Monocyte-derived inhibitor of interleukin 1 induced by human cytomegalovirus

Chlamydophila pneumoniae and human cytomegalovirus in atherosclerotic carotid plaques--combined presence and possible interactions

The aim of our study was to investigate the combination of Chlamydophila pneumoniae and human cytomegalovirus (HCMV) as a pathogenic factor in atherosclerosis. Accordingly, we tested by means of PCR and immunohistochemistry the presence of these pathogens in the same atherosclerotic carotid specimen. The histology of the samples and the patients' antibodies against these pathogens were evaluated. Further, we examined the impact of C. pneumoniae and HCMV infection on the gene expression of the human monocytic cell line U937. Six of the 22 samples contained only C. pneumoniae, 4 contained only HCMV, 7 contained both C. pneumoniae DNA and/or antigens of both pathogens, and 5 samples were negative. No correlation was found between the presence of these microbes and either the cellular structure of the plaques, or the serostatus of the patients. The infection of U937 cells with HCMV and especially C. pneumoniae induced inflammation and atherosclerosis-related genes. Furthermore, the doubly-infected cells produced higher levels of the mRNA of pro-platelet basic protein and fatty acid binding protein 4. In conclusion, C. pneumoniae is often present in combination with HCMV in atherosclerotic carotid lesions. The in vitro coinfection model reveals that the doubly-infected monocytes are potent expressors of proatherosclerotic genes, suggesting that this coinfected population may accelerate the process of atherosclerosis.

Transcriptional Regulation of ILT Family Receptors

Ig-like transcripts (ILT/leukocyte Ig-like receptor/monocyte/macrophage Ig-like receptor or CD85) are encoded on human chromosome 19q13.4, designated the human leukocyte receptor complex, and are predominantly expressed on myeloid lineage cells. We investigated the transcriptional regulation of ILT1, ILT2, and ILT4 genes to elucidate control mechanisms operating on the specific expression of ILT receptors. Inhibitory ILT2 and ILT4 both have a similar genomic structure, in which the approximately 160-bp 5'-flanking regions function as core promoters with critically important PU.1 binding sites. However, an Sp1 family-binding GC-box is more influential in trans-activation of ILT2 than ILT4. Additionally, ILT4 transcription is tightly regulated by chromatin modifications accompanied by histone acetylation, which strictly controls expression within myeloid lineage cells. Activating ILT1 carries a core promoter corresponding to the intronic region of ILT2 and ILT4, where PU.1 and Runx1 binding sites are essential, but a downstream heat shock element also augments promoter activity. Thus, each ILT is regulated by a distinct transcriptional mechanism, although PU.1 acts as a common trans-acting factor. We also found that human CMV infection strongly trans-activates inhibitory ILT2 and ILT4 genes through the expression of immediate-early proteins.

Cellular gene expression altered by human cytomegalovirus: global monitoring with oligonucleotide arrays

Mechanistic insights to viral replication and pathogenesis generally have come from the analysis of viral gene products, either by studying their biochemical activities and interactions individually or by creating mutant viruses and analyzing their phenotype. Now it is possible to identify and catalog the host cell genes whose mRNA levels change in response to a pathogen. We have used DNA array technology to monitor the level of approximately 6,600 human mRNAs in uninfected as compared with human cytomegalovirus-infected cells. The level of 258 mRNAs changed by a factor of 4 or more before the onset of viral DNA replication. Several of these mRNAs encode gene products that might play key roles in virus-induced pathogenesis, identifying them as intriguing targets for further study.

