Dysregulation of Membrane-Bound Tumor Necrosis Factor-α and Tumor Necrosis Factor Receptors on Mononuclear Cells in Human Immunodeficiency Virus Type 1 Infection: Low Percentage of p75-Tumor Necrosis Factor Receptor Positive Cells in Patients With Advanced Disease and High Viral Load

Quantitative flow cytometric analysis of expression of tumor necrosis factor receptor types I and II on mononuclear cells

BACKGROUND

Tumor necrosis factor (TNF)-α is an inflammatory cytokine, the biological effects of which are mediated by the interaction with specific membrane-bound receptors. To assess TNF-α receptor (TNFR) expression, it is important to estimate both the number of cells that carry these receptors and the number of receptors per cell, because the cell fate depends on the balance between TNFRI and TNFRII signaling.

OBJECTIVE

The aim of the present study was to develop an optimized protocol to estimate the level of expression of membrane-bound TNFRI and TNFRII, using QuantiBRITE PE calibration beads.

MATERIALS AND METHODS

The percentage of cells that expressed membrane-bound TNFRI and TNFRII and the mean number of receptors per cell were determined by flow cytometry using PE-labeled antibodies against TNFR. To create a calibration curve and convert cell fluorescence intensity values to absolute numbers of receptors, we used QuantiBRITE PE beads.

RESULTS

CD19(+) B lymphocytes had the least percentage of cells expressing TNFRI and the greatest number of receptor molecules per cell, whereas CD3(+) T lymphocytes had the greatest percentage of cells expressing TNFRII and the lowest density of these receptors. We also established that stimulation of peripheral blood mononuclear cells (PBMCs) with the lipopolysaccharide (LPS) significantly increased the number of TNFRI and TNFRII on CD14(+) monocytes.

CONCLUSION

Application of the protocol-identified differences in the percentage of cells that expressed TNFRs, as well as the absolute number of receptors per cell, among different subpopulations of PBMCs, and between PBMCs cultured with and without LPS.

Iatrogenic mitochondriopathies: a recent lesson from nucleoside/nucleotide reverse transcriptase inhibitors

The use of nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) has revolutionized the treatment of infection by human immunodeficiency virus (HIV) and hepatitis-B virus. NRTIs can suppress viral replication in the long-term, but possess significant toxicity that can seriously compromise treatment effectiveness. The major toxicity of NRTIs is mitochondrial toxicity. This manifests as serious side effects such as myopathy, peripheral neuropathy and lactic acidosis. In general, it is believed that the mitochondrial pathogenesis is closely related to the effect of NRTIs on mitochondrial DNA polymerase-γ. Depletion and mutation of mitochondrial DNA during chronic NRTI therapy may lead to cellular respiratory dysfunction and release of reactive oxidative species, resulting in cellular damage. It is now apparent that the etiology is far more complex than originally thought. It appears to involve multiple mechanisms as well as host factors such as HIV per se, inborn mitochondrial mutation, and sex. Management of mitochondrial toxicity during NRTI therapy remains a challenge. Interruption of NRTI therapy and substitution of the causative agents with alternative better-tolerated NRTIs represents the mainstay of management for mitochondrial toxicity and its clinical manifestations. A range of pharmacological approaches has been proposed as treatments and prophylaxes.

Generating aptamers for recognition of virus-infected cells

BACKGROUND

The development of molecular probes capable of recognizing virus-infected cells is essential to meet the serious clinical, therapeutic, and national-security challenges confronting virology today. We report the development of DNA aptamers as probes for the selective targeting of virus-infected living cells.

METHODS

To create aptamer probes capable of recognizing virus-infected cells, we used cell-SELEX (systematic evolution of ligands via exponential enrichment), which uses intact infected live cells as targets for aptamer selection. In this study, vaccinia virus-infected and -uninfected lung cancer A549 cells were chosen to develop our model probes.

RESULTS

A panel of aptamers has been evolved by means of the infected cell-SELEX procedure. The results demonstrate that the aptamers bind selectively to vaccinia virus-infected A549 cells with apparent equilibrium dissociation constants in the nanomolar range. In addition, these aptamers can specifically recognize a variety of target infected cell lines. The aptamers' target is most likely a viral protein located on the cell surface.

