Magnetic resonance imaging morphometric analysis of cerebral volume loss in human immunodeficiency virus infection. The HNRC Group

Neurobehavioral effects of HIV-1 infection in China and the United States: a pilot study

The HIV epidemic in China has been increasing exponentially, yet there have been no studies of the neurobehavioral effects of HIV infection in that country. Most neuroAIDS research has been conducted in Western countries using Western neuropsychological (NP) methods, and it is unclear whether these testing methods are appropriate for use in China. Twenty-eight HIV seropositive (HIV+) and twenty-three HIV seronegative (HIV-) individuals with comparable gender, age, and education distributions were recruited in Beijing and the rural Anhui province in China. Thirty-nine HIV+ and thirty-one HIV- individuals were selected from a larger U.S. cohort recruited at the HIV Neurobehavioral Research Center, in San Diego, to be matched to the Chinese sample for age, disease status, and treatment variables. The NP test battery used with the U.S. and China cohorts included instruments widely used to study HIV infection in the United States. It consisted of 14 individual test measures, each assigned to one of seven ability areas thought to be especially vulnerable to effects of HIV on the brain (i.e., verbal fluency, abstraction/executive function, speed of information processing, working memory, learning, delayed recall, and motor function). To explore the cross-cultural equivalence and validity of the NP measures, we compared our Chinese and U.S. samples on the individual tests, as well as mean scaled scores for the total battery and seven ability domains. On each NP test measure, the mean of the Chinese HIV+ group was worse than that of the HIV- group. A series of 2x2 analyses of variance involving HIV+ and HIV- groups from both countries revealed highly significant HIV effects on the Global and all Domain mean scaled scores. Country effects appeared on two of the individual ability areas, at least partly due to education differences between the two countries. Importantly, the absence of HIV-by-Country interactions suggests that the NP effects of HIV are similar in the two countries. The NP test battery that was chosen and adapted for use in this study of HIV in China appears to have good cross-cultural equivalence, but appropriate Chinese norms will be needed to identify disease-related impairment in individual Chinese people. To inform the development of such norms, a much larger study of demographic effects will be needed, especially considering the wide range of education in that country.

Human immunodeficiency virus type 1 RNA Levels in different regions of human brain: quantification using real-time reverse transcriptase-polymerase chain reaction

Human immunodeficiency virus type 1 (HIV-1) enters the central nervous system shortly after the infection and becomes localized in different regions of the brain, leading to various neurological abnormalities including motor disorders and neurocognitive deficits. Although HIV-1-associated functional abnormalities of the central nervous system (CNS) can be evaluated during life by using various test batteries, HIV-1 virus concentration in different brain regions can be measured only after death. The tissues obtained at autopsy provide a valuable source for determining the role of various factors, including that of HIV-1 viral load in the CNS, that may contribute to the regional CNS neuropathogenesis. For this study, we obtained from the National Institutes of Health-sponsored National NeuroAIDS Tissue Consortium (NNTC) the tissues from different brain regions collected at autopsy of HIV-1-positive (N = 38) and HIV-negative (N = 11) individuals, with postmortem intervals of 2 to 29 h, and measured HIV-1 RNA concentration in the frontal cortex, frontal cortex area 4, frontal cortex area 6, basal ganglia, caudate nucleus, putamen, globus pallidus, substantia nigra, and cerebrospinal fluid. Because HIV-1+ individuals were infected with the virus for up to 21 years and the majority of them had used highly active antiretroviral therapy (HAART), we used highly sensitive real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay in order to detect a wide dynamic range of HIV-1 RNA with lower detection limit of a single copy. The primers and probes were from the long terminal repeat (LTR) region of HIV genome for achieving higher specificity and sensitivity of detection and amplification. Our results demonstrate a wide variation in the concentration of HIV-1 RNA in different brain regions (5.51 and 8,144,073; log(10) 0.74 and 6.91 copies/g tissue), and despite the high specificity and sensitivity of this method, viral RNA was not detected in 50% of all the samples, and in 30% to 64% of samples of each region of HIV-1+ individuals. However, the highest concentration of viral RNA was found in the caudate nucleus and the lowest concentration in the frontal cortex and cerebrospinal fluid. The viral RNA was undetectable in all samples of HIV-negative individuals.

HIV suppression by HAART preserves cognitive function in advanced, immune-reconstituted AIDS patients

INTRODUCTION

HIV can damage neurons leading to cognitive impairment. Epidemiological observations suggest that neuropsychological impairment might progress despite successful HAART therapy, but available prevalence estimates are based on populations that were selected for impairment.

METHODS

Of 433 advanced AIDS patients with documented immune reconstitution (CD4 lymphocyte counts < 50 before and > 100 cells/microl after HAART), 286 had brief assessments of cognition (Trailmaking A/B and Digit Symbol Tests) at least once, no confounding neurological conditions, and available neuropsychological norms with comprehensive demographic corrections. At entry, most were immune reconstituted on HAART (median CD4 cell count 230 cells/microl) and HIV was suppressed (65% < 500; only 14% > 20 000 RNA copies/ml).

RESULTS

Over one quarter (27%) of participants exhibited impairment at their initial neuropsychological assessment, a rate nearly twice that expected in a normal (HIV-uninfected) reference population (14%). These impaired participants did not differ from the unimpaired group with respect to age, sex, education, race, CD4 lymphocyte counts, or HIV-RNA levels. Improved performance on neuropsychological tests was documented over a 2-year period 3-5 years after initiating HAART. This improvement was marginally associated with the continued or improving control of plasma HIV-RNA levels, but not with concurrent levels of immune recovery (CD4 lymphocyte counts).

CONCLUSION

Most advanced AIDS patients responding to HAART for prolonged periods have stable or improving cognition, but remain more likely to be impaired than the general population. During HAART, improving test performance probably reflects both practice effects and continuing neurological recovery after more than 3 years of HAART.

