Increased NADPH-diaphorase reactivity and cytokine expression in dorsal root ganglia in acquired immunodeficiency syndrome

Progress in Pathological and Therapeutic Research of HIV-Related Neuropathic Pain

HIV-related neuropathic pain (HRNP) is a neurodegeneration that gradually develops during the long-term course of acquired immune deficiency syndrome (AIDS) and manifests as abnormal sock/sleeve-like symmetrical pain and nociceptive hyperalgesia in the extremities, which seriously reduces patient quality of life. To date, the pathogenesis of HRNP is not completely clear. There is a lack of effective clinical treatment for HRNP and it is becoming a challenge and hot spot for medical research. In this study, we conducted a systematic review of the progress of HRNP research in recent years including (1) the etiology, classification and clinical symptoms of HRNP, (2) the establishment of HRNP pathological models, (3) the pathological mechanisms underlying HRNP from three aspects: molecules, signaling pathways and cells, (4) the therapeutic strategies for HRNP, and (5) the limitations of recent HRNP research and the future research directions and prospects of HRNP. This detailed review provides new and systematic insight into the pathological mechanism of HRNP, which establishes a theoretical basis for the future exploitation of novel target drugs. HIV infection, antiretroviral therapy and opioid abuse contribute to the etiology of HRNP with symmetrical pain in both hands and feet, allodynia and hyperalgesia. The pathogenesis involves changes in cytokine expression, activation of signaling pathways and neuronal cell states. The therapy for HRNP should be patient-centered, integrating pharmacologic and nonpharmacologic treatments into multimodal intervention.

From Initiation to Maintenance: HIV-1 Gp120-induced Neuropathic Pain Exhibits Different Molecular Mechanisms in the Mouse Spinal Cord Via Bioinformatics Analysis Based on RNA Sequencing

Human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), remains one of the most diverse crucial health and development challenges around the world. People infected with HIV constitute a large patient population, and a significant number of them experience neuropathic pain. To study the key mechanisms that mediate HIV-induced neuropathic pain (HNP), we established an HNP mouse model via intrathecal injection of the HIV-1 envelope glycoprotein gp120. The L3~L5 spinal cord was isolated on postoperative days 1/12 (POD1/12), 1 (POD1), and 14 (POD14) for RNA sequencing to investigate the gene expression profiles of the initiation, transition, and maintenance stages of HNP. A total of 1682, 430, and 413 differentially expressed genes were obtained in POD1/12, POD1, and POD14, respectively, and their similarity was low. Bioinformatics analysis confirmed that POD1/12, POD1, and POD14 exhibited different biological processes and signaling pathways. Inflammation, oxidative damage, apoptosis, and inflammation-related signaling pathways were enriched on POD1/12. Inflammation, chemokine activity, and downstream signaling regulated by proinflammatory cytokines, such as the MTOR signaling pathway, were enriched on POD1, while downregulation of ion channel activity, mitochondrial damage, endocytosis, MAPK and neurotrophic signaling pathways developed on POD14. Additionally, we screened key genes and candidate genes, which were verified at the transcriptional and translational levels. Our results suggest that the initiation and maintenance of HNP are regulated by different molecular mechanisms. Therefore, our research may yield a fresh and deeper understanding of the mechanisms underlying HNP, providing accurate molecular targets for HNP therapy.

Magnitude of Peripheral Sensory Neuropathy and Associated Factors Among HIV/AIDS Clients Receiving Care at Public Health Institutions, Northwest Ethiopia

Background: In the mid-1990s, the development of combination antiretroviral therapy converted HIV infection into a chronic condition, with newly diagnosed patients now living longer than the general population. HIV affects both the central and peripheral nerve systems, resulting in a variety of clinical problems, including peripheral neuropathy, which is a common neurological consequence. Despite this, there is a scarcity of data on the extent of peripheral sensory neuropathy and its underlying factors in Ethiopia, necessitating this study. Objective: The primary goal of this study is to assess the degree of peripheral sensory neuropathy and its related factors among HIV/AIDS clients on follow up at public health institutions in Northwest Ethiopia. Methodology: Institution based cross-sectional study was conducted from November 1 to 30 December 2020 at selected south Gondar zone public health institutions ART clinic. Multistage sampling technique was used to select the study participants. Standardized Questioner adapted from other study was used to collect the data. Moreover, Brief Peripheral Neuropathy Screening tool (BPNS) was used to assess peripheral sensory neuropathy. The data were entered with epi-data manager version 4.4 and analyzed using STATA version 16. Result: A total of 555 adult PLWHIV agreed to participate in the study, resulting in a response rate of 96.8%. The prevalence of Peripheral sensory neuropathy was 32.25, 95% CI (28.28, 36.26). The participant’s age, DM comorbidity, viral load level, and disease clinical stage were all found to have a statistically significant association with peripheral sensory neuropathy. Conclusion: Peripheral sensory neuropathy was incredibly common. Accordingly, peripheral sensory neuropathy was found considerably associated with age, viral load level, stage of the disease, and DM comorbidity. It is vital to integrate routine peripheral sensory neuropathy screening strategies for clients who are on ART follow up for prevention and early identification of the problem.

The Interplay Between Neuroinfections, the Immune System and Neurological Disorders: A Focus on Africa

Neurological disorders related to neuroinfections are highly prevalent in Sub-Saharan Africa (SSA), constituting a major cause of disability and economic burden for patients and society. These include epilepsy, dementia, motor neuron diseases, headache disorders, sleep disorders, and peripheral neuropathy. The highest prevalence of human immunodeficiency virus (HIV) is in SSA. Consequently, there is a high prevalence of neurological disorders associated with HIV infection such as HIV-associated neurocognitive disorders, motor disorders, chronic headaches, and peripheral neuropathy in the region. The pathogenesis of these neurological disorders involves the direct role of the virus, some antiretroviral treatments, and the dysregulated immune system. Furthermore, the high prevalence of epilepsy in SSA (mainly due to perinatal causes) is exacerbated by infections such as toxoplasmosis, neurocysticercosis, onchocerciasis, malaria, bacterial meningitis, tuberculosis, and the immune reactions they elicit. Sleep disorders are another common problem in the region and have been associated with infectious diseases such as human African trypanosomiasis and HIV and involve the activation of the immune system. While most headache disorders are due to benign primary headaches, some secondary headaches are caused by infections (meningitis, encephalitis, brain abscess). HIV and neurosyphilis, both common in SSA, can trigger long-standing immune activation in the central nervous system (CNS) potentially resulting in dementia. Despite the progress achieved in preventing diseases from the poliovirus and retroviruses, these microbes may cause motor neuron diseases in SSA. The immune mechanisms involved in these neurological disorders include increased cytokine levels, immune cells infiltration into the CNS, and autoantibodies. This review focuses on the major neurological disorders relevant to Africa and neuroinfections highly prevalent in SSA, describes the interplay between neuroinfections, immune system, neuroinflammation, and neurological disorders, and how understanding this can be exploited for the development of novel diagnostics and therapeutics for improved patient care.