CONCLUSIONS

The success of developing a panel of DNA-aptamer probes capable of recognizing virus-infected cells via a whole living cell-SELEX selection strategy may increase our understanding of the molecular signatures of infected cells. Our findings suggest that aptamers can be developed as molecular probes for use as diagnostic and therapeutic reagents and for facilitating drug delivery against infected cells.

Cytokine and sex hormone effects on zidovudine- and lamivudine-triphosphate concentrations in vitro

INTRODUCTION

Elevated zidovudine- and lamivudine-triphosphates have been observed in peripheral blood mononuclear cells (PBMCs) from females versus males and in patients with high inflammatory states versus lower inflammatory states. Consistent with high triphosphate exposures, these same patient groups also experience elevated rates of toxicity, including lipoatrophy. The purpose of this study was to evaluate the effects of oestradiol, progesterone and testosterone as well as tumour necrosis factor (TNF)-alpha and interferon (IFN)-alpha on zidovudine- and lamivudine-triphosphates in PBMCs and, for the cytokines, in 3T3-L1 adipocytes.

METHODS

Multiple replicates of adipocytes and human PBMCs were incubated with experimental versus control conditions using several cytokine and sex hormone doses. Zidovudine- and lamivudine-triphosphate concentrations were determined with validated LC-MS-MS assays. A mixed effects, cell means model that accounted for experiment number was used to evaluate the effects of experimental conditions relative to control.

RESULTS

In adipocytes, TNF-alpha doses below 2 ng/mL increased zidovudine-triphosphate by 18% (5-31%). Lamivudine-triphosphate was not detectable in adipocytes. In PBMCs, pooled IFN-alpha doses (0.1-10 U/mL) decreased zidovudine-triphosphate 26% (10-42%); 100 and 1000 ng/mL of progesterone decreased lamivudine-triphosphate by 22% (1-43%) and 47% (25-68%), respectively. Pooled testosterone doses (10-1000 ng/mL) decreased lamivudine-triphosphate by 24% (7-41%). No other statistically significant effects were observed.

CONCLUSIONS

We found evidence that sex hormones and cytokines influence zidovudine-triphosphate and lamivudine-triphosphate slightly in PBMCs and adipocytes in vitro. These findings provide insight and scientific direction to address inflammation-dependent and sex-dependent phosphorylation and responses in patients.

HIV-1 gp120 up-regulation of the mu opioid receptor in TPA-differentiated HL-60 cells

Opioid abuse has been shown to exacerbate the immunosuppressive effects and pathogenesis of HIV infection. The mu opioid receptor (MOR) is present on immune cells, such as macrophages, and mediates the direct immunomodulatory effects of opioids. Through its surface glycoprotein, gp120, HIV-1 binds to surface receptors on target cells, including macrophages, to exert its pathological effects. Binding of gp120 to macrophages stimulates the cells to release various pro-inflammatory cytokines, including TNF-alpha, which has been shown to regulate transcription of the MOR gene. In this study, we examined the effects of HIV-1 gp120 on MOR expression in HL-60 human promyelocytic leukemia cells differentiated into macrophage-like cells by TPA. Using real time RT-PCR, we found that exposure to gp120 up-regulated MOR expression in TPA-differentiated HL-60 cells at the transcriptional level. The functionality of the gp120-induced MOR in these cells was confirmed based on morphine's inhibition of forskolin-induced intracellular cAMP, which was naloxone reversible. Exposure to gp120 also stimulated the release of TNF-alpha from TPA-differentiated HL-60 cells. Treatment with TNF-alpha neutralizing antibody, as well as blockage of TNF-alpha's actions by anti-TNF-alpha receptor type II (TNFR-II) antibody, inhibited gp120-induced up-regulation of MOR mRNA. Our data suggest that one of the mechanisms by which HIV-1 gp120 up-regulates the MOR in TPA-differentiated HL-60 cells is through autocrine/paracrine actions of TNF-alpha via the TNFR-II receptor.

Stage-specific effects of Plasmodium falciparum-derived hemozoin on blood mononuclear cell TNF-alpha regulation and viral replication

BACKGROUND

The molecular immunological interactions between HIV and malaria are largely undefined. Since tumor necrosis factor (TNF)-alpha is elevated during acute malaria and increases with HIV-1 disease progression, TNF-alpha production may be an important mediator for interactions between malaria and HIV-1.

