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.

Loss of memory (CD27) B lymphocytes in HIV-1 infection.

OBJECTIVES: The mechanisms of B-cell dysfunction during HIV-1 infection, including polyclonal B-cell activation, are poorly understood. We studied the phenotype and the functionality of peripheral memory B cells in HIV-1-infected subjects. DESIGN: The phenotype of B cells and the responsiveness to T-cell dependent activation in vitro were analysed in 36 HIV-1-infected and 34 healthy subjects. METHODS: Phenotyping of B and T cells was performed by FACS. IgG content was measured in plasma (by nephelometry) and cultures (by enzyme-linked immunosorbent assay) of B lymphocytes activated through CD40 or CD27 ligation. Expression of Fas and Fas ligand was performed by FACS on B-cell subpopulations from five HIV-1-infected and four uninfected subjects. RESULTS: The peripheral memory (CD27) B cells were significantly reduced in HIV-1-infected subjects. The amount of memory B cells was low in both drug-naive subjects and patients undergoing antiretroviral therapy. Ex vivo expression of CD70 (CD27 ligand) on T cells was significantly higher in HIV-1-infected subjects and inversely correlated with the frequency of memory B cells. In spite of the reduced number of memory B cells, in vitro spontaneous and activation-induced IgG secretion was higher in HIV-1-infected patients than in uninfected controls. The hyperactivation status of B lymphocytes in HIV-1-infected patients was further confirmed by the finding of upregulation of Fas and FasL expression on memory B cells. CONCLUSIONS: Memory B lymphocytes are depleted from peripheral blood in HIV-1-infected subjects. Our ex vivo findings suggest that persistent T-cell activation may contribute to loss of memory B cells through upregulation of Fas/FasL on these cells and terminal differentiation into plasma cells.

Soluble CD23 in cerebrospinal fluid: a marker of AIDS-related non-Hodgkin's lymphoma in the brain.

BACKGROUND: AIDS-related non-Hodgkin's lymphoma (NHL) includes systemic lymphomas, often with brain involvement, and primary central nervous system (CNS) lymphomas. OBJECTIVE: To examine if measurement of soluble CD23 (sCD23) in cerebrospinal fluid (CSF) is useful in the diagnosis and follow-up of AIDS-related NHL. METHOD: sCD23 was measured by enzyme-linked immunosorbent assay and EBV DNA by nested polymerase chain reaction for a group of 134 patients. The NHL group included 14 patients with primary HIV-1 CNS lymphoma, 12 patients with brain involvement of systemic HIV-1 NHL and 10 patients with systemic HIV-1 NHL without brain involvement. These were compared with HIV-1-infected patients with cerebral toxoplasmosis (19), progressive multifocal leukoencephalitis (PML; 8) and AIDS-related dementia (17) and with asymptomatic HIV-1 carriers (54) and uninfected individuals (50). The levels of sCD23 were compared with the presence of Epstein-Barr virus (EBV) DNA in CSF. RESULTS: Significantly higher levels of sCD23 were found in the CSF of the patients with brain lymphoma than in those with systemic NHL (P < 0.002) or with cerebral toxoplasmosis, PML and AIDS-related dementia (P < 0.0001). The sensitivity and specificity of sCD23 in CSF as a marker for detection of brain NHL were 77% and 94%, respectively. High levels of sCD23 were found in CSF from patients with brain NHL independently of the presence (18 out of 26) or absence (8 out of 26) of EBV DNA. CONCLUSIONS: The sCD23 in CSF of HIV-1-infected patients may represent an additional, non-invasive marker for diagnosis of brain involvement in AIDS-related NHL.

Surrogate markers as a guide to evaluate response to antiretroviral therapy.

