Low levels of specific T cell activation marker CD27 accompanied by elevated levels of markers for non-specific immune activation in the cerebrospinal fluid of patients with AIDS dementia complex

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.

Soluble CD27 induces IgG production through activation of antigen-primed B cells

OBJECTIVES

High levels of soluble CD27 (sCD27), a marker of immune activation, are found in several infectious [including human immunodeficiency virus type-I (HIV-1)] and autoimmune diseases; however, a direct biological effect of sCD27 on B cells has not been established. The aim of this study was to investigate whether sCD27, by binding to CD70, can induce immunoglobulin G (IgG) production from B cells.

METHODS

B cells from healthy and HIV-1-infected individuals were cultured with recombinant human sCD27 (rhsCD27), and IgG production was measured. The role of rhsCD27 in inducing the expression of transcription factors involved in plasma cell differentiation was evaluated. Furthermore, we investigated the impact of different cytokines on the modulation of CD70 expression on B cells and the relationship between levels of IgG and sCD27 in serum from healthy and HIV-1-infected individuals.

RESULTS

We demonstrated that rhsCD27 induced IgG production from antigen-primed (CD27+) B cells. This effect was mediated by rhsCD27 binding to CD70 on B cells leading to activation of Blimp-1 and XBP-1, transcription factors associated with plasma cell differentiation. We found a significant correlation between levels of serum sCD27 and IgG in HIV-1-infected individuals and healthy controls.

CONCLUSIONS

sCD27 may act to enhance immunoglobulin production and differentiation of activated memory or recently antigen-experienced B cells, thus providing an activation signal to antigen-experienced B cells. This mechanism may operate during autoimmune and chronic infectious diseases, situations in which continuous immune activation leads to upregulation of CD70 expression and increased sCD27 cleavage.

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.

Markers of macrophage activation and axonal injury are associated with prospective memory in HIV-1 disease

OBJECTIVE

To use clinical specimens to better understand the neuropathogenesis of prospective memory (ProM) functioning in persons with HIV-1 infection.

BACKGROUND

Emergent evidence suggests that HIV-1 is associated with impaired ProM, but the underlying neuropathophysiology of this deficit is not known.

METHODS

Thirty-five nondemented subjects with HIV-1 infection completed measures of both ProM (ie, memory for future intentions) and retrospective memory (RM; ie, memory for past episodes). A panel of biomarkers reflecting several possible neuropathogenic mechanisms of HIV was measured in plasma and cerebrospinal fluid, including HIV-1 RNA, total tau, monocyte chemoattractant protein-1 (MCP-1), soluble receptor for tumor necrosis factor type II, and fibroblast growth factor 1.

RESULTS

After controlling for antiretroviral therapy and CD4 lymphocyte count, higher levels of MCP-1 in plasma, and soluble receptor for tumor necrosis factor type II and tau in cerebrospinal fluid were associated with ProM, but not RM. Markers of astrocytosis, growth factor depletion, and HIV-1 replication did not predict either ProM or RM.

CONCLUSIONS

ProM impairment in HIV-1 may be dissociable from RM, perhaps reflecting specific neuropathogenic mechanisms of macrophage activation and axonal injury.

Cerebrospinal fluid beta2-microglobulin, monocyte chemotactic protein-1, and soluble tumour necrosis factor alpha receptors before and after treatment with lamivudine plus zidovudine or stavudine

CSF levels of beta2-microglobulin (b2m), monocyte chemotactic protein-1 (MCP-1), soluble tumor necrosis factor receptors (sTNFRs), and HIV-1 RNA were determined in 16 neurologically asymptomatic HIV-1 infected patients before and 12 weeks after treatment with lamivudine plus zidovudine or stavudine. b2m levels were significantly higher in patients (1.7 mg/l) compared with controls (0.8 mg/l) (P < 0.001), and decreased to 1.1 mg/l during treatment (P = 0.001). MCP-1 levels were low, and did not change during treatment. Levels of sTNFR type I were elevated in patients (0.92 ng/ml) compared to controls (0.30 ng/ml) (P = 0.03), but did not change during treatment. Levels of sTNFR type II were below the limit of detection in most patients and controls. In conclusion, CSF levels of b2m and HIV-I RNA, but not sTNFRs or MCP-1, are candidate surrogate markers of treatment efficacy in early CNS infection.