Human Cytomegalovirus-Associated Immunosuppression Is Mediated Through Interferon-α

Human cytomegalovirus (HCMV) infections are commonly associated with a generalized immunologic hyporesponsiveness. The present study was designed to evaluate the potential mechanisms of HCMV-associated immunosuppression. In our initial experiments, monocytes in peripheral blood mononuclear cells (PBMCs) exposed to cell-free HCMV appeared morphologically less differentiated than monocytes in PBMCs exposed to a mock preparation. These morphologic changes were closely correlated with a decrease in monocyte oxidative activity and occurred under noncytopathic conditions. HCMV-associated suppression of monocyte differentiation did not require virus replication, occurred in PBMCs from either HCMV seropositive or seronegative donors, and required HCMV interaction with the nonadherent cells. An HCMV-induced soluble factor was found to not only reproduce the identical changes in purified monocytes but to inhibit the phagocytic activity of these cells. Additionally, the HCMV-induced factor accounted for a generalized defect in the ability of PBMCs to proliferate in response to mitogens and recall antigens. In subsequent experiments, interferon-α (IFN-α) was identified as the soluble factor involved in these immunosuppressive effects. Thus, PBMCs, when exposed to HCMV, produce a soluble factor, identified as IFN-α, that appears to be an important mediator of immunosuppression associated with HCMV infection.

The effect of human cytomegalovirus on selected functions of peripheral blood monocytes

The effect of in vitro infection of human cytomegalovirus (HCMV) on various monocyte functions relevant to antimicrobial defence mechanisms has been investigated: the phagocytic activity of monocytes, the release of lysozyme and intracellular concentration of acid phosphatase, and the release of the cytokines interleukin-1 (IL-1), IL-6, and tumour necrosis factor-alpha (TNF-alpha). HCMV significantly inhibited the release of lysozyme and intracellular concentration of acid phosphatase. Regarding the phagocytic activity and the release of cytokines, there was considerable variation in the HCMV effect among the different blood donors tested. There was no clear tendency in the observed results; both stimulation and inhibition were seen. The HCMV-specific pp65 was detected in the nucleus of about 1% of the monocytes 3 h after infection and HCMV-specific IE antigens were found in about 0.1% of the monocytes 2 days postinfection. No E- or L-gene expression was observed and no infectious virus was produced in the monocytes. Our results indicate that HCMV infection may influence monocyte functions in spite of no productive infection of these cells.

A novel mechanism for virus-induced autoimmunity in humans

A novel mechanism for virus-induced autoimmunity in humans is described. Infection of immunocompromised bone marrow-transplanted patients with human CMV results in the formation of autoantibodies specific for the cell-surface protein CD13 (aminopeptidase N). CD13 is present on all CMV-susceptible cells and infection can be specifically blocked by antibodies against CD13. CMV particles carry CD13, which is incorporated in the viral envelope during budding of viral nucleo-capsids into Golgi-derived vacuoles. Antibodies against CD13 are virus-neutralizing, in efficiency comparable to antibodies against viral envelope glycoproteins. Autoantibodies against CD13 are present in patients who develop chronic GVHD following allogeneic bone marrow transplantation. This lesion shows striking similarities to certain autoimmune diseases in humans, of which scleroderma is one example. In vivo binding of antibodies to tissue structures known to be targets for chronic GVHD has been demonstrated in patients with chronic GVHD. Finally, patient serum containing CD13-specific antibodies binds to skin and mucosa tissue sections in vitro, a binding which is inhibited by CD13-specific monoclonal antibodies. Thus a virus infection can activate an immune response against a specific autoantigen, providing possibilities for destruction of non-infected host cells, as originally proposed by Fujinami & Oldstone (1985), and also for the molecular mimicry model for induction of autoimmunity. Our findings lend support to the idea that inhibiting the transfer of CMV infection in bone marrow transplants will reduce morbidity and mortality from CMV infection but will also reduce the incidence of chronic GVHD. Elimination of CD13+ cells in bone marrow is not believed to interfere with the chance of recipient repopulation, and may be a way to decrease morbidity and mortality substantially following BMT. For all patients, every effort should be taken to prevent a post-BMT CMV infection in order to reduce the risk of the later development of chronic GVHD.

