Elevated serum levels of soluble tumour necrosis factor receptors (sTNF-R) in patients with HIV infection

Increased TNF-alpha and sTNFR2 levels are associated with high-grade anal squamous intraepithelial lesions in HIV-positive patients with low CD4 level

Compared with HIV-negative individuals, HIV-positive individuals have a higher prevalence of anogenital human papillomavirus (HPV) infection, the causative agent of anogenital cancer. TNF-alpha is a major proinflammatory cytokine. sTNFR2 is the soluble form of one of its receptors and is strongly expressed on stimulated lymphocytes. To further understand the role of TNF-alpha, sTNFR2 and other cytokines in the pathogenesis in HPV-related neoplasia, the profiles of serum cytokines in high-risk patients were analyzed for association with anal lesion status. Patients were categorized into 4 groups based on HIV status (HIV-negative vs. HIV-positive with a CD4+ level <200/uL) and anal lesion status [no lesion, low-grade anal squamous intraepithelial lesion (LSIL) vs. high-grade squamous intraepithelial lesion (HSIL)] based on high resolution anoscopy-guided biopsy. Following adjustment for multiplicity, HIV-negative men with HSIL had lower levels of sTNFR2 than HIV-positive men with low CD4 level and HSIL (p=0.02). HIV-positive men with HSIL had higher levels of TNF-alpha than HIV-negative men with HSIL (p<0.001), as well as HIV-positive men with no lesion or LSIL (p=0.03). The levels of other factors, including IL-1beta, IL-2, IL-4, IL-8, IFN-gamma, GM-CSF, sTNFR1 and DR5, were not significantly different between groups. Although the sample size was small, these results suggest that systemic activation of TNF-alpha/sTNFR2 in HIV-positive patients with a low CD4 level may promote the development of HSIL and possibly anal cancer.

Discordance between peripheral and colonic markers of inflammation during suppressive ART

OBJECTIVE

Persistent systemic inflammation is associated with the inability of some HIV-infected patients to normalize circulating CD4 T-cell levels after years of suppressive antiretroviral therapy. In this study, we sought to understand whether such systemic inflammation is also associated with detectable signs of inflammation in biopsies from the rectosigmoid colon.

DESIGN

Immunologic and virological parameters were studied in the peripheral blood and in rectosigmoid colon biopsies from individuals with viral suppression for at least 2 years and with peripheral CD4 T-cell levels of <350 cells per cubic millimeter (immunologic nonresponders, n = 18) or >500 cells per cubic millimeter (immunologic responders, n = 16).

METHODS

Peripheral blood and rectosigmoid colon biopsies were analyzed by flow cytometry, enzyme-linked immunosorbent assay, and quantitative polymerase chain reaction.

RESULTS

Nonresponders had elevated T-cell activation and inflammatory cytokines in the circulation, but inflammatory gene expression in colon biopsies was not different as compared with responders, and there was little relationship between blood and colon markers of inflammation. Blood inflammatory markers were positively associated with soluble CD14 levels indicative of monocyte activation.

CONCLUSIONS

These findings demonstrate that, in the context of treated HIV disease, it is easier to detect parameters of inflammation (including blood monocyte activation) in the peripheral blood than in isolated rectosigmoid colon biopsies. Accordingly, interventions to block such inflammation in this population might be most conveniently and accurately assessed in blood.

The soluble form of the EIAV receptor encoded by an alternative splicing variant inhibits EIAV infection of target cells

Equine lentivirus receptor 1 (ELR1) has been identified as the sole receptor for equine infectious anemia virus (EIAV) and is a member of the tumor necrosis factor receptor (TNFR) superfamily. In addition to the previously described membrane-associated form of ELR1, two other major alternative splicing variant mRNAs were identified in equine monocyte-derived macrophages (eMDMs). One major spliced species (ELR1-IN) contained an insertion of 153 nt, which resulted in a premature stop codon situated 561 nt upstream of the predicted membrane spanning domain. The other major species (ELR1-DE) has a deletion of 109 nt that causes a shift of the open reading frame and generates a stop codon 312 nt downstream. Because ELR1-DE presumably encodes a peptide of a mere 23 residues, only ELR1-IN was further analyzed. The expression of a soluble form of ELR1 (sELR1) by ELR1-IN was confirmed by Western blot and immunofluorescence analyses. Similar to ELR1, the transcription level of ELR1-IN varied among individual horses and at different time points in the same individuals. The ratio of ELR1-IN mRNA species to ELR1 mRNA was approximately 1∶2.5. Pre-incubation of the recombinant sELR1 with EIAV significantly inhibited EIAV infection in equine macrophages, the primary in vivo target cell of the virus. Fetal equine dermal (FED) cells are susceptible to EIAV in vitro, and the replication of EIAV in FED cells transiently transfected with ELR1-IN was markedly reduced when compared with replication in cells transfected with the empty vector. Finally, the expression levels of both forms of the EIAV receptor were significantly regulated by infection with this virus. Taken together, our data indicate that sELR1 acts as a secreted cellular factor that inhibits EIAV infection in host cells.

High levels of heat shock protein 70 are associated with pro-inflammatory cytokines and may differentiate early- from late-onset preeclampsia

Preeclampsia (PE), a specific syndrome of pregnancy, can be classified into early and late onset, depending on whether clinical manifestations occur before or after 34 weeks' gestation. We determined whether plasma concentrations of Hsp60 and Hsp70 were related to circulating cytokine levels, as well as kidney and liver functions, in early- and late-onset PE. Two hundred and thirty-seven preeclamptic women (95 with early- and 142 with late-onset PE) were evaluated. Plasma levels of Hsp60, Hsp70, and their specific antibodies, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1, IL-10, IL-12, and soluble TNF-α-receptor I (sTNFRI) concentrations, were determined by enzyme-linked immunosorbent assay (ELISA). Concentrations of Hsp70, TNF-α, IL-1β, IL-12, and sTNFRI were significantly elevated in patients with early-onset PE compared with women with late-onset PE; IL-10 levels were significantly lower in the early-onset PE group. Concentrations of urea, uric acid, proteinuria, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and lactate dehydrogenase (LDH) were also significantly higher in early-onset PE. The percentage of infants with intrauterine growth restriction was also significantly higher in women with early-onset PE. There were positive correlations between Hsp70 levels and TNF-α, TNFRI, IL-1β, IL-12, GOT, GPT, LDH, and uric acid concentrations in early-onset PE group. Thus, early-onset PE was associated with greater maternal and fetal impairment. There are differences in pathophysiology between early- and late-onset PE, highlighting by the difference in Hsp70 levels.

