Soluble interleukin-2 receptor and soluble CD8 in serum and cerebrospinal fluid during human immunodeficiency virus-associated neurologic disease

A biological perspective of CSF lipids as surrogate markers for cognitive status in HIV

The development and application of biomarkers to neurodegenerative diseases has become increasingly important in clinical practice and therapeutic trials. While substantial progress has been made at the basic science level in understanding the pathophysiology of HIV-Associated Neurocognitive Disorders (HAND), there are significant limitations in our current ability to predict the onset or trajectory of disease, and to accurately determine the effects of therapeutic interventions. Thus, the development of objective biomarkers is critical to further our understanding and treatment of HAND. In recent years, biomarker discovery efforts have largely been driven forward through the implementation of multiple "omics" approaches that include (but are not restricted to): Lipidomics, proteomics, metabolomics, genomics, transcriptomics, and advances in brain imaging approaches such as functional connectomics. In this paper we summarize our progress to date on lipidomic approaches to biomarker discovery, discuss how these data have influenced basic research on the neuropathology of HAND, and implications for the development of therapeutics that target metabolic pathways involved in lipid handling.

Biomarkers predicting progression of human immunodeficiency virus-related disease

Biomarkers in predicting the progression of HIV infected individuals to a state of HIV disease (AIDS) are studied over more than a decade. Use of surrogate markers in the past for tracking clinical progression of the disease was limited, as little knowledge existed about the disease. The aim of this review was to address various changes in biomarker related studies taking place over the last five years, especially the trend towards use of newer biomarkers and experimentation with novel molecules in a quest for halting HIV disease progression. An open search of PUBMED database was made with search 'key words' such as 'Biomarkers' and 'AIDS (Acquired Immunodeficiency Syndrome)'.The following were the inclusion criteria for articles: a) all articles published in English language, b) years of publication between 2002-2008 and c) articles limited to adult population. This yielded a total of 417 articles. The criteria used for further judging these studies considered a) type of research design, b) number of biomarkers studied, c) validity of the biomarkers, d) techniques to assess the biomarkers and the impact of the studies in furthering biomarker research, e) sample size for the studies and f) article title or abstracts having the following key words 'biomarker' or 'biomarkers' and 'predict progression to AIDS'. A total of 27 abstracts were reviewed and 12 studies met the above criteria. These 12 different studies consisted of three reviews, four cohort designs, three cross-sectional designs, one each of an observational, and an in-vitro design. The various biomarkers emerging as a results were primarily a mix of viral, neural, immunological, HLA (human leukocyte antigen) markers along with lymphocyte counts. Although there have been quite a few advancements in biomarker-related studies, majority of the novel biomarkers discovered need to be further evaluated and replicated in bigger, long-term efficacy trials. Efforts should also be made to discover newer genetic markers of disease progression. Biomarker feedback, a new concept, can be utilized in future studies addressing prevention of HIV infection or halting disease progression.

Biomarkers of HIV related central nervous system disease

In this review we critically assess biomarkers of the direct effects of HIV related brain disease. This area is becoming increasingly complex because of the presence of confounds and varying degrees of activity of HIV brain disease. Sensitive and specific biomarkers are urgently needed although existing biomarkers do have some utility. The review will focus on the practical implications of the more established biomarkers. We discuss blood, cerebrospinal fluid and neurophysiological biomarkers but not neuroimaging techniques as they are beyond the scope of this review.

Effects of extracorporeal photoimmunotherapy on soluble IL-2Ralpha, TNF-RI, and CD8 in patients with steroid-resistant acute graft-versus-host disease

Extracorporeal photoimmunotherapy (ECP) has been successfully used as adjunct treatment for steroid-resistant graft-versus-host disease (GvHD) after allogeneic stem cell transplantation. We serially investigated serum levels of soluble interleukin-2 receptor-alpha (sIL-2Ralpha), soluble tumor necrosis factor receptor I (sTNF-RI), and soluble CD8 (sCD8) in 19 patients with steroid-resistant acute GvHD before and after each ECP treatment. Highest levels of sIL-2Ralpha and sTNF-RI correlated with severe acute GvHD and infections. Despite an immediate sIL-2Ralpha and sTNF-RI decrease after each treatment cycle, a mean surge of sTNF-RI>sIL-2Ralpha during the first three ECP cycles was observed in infections. A delayed surge, i.e., after the third ECP cycle, of sIL-2Ralpha and elevated post-ECP sCD8 levels was observed in patients developing chronic GvHD. While levels of sIL-2Ralpha and sTNF-RI correlate with the severity of acute GvHD and infections during the early ECP treatment period, the recurring increase of post-ECP sCD8 possibly may serve as parameter for developing chronic GvHD.