The development of an increasing number of antiretroviral agents has dramatically reduced HIV-associated morbidity and mortality. However, most of these drugs have been approved through clinical trials where only surrogate markers for clinical endpoints have been used. Ideally, a surrogate marker should be biologically plausible, predictive of disease progression and measurable by standardized assays. Historically, a number of candidate markers have been explored for monitoring the course of HIV infection and response to treatment. While the level of plasma HIV RNA and the absolute numbers of peripheral CD4+ T cells have eventually become the reference markers in clinical practice, several additional parameters are still being evaluated to improve our knowledge of the virus-host interaction, discriminate between apparently equivalent stages and further refine antiretroviral treatment. Advances in molecular methods and growing elucidation of HIV dynamics in vivo have made it possible to consider several molecular virologic parameters as candidate markers for treatment response, including intracellular levels of different HIV RNA species and amount of integrated and unintegrated HIV DNA. Much effort has been recently devoted to the definition of immunological parameters as prognostic markers. The abnormal activation induced by HIV on the immune system represents a major pathogenetic feature of HIV infection. Immune activation may be evaluated by the analysis of activation markers expressed on the cell membrane and by the quantification of soluble plasma molecules released by activated cells. Such markers of immune activation have an important prognostic significance in terms of disease progression and might be suitable for the monitoring and prognosis of antiretroviral therapies. In the late years, the possibility of extending potent antiretroviral therapies to developing countries has raised the need of simple, reliable and cost-effective tests to measure prognostic markers for disease evolution and assessment of therapy efficacy. This review summarizes the benefits and limits of reference and candidate surrogate markers and their integration for optimal antiretroviral therapy.

Elevated levels of soluble Fas and Fas ligand in cerebrospinal fluid of patients with AIDS dementia complex.

We measured the levels of sFas and sFasL in CSF and serum of HIV-1 infected patients and related them to AIDS dementia complex (ADC). Specimens were obtained from 51 HIV-1 infected individuals (29 with ADC) and 39 HIV negative individuals. The sFas was detectable in all sera and 98% of CSF specimens. Measurable levels of sFasL were found in 79% of the CSF and 98% of sera samples. According to the presence or absence of ADC, we observed significant differences in CSF sFas (median and IQR 116, 132 vs. 30, 23 pg/ml, P<0.001) and sFasL (median and IQR 127, 290 vs. 15, 73 pg/ml, P<0.001) levels. The sFas in serum differed significantly between HIV-1 infected subjects and non-infected controls (P<0.001), with no correlation to ADC. On the contrary, sFasL in serum differed among HIV-1 infected subjects according to clinical signs of ADC. In the cross-sectional study, the number of cells present in CSF and CD4+ T cell counts in blood did not correlate to the levels of CSF sFas and sFasL. Interestingly, the number of HIV RNA copies in CSF correlated significantly to the levels of CSF sFasL (P=0.001) but not to sFas in the same compartment. Antiretroviral therapy reduced viral load and sFas levels in CSF in the majority of patients. sFas is a useful marker for ADC diagnosis and follow-up during antiviral treatment.

High plasma levels of soluble fas in HIV type 1-infected subjects are not normalized during highly active antiretroviral therapy.

Plasma levels of soluble Fas (sFas) are elevated in human immunodeficiency virus type 1 (HIV-1) infection, indicating dysregulation of the Fas apoptosis pathway and chronic immune activation. We performed a retrospective study to investigate the effects of HAART on plasma levels of sFas. A cross-sectional study of 27 drug-naive infected subjects and 49 patients under antiretroviral treatment showed that plasma levels of sFas were higher in HIV-1-infected subjects than in 52 HIV-1-negative controls, independently of the treatment status. In a longitudinal study of 69 patients undergoing HAART, we observed a minimal, but significant decrease in sFas plasma levels after 1 year of therapy. Levels of sFas, however, remained still higher than physiologic values. Patients undergoing HAART were further classified as nonresponders or responders on the basis of viremia suppression; no significant changes in plasma levels of sFas were observed between the two groups. These findings show that 1 year of HAART has a minor effect on the sFas levels in plasma. Long-term HAART may be required to normalize the dysregulation of the Fas apoptotic pathway and the persistent immune activation initiated by HIV-1.