Nanotechnology-based delivery systems in HIV/AIDS therapy

The therapeutic efficacy of anti-HIV agents is often hampered by poor bioavailability and lack of drug penetration in infected target tissues and cells. Using different types of nanotechnology-based delivery systems, it is possible to engineer strategies that can improve the therapeutic efficacy in HIV/AIDS by delivering drugs to cellular and anatomical viral reservoirs. The rationale for the use of nanocarrier systems relies on the fact that different types of therapeutic payloads can be encapsulated and the systemic pharmacokinetics and distribution are dictated by the properties of the nanocarriers rather than the drugs. The versatility of nanoplatforms can be further exploited in a formulation that has enhanced oral bioavailability, protects against degradation upon oral or systemic administration and prolongs the residence time at the target site. Nanocarriers can facilitate lymphatic transport, delivery across the blood–brain barrier, and efficient internalization in cells by nonspecific or receptor-mediated endocytosis. In this review, we will address the role of nanotechnology-based delivery systems in improving the delivery efficiency of anti-HIV drugs to cellular and anatomical sites of interest. Specific published examples will be highlighted with emphasis on the role of polymeric nanoparticle micelles, liposomes and nanoemulsions in improving delivery efficiency.

The impact of neuropsychological functioning and depressed mood on functional complaints in HIV-1 infection and methamphetamine dependence

Diagnosis of neurobehavioral syndromes associated with HIV infection requires the determination that neuropsychological (NP) deficits are present, are not caused by any comorbid (e.g., psychiatric) condition, and significantly affect everyday functioning. Methamphetamine (Meth) dependence and depression are common comorbid conditions with HIV and may complicate diagnosis of HIV-associated neurobehavioral syndromes. The current study examined the complex relationships between depression and NP impairment, and self-report of problems with everyday functioning, in 362 adults with HIV infection or Meth dependence, or both. Everyday functioning was measured with questionnaires of instrumental activities of daily living (IADLs) and reported cognitive difficulties. Results indicate that comorbid HIV and Meth did not increase the likelihood of complaints regarding everyday functioning, beyond what was seen with either single risk factor. Across all groups, depressive symptoms predicted greater IADL decline and cognitive complaints, while NP impairment predicted cognitive complaints more than IADL decline. Both IADL decline and cognitive complaints were associated with higher rates of unemployment and worse clinician ratings of overall functioning (Karnofsky ratings), even when depressive symptoms were controlled. These results suggest that depressive symptoms should not be used to dismiss subjective complaints related to everyday functioning even though depressive symptoms account for significant variance in self-reported complaints. Additional research is needed to clarify the potentially reciprocal causal relationships between depressive symptoms and impairment in everyday functioning.

The Effect of Recent Stimulant Use on Sustained Attention in HIV-Infected Adults

Evidence suggests that stimulant use may exacerbate the deleterious cognitive effects of HIV, and that it has similar neuropathological consequences. In the current study, we examined the effect of recent stimulant use on sustained attention in adults infected with HIV. The sample consisted of 23 non-drug users and 17 stimulant users (cocaine and/or methamphetamine), all who were HIV-positive. Drug use was determined via urine toxicology. Sustained attention was assessed with the Conners' Continuous Performance Task--second edition (CPT-II). Groups were compared on overall performance variables, as well as patterns of performance across time. Compared to the non-drug users, stimulant users showed a gradual increase in reaction time variability and omission errors. Stimulant users' scores indicated impaired vigilance relative to an age and gender-matched normative sample. The groups were equivalent on other measures of attention, global neuropsychological functioning, mood, and demographic variables. The results indicate that recent stimulant use among HIV-infected adults adversely affects sustained attention.

Nanoparticulate drug carriers for delivery of HIV/AIDS therapy to viral reservoir sites

Providing the optimum treatment of AIDS is a major challenge in the 21st Century. HIV is localised and harboured in certain inaccessible compartments of the body, such as the CNS, the cerebrospinal fluid, the lymphatic system and in the macrophages, where it cannot be reached by the majority of therapeutic agents in adequate concentrations or in which the therapeutic agents cannot reside for the necessary duration. Progression in HIV/AIDS treatment suggests that available therapy can lower the systemic viral load below the detection limit. However, on discontinuation of treatment, there is relapse of the infection from the reservoir sites and a potential for resistance development. This review discusses the aetiology and pathology of HIV, with emphasis on the viral reservoirs, current therapy of AIDS, and the opportunity for nanotechnology-based drug delivery systems to facilitate complete eradication of viral load from the reservoir sites. Literature-cited examples of drug delivery systems that are under investigation for the treatment of AIDS are discussed. The article also focuses on the future outlook and strategies for investigational drug formulations that use nanotherapeutic strategy for HIV/AIDS.

Visual attention deficits are associated with driving accidents in cognitively-impaired HIV-infected individuals

Previous research has found HIV-associated neuropsychological (NP) dysfunction to be associated with impaired driving skills. To determine whether specific impairments in visual attention impart an increased accident risk, we assessed 21 HIV seronegative (HIV-) and 42 seropositive (HIV+) participants on NP tests and the Useful Field of View (UFOV), a computerized test of visual attention. HIV+ participants performed significantly worse than the HIV- participants on the UFOV, particularly on the Divided Attention subtest. Poor UFOV performance was associated with higher accident rates in the past year, with a trend for NP impairment to also predict more accidents. The highest number of accidents occurred in the group with a "high risk" UFOV designation and NP impairment; this category correctly classified 93% of HIV+ participants as to who did, and did not, have an accident. Clinicians should attend to visual attention as well as general cognitive status in estimating which patients are at risk for impaired driving.