Soluble CD8 and ICAM-1 in serum and CSF of MS patients treated with 6-methylprednisolone

OBJECTIVE

We studied the effects of large doses of 6-methylprednisolone (6-MP) on serum and cerebrospinal fluid (CSF) soluble CD8 (sCD8) and intercellular adhesion molecule-1 (sICAM-1) levels in clinically active multiple sclerosis (MS) patients.

MATERIAL AND METHODS

Paired serum and CSF samples were from 16 patients with definite MS, treated with 6-MP (1 g daily for 6 d) during an active phase of the disease. sCD8 and sICAM-1 levels were determined with ELISA before and after the therapy.

RESULTS

Before 6-MP treatment, sCD8 levels in CSF were higher in MS patients than in patients with noninflammatory neurological disease and in healthy controls; sICAM-1 levels in serum and in CSF were higher in MS patients than in the two control groups. Ten of the 16 patients showed clinical improvement at the end of the treatment. After the therapy, serum and CSF sCD8 levels increased, whereas serum and CSF sICAM-1 levels decreased. There was no correlation between clinical improvement and laboratory parameters. We evaluated sCD8 and sICAM-1 in serum samples from 10 patients 6 months after the 6-MP treatment, when the disease was clinically silent. Neither sCD8 nor sICAM-1 levels differed from those of the control groups.

CONCLUSIONS

Our results suggest that high doses of 6-MP can influence serum and CSF sCD8 and sICAM-1 levels in active MS. At least part of the efficacy of corticosteroid treatment in MS might be ascribed to its effect both on the suppressive circuits of immune response, and on the expression of an adhesion molecule that favours lymphocyte trafficking across the blood-brain barrier.

Role of immune activation and cytokine expression in HIV-1-associated neurologic diseases

Central nervous system (CNS) involvement is common during human immunodeficiency virus type-1 (HIV-1) infection. The neurologic disease of the CNS most frequently observed during acquired immunodeficiency syndrome (AIDS) is HIV-1-associated cognitive/motor complex or AIDS dementia complex (ADC), which is most likely a direct consequence of HIV-1 infection of the CNS. The peripheral nervous system (PNS) is also affected in HIV-1-infected individuals and there are several features of immune- and cytokine-related pathogenesis in both the CNS and PNS that are reviewed. Several lines of evidence demonstrate aspects of immune activation in the CNS and peripheral nervous system (PNS) of HIV-1-infected individuals. The relative paucity of HIV-1 expression in contrast to widespread functional and pathologic changes in the CNS and PNS of AIDS patients, and the lack of evidence of productive infection of HIV-1 in neuronal cells in vivo lead to the possibility of indirect or immunopathogenic mechanisms for HIV-1-related neurologic diseases. Proposed mechanisms of neuronal and glial cell damage are injury of oligodendrocytes by tumor necrosis factor-alpha (TNF-alpha) released from activated macrophage/microglia, calcium-dependent excitoneurotoxicity induced by gp120 HIV-1 envelope protein, N-methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity by quinolinic acid (a product of activated macrophages), cell injury by HIV-1-specific cytotoxic T cells, and apoptosis of oligodendrocytes or neurons triggered by interaction between cell surface receptors and HIV-1 gp120 protein. Common to those mechanisms is the dependence on cellular activation with expression of proinflammatory cytokines (TNF-alpha, interleukin-1). Amplification of activation signals through the cytokine network by macrophage/astrocyte/endothelial cell interactions, and cell-to-cell contact between activated macrophages and neural cells by upregulation of adhesion molecules dramatically enhances the toxic effect of macrophage products. Expression of immunosuppressive cytokines such as interleukin-4, interleukin-6, and transforming growth factor-beta is also increased in the CNS and PNS of HIV-1-infected patients. This may serve as neuroprotective and regenerative mechanism against insults to nervous system tissue.