Interleukin-1 receptor antagonist

IL-1ra is the first described naturally occurring receptor antagonist of any cytokine or hormone-like molecule. IL-1ra is a member of the IL-1 family by three criteria: amino acid sequence homology of 26 to 30% to IL-1 beta and 19% to IL-1 alpha; similarities in gene structure; and common gene localization to human chromosome 2q14. Two structural variants of IL-1ra exist: sIL-1ra, a secretory molecule produced by monocytes, macrophages, neutrophils, fibroblasts, and other cells; and icIL-1ra, an intracellular molecule produced by keratinocytes and other epithelial cells, macrophages, and fibroblasts. IL-1ra production by monocytes, macrophages, and neutrophils may be regulated in a differential fashion with IL-1 beta. Human IL-1ra binds to both human IL-1RIs and IL-1RIIs on cell surfaces, although with 100-fold greater avidity to IL-1RIs. IL-1ra may bind preferentially to soluble IL-1RIs and not at all to soluble IL-1RIIs. IL-1ra competitively inhibits binding of both IL-1 alpha and IL-1 beta to cell surface receptors without inducing any discernible intracellular responses. All three forms of IL-1 may bind to IL-1 receptors in a similar fashion but IL-1ra may lack the secondary interactions necessary to trigger cell responses. A 100-fold or greater excess of IL-1ra over IL-1 may be necessary to inhibit biological responses to IL-1 both in vitro and in vivo. The roles of sIL-1ra and icIL-1ra in normal physiology or in host defense mechanisms remain unclear. The administration of IL-1ra blocks the effects of IL-1 in some animal models of septic shock, inflammatory arthritis, graft-versus-host disease, and inflammatory bowel disease. The preliminary results of clinical trials in humans indicate possible efficacy of IL-1ra in sepsis syndrome, rheumatoid arthritis, and GVHD.

Replication of human cytomegalovirus in the cells of the U937 monocytoid cell line

Human cytomegalovirus (HCMV) infection in immunocompromized hosts sometimes occurs as a result of reactivation. Cells of the monocyte-macrophage linkage are suggested to be a site of latency and persistence for HCMV. The human monocytic cell line U937 was infected with the AD169 strain and a clinical isolate of HCMV. The expression of surface antigens on the cells was assessed by flow cytometry. The polymerase chain reaction (PCR) was used to detect viral DNA from infected cells. CMV immediate early antigen, early antigen, and late antigen (LA) were detected from both clinical isolate- and AD169-inoculated U937 cells by flow cytometry. CMV DNA which code major immediate early gene (US3) and LA gene (US14) were detected from the clinical isolate-inoculated U937 over a period of 31 days as tested by PCR. These U937 cells proliferated as well as uninfected U937 cell, but only a small number of AD169-inoculated U937 cells survived after 14 days of inoculation. Interleukin-2 activities were detected in the media on days 24-40 after inoculation with AD169. This chronic CMV infection model of U937 might be utilized to study the mechanisms of persistence and reactivation.

Suppression of LPS-inducible cytotoxicity in cytomegalovirus-infected THP-1 monocytic cell cultures does not correlate with a decrease in TNF-alpha antigen

We document suppression of tumor necrosis factor alpha (TNF-alpha)-associated cytotoxic activity in a human monocytic cell line (THP-1) infected with the mycoplasma free human cytomegalovirus (CMV) strain AD169. Addition of lipopolysaccharide (LPS) to cell cultures that had been infected with CMV for 24 h resulted in a significant reduction in released cytotoxic activity to mouse L929 cells at 3-22 h post-LPS compared with mock-infected cultures. However, using an ELISA to measure TNF-alpha antigen levels in these culture supernatants, we found infected cultures had significantly higher TNF-alpha antigen levels than in mock-infected cultures following LPS induction. CMV alone also induced TNF-alpha release and possibly TNF-alpha inhibitor(s) which may have blocked TNF-alpha associated cytotoxic activity in CMV-infected THP-1 cell culture supernatants.

Circulating inhibitor of interleukin 1 activity in patients with chronic renal diseases

The effects of sera derived from patients suffering from chronic renal diseases (endemic Balkan nephropathy, glomerulonephritis and pyelonephritis) on T cell proliferative response was studied. It was found that these sera contained factors which affect interleukin 1 (IL-1) dependent events in T cell proliferative response. The factors prevent costimulatory effects of IL-1 on T cells but do not bind to IL-1, nor do they affect interleukin 2 (IL-2) dependent T cell proliferation. These findings indicate that immuno-suppression observed in some kidney disorders may be partially due to serum immunoinhibitory factors affecting IL-1 activity.