The AIDS dementia complex: clinical and basic neuroscience with implications for novel molecular therapies

The AIDS dementia complex (ADC, also referred to as HIV-associated cognitive impairment) is a common disorder among HIV-infected patients associated with both inflammatory and neurodegenerative processes. This review describes recent advances in the clinical and basic neurosciences of HIV infection and discusses the multivariable nature of what has become a chronic disorder in the context of highly active antiretroviral therapies (HAART). Since its initial description twenty years ago, advances in cell and molecular biology along with those in neuroimaging have furthered our understanding of the underlying pathogenic mechanisms. The clinical and neuropsychological profile of ADC is generally consistent with a "frontal-subcortical" pattern of injury. Neuropathogenesis is largely driven by indirect mechanisms mediated by infected, or more commonly, immune activated macrophages, which secrete viral and host-derived factors. Magnetic resonance spectroscopy (MRS) provides a robust in vivo method to measure the inflammatory and neurotoxic events triggered by these factors and their associated signals. Although the use of combined or highly active antiretroviral therapies (HAART) has significantly improved survival rates, cerebral injury and cognitive impairment remain common events. Factors such as aging and chronic infection will likely impact the course of this disease, its pathogenesis, and treatment. The combined observations presented in this review suggest a number of critical areas for future inquiry.

Potential role for white matter lysosome expansion in HIV-associated dementia

Expansion of the lysosomal apparatus occurs in subcortical white matter in brains from persons with AIDS. This study examined whether HIV-associated subcortical dementia (HAD) is significantly related to this lysosomal anomaly. Brain cortex and adjacent white matter from the middle frontal gyrus were obtained from the National NeuroAIDS Tissue Consortium. Lysosomal hydrolase activity was assayed in 57 subjects who underwent neuropsychological testing within 6 months prior to autopsy. Decedents were evaluated from 4 geographical sites in the United States: Galveston/Houston, Texas (n = 36), Los Angeles, California (n = 5), New York, New York (n = 5), and San Diego, California (n = 11). Increased beta-glucuronidase activity, a representative lysosomal glycosidase, was correlated with the amount of neurocognitive impairment. Significant correlation was present in 5 of 7 functional testing domains, including some that draw upon frontal lobe output (r = 0.419; P < 0.002). The biochemical anomaly was negligible in cerebral cortex and cerebrospinal fluid and was not correlated with brain dysfunction in those compartments. Glycosidase activation was associated significantly with increased HIV RNA concentration in brain tissue (r = 0.469; P < 0.021) and possibly with HIV RNA in cerebrospinal fluid (r = 0.266; P < 0.067). HIV RNA in blood plasma was not correlated. These results support the suggestion that abnormal metabolism in white matter glial cells contributes to cognitive slowing in persons with HAD. Because membrane turnover is routed through the endosome-lysosome apparatus, these data are in agreement with brain spectroscopic data that have suggested that there is an increase in membrane turnover in white matter glia.

Viral diseases of the central nervous system

Viral diseases of the central nervous system encompass a wide range of different processes, mainly inflammation affecting the brain (encephalitis), the meninges (meningitis), or a combined meningoencephalitis. The spinal cord can be affected as well (myelitis). Another group of viral-related disorders, sometimes without a clear pathophysiological mechanism disclosed, include post-viral illnesses. All of these groups of diseases are discussed in this article, with an emphasis on their imaging presentation, using magnetic resonance imaging.

The influence of executive functions, sensation seeking, and HIV serostatus on the risky sexual practices of substance-dependent individuals

From a public health standpoint, identifying factors that contribute to risky sexual practices among substance-dependent individuals is critical, particularly in the context of HIV infection. This study examines the respective contributions of executive neurocognitive functions, sensation seeking, and HIV serostatus in predicting risky sexual practices among poly-substance users (with a history of dependence primarily for cocaine or cocaine/heroin). HIV+ (n=109) and HIV- (n=154) substance-dependent individuals were assessed using three neurocognitive tasks of executive functions: Stroop reaction time, delayed non-matching to sample, and the Iowa Gambling Task. Sensation seeking was assessed using the Sensation Seeking Scale-V. Greater sensation seeking was associated with more risky sexual practices among HIV+ participants, particularly among those who performed best on the Iowa Gambling Task. Our findings indicate that continued risk behavior among HIV+ drug users may be driven by sensation seeking (a personality trait common among drug users); however, the impact of executive functions is less clear.

ERPs differ from neurometric tests in assessing HIV-associated cognitive deficit

The onset and time-course of HIV-associated cognitive deficits are not well established. The present experiment compared physiological and neurometric assessments of cognitive decline in HIV-asymptomatic, HIV-symptomatic, and HIV-negative control adult women. The P3 component of standard auditory, event-related electrical potentials of the brain (ERP) and standard neurometric (pencil and paper) test scores were recorded. The P3 ERP measures differentiated both of the clinical HIV groups from the control group. In contrast, the neurometric measures were more sensitive to the difference in cognitive decline between the two clinical groups. It is concluded that both P3 ERP measures and standard neurometric tests are individually useful and complementary for tracking cognitive decline in the diagnosis and treatment of opportunistic HIV-associated central nervous system impairments.

ERP evidence of impaired central nervous system function in virally suppressed HIV patients on antiretroviral therapy

OBJECTIVE

To examine the effects of human immunodeficiency virus (HIV) on central nervous system (CNS) function in patients receiving antiretroviral therapy (ART) who have suppressed viral loads.

METHODS

Event-related brain potentials (ERPs) were recorded from 15 virally suppressed HIV patients and 15 age-, sex-, and education-matched controls while they performed a 3-stimulus auditory oddball task. The amplitude and latency of the P3a, P3b, and early auditory components were examined in HIV patients and controls.

RESULTS

Virally suppressed HIV patients on ART were more depressed than controls, as determined by the Beck Depression Inventory (BDI). After controlling for the effects of depression, HIV patients had smaller P2, P3a, and P3b amplitudes and longer P3a and P3b latency than control subjects. BDI scores correlated positively with N1 latency in HIV patients and negatively with P3b amplitude in all subjects.