Large Mitochondrial DNA Deletions in HIV Sensory Neuropathy

OBJECTIVE

The primary objective of this study was to evaluate the correlation of large mitochondrial DNA (mtDNA) deletions in skin samples of people with HIV (PWH) with measures of neuropathy and prior exposure to therapy. We hypothesized that deletions would be associated with neuropathy. As secondary objectives, we determined the correlation of deletion burden with demographic data and neuropathy measures.

METHODS

In this retrospective cohort study, we measured the accumulation of large mtDNA deletions in skin biopsies from PWH recruited as part of the AIDS Clinical Trials Group (ACTG). Our cohort includes individuals with and without sensory neuropathy, as well as individuals with normal or abnormal skin biopsies. Skin biopsies, sural and peroneal nerve conduction studies, total neuropathy score, and deletion burden scores were measured, along with baseline demographic data such as age, CD4+ cell count, viral counts, and prior nucleoside reverse transcriptase inhibitor exposures.

RESULTS

Sixty-seven PWH were enrolled in the study. The mean age of the cohort (n = 67) was 44 years (SD 6.8, range 32-65 years), and 9 participants were female. The mean CD4+ T-cell count was 168 cells/mm³ (SD 97 cells/mm³, range 1-416 cells/mm³) and mean viral load was 51,129 copies/mL (SD 114,586 copies/mL, range 147-657,775 copies/mL). We determined that there was a correlation between the total mtDNA deletion and intraepidermal nerve fiber density (IENFD) (r = -0.344, p = 0.04) and sural nerve amplitude (r = -0.359, p = 0.004).

CONCLUSIONS

Both IENFD and sural nerve amplitude statistically correlate with mitochondrial mutation burden in PWH, specifically in those with HIV-associated sensory neuropathy as assessed by skin biopsy.

Schwann cell-derived CXCL1 contributes to human immunodeficiency virus type 1 gp120-induced neuropathic pain by modulating macrophage infiltration in mice

The neuroinflammatory responses to human immunodeficiency virus type 1 (HIV-1) coat proteins, such as glycoprotein 120 (gp120), are considered to be responsible for the HIV-associated distal sensory neuropathy. Accumulating evidences suggest that T-cell line tropic X4 gp120 increases macrophage infiltration into the peripheral nerves, and thereby induces neuroinflammation leading to pain. However, the mechanisms underlying X4 gp120-induced macrophage recruitment to the peripheral nervous systems remain unclear. Here, we demonstrated that perineural application of X4 gp120 from HIV-1 strains IIIB and MN elicited mechanical hypersensitivity and spontaneous pain-like behaviors in mice. Furthermore, flow cytometry and immunohistochemical studies revealed increased infiltration of bone marrow-derived macrophages into the parenchyma of sciatic nerves and dorsal root ganglia (DRG) 7 days after gp120 IIIB or MN application. Chemical deletion of circulating macrophages using clodronate liposomes markedly suppressed gp120 IIIB-induced pain-like behaviors. In in vitro cell infiltration analysis, RAW 264.7 cell (a murine macrophage cell line) was chemoattracted to conditioned medium from gp120 IIIB- or MN-treated cultured Schwann cells, but not to conditioned medium from these gp120-treated DRG neurons, suggesting possible involvement of Schwann cell-derived soluble factors in macrophage infiltration. We identified using a gene expression array that CXCL1, a chemoattractant of macrophages and neutrophils, was increased in gp120 IIIB-treated cultured Schwann cells. Similar to gp120 IIIB or MN, perineural application of recombinant CXCL1 elicited pain-like behaviors accompanied by macrophage infiltration to the peripheral nerves. Furthermore, the repeated injection of CXCR2 (receptor for CXCL1) antagonist or CXCL1 neutralizing antibody prevented both pain-like behaviors and macrophage infiltration in gp120 IIIB-treated mice. Thus, the present study newly defines that Schwann cell-derived CXCL1, secreted in response to X4 gp120 exposure, is responsible for macrophage infiltration into peripheral nerves, and is thereby associated with pain-like behaviors in mice. We propose herein that communication between Schwann cells and macrophages may play a prominent role in the induction of X4 HIV-1-associated pain.

SIV-Induced Immune Activation and Metabolic Alterations in the Dorsal Root Ganglia During Acute Infection

Human immunodeficiency virus-associated sensory neuropathy (HIV-SN) remains a frequent neurologic complication of HIV infection. Little is known about alterations in the peripheral nervous system during the early stages of HIV, a time when neuroprotective interventions may be most beneficial. We performed Nanostring gene expression analysis on lumbar dorsal root ganglia (DRG) from 6 simian immunodeficiency virus (SIV)-infected pigtailed macaques killed at 7 days post-inoculation and 8 uninfected controls. We found significant upregulation of many genes involved in immune signaling and activation in the DRG. Among genes related to glutamate metabolism, there was significant upregulation of glutamine synthetase (GS), while glutaminase (GLS) was downregulated. Several genes involved in the oxidative stress response also showed significant differential regulation in the DRG of 7d SIV-infected animals, with superoxide dismutase-2 (SOD2) showing the greatest median fold change compared to controls. Novel findings in the DRG were compared to corresponding brain data and further investigated at the protein level by Western blotting and immunohistochemistry. Together with our previous finding of significant epidermal nerve fiber loss at 14 days post-SIV infection, results of this study demonstrate that immune activation and altered cellular metabolism at in the DRG precede and likely contribute to early sensory nerve injury in HIV-SN.

HIV-1 gp120 Promotes Lysosomal Exocytosis in Human Schwann Cells

Human immunodeficiency virus type 1 (HIV-1) associated neuropathy is the most common neurological complication of HIV-1, with debilitating pain affecting the quality of life. HIV-1 gp120 plays an important role in the pathogenesis of HIV neuropathy via direct neurotoxic effects or indirect pro-inflammatory responses. Studies have shown that gp120-induced release of mediators from Schwann cells induce CCR5-dependent DRG neurotoxicity, however, CCR5 antagonists failed to improve pain in HIV- infected individuals. Thus, there is an urgent need for a better understanding of neuropathic pain pathogenesis and developing effective therapeutic strategies. Because lysosomal exocytosis in Schwann cells is an indispensable process for regulating myelination and demyelination, we determined the extent to which gp120 affected lysosomal exocytosis in human Schwann cells. We demonstrated that gp120 promoted the movement of lysosomes toward plasma membranes, induced lysosomal exocytosis, and increased the release of ATP into the extracellular media. Mechanistically, we demonstrated lysosome de-acidification, and activation of P2X4 and VNUT to underlie gp120-induced lysosome exocytosis. Functionally, we demonstrated that gp120-induced lysosome exocytosis and release of ATP from Schwann cells leads to increases in intracellular calcium and generation of cytosolic reactive oxygen species in DRG neurons. Our results suggest that gp120-induced lysosome exocytosis and release of ATP from Schwann cells and DRG neurons contribute to the pathogenesis of HIV-1 associated neuropathy.