Native cytokine antagonists

Cytokines orchestrate the complex homeostasis of cells and tissues by acting in both an autocrine and paracrine fashion. The processes responsible for regulation of cytokines is not well understood. This chapter has summarized what is known about antagonism and inhibition of the action of cytokines. Several concepts have emerged from work in this area. At least two cytokines (IL-1 alpha and IL-1 beta) have an endogenous receptor antagonist, the IL-1 receptor antagonist. This is the first example of one endogenous molecule directly blocking the binding of another molecule to its receptor: most forms of regulation occur through independent receptors. Several cytokines, including TNF, IFN-gamma, IL-2 and IL-4, are inhibited by soluble receptors. Several cytokines, including IL-10, TGF-beta and MDF, act to inhibit other cytokines. It is likely that these inhibitors will be found to have pleiotropic actions in vivo. Finally, we describe antibody inhibition of cytokines. Detailed studies will be required to understand the complex interplay of the aforementioned cytokine inhibitors and the processes they regulate.

Human cytomegalovirus-stimulated peripheral blood mononuclear cells induce HIV-1 replication via a tumor necrosis factor-alpha-mediated mechanism

Human cytomegalovirus (HCMV) is a potential cofactor in HIV-1 infection. To investigate the mechanism whereby HCMV promotes HIV-1 replication, a PBMC coculture assay which measures HIV-1 p24 antigen release was used as an index of viral replication. HCMV-stimulated PBMC were capable of inducing HIV-1 replication in cocultures with acutely infected PBMC; however, this occurred only when the PBMC were from HCMV-seropositive donors (598 +/- 207 versus 27 +/- 10 pg/ml p24 antigen with PBMC from HCMV-seronegative donors on day 6 of coculture). Upon stimulation with HCMV, PBMC obtained exclusively from HCMV-seropositive donors released tumor necrosis factor (TNF)-alpha (270 +/- 79 pg/ml at 18 h of culture). Monoclonal antibodies to TNF-alpha blocked the activity of HCMV-stimulated PBMC in cocultures both with acutely HIV-1-infected PBMC and with the chronically infected promonocytic line U1. Also, treatment of HCMV-stimulated PBMC with pentoxifylline, an inhibitor of TNF-alpha mRNA, markedly reduced HIV-1 replication in cocultures both with acutely and chronically infected cells. These results indicate that TNF-alpha is a key mediator of HIV-1 replication induced by HCMV-stimulated PBMC and support the concept that this cytokine plays an important role in the pathogenesis of HIV-1 infection.

Cerebrospinal fluid levels of IL-6 in patients with acute infections of the central nervous system

Interleukin-6 (IL-6) activity was measured in the cerebrospinal fluid (CSF) of patients with acute bacterial or viral meningitis and in AIDS patients with various cerebral disorders. Increased levels of IL-6 were detected in the CSF of patients with bacterial meningitis. On the contrary, most of the samples from patients with viral meningitis (predominantly caused by mumps virus) had no detectable IL-6 activity in CSF. A moderate increase of IL-6 levels was detected in the CSF of AIDS patients with AIDS dementia complex (ADC), progressive multifocal leukoencephalopathy and cerebral toxoplasmosis. Moreover, higher levels of IL-6 were detected in the CSF of patients with cryptococcal meningitis. We conclude that the initial events of CSF inflammation in patients with acute viral meningitis are different from those in patients with acute bacterial meningitis, and the role of IL-6 is less critical to the process.

Human cytomegalovirus productively infects primary differentiated macrophages

Monocytes are one of the predominant cell types in the peripheral blood that are infected by human cytomegalovirus (HCMV). Although virus can be detected in these cells in vivo, HCMV replication in cultured monocytes has been unsuccessful. In this study, we demonstrate efficient HCMV replication in cultured monocytes. HCMV permissiveness in these cells was dependent on nonadherent cell-induced stimulation of the monocyte, with subsequent morphological differentiation into macrophages. Approximately 40% of the cells infected by virus were detected by immunofluorescent staining with both immediate-early and late antibodies. In addition, viral plaque assays demonstrated significant productive infection of macrophages. These observations are consistent with the suggestion that the monocyte/macrophage serves as a source of viral amplification and dissemination.

