informative for its members' ability to tie the various central nervous system (CNS) phenotypes together in an interpretable fashion, now including direct extension to the classically multigenic neuropsychiatric phenotypes. Features of a promising ion channel candidate gene arise from its broad locus, gene family, nature of alleles, physiology and pharmacology, tissue expression profile, and phenotype in model organisms. KCNN3 is explored as a paradigm to consider.

Young-onset dementia: a practical approach to diagnosis

BACKGROUND

Young-onset dementia is best defined as dementia presenting at age less than 65 years. And, while cognitive impairment in the elderly is dominated by dementia of the Alzheimer type, young-onset dementia has a vast differential diagnosis.

REVIEW SUMMARY

This article reviews an extensive differential diagnosis for young-onset dementia by utilizing different clues in the historical records and laboratory findings to aid with diagnosis. Laboratory testing should be completed in at least 2 stages. In the first stage, referred to as the first "wave," we suggest more routine testing, particularly for treatable causes of dementia. The second "wave," which we also outline, emphasizes more esoteric testing that may require referral to a tertiary care medical facility. The manuscript is divided into 2 parts, with part 1 focusing on clues from the historical data, while part 2 focuses on laboratory abnormalities.

CONCLUSION

Unlike dementia presenting in the elderly, the differential diagnosis in young-onset dementia is vast. A thorough historical review of the symptoms, with special emphasis on the pattern of cognitive impairment, temporal profile of the disease, detailed family history, and extensive but coordinated laboratory and ancillary testing, may yield subtle clues to the diagnosis.

The Role of Conventional MR and CT in the Work-Up of Dementia Patients

Dementia is a clinical syndrome with many causes. There often is overlap in the clinical manifestations of various forms of dementia, making them difficult to categorize. Neuroimaging can play an important role in distinguishing one form of dementia from another. Advanced imaging techniques continue to provide greater insight into the underlying pathologic processes in patients who have dementia. Conventional MRI and CT, however, still can contribute useful information when interpreting radiologists are familiar with the patterns of volume loss and signal or density changes that are characteristic of various forms of dementia.

The imaging appearances of intracranial CNS infections in adult HIV and AIDS patients

The spectrum of pathology affecting the central nervous system (CNS) in patients suffering from acquired immunodeficiency syndrome (AIDS) is broad and comprises predominantly opportunistic infections and neoplasms. It is estimated that approximately one-third of all patients with AIDS develop neurological complications. The organisms responsible for AIDS are human retroviruses: primarily the human immunodeficiency virus type 1 (HIV). In this review we shall focus on the neurological complications of HIV and AIDS which are applicable to the more frequently occurring intracranial infective organisms. Attention will be paid specifically to those CNS manifestations occurring in the adult HIV and AIDS population as infection in the paediatric HIV and AIDS group, although bearing some similarities, demonstrates some important differences.

Lentivirus envelope protein exerts differential neuropathogenic effects depending on the site of expression and target cell

We investigated the neuropathogenic effects of feline immunodeficiency virus (FIV) envelope proteins in the context of both extracellular exposure and intracellular expression in feline neural cells. The envelope from the neurovirulent CSF-derived FIV V1 strain (V1-CSF) conferred infectivity to pseudotyped viruses in peripheral blood mononuclear cells (P < 0.01) in contrast to other cell types. Intracellular V1-CSF envelope expression in macrophages and microglia but not astrocytes resulted in the induction of host inflammatory genes contributing to neurotoxicity including IL-1beta, TNF-alpha, and indolamine 2',3'-dioxygenase (IDO) (P < 0.05) with concurrent neuronal death (P < 0.05). Upregulation of the endoplasmic reticulum stress genes was evident in brains from FIV-infected animals (P < 0.05) and in FIV-infected macrophages (P < 0.05) relative to controls. Intrastriatal implantation of an FIV envelope pseudotyped virus led to marked neuroinflammation and neuronal injury associated with neurobehavioral deficits (P < 0.01). Thus, lentivirus envelope proteins exert differential neuropathogenic effects through mechanisms that depend on the infected or exposed cell type.