Mitochondrial dysfunction in HIV-induced peripheral neuropathy

Mitochondria play an essential role in cellular energy production and calcium homeostasis. Abnormalities in mitochondrial homeostasis and function are seen in several acquired as well as genetic neuropathies, emphasizing their prominent role in neuronal cell activities. Chronic infection with HIV, even when appropriately treated, is a risk factor for developing peripheral neuropathy. In this chapter, we discuss the way in which HIV infection, the resultant toxic viral products that are generated, and some of the viral inhibitors used in its treatment may lead to abnormal mitochondrial function. Of importance are the effects on mitochondrial DNA replication and the neurotoxic effects of the viral gp120 protein. One aspect of mitochondrial dysfunction that remains unexplored is the role of the interaction between mitochondria and the endoplasmic reticulum as a possible target of disruption in HIV neuropathy.

Update of HIV-Associated Sensory Neuropathies

PURPOSE OF REVIEW

HIV-sensory neuropathy (HIV-SN) remains a common complication of HIV infection and may be associated with significant morbidity due to neuropathic pain. The overall purpose of this review is to discuss trends in the changing epidemiology in HIV-SN, new data regarding the pathophysiology of the condition, and discuss approaches to management.

RECENT FINDINGS

While HIV-SN has been historically considered the most common neurological complication of HIV infection, improved accessibility to effective combination antiretroviral therapy (cART), use of less neurotoxic antiretroviral medication regimens, and trends towards earlier introduction of treatment have impacted the condition: overall incident HIV-SN is likely decreased compared to prior rates and patients afflicted by HIV-SN may more frequently have asymptomatic or subclinical disease. Traditional predictors of HIV-SN have also changed, as traditional indices of severe immune deficiency such as low CD4 count and high viral load no longer predict HIV-SN. Emerging evidence supports the contention that both peripheral and central mechanisms underlying the generation as well as persistence of neuropathic pain in HIV-SN exist. It is important to recognize that even mild neuropathic pain in this clinical population is associated with meaningful impairment in quality of life and function, which emphasizes the clinical importance of recognizing and treating the condition. The general approach to management of neuropathic pain in HIV-SN is the introduction of symptomatic analgesic therapy. There exist, however, few evidence-based analgesic options for HIV-SN based on available clinical data. Symptomatic treatment trials are increasingly recognized to have been potentially confounded by more robust placebo response than that observed in other neuropathic pain conditions. In the authors' experience, use of analgesic therapies with proven efficacy in other neuropathic pain conditions is appropriate, bearing in consideration potential pharmacokinetic interactions with the cART regimen. Combination analgesic regimens may also achieve meaningful analgesic responses, particularly when drugs with differing mechanisms of action are utilized. It is paramount that the patient is appropriately counseled regarding expectations and the anticipated benefit of analgesic therapy, as pain relief is often incomplete but clinically meaningful improvement in pain and function can be achieved.

Peripheral neuropathy in primary HIV infection associates with systemic and central nervous system immune activation

BACKGROUND

Peripheral neuropathy (PN) is a frequent complication of chronic HIV infection. We prospectively studied individuals with primary HIV infection (<1 year after transmission) to assess the presence of and laboratory associations with PN in this early stage.

METHODS

Standardized examination and analysis of blood and cerebrospinal fluid (CSF) was performed in participants with laboratory-confirmed primary HIV infection. PN was defined as ≥1 of the following unilateral or bilateral signs: decreased distal limb position, vibration, or temperature sense or hyporeflexia; symptomatic PN (SPN) was defined as the presence of these signs with symptoms. Analysis used nonparametric statistics.

RESULTS

Overall, 20 (35%) of 58 antiretroviral-naive male subjects without diabetes evaluated at a median of 107 days post HIV transmission met criteria for PN. Thirteen (65%) of 20 PN subjects met criteria for SPN; 6 (30%) of 20 had bilateral findings. PN subjects and no PN subjects (NPN) did not differ in median age, days post HIV transmission, blood CD4 or CD8 counts, CSF or plasma HIV RNA levels, CSF white blood cell counts, or CSF to blood albumin ratio. PN and SPN subjects had elevated CSF neopterin (P = 0.003 and P = 0.0005), CSF monocyte chemoattractant protein-1 (P = 0.006 and P = 0.01), and blood neopterin (P = 0.006 and P = 0.009) compared with NPN subjects. PN subjects had a higher percentage of activated phenotype CSF CD8 T lymphocytes than NPN subjects (P = 0.009).

CONCLUSIONS

Signs of PN were detected by detailed neurologic examination in 35% of men enrolled in a neurological study at a median of 3.5 months after HIV transmission. PN during this early period may be mediated by systemic and nervous system immune responses to HIV.

Macrophage-sensory neuronal interaction in HIV-1 gp120-induced neurotoxicity‡

Background

Human immunodeficiency virus (HIV)-associated sensory neuropathy (SN) is the most frequent neurological complication of HIV disease. Among the probable mechanisms underlying HIV-SN are neurotoxicity induced by the HIV glycoprotein gp120 and antiretroviral therapies (ART). Since HIV-SN prevalence remains high in patients who have not been exposed to toxic ART drugs, here we focused on gp120-mediated mechanisms underlying HIV-SN.

Methods

We hypothesized that a direct gp120–sensory neurone interaction is not the cause of neurite degeneration; rather, an indirect interaction of gp120 with sensory neurones involving macrophages underlies axonal degeneration. Rat dorsal root ganglion (DRG) cultures were used to assess gp120 neurotoxicity. Rat bone marrow-derived macrophage (BMDM) cultures and qPCR array were used to assess gp120-associated gene expression changes.

Results

gp120 induced significant, but latent onset, neurite degeneration until 24 h after application. gp120–neurone interaction occurred within 1 h of application in <10% of DRG neurones, despite neurite degeneration having a global effect. Application of culture media from gp120-exposed BMDMs induced a significant reduction in DRG neurite outgrowth. Furthermore, gp120 significantly increased the expression of 25 cytokine-related genes in primary BMDMs, some of which have been implicated in other painful polyneuropathies. The C–C chemokine receptor type 5 (CCR5) antagonist, maraviroc, concentration-dependently inhibited gp120-induced tumour necrosis factor-α gene expression, indicating that these effects occurred via gp120 activation of CCR5.

Conclusions

Our findings highlight macrophages in the pathogenesis of HIV-SN and upstream modulation of macrophage response as a promising therapeutic strategy.