HIV-associated malignant lymphomas in Kenya (Equatorial Africa)

The clinical and pathological features of acquired immune deficiency syndrome (AIDS)-related lymphomas, including their relationship with other viruses, such as Epstein-Barr virus (EBV) and human herpes virus-8 (HHV8), have been the subject of several studies from North America and Europe. No consistent data have been reported in Africa, where AIDS runs an epidemiological and clinical course different from that observed in Western countries. We retrospectively evaluated the presence of human immunodeficiency virus (HIV), HHV8, and EBV in 146 cases of malignant lymphomas collected in Kenya (Equatorial Africa), with the use of polymerase chain reaction (PCR) and in situ hybridization (ISH). The PCR technique confirmed HIV infection in 16 HIV-seropositive subjects (11%) and showed the presence of HIV sequences in five additional cases (3%) in which the occurrence of lymphoma was the only clinical manifestation. Our findings suggest that AIDS-related lymphomas are not pathogenetically homogenous, and different mechanisms may contribute to lymphomagenesis in these severely immunocompromised patients. In our series, no association of Hodgkin's disease (HD) with HIV infection could be shown. Among non-HIV-related lymphomas, EBV was present in 94% of Burkitt lymphoma (BL) occurring in patients younger than 15 years of age, in 87% of HD independently of age, sex, and histological types, in 60% of anaplastic large cell lymphoma (ALCL), and to a lesser extent (13%) in large B-cell lymphoma (LBCL) cases. Only one tumor, a case of HD, showed HHV8 by PCR.

Fatal herpesvirus 6 encephalitis after unrelated bone marrow transplant.

A complex pattern of neurological dysfunctions with generalized seizures and visual allucinations, but without focal signs, suddenly arose 20 days after an unrelated bone marrow transplant for chronic myelogenous leukemia (CML) in a 13-year-old girl, accompanied by signs of acute skin graft-versus-host disease (GVHD). Magnetic resonance imaging (MRI) revealed multiple bilateral foci of signal abnormalities, which were exclusively localized in the grey matter, sparing the white. Extensive microbiological and virological assays of cerebrospinal fluid (CSF) allowed the identification of HHV-6, variant A, DNA. Further progression of both neurological alterations and of skin and gut GVHD led to a fatal outcome 2 weeks later. A retrospective analysis of both the recipient and donor mononuclear cell suspensions supported the hypothesis that HHV-6 had been acquired from the donor with the bone marrow graft. This report suggests a pathogenetic role of HHV-6 in viral encephalitis in immunocompromised bone marrow transplant (BMT) recipients, and its possible association with GVHD.

Increased reliability of selective PCR by using additionally mutated primers and a commercial Taq DNA polymerase enhancer.

A reliable selective PCR procedure that combines the use of additionally mutated primers with the specificity-enhancing properties of a commercial preparation (Perfect Match, Stratagene) is described. The human immunodeficiency virus type 1 pol gene point mutations known to confer in vitro resistance to azidothymidine were examined as a model for optimization of the assay. The usual strategy of deliberately introducing an additional mismatch 1 residue from the 3' end in the wild-type and mutant primers did not allow reproducible discrimination between wild-type and mutant target sequences. Addition of minimal amounts of Perfect Match to the same PCR mixtures resulted in a significantly enlarged range of selective annealing temperatures, providing a valuable and cost-effective means for reliable detection of known mutations by selective PCR.

Long-read direct infrared sequencing of crude PCR products for prediction of resistance to HIV-1 reverse transcriptase and protease inhibitors.

Patients infected with human immunodeficiency virus type 1 (HIV-1) are being treated with a number of different combinations of antiretroviral compounds that target the essential viral enzymes reverse transcriptase and protease. Different sets of HIV-1 mutations that confer drug resistance have been well defined; they allow reasonable prediction of the drug sensitivity pattern from analysis of the HIV-1 genotype in vivo. Since periodical monitoring of genotypic resistance is expected to improve clinical management in a large number of infected patients, practical and cost-effective methods are highly desirable to set at least medium-scale sequencing in clinical diagnostic settings. We present a complete protocol for direct sequencing of HIV-1 reverse transcriptase and protease-coding regions. Features making the system amenable to routine clinical use include: 1. Highly robust presequencing steps (plasma RNA extraction, reverse transcription, and nested PCR); 2. Direct use of the crude unpurified PCR product as the sequencing template; and 3. Use of infrared-labeled sequencing primers consistently allowing long reads, thus obviating the need for sequencing of both DNA strands.

[Cytostatic therapy reduces the immune defense. Children treated for leukemia have impaired immunity against measles and rubella]. / Cytostatikaterapi sänker immunförsvaret. Leukemibehandlade barn förlorar sin immunitet mot mässling och röda hund.