CONCLUSIONS

These electrophysiological results suggest that, even in the absence of detectable levels of HIV in the peripheral blood, viral replication persists in the CNS and continues to cause disease in HIV patients on ART.

The impact of HIV-associated neuropsychological impairment on everyday functioning

HIV-1 infection can be associated with neuropsychological (NP) deficits ranging from subtle to severe. The purpose of this study was to evaluate the functional, or "real-world" impact of HIV-associated NP impairment in a group of 267 HIV-infected participants. All participants received comprehensive NP, neuromedical, and standardized functional evaluations that included laboratory measures of shopping, cooking, financial management, medication management and vocational abilities. Compared to NP-normal participants, those with NP impairment performed significantly worse on all laboratory measures of everyday functioning. Multivariate analyses revealed that the NP ability domains of Abstraction/Executive Function, Learning, Attention/Working Memory and Verbal abilities most strongly and consistently predicted failures on the functional battery. Both NP impairment and impairment on the functional battery were significantly associated with subjective experiences of cognitive difficulties, as well as unemployment and increased dependence in activities of daily living; multivariate prediction models that also considered depressed mood and biological measures of disease progression revealed that impairment on the functional battery and depression were the only unique predictors of all three indicators of "real-world" functioning. The current results add to growing evidence concerning the clinical significance of HIV-associated NP impairment. Objective, laboratory based functional measures, such as those used here, may compliment NP testing in future studies directed at understanding the impact on life quality of central nervous system disorders and their treatments. Finally, there is a need for additional research investigating the apparently independent effect of depression on level of everyday functioning in HIV infected persons.

The relationship between AIDS retinal cotton wool spots and neuropsychological impairment in HIV-positive individuals in the pre-highly active antiretroviral therapy era

PURPOSE

To determine the relationship between AIDS retinal cotton wool spots (CWS) and neuropsychological impairment in HIV-positive individuals in the pre-HAART (highly active anti-retroviral therapy) era and the association between AIDS-related retinal CWS and neuropsychological impairment in HIV-positive patients not treated with HAART.

METHODS

A case-control analysis of prospectively acquired data in HIV-infected individuals who underwent prospective and longitudinal evaluations of retinal findings as well as neuropsychological testing was performed. Individuals underwent prospective retinal ophthalmic examinations with fundus photography of any retinal lesions. They also underwent periodic neuropsychological testing. The occurrence of retinal CWS was analyzed in relationship to neuropsychological impairment.

RESULTS

Thirty individuals with CWS were compared to 6o matched control AIDS patients. There was no association between either global clinical neuropsychological impairment or impairment in any of the five major domains tested and retinal CWS. There was an association between beta-2 microglobulin and CWS as well as an association between low CD4 T-cell count and the presence of retinal CWS.

CONCLUSIONS

We found no association between retinovascular disease and neurocognitive impairment in this case-control study. Retinal CWS in HIV disease are related to higher serum beta-2 microglobulin levels and lower CD4 T-cell counts, suggesting that these lesions are related to HIV disease progression but may be caused by a pathological process independent of CNS disease.

Methamphetamine dependence increases risk of neuropsychological impairment in HIV infected persons

Both HIV infection and methamphetamine dependence can be associated with brain dysfunction. Little is known, however, about the cognitive effects of concurrent HIV infection and methamphetamine dependence. The present study included 200 participants in 4 groups: HIV infected/methamphetamine dependent (HIV+/METH+), HIV negative/methamphetamine dependent (HIV-/METH+), HIV infected/methamphetamine nondependent (HIV+/METH-), and HIV negative/methamphetamine nondependent (HIV-/METH-). Study groups were comparable for age, education, and ethnicity, although the HIV-/METH- group had significantly more females. A comprehensive, demographically corrected neuropsychological battery was administered yielding a global performance score and scores for seven neurobehavioral domains. Rates of neuropsychological impairment were determined by cutoff scores derived from performances of a separate control group and validated with larger samples of HIV+ and HIV- participants from an independent cohort. Rates of global neuropsychological impairment were higher in the HIV+/METH+ (58%), HIV-/METH+ (40%) and HIV+/METH- (38%) groups compared to the HIV-/METH- (18%) group. Nonparametric analyses revealed a significant monotonic trend for global cognitive status across groups, with least impairment in the control group and highest prevalence of impairment in the group with concurrent HIV infection and methamphetamine dependence. The results indicate that HIV infection and methamphetamine dependence are each associated with neuropsychological deficits, and suggest that these factors in combination are associated with additive deleterious cognitive effects. This additivity may reflect common pathways to neural injury involving both cytotoxic and apoptotic mechanisms.

Diffusion tensor imaging in normal aging and neuropsychiatric disorders

The application of diffusion imaging to the quantitative study of the effects of normal aging and neuropsychiatric diseases on brain tissue microstructure has witnessed its greatest development just over the last few years. Measures derived from diffusion imaging have already been shown to have great utility in identifying age- and disease-related degradation of regional microstructure, particularly of white matter. Investigations comparing diagnoses hold promise for contribution to differential diagnosis. Correlations with cognitive and motor performance provide evidence for functional ramifications of these diffusion measures.

Assessing the efficacy of highly active antiretroviral therapy in the brain

The devastating effects of HIV infection have been documented for the last 2 decades. Since the 1980s over 60 million people have been infected and at present 40 million people globally are living with HIV. HIV infects the central nervous system (CNS) early in the disease process. Indeed, numerous studies document the presence of HIV within the cerebrospinal fluid (CSF). Direct infection of the brain by HIV ultimately results in HIV associated dementia (HAD), which (prior to the advent of antiretroviral therapy) affected 20% of patients. An increasing number of drugs have been developed to treat this infection and delay the development of AIDS. Current treatment is aimed at inhibiting viral replication, and thus, lowering the viral load. However a subsequent increase in viral load can occur as patients become resistant to drug therapy. In the era of HAART, the incidence of HAD has been reduced, whereas the prevalence rate is increasing as people with HIV survive longer. However, in a study of initial AIDS defining illnesses, the proportion with HIV related dementia did not decline following introduction of HAART. In a separate study, no decrease was found in the incidence of dementia per se, although there was a decrease in the incidence of all AIDS-defining illnesses during this time period. It is evident from most studies that since the introduction of HAART, its effect on HAD is not entirely clear, although the majority of findings indicate that it is beneficial. Here we will outline the issues relevant to preventing HAD by HAART.