Role of TNF block genetic variants in HIV-associated sensory neuropathy in black Southern Africans

HIV-associated sensory neuropathy (HIV-SN) is a common neurological complication of HIV infection. The TNF block is a region within the central MHC that contains many immunoregulatory genes. Polymorphisms and haplotypes of the TNF block have been associated with increased risk of HIV-SN in Asians and whites. Here we investigated genetic associations with HIV-SN in 342 black Southern Africans (190 cases and 152 neuropathy-free controls) using single nucleotide polymorphisms (SNPs) spanning the TNF block and a set of haplotypes defined by 31 SNPs in Asian and white populations (denoted FVa). We included population-appropriate tagSNPs derived from an African population (Yoruban, YRI, HapMap) and derived extended haplotypes comprising 61 SNPs (denoted FVa_ext b). We found no association between HIV-SN and carriage of two SNPs (TNF-1031/rs1799964*C and BAT1 (intron10)/rs9281523*C) associated with HIV-SN in whites and Asians. Additionally, a haplotype containing TNF-1031/rs1799964*C associated with increased risk of HIV-SN in Asians, but was not present in this African population. However, alleles of seven SNPs associated with reduced risk of HIV-SN (corrected for age, height and multiple comparisons). These were rs11796*A, rs3130059*G, rs2071594*C, NFKBIL1-62/rs2071592*A, rs2071591*A, LTA+252/rs909253*G, rs1041981*C. One haplotype (FV18_ext1), not containing these alleles, was associated with increased risk of HIV-SN after correction for age, height and multiple comparisons. Our results confirm the involvement of genes in the TNF block in altering risk for HIV-SN, but genotypes critical in this African population differed from those affecting HIV-SN in whites and Asians. These differences support the need for genetic association studies in diverse populations.

The Molecular and Pharmacological Mechanisms of HIV-Related Neuropathic Pain

Infection of the nervous system with the human immunodeficiency virus (HIV-1) can lead to cognitive, motor and sensory disorders. HIV-related sensory neuropathy (HIV-SN) mainly contains the HIV infection-related distal sensory polyneuropathy (DSP) and antiretroviral toxic neuropathies (ATN). The main pathological features that characterize DSP and ATN include retrograde ("dying back") axonal degeneration of long axons in distal regions of legs or arms, loss of unmyelinated fibers, and variable degree of macrophage infiltration in peripheral nerves and dorsal root ganglia (DRG). One of the most common complaints of HIV-DSP is pain. Unfortunately, many conventional agents utilized as pharmacologic therapy for neuropathic pain are not effective for providing satisfactory analgesia in painful HIV-related distal sensory polyneuropathy, because the molecular mechanisms of the painful HIV-SDP are not clear in detail. The HIV envelope glycoprotein, gp120, appears to contribute to this painful neuropathy. Recently, preclinical studies have shown that glia activation in the spinal cord and DRG has become an attractive target for attenuating chronic pain. Cytokines/chemokines have been implicated in a variety of painful neurological diseases and in animal models of HIV-related neuropathic pain. Mitochondria injured by ATN and/or gp120 may be also involved in the development of HIV-neuropathic pain. This review discusses the neurochemical and pharmacological mechanisms of HIV-related neuropathic pain based on the recent advance in the preclinical studies, providing insights into novel pharmacological targets for future therapy.

HIV-related neuropathy: current perspectives

Distal symmetric polyneuropathy (DSP) related to human immunodeficiency virus (HIV) is one of the most common neurologic complications of HIV, possibly affecting as many as 50% of all individuals infected with HIV. Two potentially neurotoxic mechanisms have been proposed to play a crucial role in the pathogenesis of HIV DSP: neurotoxicity resulting from the virus and its products; as well as adverse neurotoxic effects of medications used in the treatment of HIV. Clinically, HIV DSP is characterized by a combination of signs and symptoms that include decreased deep tendon reflexes at the ankles and decreased sensation in the distal extremities as well as paresthesias, dysesthesias, and pain in a symmetric stocking-glove distribution. These symptoms are generally static or slowly progressive over time, and depending on the severity, may interfere significantly with the patient's daily activities. In addition to the clinical picture, nerve conduction studies and skin biopsies are often pursued to support the diagnosis of HIV DSP. Anticonvulsants, antidepressants, topical agents, and nonspecific analgesics may help relieve neuropathic pain. Specifically, gabapentin, lamotrigine, pregabalin, amitriptyline, duloxetine, and high-dose topical capsaicin patches have been used in research and clinical practice. Further research is needed to elucidate the pathogenesis of HIV DSP, thus facilitating the development of novel treatment strategies. This review discusses the epidemiology, pathophysiology, clinical findings, diagnosis, and management of DSP in the setting of HIV.

Neuromuscular manifestations of HIV/AIDS

The human immunodeficiency virus (HIV) epidemic, now entering its fourth decade, affects approximately 33 million people living in both developed and resource-limited countries. Neurological complications of the peripheral nervous system are common in HIV-infected patients, and neuromuscular pathology is associated with significant morbidity. Peripheral neuropathy is the most common neuromuscular manifestation observed in HIV/AIDS, and in the antiretroviral era, its prevalence has increased. The purpose of this review was to describe the clinical spectrum of neuromuscular disorders in the setting of HIV infection and to provide an approach to diagnosis and management.

Painful HIV-associated sensory neuropathy

SUMMARY Painful HIV-associated sensory neuropathy (HIV-SN) is an early recognized neurological complication of HIV. The introduction of effective HIV treatments saw increased rates of HIV-SN, with some antiretrovirals (notably stavudine) being neurotoxic. Although neurotoxic antiretrovirals are being phased out, the available data suggest that incident HIV-SN will remain common, impairing quality of life, mobility and ability to work. Despite its major clinical importance, the pathogenesis and determinants of pain in HIV-SN are poorly understood, and effective prevention and analgesic strategies are lacking. Here, we review what is known about the rates and risk factors for painful HIV-SN, the laboratory models informing our understanding of neuropathic pain in HIV, and the future clinical and laboratory work needed to fully understand this debilitating condition and provide effective management strategies for those affected.

Pathogenesis of HIV-associated sensory neuropathy: evidence from in vivo and in vitro experimental models

HIV-associated sensory neuropathy (HIV-SN) is a frequent neurological complication of HIV infection and its treatment with some antiretroviral drugs. We review the pathogenesis of the viral- and drug-induced causes of the neuropathy, and its primary symptom, pain, based on evidence from in vivo and in vitro models of HIV-SN. Viral coat proteins mediate nerve fibre damage and hypernociception through direct and indirect mechanisms. Direct interactions between viral proteins and nerve fibres dominate axonal pathology, while somal pathology is dominated by indirect mechanisms that occur secondary to virus-mediated activation of glia and macrophage infiltration into the dorsal root ganglia. The treatment-induced neuropathy and resulting hypernociception arise primarily from drug-induced mitochondrial dysfunction, but the sequence of events initiated by the mitochondrial dysfunction that leads to the nerve fibre damage and dysfunction are still unclear. Overall, the models that have been developed to study the pathogenesis of HIV-SN, and hypernociception associated with the neuropathy, are reasonable models and have provided useful insights into the pathogenesis of HIV-SN. As new models are developed they may ultimately lead to identification of therapeutic targets for the prevention or treatment of this common neurological complication of HIV infection.