A study is summarized analyzing the levels of serum antibodies against vaccination antigens in 43 children treated for acute lymphoblastic leukemia. Two different therapeutical regimens were used. All children had been immunized against measles and rubella before being diagnosed with leukemia. Eight of the 24 children treated 1986-1991 lacked protective levels of antibodies against measles; four of the 24 children lacked antibodies against rubella. In the second cohort of children (n = 16) treated from 1992 and onwards, nine lacked protective levels of antibodies against measles, eight lacked antibodies against rubella.

SIRT1 and SIRT2 inhibition impairs pediatric soft tissue sarcoma growth.

Sirtuins are NAD+ dependent deacetylases and/or ADP-ribosyl transferases active on histone and non-histone substrates. The first sirtuin was discovered as a transcriptional repressor of the mating-type-loci (Silent Information Regulator sir2) in the budding yeast, where it was shown to extend yeast lifespan. Seven mammalian sirtuins (SIRT1-7) have been now identified with distinct subcellular localization, enzymatic activities and substrates. These enzymes regulate cellular processes such as metabolism, cell survival, differentiation, DNA repair and they are implicated in the pathogenesis of solid tumors and leukemias. The purpose of the present study was to investigate the role of sirtuin expression, activity and inhibition in the survival of pediatric sarcoma cell lines.We have analyzed the expression of SIRT1 and SIRT2 in a series of pediatric sarcoma tumor cell lines and normal cells, and we have evaluated the activity of the sirtuin inhibitor and p53 activator tenovin-6 (Tv6) in synovial sarcoma and rhabdomyosarcoma cell lines. We show that SIRT1 is overexpressed in synovial sarcoma biopsies and cell lines in comparison with normal mesenchymal cells. Tv6 induced apoptosis as well as impaired autophagy flux. Using siRNA to knock down SIRT1 and SIRT2, we show that the expression of both proteins is crucial for the survival of rhabdomyosarcoma cells and that the loss of SIRT1 expression results in a decreased LC3II expression. Our results show that SIRT1 and SIRT2 expressions are crucial for the survival of synovial sarcomas and rhabdomyosarcomas, and demonstrate that the pharmacological inhibition of sirtuins impairs the autophagy process and induces tumor cell death.

Proton pump inhibition induces autophagy as a survival mechanism following oxidative stress in human melanoma cells.

Proton pump inhibitors (PPI) target tumour acidic pH and have an antineoplastic effect in melanoma. The PPI esomeprazole (ESOM) kills melanoma cells through a caspase-dependent pathway involving cytosolic acidification and alkalinization of tumour pH. In this paper, we further investigated the mechanisms of ESOM-induced cell death in melanoma. ESOM rapidly induced accumulation of reactive oxygen species (ROS) through mitochondrial dysfunctions and involvement of NADPH oxidase. The ROS scavenger N-acetyl-L-cysteine (NAC) and inhibition of NADPH oxidase significantly reduced ESOM-induced cell death, consistent with inhibition of cytosolic acidification. Autophagy, a cellular catabolic pathway leading to lysosomal degradation and recycling of proteins and organelles, represents a defence mechanism in cancer cells under metabolic stress. ESOM induced the early accumulation of autophagosomes, at the same time reducing the autophagic flux, as observed by WB analysis of LC3-II accumulation and by fluorescence microscopy. Moreover, ESOM treatment decreased mammalian target of rapamycin signalling, as reduced phosphorylation of p70-S6K and 4-EBP1 was observed. Inhibition of autophagy by knockdown of Atg5 and Beclin-1 expression significantly increased ESOM cytotoxicity, suggesting a protective role for autophagy in ESOM-treated cells. The data presented suggest that autophagy represents an adaptive survival mechanism to overcome drug-induced cellular stress and cytotoxicity, including alteration of pH homeostasis mediated by proton pump inhibition.

The role of FAS to ezrin association in FAS-mediated apoptosis.