Severe, demyelinating leukoencephalopathy in AIDS patients on antiretroviral therapy

OBJECTIVES

To describe a severe form of demyelinating HIV-associated leukoencephalopathy in AIDS patients failing highly active antiretroviral therapy (HAART), its relationship to clinical and neuroimaging findings, and suggest hypotheses regarding pathogenesis.

DESIGN AND METHODS

AIDS patients who failed HAART and displayed severe leukoencephalopathy were included. All cases had detailed neuromedical, neuropsychological, neuroimaging and postmortem neuropathological examination. Immunocytochemical and PCR analyses were performed to determine brain HIV levels and to exclude other viruses.

RESULTS

Seven recent autopsy cases of leukoencephalopathy in antiretroviral-experienced patients with AIDS were identified. Clinically, all were severely immunosuppressed, six (86%) had poorly controlled HIV replication despite combination antiretroviral therapy, and five (71%) had HIV-associated dementia. Neuropathologically, all seven had intense perivascular infiltration by HIV-gp41 immunoreactive monocytes/macrophages and lymphocytes, widespread myelin loss, axonal injury, microgliosis and astrogliosis. The extent of damage exceeds that described prior to the use of HAART. Brain tissue demonstrated high levels of HIV RNA but evidence of other pathogens, such as JC virus, Epstein-Barr virus, cytomegalovirus, human herpes virus type-8, and herpes simplex virus types 1 and 2, was absent. Comparison of the stages of pathology suggests a temporal sequence of events. In this model, white matter damage begins with perivascular infiltration by HIV-infected monocytes, which may occur as a consequence of antiretroviral-associated immune restoration. Intense infiltration by immune cells injures brain endothelial cells and is followed by myelin loss, axonal damage, and finally, astrogliosis.

CONCLUSIONS

Taken together, our findings provide evidence for the emergence of a severe form of HIV-associated leukoencephalopathy. This condition warrants further study and increased vigilance among those who provide care for HIV-infected individuals.

Relationships between cognition and structural neuroimaging findings in adults with human immunodeficiency virus type-1

Infection of the central nervous system with human immunodeficiency virus type-1 (HIV) is associated with cognitive impairments that range from mild cognitive and motor difficulties to dementia. Structural neuroimaging abnormalities are also common in HIV-infected patients both with and without cognitive disturbances. The most common abnormalities include high signal intensities in the white matter and atrophy. Research over the past 12 years has helped define the relationship between these neuroimaging abnormalities and the manifestation of cognitive disturbance in HIV. In the present paper, we provide a synopsis of these studies and report the current state of the literature. Our review revealed that atrophy of the caudate nucleus is most consistently associated with cognitive impairment in HIV. The current literature does not support a strong relationship between cortical atrophy or white matter abnormalities and cognitive dysfunction in this population, though methodological issues may have influenced the results. Suggestions for study design and new research directions are provided.

Impaired spatial cognition and synaptic potentiation in a murine model of human immunodeficiency virus type 1 encephalitis

Injection of human immunodeficiency virus type 1 (HIV-1)-infected human monocyte-derived macrophages (MDMs) into the basal ganglia of severe combined immunodeficient mice recapitulates histopathologic features of HIV-1 encephalitis (HIVE). Here, we show that the neural damage in HIVE mice extends beyond the basal ganglia and is associated with cognitive impairment. Morris water maze tests showed impaired spatial learning 8 d after MDM injection. Moreover, impaired synaptic potentiation in the hippocampal CA1 subregion was demonstrated at 8 and 15 d. By day 15, post-tetanic, short-term, and long-term potentiation were reduced by 14.1, 29.5, and 45.3% in HIVE mice compared with sham-injected or control animals. Neurofilament (NF) and synaptophysin (SP) antigens were decreased significantly in the CA2 hippocampal subregion of HIVE mice with limited neuronal apoptosis. By day 15, the CA2 region of HIVE mice expressed 3.8- and 2.6-fold less NF and SP than shams. These findings support the notion that HIV-1-infected and immune-competent brain macrophages can cause neuronal damage at distant anatomic sites. Importantly, the findings demonstrate the value of the model in exploring the physiological basis and therapeutic potential for HIV-1-associated dementia.

Preclinical psychopharmacology of AIDS-associated dementia: lessons to be learned from the cognitive psychopharmacology of other dementias

Following a brief discussion of the epidemiology, underlying neuropathological mechanisms, neuropsychological symptoms and present treatment strategies of AIDS-associated dementia (AAD), parallels are drawn between the longer standing research on drugs for the treatment of other cognitive disorders, particularly senile dementia, and ongoing efforts to develop psychopharmacological approaches for the treatment of the cognitive impairments in AAD. Important aspects of hypotheses designed to guide such a research are indicated with the help of a speculative, paradigmatic hypothesis concerning the role of cortical cholinergic inputs in AAD. Furthermore, aspects of validity of animal models, and cognition as a crucial intervening variable in the effects of potential treatments, are evaluated.