METHODS

To examine the stage-specific immunological interactions between HIV and malaria, peripheral blood mononuclear cells (PBMC) and CD14 cells were isolated and cultured from rhesus macaques at different stages of SIV infection. Cultures were stimulated with lipopolysaccharide (LPS) and interferon (IFN)-gamma in the presence of Plasmodium falciparum-derived hemozoin (Hz) or synthetic Hz (sHz). TNF-alpha transcripts and soluble protein were examined by real time reverse transcription-PCR and ELISA, respectively. The effects of Hz on viral replication were determined by measurement of p27 antigen with varying concentrations of TNF-alpha neutralizing antibodies.

RESULTS

Hz and sHz significantly increased LPS- and IFN-gamma-induced TNF-alpha protein and transcripts in PBMC from animals with late stage SIV infection (i.e., AIDS). Hz and sHz also induced high levels of sustained TNF-alpha transcripts in PBMC from the AIDS group. During the late stage of disease, CD14 cells were the primary source of TNF-alpha production. Stimulation of PBMC with Hz and sHz significantly increased viral replication that was dose-dependently reduced by the addition of TNF-alpha neutralizing antibodies.

CONCLUSIONS

Hz promotes high levels of TNF-alpha production from PBMC during AIDS and increases viral replication in SIV-infected animals.

Non-induced leukocyte extract reduces HIV replication and TNF secretion

According to UNAIDS, the global HIV/AIDS epidemic increased to 40 million the number of people living with the virus around the world. Dialyzable leukocyte extract obtained by our group is a low molecular weight dialyzable material from peripheral human leukocytes previously in vitro induced with Sendai virus (DLE-ind), and more recently, from non-induced leukocytes (DLE n/i). Previous results have shown the ability of DLE-ind to inhibit HIV in vitro replication in MT4 cell; to reduce TNFalpha secretion, and to delay in vivo progression to AIDS in early stage of HIV infection. In this work we present evidences that DLE n/i also inhibits HIV in vitro replication and reduces TNFalpha secretion in human whole blood like DLE obtained from induced leukocytes. Taking together these results show that both properties of DLE, HIV in vitro inhibition and TNF production modulation, are not dependent on in vitro Sendai virus induction of leukocytes.

The cellular pharmacology of nucleoside- and nucleotide-analogue reverse-transcriptase inhibitors and its relationship to clinical toxicities

Nucleoside- and nucleotide-analogue reverse-transcriptase inhibitors (NRTIs) require intracellular phosphorylation for anti-human immunodeficiency virus (HIV) activity and toxicity. Long-term toxicities associated with NRTIs may be related to overactivation of this process. In vitro experiments have shown increased rates of NRTI and endogenous nucleoside phosphorylation to be associated with cellular activation. Patients with advanced HIV disease often have overexpression of cytokines, which corresponds to an elevated cellular activation state. These patients also have higher rates of NRTI phosphorylation and NRTI toxicity, suggesting an interaction between a proinflammatory biological state, NRTI phosphorylation, and toxicity. Studies suggest that women may have higher rates of NRTI phosphorylation than do men, as well as increased risk for NRTI-induced toxicity. Future research is needed to understand the NRTI activation process and improve the long-term toxicity profile of NRTIs. Such research should include comparisons of NRTI phosphorylation according to sex and cellular activation state (i.e., elevated vs. low).

Molecular cloning of feline tumour necrosis factor receptor type I (TNFR I) and expression of TNFR I and TNFR II in lymphoid cells in cats