HIV type 1-specific cytotoxic T lymphocytes stimulate HLA class I and intercellular adhesion molecule type 1 expression and increase beta 2-microglobulin levels in vitro

Besides acting in a direct manner, cytolytic HIV-1-specific CTLs release a variety of cytokines. To assess the potential role of cytokines released by these CTLs we tested the ability of soluble products secreted by HIV-1-specific CTLs to induce HLA class I and ICAM-1 expression and to raise beta 2-microglobulin (beta 2M) concentrations in cell culture. To this end, supernatants were derived from HIV-1-specific CTLs incubated with autologous B lymphoblasts presenting either the cognate HIV-1 epitope or a control peptide. Cell lines and peripheral blood mononuclear cells (PBMCs) were incubated with these supernatants for 24-48 hr. Similarly, cells were cocultured with CTLs and their targets. This study demonstrates that in parallel with lysis of their cognate target, HIV-1-specific CTLs secreted products that stimulated HLA class I and ICAM-1 expression on cell lines and PBMCs. As few as 1000 CTLs significantly induced the expression of these molecules. In addition, secreted products of HIV-specific CTLs enhanced beta 2M release by PBMCs and Jurkat cells. These effects were mediated primarily by IFN-gamma and suggest that HIV-specific CTLs may contribute to increased HLA class I expression in infected tissue and elevated ICAM-1 and beta 2M concentrations in serum and cerebrospinal fluid of infected individuals.

High cerebrospinal fluid and serum levels of tumor necrosis factor-alpha in asymptomatic HIV-1 seropositive individuals. Correlation with interleukin-2 and soluble IL-2 receptor

The relationship between tumour necrosis factor-alpha (TNF-alpha) and the interleukin-2 (ILL-2) system in HIV-1 infection is important in understanding the dynamics of early immune response before the development of acquired immunodeficiency syndrome. Levels of TNF-alpha, IL-2 and soluble IL-2 receptor (sIL-2R) in serum and cerebrospinal fluid (CSF) samples from 31 asymptomatic HIV-1 seropositive individuals were measured. High levels of TNF-alpha were detected in CSF of 17 (55%) and serum of 22 (71%) subjects, 15 (88%) of whom had elevated CSF IL-2 levels and 16 (94%) had high sIL-2R levels. Moreover, CSF levels of TNF-alpha significantly correlated with CSF levels of IL-2 and sIL-2R. TNF-alpha, IL-2 and sIL-2R seem to be released within the intrathecal compartment early in the course of HIV-1 infection. In view of the known cytotoxic effects of TNF-alpha, an early release may contribute to subsequent development of neurological complications.

Markers predicting progression of human immunodeficiency virus-related disease

Human immunodeficiency virus (HIV) interacts with the immune system throughout the course of infection. For most of the disease process, HIV activates the immune system, and the degree of activation can be assessed by measuring serum levels of molecules such as beta 2-microglobulin and neopterin, as well as other serum and cell surface phenotype markers. The levels of some of these markers correlate with clinical progression of HIV disease, and these markers may be useful as surrogate markers for development of clinical AIDS. Because the likelihood and timing of development of clinical AIDS following seroconversion, for any particular individual, are not readily predictable, the use of nonclinical disease markers has become critically important to patient management. Surrogate markers of HIV infection are, by definition, measurable traits that correlate with disease progression. An ideal marker should identify patients at highest risk of disease progression, provide information on how long an individual has been infected, help in staging HIV disease, predict development of opportunistic infections associated with AIDS, monitor the therapeutic efficacy of immunomodulating or antiviral treatments, and the easily quantifiable, reliable, clinically available, and affordable. This review examines the current state of knowledge and the role of surrogate markers in the natural history and treatment of HIV infection. The clinical usefulness of each marker is assessed with respect to the criteria outlined for the ideal surrogate marker for HIV disease progression.