Tumour necrosis factor haplotypes associated with sensory neuropathy in Asian and Caucasian human immunodeficiency virus patients

In human immunodeficiency virus (HIV) patients, neuropathy is a common adverse side effect to some antiretroviral treatments, particularly stavudine. As stavudine is cheap, it is widely used in Asia and Africa. We showed that increasing age and height moderately predict the development of neuropathy. This was improved by the inclusion of tumour necrosis factor (TNF)-1031 (rs1799964). To investigate this association, Malay (n = 64), Chinese (n = 74) and Caucasian patients (n = 37) exposed to stavudine were screened for neuropathy. DNA samples were genotyped for polymorphisms in the central major histocompatibility complex (MHC) near TNF, and haplotypes were derived. The haplotype group FVa6,7,8 (incorporating TNF-1031) was found to be associated with neuropathy in Chinese patients in bivariate analyses (P = 0.03), and in Malays and Chinese in a multivariate analysis correcting for age and height (P = 0.02, P = 0.03, respectively). This trend was also confirmed in Caucasians.

Initiation of antiretroviral therapy at CD4 cell counts >/=350 cells/mm3 does not increase incidence or risk of peripheral neuropathy, anemia, or renal insufficiency

BACKGROUND

US guidelines recommend deferring initiation of highly active antiretroviral therapy (HAART) for most patients with CD4 counts >350 cells/mm in part because of concerns about antiretroviral toxicity.

METHODS

Incidence rates of peripheral neuropathy, anemia, and renal insufficiency in a cohort of 2165 patients followed more than 3 years (mean) were analyzed in multivariate Cox proportional hazards models by CD4 cell counts at initiation of HAART. A nested cohort of 895 patients restricted to study participants who did or did not start HAART within a CD4 cell count stratum were also compared.

RESULTS

Incidence and risks of all 3 comorbidities decreased with initiation of HAART at CD4 counts >200 cells/mm versus <200 cells/mm. Incidence and risks of renal insufficiency were similar with HAART initiation at CD4 counts >/=350 cells/mm versus 200 to 349 cells/mm, but risk of peripheral neuropathy and anemia were further decreased in persons starting HAART at a CD4 count >/=350 cells/mm. The incidence of these conditions was highest during the first 6 months of treatment at any CD4 cell count and declined up to 19-fold with further therapy.

DISCUSSION

Initiating HAART at CD4 cell counts >/=200 cells/mm reduced the incidence and risk of the 3 comorbid conditions and for anemia and peripheral neuropathy as well by starting at CD4 counts >/=350 cells/mm. The incidence of each condition decreased rapidly and remained low with increasing time on HAART.

Cytokine genotype suggests a role for inflammation in nucleoside analog-associated sensory neuropathy (NRTI-SN) and predicts an individual's NRTI-SN risk

Nucleoside analog-associated sensory neuropathy (NRTI-SN) attributed to stavudine, didanosine, or zalcitabine (the dNRTIs) and distal sensory polyneuropathy (DSP) attributed to HIV are clinically indistinguishable. As inflammatory cytokines are involved in DSP, we addressed a role for inflammation in NRTI-SN by determining the alleles of immune-related genes carried by patients with and without NRTI-SN. Demographic details associated with risk of various neuropathies were included in the analysis. Alleles of 14 polymorphisms in 10 genes were determined in Australian HIV patients with definite NRTI-SN (symptom onset <6 months after first dNRTI exposure, n = 16), NRTI-SN-resistant patients (no neuropathy despite >6 months on dNRTIs, n = 20), patients with late onset NRTI-SN (neuropathy onset after >6 months of dNRTIs, n = 19), and HIV-negative controls. Carriage of TNFA-1031*2 was highest in NRTI-SN patients, suggesting potentiation of NRTI-SN. Carriage of IL12B (3' UTR)*2 was higher in NRTI-SN-resistant patients than controls or NRTI-SN patients, suggesting a protective role. BAT1 (intron 10)*2 was more common in NRTI-SN than resistant patients, but neither group differed from controls. This marks the conserved HLA-A1, B8, DR3 haplotype. Of the demographic details considered, increasing height was associated with NRTI-SN risk. A model including cytokine genotype and height predicted NRTI-SN status (p < 0.0001, R(2) = 0.54). Late onset NRTI-SN patients clustered genetically with NRTI-SN-resistant patients, so these patients may be genetically "protected." In addition to patient height, cytokine genotype influenced NRTI-SN risk following dNRTI exposure, suggesting inflammation contributes to NRTI-SN.

Characterization of rodent models of HIV-gp120 and anti-retroviral-associated neuropathic pain

A distal symmetrical sensory peripheral neuropathy is frequently observed in people living with Human Immunodeficiency Virus Type 1 (HIV-1). This neuropathy can be associated with viral infection alone, probably involving a role for the envelope glycoprotein gp120; or a drug-induced toxic neuropathy associated with the use of nucleoside analogue reverse transcriptase inhibitors as a component of highly active anti-retroviral therapy. In order to elucidate the mechanisms underlying drug-induced neuropathy in the context of HIV infection, we have characterized pathological events in the peripheral and central nervous system following systemic treatment with the anti-retroviral agent, ddC (Zalcitabine) with or without the concomitant delivery of HIV-gp120 to the rat sciatic nerve (gp120+ddC). Systemic ddC treatment alone is associated with a persistent mechanical hypersensitivity (33% decrease in limb withdrawal threshold) that when combined with perineural HIV-gp120 is exacerbated (48% decrease in threshold) and both treatments result in thigmotactic (anxiety-like) behaviour. Immunohistochemical studies revealed little ddC-associated alteration in DRG phenotype, as compared with known changes following perineural HIV-gp120. However, the chemokine CCL2 is significantly expressed in the DRG of rats treated with perineural HIV-gp120 and/or ddC and there is a reduction in intraepidermal nerve fibre density, comparable to that seen in herpes zoster infection. Moreover, a spinal gliosis is apparent at times of peak behavioural sensitivity that is exacerbated in gp120+ddC as compared to either treatment alone. Treatment with the microglial inhibitor, minocycline, is associated with delayed onset of hypersensitivity to mechanical stimuli in the gp120+ddC model and reversal of some measures of thigmotaxis. Finally, the hypersensitivity to mechanical stimuli was sensitive to systemic treatment with gabapentin, morphine and the cannabinoid WIN 55,212-2, but not with amitriptyline. These data suggests that both neuropathic pain models display many features of HIV- and anti-retroviral-related peripheral neuropathy. They therefore merit further investigation for the elucidation of underlying mechanisms and may prove useful for preclinical assessment of drugs for the treatment of HIV-related peripheral neuropathic pain.