Tumour necrosis factor (TNF)-alpha is a pro-inflammatory cytokine produced by many types of cells. It has been shown that two distinct TNF receptors (TNFRs), TNFR type I (TNFR I) and TNFR type II (TNFR II), have different functions in signal transduction, which is possibly associated with the development of a variety of diseases. In this study, we isolated a feline TNFR I cDNA clone and analysed the expression of TNFR I and TNFR II mRNA in feline lymphoid cells. The deduced amino acid sequence of feline TNFRI cDNA showed 75.8, 62.5 60.9 and 72.1% similarity with those of its human, mouse, rat, and pig counterparts, respectively. The feline TNFR I cDNA was shown to encode extracellular, transmembrane and intracellular domains fundamentally conserved in the homologues of other species. Expression of TNFR I and TNFR II mRNAs was shown to be up-regulated in feline peripheral blood mononuclear cells (PBMC) by stimulation with concanavalin A. Five of six feline lymphoma cell lines were shown to express both TNFR I and TNFR II mRNAs. The expression of TNFR I in PBMC was up-regulated in cats infected with feline immunodeficiency virus (FIV), whereas the expression of TNFR II in PBMC was not different between FIV-infected cats and uninfected cats. The present study indicate that expression of TNFR I and TNFR II may be associated with disease progression, especially in retrovirus infections in cats.

Increased sensitivity of T lymphocytes to tumor necrosis factor receptor 1 (TNFR1)- and TNFR2-mediated apoptosis in HIV infection: relation to expression of Bcl-2 and active caspase-8 and caspase-3

The destruction of CD4 T cells in human immunodeficiency virus (HIV) infection is associated with activation of apoptotic programs, partly mediated by death receptors. The role of CD95L/CD95 in depletion of patients' CD4 T cells is well documented, but the possible contribution of the tumor necrosis factor/tumor necrosis factor receptor (TNF/TNFR) pathway has not been examined. In this study, we found that both TNFR1 and TNFR2 induced marked apoptosis in peripheral T cells from HIV-infected persons, involving both CD4 and CD8 T cells. Longitudinal follow-up of HIV(+) patients suggests an association between the in vivo evolution of CD4 T-cell numbers and variations in susceptibility to TNFR-induced apoptosis. Analysis of molecular mechanisms involved showed that it was not related to altered ex vivo expression of TNFR1-associated death domain, receptor interacting protein, or TNFR-associated factor 2. Susceptibility to TNFR-mediated apoptosis was rather related to Bcl-2 expression, because patients' T cells expressing high levels of Bcl-2 were completely protected from TNFR1- and TNFR2-induced cell death, whereas T cells expressing normal levels of Bcl-2 were not protected in patients in contrast to controls. Early recruitment of caspase-8 and caspase-3 is needed to transduce the apoptotic signals, and expression of both caspases in their active form was detected in blood T cells from HIV(+) patients, whereas it was hardly detected in controls. Moreover, ligation of TNFRs induced increased activation of both caspases in patients' T cells. Together these data demonstrate that exacerbated TNFR-mediated cell death of T cells from HIV-infected individuals is associated with both alteration of Bcl-2 expression and activation of caspase-8 and caspase-3 and may contribute to the pathogenesis of acquired immunodeficiency syndrome.

Expression of co-stimulatory and adhesion molecules and chemokine or apoptosis receptors on acute myeloid leukaemia: high CD40 and CD11a expression correlates with poor prognosis

The expression of adhesion and co-stimulatory molecules, and chemokine and death receptors such as tumour necrosis factor (TNF) and FAS on acute myeloid leukaemia (AML) may influence the biology of the disease and response to chemotherapy and immunotherapy. In this study, we analysed the expression of these molecules in 99 AML patients using monoclonal antibodies and flow cytometry, and correlated the expression with French-American-British (FAB) classification and survival. The following molecules were studied: the co-stimulatory molecules CD80, CD86 and CD40; the adhesion molecules CD11a-c, CD31, CD43, CD50, CD54, CD102, CD58 and CD62L; the chemokine receptor CXCR4; and the death receptors TNFR1 and TNFR2 and FAS. The expression of all molecules was significantly higher in the M4/M5 FAB subgroups except for CD80, CD43, CD54 and CD62L. The AML M3 subgroup had a significant lower expression of CD11a (P = 0.02) and CD11c (P = 0.03). Five-year survival was significantly shorter in cases of high CD40 expression [> 20% positive cells, relative risk (RR) 2.56, P = 0.02] or high CD11a expression (> 80% positive cells, RR 2.6, P = 0.03). This effect was most prominently present in the AML M4/M5 FAB subgroups. We conclude that the expression levels of adhesion and co-stimulatory molecules, CXCR4 and apoptosis-receptors are predominantly FAB subtype-related with high CD40 and CD11a expression as poor prognostic factors.