Interleukin-2 secreting cells in multiple sclerosis and controls

To evaluate systemic T cell activation and reactivity against putative autoantigens in multiple sclerosis (MS), numbers of interleukin-2 (IL-2) secreting cells were determined in peripheral blood of 32 patients with MS, 7 patients with acute aseptic meningitis (AM) and 12 patients with tension headache (TH). Numbers of IL-2 secreting cells were higher in MS patients compared to patients with AM + TH after stimulation with myelin proteolipid protein (PLP), myelin associated glycoprotein (MAG) and myelin oligodendrocyte glycoprotein (MOG), but not after stimulation with myelin basic protein (MBP). In response to MAG, MOG and acetylcholine receptor (AChR) the frequencies of IL-2 secreting cells were higher in patients with MS than TH, while there were no differences between AM and TH to any of the tested antigens. Between patients with MS and AM there was no difference regarding frequency of IL-2 secreting cells in response to any of the tested antigens except MAG to which the response was higher in MS patients. Six of 10 MS patients had IL-2 secreting cells in response to all four myelin antigens (MBP + PLP + MAG + MOG) or to three antigens, while this broad reactivity was not found in any control patient. There was no correlation between numbers of IL-2 secreting cells in MS patients and clinical variables, including exacerbation versus remission, disability and duration of disease. The results suggest that the systemic T cell response in patients with MS is directed to several antigens.

CD8 and beta 2-microglobulin-free MHC class I molecules in T cell immunoregulation

Intracellular assembly of MHC class I heavy chains with beta 2-microglobulin occurs prior to the expression of the antigen-presenting complex on the cell surface. The association of beta 2-microglobulin with newly synthesized class I heavy chains is thought to be a strict prerequisite for their transport to the cell surface. However, MHC class I molecules not associated with beta 2-microglobulin (beta 2-microglobulin-free class I heavy chains) have been detected on the surface of activated lymphoid cells. These molecules have different conformations. Therefore, their interactions with other membrane proteins and biological functions may be different from those assigned to beta 2-microglobulin-associated MHC class I molecules. The two forms of MHC class I molecules on the surface of activated cells can self-associate and also form complexes with distinct proteins. Upon interaction with the appropriate ligands these molecular complexes transduce signals regulating cell activation. The ligand for beta 2-microglobulin-free class I heavy chains appears to be soluble CD8. A model is presented describing a novel mechanism of immunoregulation mediated by both soluble and membrane-bound forms of CD8 and beta 2-microglobulin-free class I heavy chains.

Circulating cytotoxic immune components in dominant Charcot-Marie-Tooth syndrome

Activated T cells, measured repeatedly in the demyelinating peripheral neuropathy, Charcot-Marie-Tooth syndrome (CMT; hereditary motor sensory neuropathy), might participate in myelin loss by a destructive inflammatory autoimmune process. To explore this possibility, plasma proportions of hydroxyleukotrienes, their fatty acid precursor, arachidonic acid, and lymphocyte epitopes associated with immune cell activation expression were measured in 18 adults with dominant, Type I CMT. Compared to age-matched normal controls, CMT I patients showed eicosanoid-linked immunoactivation by an elevated content of 12-hydroxy-eicosatetraenoic acid (12-HETE) in parallel with a decreased plasma percentage of its fatty acid precursor, arachidonic acid. CMT patients also had increased numbers of peripheral lymphocytes expressing activation-related epitopes, CD25+, CD26+, CD4+, and CD4/CD45RO+ primed memory cells, with enhanced CD8+ cytotoxic cells and soluble CD8 protein content. Therefore, endogenously stimulated CMT I lymphocytes include functional cytotoxic cells which appear to deplete the plasma fatty acid precursor of prostenoid agents during the secretion of potentially destructive cytokines.