Pharmacological, behavioural and mechanistic analysis of HIV-1 gp120 induced painful neuropathy

A painful neuropathy is frequently observed in people living with human immunodeficiency virus type 1 (HIV-1). The HIV coat protein, glycoprotein 120 (gp120), implicated in the pathogenesis of neurological disorders associated with HIV, is capable of initiating neurotoxic cascades via an interaction with the CXCR4 and/or CCR5 chemokine receptors, which may underlie the pathogenesis of HIV-associated peripheral neuropathic pain. In order to elucidate the mechanisms underlying HIV-induced painful peripheral neuropathy, we have characterised pathological events in the peripheral and central nervous system following application of HIV-1 gp120 to the rat sciatic nerve. Perineural HIV-1 gp120 treatment induced a persistent mechanical hypersensitivity (44% decrease from baseline), but no alterations in sensitivity to thermal or cold stimuli, and thigmotactic (anxiety-like) behaviour in the open field. The mechanical hypersensitivity was sensitive to systemic treatment with gabapentin, morphine and the cannabinoid WIN 55,212-2, but not with amitriptyline. Immunohistochemical studies reveal: decreased intraepidermal nerve fibre density, macrophage infiltration into the peripheral nerve at the site of perineural HIV-1 gp120; changes in sensory neuron phenotype including expression of activating transcription factor 3 (ATF3) in 27% of cells, caspase-3 in 25% of cells, neuropeptide Y (NPY) in 12% of cells and galanin in 13% of cells and a spinal gliosis. These novel findings suggest that this model is not only useful for the elucidation of mechanisms underlying HIV-1-related peripheral neuropathy but may prove useful for preclinical assessment of drugs for the treatment of HIV-1 related peripheral neuropathic pain.

Brain macrophage surface marker expression with HIV-1 infection and drug abuse: a preliminary study

GOAL

To determine the heterogeneity of surface marker expression of macrophages in the temporal lobe of patients who died with AIDS who were also Drug Abusers (DAs). We studied the expression of macrophage surface markers CD11c, CD14, CD68, and HLA-DR and T cell surface markers CD4, and CD8.

BACKGROUND

The macrophage is the prime locus for HIV-1-associated pathology, is the most frequently infected cell in the brain, and has the highest virus load compared to other cells. We previously described the heterogeneity of macrophage surface marker expression and performed morphometric analysis in peripheral nerves of patients who died from AIDS compared to HIV-1 negative individuals. We showed that the HIV-related neuropathy in AIDS is a multifocal process. It is similarly important to determine the expression of macrophage surface markers in brain. Temporal lobe tissue was selected for this preliminary study because we previously found elevated HIV-1 proviral DNA load and inflammatory processes in this neuroanatomic location for subjects who died with AIDS. There is a high prevalence of Drug Abuse in Miami, Florida, associated with AIDS that may interactively affect HIV-associated pathology.

METHODS

Temporal lobe tissue was examined from 17 HIV-1-seropositive patients (4 with Drug Abuse and 13 without Drug Abuse) and 11 HIV-seronegative individuals (5 with Drug Abuse and 6 without Drug Abuse). Standard immunohistochemistry utilized alkaline phosphatase conjugate secondary antibody and fuchsin substrate.

RESULTS

We found that HIV-1 infection and the interaction of HIV-1 infection and Drug Abuse produced changes in macrophage surface marker expression. Macrophage surface markers, CD11c, CD14, CD68, and HLA-DR, and T-cell marker CD4 were increased with statistical significance due to HIV-1 infection (all p < .001) whereas CD8 remained unchanged. Changes due to Drug Abuse alone were not significant. Interaction of Drug Abuse and HIV-infected individuals showed increased expression of CD68 (p = .011), HLA-DR (p = .001), CD4 (p = .027), and CD8 (p = .016).

CONCLUSION

Drug Abuse and HIV-1 infection are factors that differentially and interactively result in multiple macrophages surface marker effects. In HIV-1 infected individuals, Drug Abuse stimulates surface marker expression. Since brain macrophage surface makers do not change uniformly as a result of Drug Abuse and HIV infection, these cells may be heterogeneous and contain sub-types (sub-sets). It remains to be determined which macrophage sub-types may be most pathognomic for pathology.

CD8+ lymphocyte-mediated injury of dorsal root ganglion neurons during lentivirus infection: CD154-dependent cell contact neurotoxicity

Neuronal damage in dorsal root ganglia (DRGs) with accompanying axonal injury is a key feature of human immunodeficiency virus (HIV)-related distal sensory polyneuropathy (DSP). In a model of HIV-related DSP, we observed numerous CD3+ T lymphocytes (p < 0.05) in DRGs from feline immunodeficiency virus (FIV)-infected animals, which also exhibited low CD4+ and high CD8+ lymphocyte levels in blood accompanied by a selective loss of small-diameter sural nerve axons (p < 0.05). FIV-infected lymphocytes cocultured with syngeneic DRGs caused neuronal damage, indicated by neurite retraction, neuronal soma atrophy, and loss (p < 0.05). In contrast, supernatants from FIV-infected or uninfected lymphocytes were minimally neurotoxic, despite high FIV virion levels. Among lymphocyte subsets cocultured with DRG cultures, CD8+ T cells from both FIV-infected and uninfected lymphocytes selectively caused DRG neuronal injury (p < 0.05). FIV-infected CD8+ T cells showed markedly increased CD154 expression (p < 0.05), whereas neurons were the predominant cells expressing CD40 in DRGs. Blocking CD154 on activated CD8+ T cells protected DRG neurons (p < 0.05). These findings indicated that CD8+ T cells were principal effectors of DRG neuronal injury after FIV infection through a CD40-CD154 interaction in a cell contact-dependent manner.

Regulation of neural cell survival by HIV-1 infection

Infection by the lentivirus, human immunodeficiency virus type 1 (HIV-1), results in a variety of syndromes involving both the central (CNS) and the peripheral (PNS) nervous systems. Productive HIV-1 infection of the CNS is chiefly detectable in perivascular macrophages and microglia. HIV-1 encoded transcripts and proteins have also been detected in the PNS; however, productive viral replication appears to be sparse and restricted to the macrophage cell population. Despite the absence of productive infection of neurons, HIV-1 infection has been associated with neuronal loss in distinct regions of the brain. Neuronal cell loss may occur through both necrosis and apoptosis, although neuronal apoptosis appears to be a feature of AIDS, as only rare apoptotic neurons have been demonstrated in a few pre-AIDS cases. Although there is no clear consensus as to the underlying mechanism of HIV-induced neuropathogenesis, two complementary concepts predominate. Firstly, HIV-1 encoded proteins injure neurons directly without requiring the intermediary functions of nonneuronal cells. Alternatively, neuronal apoptosis may result indirectly from the secretion of neurotoxic host molecules by resident brain macrophages or microglia in response to HIV-1 infection, stimulation by viral proteins or immune activation. Herein, we review the neurological disorders and their underlying mechanisms associated with HIV infection, focusing on HIV-associated dementia (HAD) and HIV sensory neuropathy (HIV-SN). The evidence that neuronal loss in HIV-1-infected individuals may be due to neuronal apoptosis is then discussed. This review also summarizes the current data supporting both the direct and indirect mechanisms by which neuronal death may occur during infection with HIV-1 or the closely related lentiviruses SIV and FIV. Lastly, strategies are examined for treating or preventing HAD by targeting specific neurotoxic mechanisms.