Host immune responses in the course of bovine leukemia virus infection

Bovine leukemia virus (BLV) is a type C retrovirus infecting bovine B cells and causing enzootic bovine leukosis. Since it takes long periods to develop the disease, it is believed that BLV and host immune responses are closely related. In this review, the accumulated data showing close relationship between BLV and host immune responses are summarized in 4 sections. First, we discuss the role of cell-mediated immunity in protecting hosts from BLV infection. Second, several reports showing the relationship between the disease progression and the change of cytokine profiles are summarized. In the third section, we have focused on tumor necrosis factor alpha (TNFalpha) and its two types of receptors, and the possible involvement of TNFalpha in the BLV-induced leukemogenesis is discussed. The expression of TNFalpha has been shown to be regulated by major histocompatibility complex (MHC) haplotype. The resistance to BLV infection is supposed to be established by some innate factors, which are closely related to MHC haplotype. Finally, we propose that a breeding strategy based on the MHC haplotype could be a good approach to control BLV infection. This review includes some recent data from us and other groups.

Autoantibodies to TNFalpha in HIV-1 infection: prospects for anti-cytokine vaccine therapy

Tumor necrosis factor alpha (TNFalpha) is a proinflammatory cytokine principally involved in the activation of lymphocytes in response to viral infection. TNFalpha also stimulates the production of other cytokines, activates NK cells and potentiates cell death and/or lysis in certain models of viral infection. Although TNFalpha might be expected to be a protective component of an antiviral immune response, several lines of evidence suggest that TNFalpha and other virally-induced cytokines actually may contribute to the pathogenesis of HIV infection. Based on the activation of HIV replication in response to TNFalpha, HIV appears to have evolved to take advantage of host cytokine activation pathways. Antibodies to TNFalpha are present in the serum of normal individuals as well as in certain autoimmune disorders, and may modulate disease progression in the setting of HIV infection. We examined TNFalpha-specific antibodies in HIV-infected non-progressors and healthy seronegatives; anti-TNFalpha antibody levels are significantly higher in GRIV seropositive slow/non-progressors (N = 120, mean = 0.24), compared to seronegative controls (N= 12, mean = 0.11). TNFalpha antibodies correlated positively with viral load, (P = 0.013, r = 0.282), and CD8+ cell count (P = 0.03, r = 0.258), and inversely with CD4+ cell count (P = 0.003, r = - 0.246), percent CD4+ cells (P = 0.008, r = -0.306), and CD4 :CD8 ratio (P = 0.033, r = - 0.251). TNFalpha antibodies also correlated positively with antibodies to peptides corresponding to the CD4 binding site of gp160 (P = 0.001, r = 0.384), the CD4 identity region (P = 0.016, r = 0.29), the V3 loop (P = 0.005, r = 0.34), and the amino terminus of Tat (P = 0.001, r = 0.395); TNFalpha antibodies also correlated positively with antibodies to Nef protein (P = 0.008, r = 0.302). The production of anti-TNFalpha antibodies appears to be an adaptive response to HIV infection and suggests the potential utility of modified cytokine vaccines in the treatment of HIV infections as well as AIDS-related and unrelated autoimmune and CNS disorders.

The 75-kD tumour necrosis factor (TNF) receptor is specifically up-regulated in monocytes during Q fever endocarditis

Q fever is an infectious disease caused by Coxiella burnetii, an obligate intracellular microorganism that inhabits monocytes/macrophages. The dysregulated production of TNF-alpha in Q fever endocarditis has been associated with defective killing of C. burnetii by patient monocytes. As soluble receptors for TNF-alpha (TNF-R55 and TNF-R75) regulate TNF-alpha activity, we investigated their release by monocytes in Q fever. Spontaneous and C. burnetii-stimulated release of TNF-R75, but not of TNF-R55, was up-regulated in patients with ongoing endocarditis compared with controls. The increase in TNF-R75 release was related to the activity of Q fever endocarditis, since TNF-R75 release was similar in patients with cured endocarditis and controls. While spontaneous release of TNF-R75 by monocytes from patients with ongoing Q fever endocarditis occurred without changes in its membrane expression, C. burnetii increased the surface expression of TNF-R75. In addition, TNF-R75 transcripts were increased in resting and C. burnetii-stimulated monocytes from patients with ongoing endocarditis. On the other hand, TNF-R75 release was not related to TNF-alpha secretion. These results indicate that the modulation of TNF-R75 is a critical feature of the pathophysiology of Q fever endocarditis.