Infection of human monocytes with HIV-1Ba-L. Effect on accessory cell function for T-cell proliferation in vitro

Major laboratory manifestations of human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) include altered levels of circulating CD4+ lymphocytes and decreased in vitro T-cell mitogenic responses. Since T-cell proliferation is regulated by monocytes (M phi), studies were undertaken to determine whether defective M phi function contributes to these poor mitogenic responses. M phi were isolated from peripheral blood mononuclear cells (PBMC) of normal donors by adherence to plastic. After 5 days in culture, the adherent cells were inoculated with the HIV-1 M phi-tropic strain, Ba-L. Under these conditions HIV infection in M phi can be detected 5-7 days after inoculation. Ten to fourteen days postinoculation, the adherent cells were harvested with lidocaine and cocultured with fresh autologous T cells and T-cell mitogens in a 3-day assay. We found decreased proliferative anti-CD3 responses to Leu4 and OKT3 and variable responses to concanavalin A (Con A) by T cells cultured with HIV-infected monocytes compared with T cells cultured with uninfected M phi. Supernatants from HIV-infected M phi cultures decreased proliferative responses of normal PBMC to anti-CD3 monoclonal antibodies. Heat-activated supernatants had the same effect. Inhibitors of HIV binding did not restore proliferative responses of HIV-infected cultures to normal levels. These results indicate that HIV infection of M phi causes the release of soluble factor(s) that suppress anti-CD3-induced T-cell proliferative responses.

IGG-stimulated and LPS-stimulated monocytes elaborate transforming growth factor type beta (TGF-beta) in active form

Mononuclear cells (MNC) stimulated either with lipopolysaccharide (LPS) or with surface-adsorbed IgG elaborated significant amounts of tumor necrosis factor (TNF) bioactivity, as well as immunoenzymatically detectable TNF-alpha and interleukin-1 beta. (IL1-beta). In contrast, IgG-stimulated cells released little IL1 bioactivity, but released an IL1 inhibitor, as determined by the thymocyte costimulatory assay (LAF assay). This inhibition was not due to an inhibitory effect of cyclooxygenase products, e.g. prostaglandin-E2 in the LAF assay. In contrast, antibodies against transforming growth factor type beta (TGF-beta), which is an important inhibitor of the LAF assay, augmented the LAF activity of supernatants from LPS-stimulated and IgG-stimulated MNC. Anti-TGF-beta-modulated LAF inhibition was enhanced by acid treatment of supernatants from mononuclear cells, but not of those from purified monocytes. Antibody blocking experiments point for the first time to a TGF-beta species other than type 1 as a monocyte-derived TGF-beta activity. Thus, TGF-beta released in active form from monocytes may be the more important antagonist of IL1 than cyclooxygenase-derived mediators. It implies that the LAF assay, in the absence of anti-TGF-beta antibodies, is an inadequate indicator of IL1 activity.

A macrophage-derived factor induced by alpha 1-acid glycoprotein that inhibits IL-1 comitogenic activity

After exposure to a concanavalin A (Con A)-unreactive variant of alpha 1-acid glycoprotein (AGP), macrophages released an inhibitor of interleukin-1 (IL-1) proliferative activity in the thymocyte comitogenic assay. This effect was observed with AGP concentrations above 100 micrograms/ml in the macrophage supernatant and would appear to be mediated by the macrophages, since native AGP had no activity on thymocyte proliferation. Preliminary physicochemical characterization showed that the factor was partially resistant to heating, undialyzable, and eluted with an apparent molecular mass of 50-100 kDa when subjected to Sephacryl S-200 chromatography. Murine IL-1 and human (h) recombinant (r) IL-1 were affected by this factor to the same extent. IL-1 and IL-2 co-induced thymocyte proliferation, which is mitogen-independent, was also inhibited, whereas hrIL-2 activity was not suppressed when assayed in thymocytes with PHA at a submitogenic concentration or in CTLL cells. The factor did not interfere with TNF alpha or hrIL-6 activity when tested against their specific cell line. These data indicate that the inhibitor may act specifically against IL-1 activity and further elucidate the possible role of AGP in the modulation of IL-1 activity via the secretion of an inhibitor.