Intrathecal synthesis of interleukin-2 and soluble IL-2 receptor in asymptomatic HIV-1 seropositive individuals. Correlation with local production of specific IgM and IgG antibodies

The relationship between the interleukin-2 (IL-2) system and the humoral response against human immunodeficiency virus type-I (HIV-1) is important in understanding the immune reaction before the development of AIDS. Levels of IL-2 and soluble IL-2 receptor (sIL-2R) in serum and cerebrospinal fluid (CSF) samples from 31 asymptomatic HIV-1 seropositive individuals were measured and correlated with levels of anti-1 IgG and IgM antibodies. High IL-2 levels were detected in the CSF of 20 (65%) subjects, 18 (90%) of whom had evidence of intrathecal synthesis of HIV-1-specific IgM antibodies. Similarly, IgG antibodies were detected in 10 subjects who had elevated IL-2 levels in the CSF. Moreover, intrathecal levels of IL-2 and sIL-2R correlated with intrathecal synthesis of both IgG and IgM antibodies. Local release of IL-2 seems to play an important role in the initiation of the antibody response against HIV-1 in early stages of infection and may be utilised in devising effective therapeutic strategies.

Immunologic significance of increased soluble CD8/CD4 molecules in patients with active systemic lupus erythematosus

This study attempted to estimate soluble CD4(sCD4)/CD8(sCD8) molecules in active systemic lupus erythematosus (SLE) patients. Measurements were made by solid-phase enzyme-linked immunosorbent assay. sCD8 or sCD4 molecules were significantly increased in the patients as compared to control subjects. sCD8 correlated with the erythrocyte sedimentation rate. sCD4 correlated with the anti DNA antibody titer, the IgG concentration, and negatively with the complement titer. An association of these molecules with immunologic abnormalities and disease activity exists in SLE patients.

Cerebrospinal fluid (CSF) analyses in HIV-1 primary neurological disease

This paper will focus on CSF findings in HIV-1 Neurological Disease (ND). Why use CSF as exploration window of the HIV-CNS involvement? Traditionally, CSF analysis has been an effective diagnostic method as well as a means of monitoring treatment in several infectious and immune pathologies of the CNS. Consequently there is an abundance of mature background information [113, 145, 147] particularly in terms of detecting infectious agents, using IgG findings as immunological indexes, and utilizing CSF findings to map the evolution of ND. We will explore the papers that utilize CSF variables as dependent measures to explore the effects of HIV disease, particularly HIV ND, cited in Index Medicus and MEDLINE data base, and published in Spanish, Italian and English, between 1985 to 1991. We will restrict our review to those studies that exclude HIV cases with CNS opportunistic infections or neoplasms, and thus focus on what the CSF can tell us about the primary effects of HIV on the brain as defined above. The primary long-term goal is to find some elements of the CSF that would lead to an understanding of the etiopathogenesis of HIV ND. However, an almost equally important aim is to determine which CSF variables may be clinically predictive of HIV ND occurrence and progression. The latter variables can also be expected to provide the best measures of HIV ND treatment efficacy. This is particularly important since it is our contention that treatment of HIV ND will eventually be initiated and monitored on the basis of laboratory markers of HIV ND, most likely from the CSF. Finally, this summarized information would be useful in drafting a CSF profile in order to have a reference pattern for cases with complications. The data of this review will be broken down, when the information permits, according to clinical stage and presence or absence of clinical manifestations of ND.

Increased levels of beta 2-microglobulin, soluble interleukin-2 receptor, and soluble CD8 in patients with subacute sclerosing panencephalitis

We measured beta 2-microglobulin (beta 2-M), soluble interleukin-2 receptor (sIL-2R), and soluble CD8 (sCD8) antigen levels in paired cerebrospinal fluid (CSF) and sera from patients with subacute sclerosing panencephalitis (SSPE), multiple sclerosis (MS), and other neurological diseases (OND) using enzyme-linked immunosorbent assay. beta 2-M was significantly increased in CSF of the SSPE group compared to the MS or the OND group. Similarly, beta 2-M in the MS versus OND group was significantly increased in CSF. Although serum levels of beta 2-M were similar in the three groups, the CSF/serum ratios were higher in SSPE versus the MS group and in the MS versus the OND group. Levels of sIL-2R and sCD8 were higher in SSPE CSF than OND CSF; however, there were no differences between levels in SSPE and MS CSF. The levels of sIL-2R were increased in SSPE sera compared to those of MS or the OND group, whereas levels of sCD8 in serum from the three groups were similar. The findings of increased CSF/serum ratio of beta 2-M and higher levels of serum sIL-2R and CSF sCD8 in SSPE patients are consistent with those seen in patients with acute and chronic viral infections. When the levels between the initial and follow-up CSF and serum samples from SSPE patients were compared, the data showed that CSF levels of sCD8 elevated during periods of clinical worsening and decreased during clinical improvement. In contrast, serum beta 2-M decreased during periods of worsening and increased during improvement. The measurement of serum beta 2-M and CSF sCD8 may be useful in SSPE patients as markers to monitor disease activity.