Neurological complications of HIV infection

Cognitive disorders, vacuolar myelopathy, and sensory neuropathies associated with HIV are the most common disorders in patients with HIV AIDS, and are the focus of this review. These disorders are treatable and of those associated with HIV AIDS the pathogenic mechanisms are the most understood. Although triggered by productive HIV macrophage infections, aberrant immune activation plays a major role in inducing the CNS disorders. Novel therapies aimed at these inflammatory mechanisms can be effective. The sensory neuropathies associated with HIV infection are a major cause of morbidity; incidence may be increased by the toxic effects of specific antiretroviral drugs within the peripheral nervous system.

HIV-associated neuropathic pain: epidemiology, pathophysiology and management

Peripheral neuropathy is associated with numerous systemic illnesses including HIV infection. Neuropathic pain constitutes approximately 25-50% of all pain clinic visits. Distal symmetrical polyneuropathy (DSP) is the most common form of peripheral neuropathy in individuals with HIV infection. DSP is distinguished from other forms of neuropathy on the basis of history and neurological examination. The pain associated with DSP can be debilitating. Therefore, it is important to diagnose HIV-associated DSP properly and treat the neuropathic pain in order to improve quality of life. We review the clinical manifestations, epidemiology, pathophysiology and management strategies for HIV-associated DSP.

Peripheral nerve-derived HIV-1 is predominantly CCR5-dependent and causes neuronal degeneration and neuroinflammation

HIV-related peripheral neuropathy is a major neurological complication of HIV infection, although little is known about its pathogenesis. We amplified HIV-1 C2V3 envelope sequences from peroneal nerves obtained from HIV/AIDS patients. Sequence analysis and infectious recombinant viruses containing peripheral nerve-derived C2V3 sequences indicated a predominance of CCR5-dependent and macrophage-tropic HIV-1, although dual tropic viruses using both CCR5 and CXCR4 were identified. The neuropathogenic effects of recombinant HIV-1 clones were investigated using a novel dorsal root ganglion culture system that was comprised of sensory neurons, macrophages and Schwann cells from transgenic rats expressing human CD4 and CCR5 on monocytoid cells. Despite restricted viral replication, HIV-1 infection caused a reduction in the percentage of neurons with neuritic processes together with significant neurite retraction, which was accompanied by induction of IL-1beta and TNF-alpha expression, depending on the individual virus. Our results suggest that HIV-1 infection of the peripheral nervous system causes axonal degeneration, possibly through the induction of pro-inflammatory cytokines.

Modification of the incidence of drug-associated symmetrical peripheral neuropathy by host and disease factors in the HIV outpatient study cohort

BACKGROUND

We sought to identify factors associated with the clinical diagnosis of symmetrical peripheral neuropathy (SPN) during the era of highly active antiretroviral therapy (HAART) in a retrospective, longitudinal cohort analysis.

METHODS

Patients infected with human immunodeficiency virus type 1 were evaluated for clinical signs of SPN and its association with immunologic, virologic, clinical, and drug treatment factors by means of univariate and multivariate logistic regression analyses.

RESULTS

Of 2515 patients, 329 (13.1%) received a diagnosis of SPN. In the logistic regression analysis, statistically significant non-drug-based risk factors for SPN were age >40 years (adjusted odds ratio [aOR], 1.17), diabetes mellitus (aOR, 1.79), white race (aOR, 1.33), nadir CD4(+) T lymphocyte count <50 cells/mm(3) (aOR, 1.64), CD4(+) T lymphocyte count 50-199 cells/mm(3) (aOR, 1.40), and viral load >10,000 copies/mL at first measurement (aOR, 1.44). Although initial use of didanosine, stavudine (40 mg b.i.d.), nevirapine, or 4 protease inhibitors was associated with SPN (ORs for all 4 treatments, >1.41), the strength of association decreased with continued use of all medications studied.

CONCLUSION

Since HAART was introduced, the incidence of SPN has decreased. Host factors and signs of increased disease severity were associated with an increased risk of developing SPN during the initial period of exposure to drug therapy. Immunity improved and the risk of SPN decreased with continued use of HAART. Delaying the initiation of therapy may select those individuals who will be more likely to develop SPN, and earlier initiation of HAART may decrease the risk of developing this common problem, as well as increase the therapeutic effects and decrease the toxic effects of the drugs.

Neuromuscular complications in HIV

HIV affects many organs of the body, including the nervous system. As a result, a series of neurologic complications have created challenges for scientists and clinicians alike. Among these, HIV-associated neuropathy and myopathy may occur at all stages of the disease process. Of the neuropathies, distal symmetrical polyneuropathy is the most common form. The pathogenesis of primary HIV neuropathy is unknown. Other types of neuropathy seen in HIV-infected subjects include toxic neuropathy, inflammatory demyelinating polyneuropathy, progressive polyradiculopathy, and mononeuritis multiplex. In this review, we present the clinical manifestations, pathogenesis, diagnosis, and management of different types of neuropathy in HIV infection. Myopathy, another complication of HIV, is not associated with any particular stage of immunosuppression. Symptoms include symmetrical weakness of the proximal muscles in the extremities. Serum creatine kinase levels are often moderately elevated. Electromyography and muscle biopsy are helpful tests for diagnosis. Treatment of HIV myopathy includes corticosteroids, nonsteroidal anti-inflammatory agents, and intravenous immunoglobulin.

Schwann cell chemokine receptors mediate HIV-1 gp120 toxicity to sensory neurons

Human immunodeficiency virus (HIV)-associated sensory neuropathy (HIV-SN) is the most common neurological complication of HIV infection. Currently, the pathogenesis of HIV-SN is unknown. Because there is no convincing evidence of neuronal infection, HIV neurotoxicity is likely to be effected either by secreted viral proteins such as the envelope glycoprotein gp120 or by neurotoxic cytokines released from infected/activated glial cells. We describe a model of gp120 toxicity to primary sensory neurons, in which gp120 induces neuritic degeneration and neuronal apoptosis. We show that Schwann cells, the cells that ensheath peripheral nerve axons, and which traditionally have been viewed as having a passive, supporting role, mediate this neurotoxicity. Ligation of the chemokine receptor CXCR4 on Schwann cells by gp120 resulted in the release of RANTES, which induced dorsal root ganglion neurons to produce tumor necrosis factor-alpha and subsequent TNFR1-mediated neurotoxicity in an autocrine fashion. This newly described Schwann cell-neuron interaction may be pathogenically relevant not only in HIV-SN but also in other peripheral neuropathies.