Up-regulation of tumor necrosis factor alpha mRNA is associated with bovine-leukemia virus (BLV) elimination in the early phase of infection

Protective immune responses were analyzed in eight sheep vaccinated with BLV envelope peptides and experimentally infected with bovine-leukemia virus (BLV). Five of eight peptide-immunized sheep showed a high T-cell proliferative response to the BLV peptides and all of these were protected from the infection. The other three peptide-immunized sheep showed no T-cell proliferative responses to any BLV antigens similar to control sheep, though they also exhibited resistance to BLV challenge. To investigate other mechanisms which suppress BLV expansion in these non-responding sheep, we measured the levels of the cytokine expressions before, and after, BLV challenge using competitive reverse-transcriptase polymerase chain-reaction systems. It was revealed that the expression of tumor necrosis factor alpha (TNFalpha) was higher in BLV-resistant sheep than in BLV-susceptible sheep. Thus, TNFalpha expression rather than specific T-cell activity may play an important role in the protective mechanism against BLV infection, at least during the primary viremia phase.

Detection of Human Serum Tumor Necrosis Factor-α in Healthy Donors, Using a Highly Sensitive Immuno-PCR Assay

Background: Tumor necrosis factor-α (TNFα) is an important mediator of inflammatory and autoimmune diseases. Analysis of its pathophysiologic roles has been difficult because low concentrations of TNFα, including those in healthy controls, cannot be measured by existing methods.

Methods: We developed a sensitive immuno-PCR assay for the detection of TNFα in human serum. The DNA label was generated by PCR amplification using biotinylated primer and was bound with streptavidin to the biotinylated third antibody. TNFα sandwiched by antibodies was detected by amplification of the DNA label using PCR.

Results: The limit of detection of the assay was 0.001 ng/L, an ∼5 × 104-fold improvement compared with a conventional ELISA. The mean serum TNFα concentration (± SD) in healthy donors was 0.021 ± 0.044 ng/L in men (n = 29) and 0.033 ± 0.065 ng/L in women (n = 25).

Conclusion: This method may be useful for analyzing the significance of TNFα concentration in various diseases.

Soluble tumor necrosis factor receptor type II (sTNFRII) in HIV-infected patients: relationship with the plasma level of HIV-1 RNA

The value of soluble receptor for tumor necrosis factor type II (sTNFRII) as a strong and early predictor of HIV disease progression was suggested. Recently it has been reported that sTNFRII may provide an indication of the HIV load. In this work we focused on the relationship between sTNFRII and HIV burden in 95 HIV-1+ patients without AIDS grouped according to the 1993 classification of the CDC as group A, n = 55, and group B, n = 40. Compared with healthy controls, higher values of sTNFRII were obtained in all groups of HIV-1 infected patients (P < 0.001), but we found no inverse correlation between sTNFRII and CD4+ lymphocyte counts in CDC group A and B of the disease, and no correlation with log RNA copy number in patients with CD4 T-cell counts > 499/microl. A correlation was obtained between sTNFRII and the viral load in patients with CD4 T-cell counts ranging from 200 to 499/microl, but only in CDC group B patients (P < 0.01, n = 26). There was no correlation between the variations of sTNFRII and HIV-1 RNA levels in 19 CDC group A and 15 CDC group B clinically stable patients in the course of a short follow up. The plasma level of sTNFRII do not appear as a valuable surrogate marker of the plasma level of HIV-1 RNA in patients. Further investigations are needed to define the mechanism of the raised level of sTNFRII in HIV-1 infected patients.

Protease inhibitor and triple-drug therapy: cellular immune parameters are not restored in pediatric AIDS patients after 6 months of treatment

OBJECTIVE

To assess whether treatment of HIV-positive children by antiretroviral drugs for a 6-month period would improve immune function significantly.