Serum concentrations of TNF α and its soluble receptors in patients with adrenal tumors treated by surgery

The peripheral blood levels of TNF α and its soluble receptors were studied in 39 patients with malignant and benign adrenal tumors treated by adrenalectomy. The concentrations of TNF α were significantly elevated in patients with malignant tumors of the adrenal cortex and in patients with Conn’s syndrome compared to control. In patients with non-functioning adenomas and pheochromocytomas, TNF α levels were similar to those detected in the control. In subjects with myelolipomas, the serum concentration of TNF α was lower compared to the control. After adrenalectomy, the levels of TNF α were decreased in patients with malignant tumors and in patients with Conn’s syndrome, nonfunctioniong adenomas and pheochromocytomas compared to the concentration before surgery. The serum concentrations of soluble receptors of TNF α did not differ among different patient groups and compared to the control. After adrenalectomy, the blood concentrations of TNF α R1 and TNF α R2 were decreased in patients with Conn’s syndrome. However, to confirm practicality of the evaluation of TNF α and its soluble receptors in differential diagnosis in patients with adrenal tumors, a larger study group is needed.

Chronicles of a death foretold: dual sequential cell death checkpoints in TNF signaling

The kinase RIP1 wears a coat of many colors during TNF receptor signaling and can regulate both activation of pro-survival NFkB and programmed cell death pathways. In this review, we outline how coating RIP1 with K63-linked ubiquitin chains forms a protective layer that prevents RIP1 from binding apoptotic regulators and serves as an early guard against cell death. Further on, binding of NFkB signaling components to the ubiquitin coat of RIP1 activates long-term pro-survival signaling and forms a more impenetrable suit of armor against cell death. If RIP1 is not decorated with ubiquitin chains it becomes an unstoppable harbinger of bad news: programmed cell death.

Serum cytokine levels in patients with chronic low back pain due to herniated disc: analytical cross-sectional study

CONTEXT AND OBJECTIVE

the role of immune response and proinflammatory cytokines in the pathogenesis of chronic pain has been of growing interest. In order to evaluate whether there is any association between disc herniation and elevated cytokine levels, we measured cytokine levels in patients with chronic low back pain and in healthy subjects.

DESIGN AND SETTING

analytical cross-sectional study at the Pain Clinic of Universidade Federal da Bahia (UFBA).

METHODS

cytokine levels were measured using the enzyme-linked immunosorbent assay (ELISA) technique on 23 patients with low back pain (G1) and on 10 healthy subjects (G2).

RESULTS

the levels of tumor necrosis factor-alpha [TNF-alpha] (G1 = 5.6 ± 2.3 pg/ml; G2 = 1.6 ± 0.5 pg/ml; P = 0.01) and interleukin-6 [IL-6] (G1 = 4.1 ± 3.0 pg/ml; G2 = 0.9 ± 0.4 pg/ml; P = 0.01) were higher in G1. There were no statistically significant differences in relation to interleukin-1 [IL-1] (G1 = 0.5 ± 0.3 pg/ml; G2 = 0.5 ± 0.1 pg/ml; P = 1) or soluble tumor necrosis factor receptor [sTNF-R] (G1 = 572 pg/ml ± 36; G2 = 581 ± 50 pg/ml; P = 0.87).

CONCLUSION

The patients with chronic low back pain due to disc herniation presented higher levels of TNF-alpha and IL-6, but not of IL-1 or sTNF-R.

Dendritic cells infected with vpr-positive human immunodeficiency virus type 1 induce CD8+ T-cell apoptosis via upregulation of tumor necrosis factor alpha

Human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) plays a crucial role in viral replication and pathogenesis by inducing cell cycle arrest, apoptosis, translocation of preintegration complex, potentiation of glucocorticoid action, impairment of dendritic cell (DC) maturation, and T-cell activation. Recent studies involving the direct effects of Vpr on DCs and T cells indicated that HIV-1 containing Vpr selectively impairs phenotypic maturation, cytokine network, and antigen presentation in DCs and dysregulates costimulatory molecules and cytokine production in T cells. Here, we have further investigated the indirect effect of HIV-1 Vpr(+) virus-infected DCs on the bystander CD8(+) T-cell population. Our results indicate that HIV-1 Vpr(+) virus-infected DCs dysregulate CD8(+) T-cell proliferation and induce apoptosis. Vpr-containing virus-infected DC-mediated CD8(+) T-cell killing occurred in part through enhanced tumor necrosis factor alpha production by infected DCs and subsequent induction of death receptor signaling and activation of the caspase 8-dependent pathway in CD8(+) T cells. Collectively, these results provide evidence that Vpr could be one of the important contributors to the host immune escape by HIV-1 through its ability to dysregulate both directly and indirectly the DC biology and T-cell functions.

Neopterin in HIV-1 infection

Neopterin is well established as a reliable marker in HIV-1 infection. Neopterin concentrations measured in urine or serum indicate sensitively the course and progression of the disease as well as efficacy of anti-retroviral therapy. The main trigger for neopterin production is Th1-type cytokine interferon-gamma. During acute HIV-1 infection, enhanced formation of neopterin occurs already at a very early time point, before antibody seroconversion takes place. After this stage, neopterin concentrations in serum and urine closely correlate with virus load in the circulation of HIV-1-infected patients. Data provide evidence for an important role of immune activation and Th1-type cytokine interferon-gamma in the pathogenesis of HIV-1 infection. This review subsumes the importance of neopterin as a marker in HIV-1 infection. Further evidence is increasing, that neopterin derivatives might modulate immune response by interfering with the cellular redox balance, activating redox-sensitive transcription factors, or inducing apoptosis in specific cell types. The possible impact of neopterin derivatives and of other biochemical pathways induced by interferon-gamma such as indoleamine 2,3-dioxygenase in chronic diseases like HIV-1 infection is discussed.

HIV‐1 Nef equips dendritic cells to reduce survival and function of CD8 + T cells: a mechanism of immune evasion

The accessory HIV-1 Nef protein is a crucial determinant for viral replication and pathogenesis. During HIV infection, loss of immune control in the setting of a strong and broad HIV-specific T-lymphocyte response, leads to a lethal outcome through AIDS. Moreover, dysfunction of dendritic cells (DCs) may contribute to the immune suppression associated with AIDS progression. We recently demonstrated that exogenous Nef selectively activates immature DCs manipulating their phenotypical, morphological, and functional developmental program. Here, we tracked whether Nef, targeting DCs, could be involved in the dysregulation of CD8+ T cell responses. We found that Nef inhibits the capacity of DCs to prime alloreactive CD8+ T cell responses down-regulating their proliferation and functional competence. This coincides with the induction of CD8+ T cell apoptosis. Nef oversees apoptotic killing of CD8+ T cells up-regulating TNF-alpha and FasL production by DCs and interfering with the death receptor pathway in CD8+ T cells and thus activating caspase 8. Our findings suggest that Nef may contribute to the immune evasion associated with HIV-1 infection, subverting DC biology. This may help explain the pleiotropic function that Nef plays during infection and makes this protein an attractive target for preventive and therapeutic intervention.

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.