White matter abnormalities in HIV-1 infection: a diffusion tensor imaging study

Diffuse white matter pallor is the most frequent neuropathological feature of HIV-1 infection and has been found to be particularly prominent in the advanced stages of the disease. The purpose of this study was to determine whether subtle white matter abnormalities can be detected in medically stable, ambulatory HIV-1 patients, in vivo, using diffusion tensor imaging (DTI). DTI is a magnetic resonance imaging (MRI) technique that is uniquely suited for the study of subtle white matter abnormalities. DTI was performed in six HIV-1 patients and nine controls. The two groups were similar in age. Abnormal fractional anisotropy was found in the white matter of the frontal lobes and internal capsules of the HIV-1 patients, in the absence of group differences in mean diffusivity, computed proton density, and computed T2. DTI may be more sensitive than conventional MRI methods for detecting subtle white matter disruptions in HIV-1 disease.

Rapid and effective correction of RF inhomogeneity for high field magnetic resonance imaging

The well-known variability in the distribution of high frequency electromagnetic fields in the human body causes problems in the analysis of structural information in high field magnetic resonance images. We describe a method of compensating for the purely intensity-based effects. In our simple and rapid correction algorithm, we first use statistical means to determine the background image noise level and the edges of the image features. We next populate all "noise" pixels with the mean signal intensity of the image features. These data are then smoothed by convolution with a gaussian filter using Fourier methods. Finally, the original data that are above the noise level are normalized to the smoothed images, thereby eliminating the lowest spatial frequencies in the final, corrected data. Processing of a 124 slice, 256 x 256 volume dataset requires under 70 sec on a laptop personal computer. Overall, the method is less prone to artifacts from edges or from sensitivity to absolute head position than are other correction techniques. Following intensity correction, the images demonstrated obvious qualitative improvement and, when subjected to automated segmentation tools, the accuracy of segmentation improved, in one example, from 35.3% to 84.7% correct, as compared to a manually-constructed gold standard.

Volume distribution of cerebrospinal fluid using multispectral MR imaging

The goal of this study was to design a reliable method to quantify and visualize the anatomical distribution of cerebrospinal fluid (CSF) intracranially. The method should be clinically applicable and based on multispectral analysis of three-dimensional (3D) magnetic resonance images. T1-weighted, T2-weighted and proton density-weighted fast 3D gradient pulse sequences were used to form high resolution multispectral 3D images of the entire head. Training on single 2D slices, the Mahalanobis distances between the resulting multivariate tissue-specific densities were studied as functions of the feature vector composition and dimension. Multispectral analysis was applied to the images of four human brains. One feature vector with three components gave CSF volumes that were in the normal range and corresponding anatomical distributions that largely agreed with general anatomical knowledge. The exception was CSF missing around the basal parts of the brain due to signal artifacts. These artifacts were almost certainly due to the coil effect and magnetic field inhomogeneities induced by the imaged head. Such misclassifications could probably be reduced by bias field estimation and proper image restoration. Most CSF voxels formed large connected components that were found automatically, so the manual post-processing of the classified 3D image to locate CSF voxels was moderate. It is concluded that some of the fast, high resolution 3D gradient echo pulse sequences that have become available on conventional clinical scanners can be used to obtain good estimates of brain cerebrospinal fluid anatomical distribution and volume.

Does an increase in sulcal or ventricular fluid predict where brain tissue is lost?

Quantitative volumes of cerebrospinal fluid (CSF) and brain tissue were measured on magnetic resonance images (MRIs) of 287 individuals from 5 diagnostic groups: Alzheimer's disease (AD), chronic alcoholics (ALC), individuals positive for human immunodeficiency virus (HIV), schizophrenia subjects (SZ), and normal comparison subjects (NC) older than 50 years of age. Within each group, mean volumes were calculated for ventricular CSF, cortical (sulcal) CSF, cortical gray matter, total white matter, basal ganglia gray matter, and thalamic gray matter. Correlations of CSF measures with brain tissue measures were determined, and multiple regression analyses were performed to try and predict volume of gray matter or white matter region from volume of CSF compartment. Results indicated the following: 1. Enlarged cortical fluid volume significantly predicts cortical gray matter deficits for subjects with AD and those who are ALC and SZ but not for subjects with HIV or NC. 2. Enlarged cortical fluid volume also significantly predicts white matter deficits in all five groups. 3. Enlarged ventricular fluid volume significantly predicts basal ganglia deficits in AD, HIV, and NC but not in SZ or ALC. 4. Enlarged ventricular volume has no predictive value for thalamic volume for any of the groups. This study supports the clinical practice of predicting brain tissue volume loss from CSF enlargement but not for all brain regions in all diagnoses.

Frontal lobe neuronal injury correlates to altered function in FIV-infected cats

Six cats infected intravenously at 8 weeks of age with feline immunodeficiency virus Maryland isolate (FIV-MD), were evaluated at 8 and 14 months of age (6 months and 12 months postinfection, respectively) with high spatial resolution proton magnetic resonance spectroscopy (MRS) of the frontal cortex. Two separate control cat groups were evaluated at 8 months and 16 months of age. Single voxel two-dimensional high-resolution proton magnetic resonance imaging was performed using the PRESS sequence by selecting a 0.125 ml volume of interest in the medial frontal cortex. A significant reduction in both N-acetylaspartate (NAA) and NAA: choline ratio was found in the FIV 14-month-old group compared with FIV 8-month-old cats, and to the respective age-matched control 16-month-old cats. A negative correlation between NAA and CD4 lymphocyte count was seen in the FIV-14 group only. This group of FIV cats also exhibited a higher proportion of quantitative electroencephalographic relative slow wave activity (RSWA) that correlated to lower NAA content in the frontal cortical voxel. Although peripheral blood proviral load increased over time of infection, no correlation was found between proviral blood or lymph node load and NAA values, CD4 lymphocyte counts, or frontal cortical RSWA. Thus, this study demonstrated that neurologic functional disruption of the frontal cortex correlated strongly with neuronal injury and/or loss in FIV-MD-infected cats independent of peripheral proviral load. The ability to define in vivo neurodegeneration further in this animal model helps in understanding the neuropathogenesis of lentivirus infection, and possibly, a means to follow progression and reversibility during the initial stages of brain infection as therapeutic agents are identified.