Aberrant expression of CD27 and soluble CD27 (sCD27) in HIV infection and in AIDS-associated lymphoma

CD27 is a member of the tumor necrosis factor receptor superfamily that is expressed primarily on T cells, as well as on subsets of B cells and NK cells. CD70, which is expressed on activated B and T cells, but not on resting lymphocytes, is a ligand for CD27. Cell surface CD27 can be proteolytically cleaved to produce a 32-kDa soluble CD27 (sCD27) molecule. Elevated levels of sCD27 are seen in a number of disease states and malignancies. Although it has been reported that cerebrospinal fluid sCD27 levels were elevated in people who had AIDS dementia, little is known about CD27 expression in HIV disease. To determine if sCD27 levels were elevated in those with HIV infection, and/or in those with AIDS-associated non-Hodgkin's lymphoma (AIDS-NHL), sCD27 levels were measured in HIV-negative and HIV-positive subjects as well as in people who developed AIDS-NHL. Serum sCD27 levels were seen to be elevated in HIV+ subjects. Furthermore, sCD27 levels were particularly elevated in those subjects who went on to develop AIDS-NHL, with serum sCD27 levels in AIDS-NHL subjects being significantly higher than those in HIV+ subjects who did not develop lymphoma. Most AIDS-NHL cell lines and primary AIDS-NHL tumor specimens expressed both CD27 and its ligand, CD70. The proportion of circulating B cells that expressed cell surface CD27 was substantially reduced in those with HIV infection, and B cells from HIV-infected subjects produced decreased levels of sCD27 in culture. Together, these results indicate that CD27/sCD27 expression is abnormal in HIV infection and suggest that this molecule merits further examination as a potential marker for AIDS-NHL.

Soluble CD27 in thyroid disorders

We measured the soluble cytokine CD27 in a variety of thyroid disorders. Soluble CD27 was increased in untreated Graves' hyperthyroidism and in euthyroid ophthalmopathy. Levels of sCD27 were normal after the establishment of euthyroidism with propylthiouracil (PTU) or radio iodine in primary hypothyroidism, chronic thyroiditis, and the hyperthyroid and euthyroid phases of subacute thyroiditis. Soluble CD27 is a marker for cellular activation as in Graves' hyperthyroidism, but it is not predictive of the outcome of PTU therapy.

Differential expression of cytokine genes in CD27-positive and -negative CD4 lymphocyte subsets from healthy humans and rheumatoid arthritis patients

Immunofluorescence analysis of CD27 expression by CD4 lymphocytes from the peripheral blood of healthy humans or rheumatoid arthritis (RA) patients and from the synovial fluid (SF) of RA patients was carried out, along with the estimation of cytokine gene [interleukin (IL) 2, IL-3, IL-4, IL-5, IL-6, IL-6R, IL-10 and interferon-gamma (IFN-gamma)] expression in these lymphocyte subsets by RT-PCR. Although no differences in CD27-positive and -negative peripheral blood CD4 cell subset distribution were revealed, marked differences in IL-3, IL-4, IL-5 and IFN-gamma mRNA expression were detected between these lymphocyte subsets and between control and disease states. These results showed that phenotyping of different cell subsets in disease cannot provide adequate information about lymphocyte functional status. To estimate differences in cytokine gene expression, CD4 lymphocytes from the peripheral blood and SF of RA patients were compared. In both cases, mRNAs for IL-2, IL-4, IL-10 and IFN-gamma were detected, but CD4 cells from SF failed to express detectable levels of IL-5 mRNA despite our findings of a CD27-cell accumulation within the synovial population of CD4 lymphocytes. These are the first data to demonstrate that expression of the IL-5 gene in RA SF CD27- lymphocytes is down-regulated and that IL-5 disregulation in RA cannot be ruled out.

Soluble receptors for tumour necrosis factor in clinical laboratory diagnosis

Soluble tumour necrosis factor receptors (sTNF-Rs) play a role as modulators of the biological function of tumour necrosis factor-alpha (TNF-alpha) in an agonist/antagonist pattern. In various pathologic states the production and release of sTNF-Rs may mediate host response and determine the course and outcome of disease by interacting with TNF-alpha and competing with cell surface receptors. The determination of sTNF-Rs in body fluids such as plasma or serum is a new tool to gain information about immune processes and provides valuable insight into a variety of pathological conditions. Regarding its immediate clinical use, sTNF-Rs levels show high accuracy in the follow-up and prognosis of various diseases. In HIV infection and sepsis, sTNF-Rs concentrations strongly correlate with the clinical stage and the progression of disease and can be of predictive value. Determination of sTNF-Rs also gives useful information for monitoring cancer and autoimmune diseases. The information provided is often even superior to that obtained with classical disease markers, probably due to the direct involvement of the "TNF system" in the pathogenetic mechanisms in these patients. The available data imply that the measurement of sTNF-Rs, especially of the sTNF-R 75kD type, is a useful adjunct for quantification of the Th1-type immune response, similar to other immune activation markers such as neopterin and beta 2-microglobulin. Endogenous sTNF-Rs concentrations appear to reflect the activation state of the TNF-alpha/TNF receptor system.