Ex vivo modulation of RANTES and sCD30 by proinflammatory stimuli in HIV-seropositive and -negative individuals

RANTES and sCD30 were measured in ex vivo culture supernatants of unstimulated or stimulated PBMC in order to investigate their potential role as markers of acute immune activation. Patients in an advanced stage of HIV infection (AIDS A) were compared to AIDS patients who were evaluated for pneumonia at the time of blood withdrawal (AIDS B); HIV(+) individuals with nonprogressive infection (LTNP) and healthy donors (N) served as controls. Constitutive levels of RANTES were significantly elevated in AIDS B patients (P 0.0001), whereas spontaneous release of sCD30 was strongly correlated with the presence of both pneumonia (P 0.002) and HIV infection (P 0.004). LPS was a strong inducer of RANTES in all four categories; however, in AIDS B patients a negative and positive correlation between constitutive and induced levels was observed with LPS (P 0.0004) and IFN-gamma (P 0.006), respectively. We clearly showed that IFN-gamma reached a fourfold superinduction of sCD30 release in both HIV-positive and -negative individuals, whereas IL-6-driven production of both sCD30 and RANTES occurred only in healthy donors. Ex vivo RANTES levels may also be monitored as an index of acute immune activation under conditions of chronic activation of the immune system, whereas sCD30 release may be equally indicative of both acute and chronic processes of T cell activation. Proinflammatory stimuli differentially affected RANTES and sCD30 secretion in ex vivo PBMC cultures, suggesting complex pathways in the in vivo regulation of these two molecules.

Human immunodeficiency virus type 1 Nef mediates sustained membrane expression of tumor necrosis factor and the related cytokine LIGHT on activated T cells

Human immunodeficiency virus (HIV) Nef downregulates the antigen recognition molecules major histocompatibility complex class I and CD4. Downregulation of surface CD4 by Nef relies on the ability of this viral protein to redirect the endocytic machinery to CD4. However, by redirecting the endocytic machinery, Nef may affect the internalization rates of other proteins. Here we show that Nef simultaneously enhances surface expression of the effector cytokines tumor necrosis factor (TNF) and LIGHT, leading to enhanced cytokine activity. A dileucine motif in Nef, which is essential for CD4 downregulation and is involved in the recruitment of adapter protein complexes by Nef, was required to increase surface levels of both cytokines. The physiological impact of the Nef-mediated interference with endocytosis was demonstrated by the fact that a TNF-responsive T-cell line chronically infected with HIV produced higher levels of p24 viral protein following expression of a Nef-green fluorescent protein (GFP) fusion protein. This enhancement was dependent on the levels of membrane-bound TNF, since it was abrogated by a recombinant soluble TNF receptor. Expression of Nef-GFP in human 293T cells reduced the endocytosis of LIGHT, whereas at the same time CD4 internalization was accelerated. Taken together, these results suggest that in infected cells Nef interferes with the internalization of these effector cytokines. By increasing TNF expression, Nef could accelerate disease progression in infected individuals. These findings may help explain the pleiotropic functions that Nef plays during infection and disease.

Soluble tumor necrosis factor receptor type I enhances tumor development and persistence in vivo

Secretion of human soluble tumor necrosis factor receptor type I (sTNFRI) by the mouse fibrosarcoma cell line, L929, previously has been demonstrated to confer resistance to in vitro lysis by TNF and to LAK- and CTL-mediated cytolysis. These findings suggest that, in vivo, sTNFRI contributes to tumor survival by inhibiting these immunologic mechanisms. To evaluate this hypothesis, we compared the growth of sTNFRI-secreting L929 cells with that of the unmodified parental fibrosarcoma in an in vivo mouse transplantation model. Secretion of sTNFRI by L929 cells markedly enhanced their tumorigenicity and persistence in syngeneic recipients. This benefit was abrogated by sTNFRI-neutralizing antibodies induced by immunization prior to tumor challenge. These data demonstrate that sTNFRI directly influences tumor formation and persistence in vivo and suggest the selective removal and/or inactivation of sTNFRI as a promising new avenue for cancer immunotherapy.

Soluble tumor necrosis factor alpha receptors (sTNF-Rs) in HIV-1-infected intravenous drug users: change in circulating sTNF-R type II level and survival for AIDS patients

This study in intravenous drug users (IVDUs) investigated differences in serum soluble tumor necrosis factor types I and II (sTNFR-I and II) concentrations in HIV-1-infected IVDUs and controls. This study also investigated whether changes of sTNFRs concentration affect the risk of death among patients with AIDS. A cross-sectional study of 54 subjects with AIDS, 47 HIV-seropositive IVDUs, 47 HIV-seronegative IVDUs, and 21 healthy subjects showed that sTNFRs concentration increases from healthy controls to AIDS patients through HIV-seronegative and HIV-seropositive subjects (p < 0.01). sTNFR-I concentration, however, was shown to be similar in HIV-seronegative IVDUs and healthy controls. In the longitudinal study, serum concentration of sTNFRs was determined near AIDS diagnosis in 21 IVDUs and 1 year later (start for the survival study). Cox proportional hazards regression was performed to assess the prognostic value of percent change of sTNFR level alone and in combination with T lymphocyte subsets, HIV-p24 antigenemia and opportunistic infections for death within 240 days. Uni- and multivariate Cox modelling for dichotomised variables according to its median showed an increase of sTNFR-II by at least 30% to be single significant predictor of death: crude relative risk 3.69, p = 0.03; adjusted relative risk 5.67, p = 0.02. Mean survival was 126 days in 11 patients whose sTNFR-II level increased by at least 30%, and 176 days in 10 patients with less change in sTNFR-II (p = 0.02).

CONCLUSIONS

sTNFRs concentration is higher in IVDUs than in healthy controls and is highest in AIDS patients. Survival of patients with AIDS is associated with variation in the concentration of sTNFR-II.

Tumor necrosis factor (TNF)-alpha and TNF receptors in viral pathogenesis

Tumor necrosis factor-alpha (TNF-alpha) and TNF receptors (TNFR) are members of the growing TNF ligand and receptor families that are involved in immune regulation. The present report will focus on the role of the prototypic ligand TNF and its two receptors, TNFR1 and TNFR2, in viral pathogenesis. Although TNF was reported years ago to modulate viral infections, recent findings on the molecular pathways involved in TNFR signaling have allowed a better understanding of the molecular interactions between cellular and viral factors within the infected cell. The interactions of viral proteins with intracellular components downstream of the TNFR have highlighted at the molecular level how viruses can manipulate the cellular machinery to escape the immune response and to favor the spread of the infection. We will review here the role of TNF and TNFR in immune response and the role of TNF and TNFR signaling in viral pathogenesis.

Regulation of tumour necrosis factor (TNF) induced apoptosis by soluble TNF receptors in Helicobacter pylori infection

BACKGROUND

Tumour necrosis factor (TNF) is a predominant cytokine produced in the gastric mucosa of patients with Helicobacter pylori infection. TNF induces apoptosis in a variety of cells. The soluble TNF receptors (sTNF-Rs) can be divided into sTNF-RI and sTNF-RII, both of which inhibit TNF activity. However, their precise mechanisms remain unclear.