HIV neuropathy: insights in the pathology of HIV peripheral nerve disease

HIV-associated neuropathies (HIV-N) have become the most frequent neurological disorder associated with HIV infection. The most common forms of HIV-N are the distal sensory polyneuropathy (DSP) and antiretroviral toxic neuropathies (ATN), disorders characterized mostly by sensory symptoms that include spontaneous or evoked pain that follow a subacute or chronic course. The main pathological features that characterize DSP and ATN include "dying back" axonal degeneration of long axons in distal regions, loss of unmyelinated fibers, and variable degree of macrophage infiltration in peripheral nerves and dorsal root ganglia. Marked activation of macrophages as well as the effect of pro-inflammatory cytokines appear to be the main immunopathogenic factors in DSP. Interference with DNA synthesis and mitochondrial abnormalities produced by nucleoside antiretrovirals have been hypothesized as pathogenic factors involved in ATN. The use of skin biopsy has become a useful tool in the evaluation of HIV-N. Reduction in fiber density, increased frequency of fiber varicosities and fiber fragmentation are prominent features of skin biopsies from patients with HIV-N. Other forms of HIV-N include acute or chronic inflammatory polyneuropathies, uncommon disorders that may ocur during seroconversion or early stages of HIV infection. Opportunisitic infections, mostly associated with cytomegalovirus or herpes zoster virus infection occur in late stages of AIDS and produce characteristic clinical features such as mononeuritis multiple or radiculopathies.

HIV-1-Associated Neuropathies

Peripheral neuropathy associated with human immunodeficiency virus type 1 (HIV-1) infection is a major cause of morbidity in this patient population. Due to the associated chronic pain, its management has come within the purview of neuropsychiatrists. This paper will focus on the primary pathogenic aspects of HIV-1-associated peripheral neuropathies. The specific syndromes of greatest concern are distal sensory polyneuropathy, toxic neuropathy, inflammatory demyelinating polyradiculoneuropathy, and cytomegalovirus-related progressive polyradiculoneuropathy. The treatments available for these conditions and their efficacy are discussed.

Morphometric analysis of the peripheral neuropathy of AIDS

A morphometric study of the peripheral nervous system at autopsy was undertaken in 11 AIDS patients and 10 controls. The left L4, L5, and S1 dorsal root ganglia (DRG) and samples of the sciatic nerve at the buttock, tibial nerve at the knee, and sural nerve at the ankle were collected. Indices of neuronal/axonal degeneration and of segmental demyelination/ remyelination were measured at each level. The small number of cases and evidence of neuropathy in a number of the control cases resulted in statistical significance for only a limited number of comparisons. Nodules of Nageotte in the DRG were increased fivefold in AIDS cases compared with controls, and axonal degeneration in single-teased nerve fibers was increased 9-fold in the sciatic nerve, 28-fold in the tibial nerve, and 12-fold in the sural nerve. The ratios of AIDS to controls for the density of remaining DRG neurons and large myelinated axons were reduced to 0.71 in the DRG, 0.84 in the sciatic nerve, 0.84 in the tibial nerve, and 0.66 in the sural nerve. Axonal regeneration in single-teased nerve fibers was increased threefold at the sciatic nerve level in AIDS, but was markedly reduced at distal levels. Acute segmental demyelination in single-teased nerve fibers was present to a greater extent than in controls at all levels of the peripheral nerves in the AIDS cases. Remyelinating fibers were increased compared with controls only in the proximal sciatic nerve. No case showed the changes of cytomegalovirus infection. In a parallel immunohistochemical study of these AIDS peripheral nerves, T-cell and macrophage infiltration, with cytokine expression, was demonstrated. The pathological process in the neuropathy of terminal AIDS appears to be a multifocal immunologically mediated inflammatory disease, with increased density of macrophages and T cells at all levels of the peripheral nervous system, producing segmental demyelination and axonal degeneration. Reparative processes (axonal regeneration and remyelination) occurred only at the most proximal levels of the nerves.

Heterogeneity of Macrophage and T Cell Subpopulations in Peripheral Nerves from HIV Infected Individuals

GOAL

To determine the heterogeneity of surface marker expression of macrophages in peripheral nerve of patients who died with AIDS.

BACKGROUND

Peripheral neuropathy occurs in 20%-40% of AIDS patients. There is evidence that activated macrophages may be involved in the neural damage associated with HIV-1 infection. We studied the expression of macrophage surface markers CD14, CD11c, CD68, and HLA-DR and also T cell surface markers CD3, CD4, and CD8 in peripheral nerves of AIDS patients.

METHODS

Three levels of peripheral nerves (sciatic, tibial, or sural) were examined from a limited number of subjects consisting of 4 HIV-seropositive and 5 HIV-seronegative individuals. Standard immunohistochemical technique utilized alkaline phosphatase conjugate and fuchsin substrate.

RESULTS

Surface antigen expression was significantly (p < .0025 increased in HIV-positive tissues compared with HIV-negative controls for CD14 and CD4 in sciatic nerves, CD68 and CD4 in tibial nerves, and CD68 in sural nerves. There were trends for increased expression of HLA-DR, CD3, and CD8 in sciatic nerves, CD11c and CD14 in tibial nerves, and CD14, HLA-DR, and CD4 in sural nerves in HIV-positive tissues compared with HIV-negative controls.

CONCLUSION

During the course of AIDS there may be an involvement of all three levels of peripheral nerves suggesting that HIV-related neuropathy is a multifocal process.

HIV-1 proviral DNA load across neuroanatomic regions of individuals with evidence for HIV-1-associated dementia

A definitive relation between HIV-1 load and the clinical diagnosis of HIV-1-associated dementia (HAD) has not yet been established. Knowledge of the neuroanatomic distribution of HIV-1 load in the brain of individuals with HAD and HIV-1 encephalitis may facilitate elucidation of this relation. Nine individuals with AIDS were analyzed postmortem by three independent methods with each assessment performed blinded to the others: 1) a neuropsychiatric review of clinical records for evidence of possible HAD, 2) HIV-1 DNA load determination by quantitative polymerase chain reaction (PCR) across several neuroanatomic regions, and 3) a pathologic examination for diagnosis of HIV-1 encephalitis by immunohistochemical techniques. Of eight AIDS cases with clinical records sufficient for neuropsychiatric review, seven were shown to have evidence for HAD. HIV-1 DNA was detected and quantified in specimens from all of the medial temporal lobe regions analyzed but was not detectable in the frontal lobe at the same level of sensitivity in two of these cases (<1 per 1000 cellular genomes). HIV-1 DNA load in the medial temporal lobe region was significantly larger than that in the frontal lobe. Only four of seven cases with evidence for HAD were also diagnosed with HIV-1 encephalitis.