HIV-associated dementia: new insights into disease pathogenesis and therapeutic interventions

Remarkable progress was made in recent years in the therapeutics of HIV-1-associated dementia (HAD) and in unraveling the complex pathophysiology that follows viral invasion of the central nervous system (CNS). Viral replication in and outside of the CNS was significantly reduced in HIV-1 infected subjects by new potent antiretroviral therapies. This has resulted in partial repair of cellular immune function with improvement in, and the prevention of, neurologic deficits associated with progressive HIV-1 disease. In regard to HAD pathophysiology, it is now known that CNS damage induced by HIV-1 infection occurs indirectly. Neuronal loss is mediated through immune activation and viral infection of mononuclear phagocytes (MPs) (brain macrophages and microglia). Cellular and viral factors secreted by brain MPs produce, over time, neuronal damage and drop out. Viral growth in the brain appears necessary, but not sufficient, to produce cognitive and motor impairments in affected individuals. Indeed, the best predictor for neurologic impairment following HIV-1 infection is the absolute number of immune-competent macrophages; not the level of viral production in affected brain tissue. As yet, an understanding of macrophage-related neurodegeneration has not translated into significant improvements in the treatment of this devastating complication of HIV disease. Nonetheless, adjunctive antiinflammatory and neuroprotective therapies are being developed. New ideas regarding HAD neuropathogenesis, and implications for the diagnosis and treatment of HAD are summarized in this article.

Imaging in acquired immune deficiency syndrome dementia complex (AIDS dementia complex): a review

1. Since 1986, the AIDS dementia complex has been recognized increasingly as a significant sequela of HIV infection. Though the pathogenesis remains poorly characterized and the diagnosis is one of exclusion, research utilizing various imaging techniques has resulted in greater understanding of the progressive character of ADC. 2. CT and MR studies have revealed general atrophy, atrophy of the basal ganglia, and white matter lesions that appear to increase in severity with progression of HIV infection. 3. CT and MR are relatively insensitive to the presence of clinical dementia, neurological signs, or positive findings on neuropsychological tests. In addition, they show poor correlation with histopathologic findings. 4. PET, SPECT, and MRS show the greatest sensitivity to changes wrought by primary HIV infection of the CNS and thus the greatest potential for early diagnosis of ADC. 5. PET, SPECT, and MRS show involvement of the basal ganglia, bloodflow abnormalities, and metabolite disturbances in HIV-seropositive subjects without findings on examination or neuropsychological tests.

Decline in working memory associated with HIV infection. HNRC Group

HIV infection has been associated with decline in a number of cognitive functions that are components of 'working memory'. Thus, tests of working memory that require the interaction of these components may be particularly sensitive to cognitive dysfunction that arises from HIV infection. To assess this possibility, working memory was examined in 147 HIV-seropositive (HIV+) and 38 HIV-seronegative (HIV-) males using the Reading Span Test and the Digit Span subtest from the Wechsler Memory Scale-Revised (WMS-R). Speed of information processing, a component of some working memory tasks, was assessed with a version of the Sternberg Memory Scanning task. Results indicated that symptomatic HIV+ subjects were impaired relative to HIV- control subjects on the Reading Span and Digit Span tests. Asymptomatic and mildly symptomatic HIV+ groups exhibited a trend toward impairment on these tests, and on the whole, a greater proportion of HIV+ subjects than HIV- subjects were impaired. The groups did not differ significantly in information processing speed. These results indicate that deficits in working memory are apparent in at least a subset of HIV-infected individuals. These deficits are most apparent in symptomatic HIV+ individuals, but the decline may begin during the asymptomatic phase of infection.

Spatial data analysis in the quantitative assessment of cerebral white matter pathology on MRI in HIV infection

This study was carried out using MRI (proton density--and T2-weighted) on 16 HIV-negative controls, 9 symptom-free HIV-positive patients and 25 with CDC IV HIV disease. The studies from this last group had previously been allocated by a radiologist to the following categories: 8 with focal mass lesions and normal-appearing white matter; 9 with diffuse encephalopathy (high signal on T2-weighted images, affecting most or all of the white matter) and 8 with patchy encephalopathy (high signal affecting only one or two areas within the white matter). Moran's I, a statistic of spatial autocorrelation, was calculated for the grey-scale values of a sampled pixel array from a central white matter region of each of the images. All values of Moran's I calculated in this study showed a large positive excess over the expected value under randomisation, indicating highly significant positive auto-correlation in the spatial arrangement of the grey-scale values. On T2-weighted images a statistically significant increase in the mean value of Moran's I, compared with controls, was found in the diffuse encephalopathy group, indicating that quantifiable changes in the spatial autocorrelation of pixel data can be related to recognised qualitative changes in the appearance of white matter in subjects with HIV disease. A lesser, but significant, rise in the mean value of Moran's I was also found in the focal mass lesion group, suggesting that changes in spatial autocorrelation may indicate pathological change in advance of qualitative MRI changes.

The snout and palmomental reflexes in HIV disease in Tanzania

Following earlier observations on the snout (SR) and palmomental(PMR) reflexes in AIDS in Tanzania, a series of 1127 adults, 649 HIV-positive and 478 HIV-negative, from 4 groups at different risk of HIV infection were examined neurologically between 1987 and 1992. The prevalence of SR and PMR was calculated according to HIV status, HIV stage, demographic factors and neurologic findings. In the total series of HIV positives the prevalence ranged from SR 39.3% and PMR 22.6% in asymptomatic HIV disease to SR 87% and PMR 69% in terminal AIDS. In HIV negatives the prevalence of SR was 19.2% and PMR 15.3%, and increased with age. There was no relationship with age in the HIV positives and no gender differences. SR and PMR were also associated with neuropathy, myelopathy and AIDS dementia complex independent of HIV stage. This study shows a strong association between SR and PMR and HIV disease in Africa. The prevalence increased with HIV stage and related neurological disorders.