AIM

To investigate the role of sTNF-Rs in H pylori infection.

METHODS

In 40 patients, production of TNF and sTNF-Rs in gastric mucosa was measured using biopsy specimens. In addition, in gastric epithelial cells, sTNF-R release in response to TNF and the protective effect of sTNF-Rs against the cytotoxic and apoptotic activities of TNF were examined.

RESULTS

TNF and sTNF-R expression was significantly higher in H pylori positive than H pylori negative patients. TNF dose-dependently induced sTNF-RI release from gastric epithelial cells. sTNF-RII was also released from the cells. TNF decreased cell viability, but the effect was very small. A combination of anti-sTNF-RI and anti-sTNF-RII monoclonal antibodies significantly increased TNF induced cytotoxicity and apoptosis of gastric epithelial cells.

CONCLUSIONS

These results show that sTNF-Rs are actively produced in H pylori infected gastric mucosa. sTNF-Rs appear to protect gastric epithelial cells from TNF induced apoptosis in H pylori infection.

Soluble tumour necrosis factor (TNF)-receptor levels in serum as markers of anti-viral host reactivity

The role of soluble receptors for TNF-alpha (sTNF-Rs) as markers of virus-induced host responses was studied by the use of murine model infections. A marked elevation in serum levels of sTNF-R75, but not sTNF-R55, was found 1 day after infection with vesicular stomatitis virus (VSV). In mice infected with lymphocytic choriomeningitis virus (LCMV), an early increase was also revealed, but peak levels of sTNF-R75 were observed later temporally related to maximal T cell-mediated anti-viral activity. Analysing different well characterized knockout mice, it was found that elevated release of sTNF-R75 into serum early after VSV infection was independent of T cells, whereas interferon (IFN)-alpha/beta seemed to be a major mediator. In contrast, increased release of sTNF-R75 into serum 8 days post-LCMV infection was mediated via T cells but independently of both CD40 ligand and IFN-gamma. A simple correlation between release of sTNF-Rs in vivo and macrophage activation in vitro was not present. These findings indicate that sTNF-R75 is indeed a sensitive marker of both innate and specific cell-mediated host reactivity during viral infection, but it is not correlated to a single immunological parameter.

The role of therapeutic apheresis in the treatment of cancer: a review

Immunosuppression is a hallmark of advanced malignancies in man. Over the past 40 years, many investigators have identified soluble immunosuppressive factors in blood, serum, ascitic fluid, and pleural fluid from cancers in man and other species. Suppressive factors have also been identified that are produced by tumors. The description of immunosuppressive factors in the blood of vertebrates who either have cancer or who are pregnant is significant, for only in pregnancy and cancer does a seemingly normal immune system tolerate immunogenic neoantigen. Tumor necrosis factors (TNFs) are known to be pleiotropic cytotoxic cytokines that are produced by macrophages and lymphocytes. These cells are thought to be suppressed in patients who have cancer or who are pregnant. Recently, elevated blood levels of soluble tumor necrosis factor receptors (sTNFRs) have been reported in the blood in a variety of cancers and pregnancy. In 1990, after our initial publication of the discovery of sTNFRs in the serum and low molecular weight ultrafiltrates of serum from a variety of cancer patients, others confirmed significant elevations of sTNFRs in cancer patients. This elevation was found to correlate with a poor prognosis. The biologic activity of proinflammatory cytokines as well as the suppressive role of their shed receptors is herein reviewed. Work with cancer patients using ultrapheresis to reduce these suppressive molecules by the authors and others is reviewed. Several recommendations are made for future directions.

The intron 5-inserted form of rat erythropoietin receptor is expressed as a membrane-bound form

The cDNA encoding an intron 5-inserted form of the erythropoietin receptor (I5Epo-R) has been cloned from rat. DNA sequence analysis reveals that the insertion of intron 5, which consists of 79 bp, causes a shift in reading frame and results in termination in the region of exon 7. The deduced amino acid sequence is composed of 316 amino acid residues, which is a molecular weight of 34220. To study the function of rat I5Epo-R, we established a Chinese hamster ovary cell line expressing rat I5Epo-R. Western blot analysis and binding studies with 125I-recombinant human erythropoietin showed that the transfected cells expressed rat I5Epo-R with a molecular size of 36 kDa as a membrane-bound form, but not as a soluble form, and had a single class of binding sites with a Kd of 700 pM.

Increased levels of soluble tumour necrosis factor receptor-I (P55) and decreased IgG1 reactivities in HIV-1 patients with cytomegalovirus disease

The purpose of the study was to investigate potential associations between tumour necrosis factor (TNF), soluble TNF receptors (sTNF-Rs), immunoglobulin (Ig)G subclasses and development of cytomegalovirus (CMV) disease amongst human immunodeficiency virus (HIV)-1 patients. We enrolled HIV-1 patients with CD4 counts less than 100/microl in a prospective study and followed them over 1 year for development of CMV disease. Concentrations of TNF, sTNF-RI, sTNF-RII and IgG subclass reactivities were measured by ELISA; levels of CMV pp65 antigenaemia were determined as numbers of pp65 expressing cells/100,000 cells and were measured by staining of leucocytes; and HIV-1 RNA loads were measured by polymerase chain reaction (PCR). Eighteen patients studied with CMV disease had higher levels of sTNF-RI than 18 similar patients without CMV disease. Concentrations of sTNF-RI correlated with levels of CMV antigenaemia in blood samples collected before the development of CMV disease. Patients with CMV disease had lower levels of IgG1 reactivities to CMV than patients without CMV disease. We conclude that increased levels of sTNF-RI and decreased IgG1 reactivities are associated with an increased risk of development of CMV disease among HIV-1 patients.

9-Nitrocamptothecin inhibits tumor recrosis factor-mediated activation of human immunodeficiency virus type 1 and enhances apoptosis in a latently infected T cell clone

Transition from latency to active replication is a crucial stage for the process of human immunodeficiency virus type 1 (HIV-1) infection and life cycle. HIV-1 replication in latently infected cells can be strongly induced by the cytokine tumor necrosis factor alpha (TNF-alpha) and the proliferation-arresting chemical sodium butyrate (NaB). We have investigated the ability of the drug 9-nitrocamptothecin (9NC), a potent cellular topoisomerase I (topo I) inhibitor currently in clinical trials in cancer patients, to regulate HIV-1 replication in latently infected lymphocytic ACH-2 cells on reactivation with either TNF-alpha or NaB. Treatment of ACH-2 cells with 9NC alone resulted in increased levels of viral transcripts, while there was a slight reduction or no change in the levels of host cell transcripts. However, pretreatment of ACH-2 cells with 9NC inhibited TNF-alpha-induced extracellular HIV-1 p24 levels up to approximately 95% and nearly 80% of the cell-associated viral RNAs. The quantitative decrease in viral products was concomitant with a decrease in cellular gene expression and induction of apoptosis in the host cells. 9NC blocked the infected cells at the boundary of the S and G2 phases, resulting in an accelerated apoptosis that was further enhanced with TNF-alpha treatment. Similar results were observed following concurrent exposure to TNF-alpha and 9NC, but 9NC failed to inhibit upregulation of HIV-1 mRNA in ACH-2 cells exposed to TNF-alpha before 9NC treatment. Further, 9NC had no inhibitory effect on NaB-induced apoptosis and upregulation of HIV-1 mRNA expression regardless of whether 9NC and NaB were used concurrently or in various treatment sequences. In uninfected lymphocytic CEM cells derived from a common parental cell line, a slight downregulation of cellular gene expression was detected along with low-level apoptosis. These results demonstrate that 9NC impairs TNF-alpha-induced, but not NaB-induced, HIV-1 activation, and suggest a means of inhibiting active HIV-1 viremia arising as a result of elevated TNF-alpha levels.