Cytokine expression in the brain during the acquired immunodeficiency syndrome

The pathogenesis of central nervous system (CNS) disease in acquired immunodeficiency syndrome (AIDS) is poorly understood but may be related to specific effects of the immune system. Cytokines such as tumor necrosis factor and interleukin-1 may have toxic effects on CNS cells and have been postulated to contribute to the pathogenesis of the neurological complications of human immunodeficiency virus (HIV) infection. To characterize viral and immunological activity in the CNS, frozen specimens taken at autopsy from the cerebral cortex and white matter of HIV-seropositive and -seronegative individuals were stained immunocytochemically for mononuclear cells, major histocompatibility complex (MHC) antigens, HIV, astrocytes, and the cytokines interleukin-1 and -6, tumor necrosis factor-alpha and -beta, and interferon gamma. Levels of soluble CD4, CD8, and interleukin-2 receptor, as well as interferon gamma, tumor necrosis factor-alpha, beta 2-microglobulin, neopterin, and interleukin-6 and -1 beta were assayed in the cerebrospinal fluid and plasma of many of these individuals during life. The HIV-seropositive group included individuals without neurological disease, those with CNS opportunistic infections, and those with HIV encephalopathy. Perivascular cells, consisting primarily of macrophages with some CD4+ and CD8+ T cells and rare B cells, were consistently MHC class II positive. MHC class II antigen was also present on microglial cells, which were frequently positive for tumor necrosis factor-alpha. HIV p24 antigen, when present, was found on macrophages and microglia. Endothelial cells were frequently positive for interleukin-1 and interferon gamma and less frequently for tumor necrosis factor and interleukin-6. There were gliosis and significant increases in MHC class II antigen, interleukin-1, and tumor necrosis factor-alpha in HIV-positive patients compared to HIV-negative brains. Cerebrospinal fluid from most of the patients tested had increased levels of tumor necrosis factor, beta 2-microglobulin, and neopterin. There was no correlation in HIV-positive individuals between levels of cytokines and the presence or absence of CNS disease. These data indicate that there is a relative state of "immune activation" in the brains of HIV-positive compared to HIV-negative individuals, and suggest a potential role for the immune system in the pathogenesis of HIV encephalopathy.

Immunoregulators in the nervous system

The nervous system, through the production of neuroregulators (neurotransmitters, neuromodulators and neuropeptides) can regulate specific immune system functions, while the immune system, through the production of immunoregulators (immunomodulators and immunopeptides) can regulate specific nervous system functions. This indicates a reciprocal communication between the nervous and immune systems. The presence of immunoregulators in the brain and cerebrospinal fluid is the result of local synthesis--by intrinsic and blood-derived macrophages, activated T-lymphocytes that cross the blood-brain barrier, endothelial cells of the cerebrovasculature, microglia, astrocytes, and neuronal components--and/or uptake from the peripheral blood through the blood-brain barrier (in specific cases) and circumventricular organs. Acute and chronic pathological processes (infection, inflammation, immunological reactions, malignancy, necrosis) stimulate the synthesis and release of immunoregulators in various cell systems. These immunoregulators have pivotal roles in the coordination of the host defense mechanisms and repair, and induce a series of immunological, endocrinological, metabolical and neurological responses. This review summarizes studies concerning immunoregulators--such as interleukins, tumor necrosis factor, interferons, transforming growth factors, thymic peptides, tuftsin, platelet activating factor, neuro-immunoregulators--in the nervous system. It also describes the monitoring of immunoregulators by the central nervous system (CNS) as part of the regulatory factors that induce neurological manifestations (e.g., fever, somnolence, appetite suppression, neuroendocrine alterations) frequently accompanying acute and chronic pathological processes.