DESIGN AND METHODS

Immunological assessment of 89 HIV-positive children who received protease inhibitor monotherapy for 12-16 weeks as part of phase I/II studies, followed by triple antiretroviral therapy for an additional 12 weeks, was conducted. Immunological parameters were assessed in vitro at four time points (at enrollment, at weeks 2-4, at weeks 12-16, and at weeks 24-28). Assessments included: cytokine production by monocytes, T-cell proliferation to mitogen or recall antigens (including an HIV antigen) and apoptotic cell death. Plasma levels of tumor necrosis factor (TNF)-alpha and soluble TNF receptor (sTNF-R) were also measured, in addition to CD4+ T-lymphocyte counts and viral load. In addition, limited analyses were performed on samples from 17 children after 120 weeks of therapy, including 104 weeks of triple therapy.

RESULTS

At enrollment, the 89 children exhibited severe immune defects. Antiretroviral therapy raised CD4+ T-lymphocyte counts significantly and decreased viral loads. In contrast, the in vitro immune parameters studied were not improved, except for plasma levels of sTNF-RII which decreased in parallel with the decrease in viral load. In addition, there was a trend towards increased skin test reactivity for the ritonavir-treated children. No differences were seen in the immune parameters whether the patients were treated with mono- or triple therapy. Results obtained after 120 weeks of therapy demonstrated that defective interleukin-12 production was not restored by long-term therapy.

CONCLUSIONS

After 6 months of therapy, with the exception of decreased sTNF-RII levels, and a trend towards increased skin test reactivity, restoration of several defective cellular immune responses did not occur despite significantly decreased viral loads and increased CD4+ T-lymphocyte counts.

Severe deficiency of 1,25-dihydroxyvitamin D3 in human immunodeficiency virus infection: association with immunological hyperactivity and only minor changes in calcium homeostasis

The serum level of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D], the biologically most potent metabolite of vitamin D, is tightly regulated within narrow limits in human healthy adults. 1,25-(OH)2D deficiency is rare and is associated with disturbances in calcium and bone metabolism. We have previously reported a marked decrease in serum levels of 1,25-(OH)2D in human immunodeficiency virus (HIV)-infected patients. The present study was designed to further examine the causes and consequences of severe 1,25-(OH)2D deficiency in these patients. The design was a prospective cohort study. Fifty-four HIV-infected patients clinically classified according to the revised criteria from Centers for Disease Control and Prevention and healthy controls were studied. Parameters related to vitamin D and calcium metabolism as well as immunological and nutritional status were determined. Twenty-nine of the patients (54%) had serum levels of 1,25-(OH)2D below the lower reference limit, and 18 of these had undetectable levels. In contrast, HIV-infected patients had normal serum levels of 25-hydroxyvitamin D and vitamin D-binding protein. HIV-infected patients as a group had modestly depressed serum calcium and PTH levels. There were, however, no correlations between these parameters and serum levels of 1,25-(OH)2D. There were no differences in serum calcium or PTH levels or nutritional status when patients with severe 1,25-(OH)2D deficiency were compared to other patients, but patients with undetectable 1,25-(OH)2D had significantly elevated serum phosphate levels. Furthermore, patients with undetectable 1,25-(OH)2D levels were characterized by advanced clinical HIV infection, low CD4+ lymphocyte counts, and high serum levels of tumor necrosis factor-alpha (TNFalpha). We conclude that inadequate 1alpha-hydroxylation of 25-hydroxyvitamin D seems to be the most likely cause of 1,25-(OH)2D deficiency in HIV-infected patients, possibly induced by an inhibitory effect of TNFalpha. The low 1,25-(OH)2D and high TNFalpha levels observed may impair the immune response in HIV-infected patients both independently and in combination and may represent an important feature of the pathogenesis of HIV-related immunodeficiency. Markedly depressed 1,25-(OH)2D serum levels are also present in certain other disorders characterized by immunological hyperactivity. Thus, the findings in the present study may not only represent a previously unrecognized immune-mediated mechanism for induction of 1,25-(OH)2D deficiency in human disease, but may also reflect the importance of adequate serum levels of 1,25-(OH)2D for satisfactory performance of the immune system in man.