The acquisition of a cell polarity is a crucial requirement for a number of cellular functions, including apoptosis. Cell polarization is an actin cytoskeleton-driven process, through a connection between actin and an increasing number of membrane proteins. The major actors in this connection are ezrin, radixin and moesin, a family of proteins with a high level of homology. Their structure includes an epitope that links to membrane proteins and the other that binds to the actin molecule. In this review we discuss recent data showing that the Fas linkage to the actin cytoskeleton is ezrin mediated and it is an essential requirement for susceptibility to the Fas-mediated apoptosis. The ezrin region responsible of Fas binding consists of 18 aminoacids mapped on the median lobe of the ezrin FERM domain. This binding is specific and of key importance in the control of cell homeostasis. Moreover, Fas-ezrin co-localization, ezrin phosphorylation and early acquisition of susceptibility to Fas-mediated apoptosis, may have a role in some human diseases in which programmed cell death seems to be a central pathogenetic mechanism, such as AIDS.

Clinical evaluation of an in-house reverse transcription-competitive PCR for quantitation of human immunodeficiency virus type 1 RNA in plasma.

An in-house reverse transcription (RT)-competitive PCR (RT-cPCR) for the quantitation of human immunodeficiency virus type 1 (HIV-1) RNA in plasma samples was developed and validated. The procedure involves (i) extraction of RNA with spin columns, (ii) ready-to-use bead-mediated RT, (iii) competitive PCR in a microtiter plate, (iv) agarose gel electrophoresis of the reaction products, and (v) densitometric analysis of the digitized image of the gel. Quadruplicate tests and dilution studies showed that the sensitivity and intertest coefficient of variability of the RT-cPCR are comparable to those of the reference AMPLICOR HIV-1 MONITOR test. The results obtained by the two assays with a panel of 45 clinical samples were in good agreement (mean difference, 0.36 +/- 0.25 log units). Analysis of 1,982 clinical samples by the in-house RT-cPCR yielded the typical range of plasma HIV-1 RNA levels with the expected inverse correlation between CD4 counts and HIV-1 RNA titers. In addition, testing of plasma from 36 subjects at weeks 0 and 4 with respect to the time of initiation of protease inhibitor therapy detected a significant decrease in HIV-1 viremia. The mean reduction in the HIV-1 RNA level was 0.914 log unit for those receiving saquinavir (P = 0.0210), 1.584 log units for those receiving indinavir (P = 0.0047), and 1.904 log units for those receiving ritonavir (P < 0.0001). The in-house RT-cPCR assay is simple to develop and perform and allows quantitation of HIV-1 RNA in 100 to 200 samples per operator per week. Since the cost is 1/8 to 1/10 of those of reference commercial assays, this procedure could be conveniently used in medium-scale laboratories.

Evaluation of cell-free and cell-associated peripheral blood human immunodeficiency virus type 1 RNA response to antiretroviral therapy.

Plasma human immunodeficiency virus (HIV) type 1 RNA load is the reference marker for response to antiretroviral therapy. To compare peripheral blood mononuclear cell (PBMC)-associated and plasma HIV-1 RNA response to treatment, HIV-1 RNA was quantified by reverse transcription-competitive polymerase chain reaction in 20 patients at 0, 12, and 24 weeks following addition of saquinavir to their treatment regimens. HIV-1 RNA was undetectable in 15 plasma samples but in only 2 PBMC samples (P=.002) and CD4 cell counts correlated more with PBMC than with plasma HIV-1 RNA load. Changes in HIV-1 RNA load in PBMC and in plasma were correlated, and the decrease was higher in plasma than in PBMC at weeks 12 (P=.002) and 24 (P=.017). Moreover, PBMC, but not plasma HIV-1 load, at week 12 was predictive of HIV-1 RNA levels at week 24 in both plasma (P=.004) and PBMC (P<. 001). Thus, measurement of PBMC HIV-1 RNA may be useful during antiretroviral therapy.

Optimal conditions for detection of human immunodeficiency virus type 1 DNA by polymerase chain reaction with nested primers.