A randomized double-blind controlled study of 6 months of oral nutritional supplementation with arginine and omega-3 fatty acids in HIV-infected patients. Swiss HIV Cohort Study

OBJECTIVE

To evaluate the effects of an oral nutritional supplement enriched with two potentially immunostimulant compounds (arginine and omega-3 fatty acids) on the changes in food intake, body composition, immune parameters and viraemia in HIV-infected outpatients.

DESIGN

Six-month prospective randomized double-blind controlled study.

SETTING

University hospital outpatient nutrition clinic.

PATIENTS

Sixty-four HIV-infected outpatients with CD4 lymphocyte count > or = 10O x 10(6)/l.

INTERVENTION

All patients received a daily oral nutritional supplement (606 kcal supplemented with vitamins, trace elements and minerals). In addition, half of the patients were randomized to receive 7.4 g arginine plus 1.7 g omega-3 fatty acids.

MAIN OUTCOME MEASURES

Disease progression measured by AIDS-defining events, CD4 and CD8 lymphocyte counts, viraemia, tumour necrosis factor soluble receptors, nutritional status determined by anthropometric, bioelectrical impedance and dietetic assessment.

RESULTS

Fifty-five patients completed the protocol. Compliance with and tolerance of oral nutritional supplement during the 6-month period was excellent. In both groups of patients the following were found: total energy intake was transiently increased and then returned to baseline level; nitrogen/energy intake ratio was increased throughout the study; gain of body weight and fat mass were approximately 2 and 1kg, respectively, over 6 months, and were similar in both groups. In addition, CD4 and CD8 lymphocyte counts, viraemia, tumour necrosis factor soluble receptors remained statistically unchanged and were similar in both groups.

CONCLUSIONS

Enrichment of an oral nutritive supplement with arginine and omega-3 fatty acids did not improve immunological parameters. However, body weight increased in both groups.

55- and 75-kilodalton tumor necrosis factor receptors mediate distinct actions in regard to human immunodeficiency virus type 1 replication in primary human macrophages

We report in this study that repeated tumor necrosis factor alpha (TNF-alpha) pretreatment, starting before and continued after infection by human immunodeficiency virus type 1 (HIV-1), inhibits replication of the monocytotropic Ada strain in primary tissue culture-differentiated macrophages (TCDM), as assessed by sixfold lower levels of reverse transcriptase (RT) activity than that in untreated cells and absence of syncytium formation in TCDM cultures. In order to determine the pathways involved in inhibition of HIV-1 replication in primary TCDM pretreated with TNF-alpha, we tested TNF-alpha mutants T55 and T75, which recognize either the 55-kDa (TNF-R1) or the 75-kDa (TNF-R2) TNF receptor, respectively. Pretreatment of TCDM with the T75 mutant decreased the RT activity compared with that in untreated infected control cells fivefold and almost totally inhibited syncytium formation. In contrast, when TCDM were pretreated with the T55 mutant alone, syncytia were observed and RT activity was decreased about one-half. These results suggest that the inhibition of HIV-1 replication in TCDM pretreated with TNF-alpha might be mediated mainly through the 75-kDa TNF receptor (TNF-R2) rather than through the 55-kDa receptor (TNF-R1). Inhibition of HIV-1 replication in TCDM was observed with both T75 mutant pretreatment and posttreatment, starting at 1 h or 3 days after infection, whereas posttreatment with the T55 mutant, but not pretreatment, stimulated HIV-1 growth in primary TCDM. Both pre- and posttreatment with TNF-alpha inhibited HIV-1 replication in primary TCDM. The stimulation of HIV-1 replication by TNF-alpha in a chronically infected promonocytic cell line, U1, which contains two copies of integrated provirus, was mediated through the 55-kDa TNF-R1 alone and not through the 75-kDa TNF-R2. These results demonstrate that the 55-kDa TNF-R1 is involved in postintegration stimulation of HIV-1 while the 75-kDa TNF-R2 is involved in the inhibition of an early step of the viral life cycle in primary human TCDM.

Development of a novel TNF alpha ligand-receptor binding assay for screening NATCHEM Libraries

The TNF alpha receptor is a major therapeutic target since over production of TNF alpha plays a key role in the development of septic shock following bacterial infection and has been implicated in the pathogenesis of many inflammatory disorders such as rheumatoid arthritis. To screen our NATCHEM Libraries for novel natural product inhibitors of this target we have developed a sensitive immobilised TNF alpha receptor binding assay based on a commercially available recombinant soluble TNF alpha receptor (p55) and [125I]-TNF alpha.

T helper cell activation and human retroviral pathogenesis

T helper (Th) cells are of central importance in regulating many critical immune effector mechanisms. The profile of cytokines produced by Th cells correlates with the type of effector cells induced during the immune response to foreign antigen. Th1 cells induce the cell-mediated immune response, while Th2 cells drive antibody production. Th cells are the preferential targets of human retroviruses. Infections with human T-cell leukemia virus (HTLV) or human immunodeficiency virus (HIV) result in the expansion of Th cells by the action of HTLV (adult T-cell leukemia) or the progressive loss of T cells by the action of HIV (AIDS). Both retrovirus infections impart a high-level activation state in the host immune cells as well as systemically. However, diverging responses to this activation state have contrasting effects on the Th-cell population. In HIV infection, Th-cell loss has been attributed to several mechanisms, including a selective elimination of cells by apoptosis. The induction of apoptosis in HIV infection is complex, with many different pathways able to induce cell death. In contrast, infection of Th cells with HTLV-1 affords the cell a protective advantage against apoptosis. This advantage may allow the cell to escape immune surveillance, providing the opportunity for the development of Th-cell cancer. In this review, we will discuss the impact of Th-cell activation and general immune activation on human retrovirus expression with a focus upon Th-cell function and the progression to disease.