The HNRC 500--neuropsychology of HIV infection at different disease stages. HIV Neurobehavioral Research Center

The present study examined neuropsychological (NP) functioning and associated medical, neurological, brain magnetic resonance imaging (MRI), and psychiatric findings in 389 nondemented males infected with Human Immunodeficiency Virus-Type 1 (HIV-1), and in 111 uninfected controls. Using a comprehensive NP test battery, we found increased rates of impairment at each successive stage of HIV infection. HIV-related NP impairment was generally mild, especially in the medically asymptomatic stage of infection, and most often affected attention, speed of information processing, and learning efficiency; this pattern is consistent with earliest involvement of subcortical or frontostriatal brain systems. NP impairment could not be explained on the bases of mood disturbance, recreational drug or alcohol use, or constitutional symptoms; by contrast, impairment in HIV-infected subjects was related to central brain atrophy on MRI, as well as to evidence of cellular immune activation and neurological abnormalities linked to the central nervous system.

Validity of the Quality of Well-Being Scale for persons with human immunodeficiency virus infection. HNRC Group. HIV Neurobehavioral Research Center

To evaluate the validity of the Quality of Well-Being Scale (QWB) for studies of patients with human immunodeficiency virus (HIV) disease, 514 men were studied who were divided among four categories: Centers for Disease Control and Prevention (CDC) Group A (N = 272), CDC-B (N = 81), CDC-C (N = 47), and uninfected male controls (N = 114). The QWB and a variety of medical, neuropsychological, and biochemical measures were administered to all participants. When QWB scores were broken down by HIV group, the CDC-C group was significantly lower (.614) than the CDC-B (.679), CDC-A (.754), or control group (.801). The difference between Groups CDC-C and CDC-A was about .14 units of well-being, which suggests that individuals lose 1/7 equivalents of 1 well year of life for each year they are in Group CDC-C in comparison to the asymptomatic group (Group CDC-A). In comparison to the controls, this would equal a 1-year of life loss for each seven infected individuals. The QWB was shown to be significantly associated with CD4+ lymphocytes (p < .001), clinician ratings of neuropsychological impairment (p < .04), neurologists ratings of dysfunction (p < .001), and all subscales of the Profile of Mood States. Baseline QWB scores were significant prospective predictors of death over a median follow-up time of 30 months. Multivariate models demonstrated high covariation between predictors of QWB. It was concluded that the QWB is a significant correlate of biological, neuropsychological, neurological, psychiatric, and mortality outcomes for male HIV-infected patients.

Prospective utility of cerebral proton magnetic resonance spectroscopy in monitoring HIV infection and its associated neurological impairment

Neurological manifestations of HIV disease occur in most adults and children with AIDS. Many of those affected will inevitably suffer clinical neurological deficits involving mental function, movement, and sensation. Surprisingly, there are not as yet adequate monitoring systems to predict the onset and/or progression of HIV infection of the CNS. Neurological, neuropsychological, CSF, and magnetic resonance imaging (MRI) analyses cannot accurately detect mental deterioration during advancing HIV disease. Reports suggest that in vivo proton MR spectroscopy (1H MRS) of the brain could be a predictor of virus-induced neurological deterioration. H MRS can measure N-acetylaspartate (NAA), a metabolite present only in neurons. Decreased NAA reflects neuronal loss seen during HIV infection of brain. To uncover possible associations between NAA levels and HIV-induced neurological disease we performed serial 1H MRS brain tests in HIV-infected patients with or at risk for encephalopathy. Serial testing, for 1 year, of 10 patients showed that brain NAA levels decreased in all HIV-infected subjects. The most severe NAA reductions were associated with progressive neurological impairment. These findings suggest that NAA can be used as a noninvasive measure of neuronal loss in patients with HIV disease. Most important, the results suggest that 1H MRS could be used to monitor therapeutics directed against HIV infection within the CNS.

N-acetylaspartate reductions measured by 1H MRSI in cognitively impaired HIV-seropositive individuals

We used magnetic resonance imaging (MRI) and water-suppressed proton MR spectroscopic imaging (1H MRSI) to study the effects of human immunodeficiency virus (HIV) infection on the brain. Our recent in vivo finding of lower N-acetylaspartate (NAA), a putative marker of neurons, in the supraventricular brain of cognitively impaired HIV-seropositive patients (CISP) compared to noninfected controls was replicated in a new cohort of 13 CISP patients and extended to include 10 high-risk homosexual HIV-seronegative controls. Throughout the supraventricular brain the ratio of NAA to choline-containing metabolites (NAA/Cho) was lower in CISP subjects than in high-risk controls (1.98 +/- 0.36 vs. 2.35 +/- 0.29, p = 0.016), and the ratio of NAA to creatine-containing metabolites (NAA/Cr) was also lower in CISP subjects than in high-risk controls (3.02 +/- 0.44 vs. 3.56 +/- 0.39, p = 0.007) with Cho/Cr unchanged in both groups. These findings indicate a NAA reduction which suggests neuron loss and/or dendritic and axonal damage. Homosexual high-risk HIV-seronegative controls had metabolite measures similar to previously studied heterosexual HIV-seronegative controls. NAA measures in six cognitively normal HIV-seropositive subjects (CNSP) (NAA/Cho = 2.34 +/- 0.39, NAA/Cr = 3.42 +/- 0.69) were similar to those of controls and tended to be increased relative to those in cognitively impaired HIV-seropositive subjects. This study demonstrates that reduced NAA in the supraventricular brain is associated with the development of severe cognitive impairments secondary to HIV infection and that 1H MRSI methodology reliably detects HIV effects on the brain.(ABSTRACT TRUNCATED AT 250 WORDS)