An assessment of optimal conditions for nested primer amplification of low copy number target DNA sequences was made using a human immunodeficiency virus type 1 (HIV-1) model. In this polymerase chain reaction (PCR) strategy, an outer primer pair is first used to amplify the target sequence and a fraction of the amplification product is further amplified with a pair of inner (nested) primers. Several methodological parameters were evaluated, including number of cycles in the first and second step of the reaction, proportion of preamplified material to be used as the template for the second amplification, concentrations of primers, deoxynucleotides, and Taq DNA polymerase in the outer and inner PCR. The two-step PCR required minimal amounts of reaction components and was shown to be highly flexible, resulting in exquisite and specificity over a wide range of technical conditions. Potential drawbacks of this practical and effective amplification procedure are also discussed.

Low frequency of plasma nerve-growth factor detection is associated with death of memory B lymphocytes in HIV-1 infection.

Nerve growth factor (NGF) regulates B cell activation and differentiation and is an autocrine survival factor for memory B lymphocytes. We have reported recently that the number of memory B cells is reduced during HIV-1 infection. In this study we evaluated whether alteration in the NGF supply was involved in memory B cell loss in HIV-1-infected subjects. High rate of cell death in vitro was observed in memory B cells from HIV-1-infected individuals compared to uninfected donors (26.2 +/- 2.5%versus 7.9 +/- 1.4%, P < 0.001). The increased expression of Fas on memory B cells from infected subjects did not enhance the susceptibility of the cells to Fas-mediated apoptosis in vitro. The frequency of NGF detection in plasma from HIV-1-infected subjects was significantly lower than in healthy donors (33.6%versus 63.6%, P < 0.001). Also, the median plasma NGF in HIV-1-infected individuals was significantly lower than in uninfected controls (5 versus 14 pg/ml, respectively, P < 0.01). Interestingly, the plasma NGF level was correlated directly 1 to the percentage of memory B cells (P < 0.05). HIV-1-infected subjects with a low number of peripheral memory B cells had a reduced incidence of plasmatic NGF (7.4%) compared to patients with a normal level of memory B cells (37%, P < 0.01). Moreover, the addition of recombinant NGF (1 micro g/ml) to cultures of purified B cells reduced cell death of memory B cells from HIV-1-infected subjects from 24.04 +/- 3.0% to 17.4 +/- 1.3% (P < 0.01). HIV-1-infected individuals also carried higher levels of natural anti-NGF autoantibodies compared to uninfected subjects. In conclusion, we found that memory B cells from HIV-1-infected individuals are primed for cell death. Our study suggests an association between low frequency of plasma NGF detection and the increased cell death of memory B lymphocytes observed during HIV-1 infection. Low levels of NGF in plasma may be due to reduced supply or to NGF binding to natural anti-NGF autoantibodies.

Plasma levels of soluble CD27: a simple marker to monitor immune activation during potent antiretroviral therapy in HIV-1-infected subjects.

Plasma levels of soluble CD27 (sCD27) are elevated in diseases characterized by T cell activation and are used as a marker of immune activation. We assessed the usefulness of determining plasma sCD27 as a marker for monitoring immune activation in HIV-1-infected patients treated with highly active antiretroviral therapy (HAART). A first cross-sectional examination of 68 HIV-1-infected and 18 normal subjects showed high levels of sCD27 in HIV-1 infection; plasma sCD27 was correlated to HIV-1 viraemia and inversely correlated to CD4+ T cell count. Twenty-six HIV-1-infected patients undergoing HAART were studied at baseline and after 6, 12, 18 and 24 months of therapy. Seven additional patients under HAART were analysed at baseline, during and after interruption of therapy. In the total population, HAART induced a significant and progressive reduction, but not a normalization, of plasma levels of sCD27 after 24 months. A full normalization of plasma sCD27 was observed in the virological responders (undetectable HIV-1 RNA at months 18 and 24) and also in patients with moderate immunodeficiency at baseline (CD4+ T cell count >200 cells/mm3). Changes in plasma neopterin paralleled the changes in sCD27 but only baseline sCD27 levels were predictive of a greater increase in CD4+ T cell count during the follow-up. Discontinuation of therapy resulted in a rapid increase of sCD27 plasma levels associated with viraemia rebound and drop in CD4+ T cell count. Our findings suggest that plasma sCD27 may represent an alternative and simple marker to monitor immune activation during potent antiretroviral therapy. HIV-1-induced immune activation can be normalized by HAART in successfully treated patients where the disease is not advanced.