Plasma levels of sTNFR p75 and IL-8 in patients with HIV-1 infection

We determined the degree of activation of the TNF alpha system and the levels of IL-8 in HIV-1 infection. TNF alpha is one of the most potent agents for the induction of IL-8. TNF alpha may be cleared rapidly from the circulation, however soluble tumor necrosis factor receptor (sTNFR) p75 which is more stable may reflect the degree of activation of the TNF alpha system. We measured concentrations of sTNFR p75 and IL-8 with immunoassays in the plasma of 99 HIV-1-infected patients at different stages of disease (Centers for Disease Control classification) and in 20 healthy control subjects. Plasma levels of sTNFR p75 were elevated in most of the asymptomatic seropositive patients without CD4+ T cell depletion (Stage IIA) and in most of patients of all clinical groups compared with controls. However, in the majority of those patients plasma levels of IL-8 were not higher than those of controls. Our results suggest that sTNFR p75 levels but not IL-8 levels in circulating blood are high in the course of HIV-1 infection.

High levels of sTNFR p75 and TNF alpha in dengue-infected patients

Soluble forms of the two molecular species of the cell surface TNF receptors (sTNFR p55 and sTNFR p75) can reduce the activity of TNF alpha but they may also enhance its function by stabilizing the active TNF alpha oligomer. Considering the pathophysiological importance of sTNFR p75 for the regulation of the bioavailability of TNF alpha in the body, we determined the serum levels of sTNFR p75 and TNF alpha in 45 children and 28 adults with laboratory-confirmed dengue infection by using immunoassays. The serum samples were obtained from day 1 to day 15 after the onset of the disease during the 1989-1990 outbreak of dengue-3 in Tahiti, French Polynesia. The patients were clinically classified as having dengue hemorrhagic fever (DHF) and graded according to the criteria of the World Health Organization (WHO) into four grades from less severe (grade I) to severe (grade IV). The sera of both children and adult patients of all severity grades contained higher levels of sTNFR p75 than the sera of control subjects. Although high levels of TNF alpha were also detected in children and adults among grade I, II, III and IV patients, we found no correlation between sTNFR p75 and TNF alpha. We observed in adults a moderate elevation of sTNFR p75 and TNF alpha in sera compared with that observed in children. The raised levels of immunoreactive sTNFR p75 and TNF alpha in all clinical groups of dengue-infected patients strongly indicate activation of the TNF alpha system during dengue infection. The balance between sTNFR p75 and TNF alpha may be altered in dengue infection. Further investigations are needed to understand the role of sTNFR p75 and TNF alpha in the pathogenesis of DHF and to improve the management of dengue infection.

TNF-receptors on human peritoneal mesothelial cells: regulation of receptor levels and shedding by IL-1 alpha and TNF alpha

Human peritoneal mesothelial cells (HPMC) respond to tumor necrosis factor alpha (TNF alpha) by releasing various cytokines that may activate the endothelium and induce recruitment of leukocytes during peristonitis. We characterized the receptors for TNF on HPMC to elucidate their functions in peritonitis. Scatchard analysis determined the presence of 70 x 10(3) TNF receptors/cell with a kDa of 0.44 nM. TNF receptor 1 (TNF-R1, p55) and TNF-R2 (p75) mRNA were demonstrated by reverse-transcriptase-PCR (RT-PCR). TNF-R1 protein was solely detected by flow cytometry (FCM). Interleukin-1 alpha (IL-1 alpha) induced down-regulation of TNF-R1. This was concomitant with accumulation of soluble TNF-R1 (sTNF-R1) detected by specific ELISA. LPS had a lower TNF-R1-shedding activity while TNF alpha did not induce shedding. The IL-1-induced-sTNF-R1-shedding was suppressed by the protein-kinase-A (PKA) inhibitor, H-8, or by H-7, the inhibitor of both PKC and PKA, but not by the specific PKC inhibitor GF. These experiments suggest a role for PKA in the IL-1-shedding signal. No change in TNF-R1 mRNA levels was observed after IL-1 alpha or TNF alpha stimulation while TNF-R2 (p75) mRNA basal levels transiently increased three to fivefold, reaching a peak after four hours followed by an accumulation of sTNF-R2 in the supernatant. Our data suggest that the main receptor expressed on HPMC is TNF-R1. Down-regulation and shedding of TNF-R1 induced by IL-1, and the transient expression of TNF-R2 induced by IL-1 and TNF, may regulate the responses to TNF by HPMC. These results may be important in understanding the inflammatory process of peritonitis were TNF plays a major role.

Increased serum levels of soluble tumor necrosis factor receptors (sTNF-Rs) in children and adolescents with vertically and horizontally transmitted HIV infection

Two different receptors exist for tumor necrosis factor-alpha (TNF-alpha), designated as p55 (TNF-RI) and p75 (TNF-RII). Soluble (= s) forms of TNF-Rs are secreted after proteolytic cleavage and block the effects of TNF-alpha. sTNF-RI, sTNF-RII and the soluble interleukin 2 receptor (sIL-2R) were determined by ELISA in serum samples of HIV-infected children and adolescents. Twelve children with vertical HIV infection (mean age +/- SD, 5.9 +/- 3.8 years) and 17 horizontally infected patients (16.1 +/- 7.3 years) were classified according to the revised CDC criteria. Twenty healthy control persons (6.4 +/- 5.8 years) showed the following receptor concentrations (median): sTNF-RI 888 pg/ml, sTNF-RII 1,741 pg/ml, sIL-2R 94 pM. Compared to controls, horizontally HIV-infected patients had significantly (Mann-Whitney U test) higher levels for sTNF-RI (median 1,192 pg/ml), sTNF-RII (3,481 pg/ml) and sIL-2R (128 pM). For vertically infected children only sTNF-RII (2,944 pg/ml) was significantly elevated compared to controls. There were no differences in soluble receptor levels between vertical or horizontal transmission. Surprisingly, no significant differences for sTNF-RI, sTNF-RII and sIL-2R occurred when 19 patients in stage CDC I were compared to ten patients in stages II or III. The clearly elevated sTNF-RII levels in patients with horizontal and vertical HIV infection indicate the activation of the monocyte/macrophage system in both groups.

Immunotherapy for sepsis

In recent years, an improved understanding of the pathogenesis of sepsis, along with an explosion in the biotechnology industry, has led to the development of a variety of agents with potential to interdict the pathogenesis of sepsis at many points. This article reviews the rationale, efficacy and shortcomings of these immunotherapeutic agents as they relate to the management of human septic shock.