Human immunodeficiency virus-associated peripheral neuropathies

Peripheral neuropathy has emerged as the most common neurologic complication of human immunodeficiency virus (HIV) infection. It will continue to play an Important role in HIV Infection given the fact that HIV-infected Individuals are living longer, are at risk of long-term metabolic complications, and face an Increasing exposure to potentially neurotoxic antiretroviral drugs. We review the various types of peripheral neuropathy that have been associated with HIV infection, including distal symmetrical polyneuropathy, toxic neuropathy from antiretroviral drugs, diffuse infiltrative lymphocytosis syndrome, inflammatory demyelinating polyneuropathies, multifocal mononeuropathies, and progressive polyradiculopathy.

The role of conventional MR and CT in the work-up of dementia patients

Neuroimaging can play an important role in distinguishing one form of dementia from another. Advanced imaging techniques continue to provide greater insight into the underlying pathologic processes in patients who have dementia. Conventional MRI and CT, however, can contribute useful information when interpreting radiologists are familiar with the patterns of volume loss and signal or density changes that are characteristic of various forms of dementia.

Association of human endogenous retroviruses with multiple sclerosis and possible interactions with herpes viruses

The hypothesis that human endogenous retroviruses (HERVs) play a role in autoimmune diseases is subject to increasing attention. HERVs represent both putative susceptibility genes and putative pathogenic viruses in the immune-mediated neurological disease multiple sclerosis (MS). Gammaretroviral HERV sequences are found in reverse transcriptase-positive virions produced by cultured mononuclear cells from MS patients, and they have been isolated from MS samples of plasma, serum and CSF, and characterised to some extent at the nucleotide, protein/enzyme, virion and immunogenic level. Two types of sequences, HERV-H and HERV-W, have been reported. No known HERV-H or HERV-W copy contains complete ORFs in all prerequisite genes, although several copies have coding potential, and several such sequences are specifically activated in MS, apparently resulting in the production of complete, competent virions. Increased antibody reactivity to specific Gammaretroviral HERV epitopes is found in MS serum and CSF, and cell-mediated immune responses have also been reported. Further, HERV-encoded proteins can have neuropathogenic effects. The activating factor(s) in the process resulting in protein or virion production may be members of the Herpesviridae. Several herpes viruses, such as HSV-1, VZV, EBV and HHV-6, have been associated with MS pathogenesis, and retroviruses and herpes viruses have complex interactions. The current understanding of HERVs, and specifically the investigations of HERV activation and expression in MS are the major subjects of this review, which also proposes to synergise the herpes and HERV findings, and presents several possible pathogenic mechanisms for HERVs in MS.

Adenosine receptors control HIV-1 Tat-induced inflammatory responses through protein phosphatase

Recently, adenosine has been proposed to be a "metabolic" switch that may sense and direct immune and inflammatory responses. Inflammation and pro-inflammatory cytokine production are important in development of HIV-1 associated dementia, a devastating consequence of HIV-1 infection of the CNS. The HIV-1 protein Tat induces cell death in the CNS and activates local inflammatory responses partially by inducing calcium release from the endoplasmic reticulum. Because activation of adenosine receptors decreases production of the pro-inflammatory cytokine TNF-alpha in several experimental paradigms both in vitro and in vivo, we hypothesized that adenosine receptor activation would control both increased intracellular calcium and TNF-alpha production induced by Tat. Treatment of primary monocytes with Tat significantly increased the levels of intracellular calcium released from IP3 stores. Activation of adenosine receptors with CGS 21680 inhibited Tat-induced increases of intracellular calcium by 90 +/- 8% and was dependent on protein phosphatase activity because okadaic acid blocked the actions of CGS 21680. Tat-induced TNF-alpha production was inhibited 90 +/- 6% by CGS 21680 and concurrent treatment with okadaic acid blocked the inhibitory actions of CGS 21680. Using a model monocytic cell line, CGS 21680 treatment increased cytosolic serine/threonine phosphatase. Together, these data indicate that A2A receptor activation increases protein phosphatase activity, which blocks IP3 receptor-regulated calcium release and reduction of intracellular calcium inhibits TNF-alpha production in monocytes.