High plasma level of soluble tumor necrosis factor receptor type II (sTNFRII) in asymptomatic HIV-1-infected patients

Plasma concentrations of soluble receptors for tumor necrosis factor type II (sTNFRII) and CD4+ lymphocyte counts were determined in patients with HIV-1 infection grouped according to the 1993 classification of the CDC. Compared with healthy controls (mean +/- SD = 2.83 +/- 0.70 ng/ml; n = 20), higher values of sTNFRII were obtained in most of patients of all groups of HIV-1-infected patients. The levels of sTNFRII were 5.29 +/- 1.75 ng/ml (n = 23) for stage A1 patients, 5.27 +/- 2.25 ng/ml (n = 37) for stage A2 patients, 6.03 +/- 1.9 ng/ml (n = 14) for stage A3 patients, 7.41 +/- 3.25 ng/ml (n = 21) for stage B and stage C patients. Intra-individual variance in sTNFRII levels in eight clinically stable patients with HIV-1 infection was observed in the course of a short-time follow-up. The increase of sTNFRII plasma levels in five out of ten patients was shown at time lapses of 3 years. In contrast to previous reports no inverse correlation between sTNFRII and CD4+ lymphocyte counts was found in all stages of disease. The increased level of sTNFRII in circulating blood might reflect the activation of the TNF alpha system. These results support an activation of this system occurring early in the course of HIV infection.

Immune-based therapies for treatment of HIV infection

OBJECTIVE

To review the in vitro, animal, and clinical data on immune-based therapies for treatment of HIV infection.

DATA SOURCES

An extensive MEDLINE search was performed for interleukins, interferons, immunotoxins, tumor necrosis factor (TNF)-directed agents, vaccines, and gene therapy.

STUDY SELECTION

In vitro experiments with immune-based agents in cell lines infected with HIV were included. In addition, all human studies and case reports that used these agents in patients infected with HIV were selected. Additional literature included abstracts from international meetings on HIV and AIDS.

DATA EXTRACTION

Data regarding activity, efficacy, and toxicity were extracted from in vitro and in vivo studies. When conflicting data were observed, both viewpoints were stated to give an unbiased analysis. Because HIV research involves multiple social, ethical, and scientific issues, perspectives on these problems were addressed, where appropriate.

DATA SYNTHESIS

Current antiretroviral therapy is limited to short-term responses and has minimal effect on overall survival. Because the human immune response to HIV infection is effective at keeping the virus suppressed for a number of years, a focus of HIV research has been to examine immune-based therapies for treatment of HIV infection that attempt to augment enhance, or boost the patient's immune system. Interleukins, interferons, immunotoxins, TNF-directed therapies, vaccines, and gene therapy have been studied in patients infected with HIV. Properties shared among these therapeutic modalities include adverse effect profiles, response rates dependent on baseline immunocompetence, the potential to activate viral replication, the need for supportive care, and sensitive laboratory tests required for monitoring.

CONCLUSIONS

Immune-based agents represent a new approach to the treatment of HIV infection. Whereas antiretrovirals only inhibit viral replication, these agents are designed to enhance the immune system of the patient. Future attempts to manage HIV infection may combine standard nucleoside analogs with immune-based therapies.

Increased soluble tumor necrosis factor receptor expression and release by human immunodeficiency virus type 1 infection

High levels of circulating soluble tumor necrosis factor receptors (sTNF-R) are associated with HIV-1 infection and disease. To understand better this association, we have investigated p55 and p75 TNF-R expression on peripheral blood mononuclear cell (PBMC) subsets and in the promonocytic cell line U937, with or without HIV infection. Using flow cytometry and monoclonal antibodies both to sTNF-R and to PBMC subsets, TNF-R were found to be expressed mostly by monocytes and in decreasing amounts and intensity in the following order: CD14+ cells > CD8+ cells > CD4+ cells. Expression of TNF-R was higher on cells obtained from HIV-infected than from noninfected subjects, and expression of p75 sTNF-R was much higher than that of p55 sTNF-R. Studying the U937 cells revealed that over 80% of the cells expressed both sTNF-R, but with greater fluorescence intensity in the HIV-1 chronically infected cells (U-937-IIIB). Treatment of the cells with PMA caused an accelerated release into the medium of both sTNF-R, with a sharp decline in their cell surface expression. Basal levels of mRNA transcripts for p75 TNF-R were higher in the U-937-IIIB cells than in the uninfected cells, but p55 TNF-R mRNA was expressed only in the HIV-1-infected cells. These findings show that HIV-1 infection is accompanied by predominant elevation of p75 TNF-R surface expression on monocytes and CD8+ lymphocytes, and results in both increased message and expression of these receptors in monocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Biologic control of the tumor necrosis factor and interleukin-1 signaling cascade

It is clear that activation of the proinflammatory cytokine cascade is both the cause and the consequence of renal injury. Recently, it has been appreciated that a rich network of signaling pathways contributes to modulation of tumor necrosis factor-alpha (TNF) and interleukin-1 (IL-1) bioactivity, both in vitro and in vivo. Insight into the checks and balances that intervene or temper endogenous cytokine effector mechanisms has arisen from an explosion of new information on the cell biology of proinflammatory cytokines. Novel mechanisms of cytokine regulation are currently being described and hold promise for therapeutic potential: soluble cytokine receptors, endogenous receptor antagonists, and anti-inflammatory cytokines such as IL-4, IL-10, and IL-13.

Enhancement by TNF-alpha of reactivation and replication of latent herpes simplex virus from trigeminal ganglia of mice

The influence of tumor-necrosis-factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukine-1 (IL-1) and IL-3 on the in vitro reactivation frequency and replication rate of trigeminal ganglia of mice latently infected with herpes simplex virus (HSV) strain KOS was studied. It could be demonstrated that TNF-alpha and possibility GM-CSF, but not IL-1 and IL-3, enhanced the reactivation frequency and replication of HSV. Interferon alpha/beta (IFN alpha/beta) prevented reactivation and replication.

Evaluation of soluble IL-6 receptor concentration in serum and epithelial lining fluid from patients with interstitial lung diseases

We measured soluble IL-6 receptor (sIL-6R) levels in serum and bronchoalveolar lavage fluids (BALF) from patients with interstitial pneumonia of unknown etiology (IP) (n = 17), sarcoidosis (n = 8) and normal control subjects (n = 10), to investigate its role in pulmonary diseases. Soluble IL-6R was determined by an ELISA. The volume of epithelial lining fluid (ELF) in BALF was estimated using an urea method. We found that levels of sIL-6R in serum, BALF, and ELF from patients with IP or sarcoidosis were significantly higher than those from normal subjects. Furthermore, levels of sIL-6R in BALF or ELF were significantly correlated with those of albumin, indicating that sIL-6R, together with albumin, may enter ELF as a result of the increased permeability caused by pulmonary inflammation. Thus most of the sIL-6R in ELF would be from serum, and relatively small amounts of it might be produced locally. However, sIL-6R levels in ELF, but neither serum nor BALF, were significantly correlated with levels of C-reactive protein in patients with IP. These results suggest that both systemic and local production of sIL-6R are increased, and raised sIL-6R is involved in the modulation of systemic and local inflammatory responses in patients with IP and sarcoidosis.

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.

Tumor necrosis factor (TNF)-dependent shedding of the p55 TNF receptor in a baboon model of bacteremia

We have tested the hypothesis that the tumor necrosis factor (TNF) plays a significant role in vivo in TNF receptor shedding and studied the release of TNF-binding protein 1 (TNF-BP1), the soluble fragment of the 55- to 60-kDa TNF alpha (TNF) receptor, in a baboon model of Escherichia coli bacteremia, using three different doses of bacteria in acute infection (8 h) experiments (n [animals] = 11) and a single dose in a subchronic infection (72 h) experiment. In the subchronic infection study, one group of animals (n = 6) was pretreated with a neutralizing murine monoclonal antibody to TNF (CB0006). Concentrations of TNF and TNF-BP1 in plasma were determined in specific, monoclonal antibody-based immunoassays. Untreated animals (n = 6) showed undetectable TNF concentrations (< 10 pg/ml at baseline), whereas TNF-BP1 levels in plasma were in the range of 2 ng/ml, similar to concentrations observed in humans. Infusion of bacteria resulted in a rapid, dose-dependent increase in plasma TNF concentrations that reached a maximal level after 2 h and returned to baseline within 6 h. TNF-BP1 concentrations also showed a dose-dependent increase to peak concentrations three- to fivefold above baseline within 2 h but, in contrast to TNF levels, remained significantly elevated for up to 48 h. In animals pretreated with antibody CB0006, circulating TNF was completely neutralized, and TNF-BP1 was significantly reduced. We conclude that TNF-BP1 is released in bacteremia and that release in vivo is partially dependent on the presence of TNF.

Determination of human tumour necrosis factor-alpha (TNF-alpha) by time-resolved immunofluorometric assay

We have developed a 'sandwich'-type time-resolved immunofluorometric assay (IFMA) for tumour necrosis factor alpha (TNF-alpha) using two monoclonal antibodies (mAb) and the streptavidin/biotin (SAB) system. In this simple and fast streptavidin/biotin IFMA (SAB-IFMA) we used streptavidin coated wells to which we added biotinylated mAb for 3 h. After washing, the serum sample was added and incubated for 2 h followed by washing. Another monoclonal europium-labelled tracer antibody was added and incubated for 1 h, the wells were washed and the fluorescence of Eu measured. We tested various assay conditions in order to optimize the assay for sensitivity and measuring range. Purification of the labelled antibody by hydrophobic interaction chromatography was found to be essential to improve sensitivity. With a sample volume of 50 microliters the detection limit was 6 ng l-1 and the analytical range large, i.e. 10,000-fold. The median concentration in serum from healthy subjects was 12 ng l-1 and the reference range < 39 ng l-1. The mean analytical recovery in plasma was 76% and in serum 83%. Separation of serum by gel filtration and assay of TNF-alpha in fractions showed that the assay also measured the high molecular weight (MW) form of TNF-alpha, apparently corresponding to its complex with soluble receptors. Advantages of our SAB-IFMA were high sensitivity and low consumption of mAb. The assay performance of the SAB-IFMA was compared to two commercially available enzyme immunoassays also using the SAB system.

The nutrition implications of cardiac cachexia

Weight loss is a frequent sequela in patients with congestive heart failure and is commonly referred to as cardiac cachexia. This weight loss is unlike that seen in simple starvation because it preferentially involves the depletion of lean body mass. In addition, the presence of cardiac cachexia can have profound clinical implications for patients in terms of complications, clinical outcome, and overall cost. The mechanism for the alterations in body composition is multifactorial, but a major cause may be the cytokine-mediated host response to the underlying disease. This article reviews the syndrome of cardiac cachexia in light of recent evidence regarding the role of cytokines, as well as potential therapies.

Induction of soluble tumor necrosis factor receptor (sTNF-R75) release by HIV adsorption on cultured human monocytes

Soluble tumor necrosis factor (TNF) receptors were recently detected in the circulation of patients with early HIV-induced disease, at significantly higher levels than in control subjects. They were proposed as markers of disease progression and of the degree of immunodeficiency. We report that adsorption of heat-inactivated HIV-1 LAI to isolated human monocytes triggers the release of both TNF-alpha and its natural specific inhibitor, the soluble TNF receptor (sTNF-R)75, but not that of sTNF-R55. Only limited inhibition of sTNF-R release was obtained in the presence of a fully neutralizing anti-TNF-alpha monoclonal antibody, suggesting that stimulation by TNF-alpha was only partially responsible for sTNF-R release. HIV-1 LAI induced a higher sTNF-R/TNF ratio than lipopolysaccharide, a well-known monocyte activator. Monocytes thus represent a cellular source of sTNF-R that can be detected in the circulation of HIV-infected patients from seroconversion onwards. The release of sTNF-R could be of great significance in the control of HIV infection via the cytokine network and especially TNF-alpha.

Tumor necrosis factor alpha and soluble tumor necrosis factor receptors in individuals with human immunodeficiency virus infection

There is some ongoing debate as to whether tumor necrosis factor (TNF) alpha levels are elevated in human immunodeficiency virus infection (HIV), however TNF alpha is rapidly cleared from the circulation and long-term markers have to be analyzed. Two distinct TNF alpha receptors have been identified, which also exist in soluble forms. The aim of this study was to investigate whether an association in HIV infection exists between the serum levels of TNF alpha, the two soluble TNF receptors (sTNFRs) and other soluble immune activation markers, namely neopterin and beta 2-microglobulin, and the number of CD4+ T-cells. We investigated 63 individuals with HIV infection for serum levels of TNF alpha, sTNFR 55, sTNFR 75, beta 2-microglobulin and urinary neopterin. The study population comprised all stages of HIV infection: 35 were asymptomatic, 8 had oral candidiasis, 4 had constitutional signs and 16 had AIDS. Circulating levels of TNF alpha were detectable in 22 of 63 (34.9%) individuals. For those with detectable TNF alpha levels the median concentration was 40 pg/ml. The frequency and extent of TNF alpha levels found in those with advanced HIV infection as defined by a CD4+ T-cell count below 320 x 10(6)/l did not differ significantly compared to those with a higher CD4+ T-cell count. Increased concentrations were found in 69.8% of the patients for sTNFR 55 and in 87.3% for sTNFR 75. Serum concentrations of sTNFR 55 and sTNFR 75 were higher in the group with the lower CD4 T-cell count (P = 0.006 and P = 0.0003). TNF alpha correlated with sTNFR 75 and weakly with sTNFR 55 and beta 2-microglobulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine changes in the postoperative period

The trauma of elective surgery leads to the release of cytokines, many of which act primarily at local level having been released from tissue macrophages, circulating monocytes or other activated tissues. There is also a reproducible response in plasma IL-6, the magnitude of which relates to the magnitude of operative trauma. It seems likely that cytokines have an important role in mediating the anorexia associated with the postoperative period, and this may be associated with increased release of CRF from the hypothalamus. Further studies on the interrelationship between cytokine and neuroendocrine systems will lead to a greater understanding of the control of food intake following injury, and will permit the development of new strategies to improve the effectiveness of nutrition at this time.