Inhibitory effect of African swine fever virus on lectin-dependent swine lymphocyte proliferation

The incubation of swine peripheral blood mononuclear cells (PBMC) with African swine fever (ASF) virus preparations strongly inhibited the proliferative response of lymphocytes to PHA and other lectins. The inhibition, which persisted after inactivation of the virus by UV radiation, was dependent upon the dose and the time that virus preparations were present in cultures. When virus preparations were fractionated by ultracentrifugation, the inhibitory activity resulted to be soluble, whereas no activity was found in the sedimented viral fraction. However, the preincubation during 4 days of this sedimented fraction with swine PBMC, before the addition of the mitogen, restored the inhibitory activity. The results obtained suggest that the inhibition is mediated by one or more soluble factors released by swine PBMC after coincubation with ASF virus in a time dependent process. These factors show a molecular weight between 40 and 80 kDa by gel filtration chromatography. The inhibitory activity described in the present paper is an indication of inhibition of lymphocyte function produced by ASF virus which can help to understand how this virus escapes from the host immune system.

Lymphocytic choriomeningitis virus-induced immunodepression: inherent defect of B and T lymphocytes

Infection of mice with lymphocytic choriomeningitis virus (LCMV) produces a rapidly induced immuno-suppression manifested by low lymphocyte proliferation in response to lipopolysaccharide (LPS) and concanavalin A (ConA). Analysis of the mechanisms underlying the unresponsiveness to these mitogens was undertaken at the cellular and molecular levels 7 days after infection. The selective elimination of CD8+ T cells and the results of coculture experiments demonstrated that unresponsiveness was not due to suppressor cells. Similarly, the role of inhibitory factors such as prostaglandins was excluded, since indomethacin, which inhibits their production, did not reverse the unresponsiveness. Analysis of different cytokines secreted by ConA-activated macrophages or T cells revealed that interleukin-1 (IL-1), synthesized during the T-dependent activation of macrophages by ConA, was normally produced by cells from LCMV-infected mice. In contrast, IL-2, which is produced by activated CD4+ T cells, was undetectable. Addition of exogenous IL-2 did not restore the proliferative response, although the p55-kilodalton protein of the IL-2 receptor was induced by ConA on CD4+ cells from LCMV-infected mice. Our results can be interpreted as showing that (i) unresponsiveness to mitogens of cells from LCMV-infected mice is not due to altered functions of the macrophages with respect to IL-1 production; (ii) CD4+ cells are activated, since the p55 chain of the IL-2 receptor is induced; (iii) the lack of IL-2 production cannot explain T-cell unresponsiveness, since addition of exogenous IL-2 did not restore the proliferative response. Taken together, these data suggest that T-lymphocyte unresponsiveness should be related to an inherent proliferative defect subsequent to T-cell activation and IL-2 receptor expression.

Modulation of interleukin 1 beta gene expression by the immediate early genes of human cytomegalovirus

The immediate early (IE) genes of human cytomegalovirus (HCMV) can be expressed in monocytes/macrophages and are known to regulate other viral genes. The purpose of these studies was to determine if HCMV IE gene products also modulate expression of a monocyte/macrophage-derived gene, interleukin 1 (IL-1) beta. Steady-state cell-derived IL-1 beta mRNA was increased in lipopolysaccharide (LPS)-stimulated THP-1 cells when transfected with the HCMV IE1 + 2 genes, when compared to cells transfected with a control DNA. LPS-stimulated THP-1 cells also exhibited approximately 30-fold higher IL-1 CAT activity when cotransfected with IE1 + 2 than was observed for the same cells cotransfected with IL-1 CAT and a control plasmid containing the IE promoter alone. LPS increased IL-1 CAT activity in the absence of HCMV genes only twofold. IE1, by itself, increased IL-1 CAT activity in LPS-stimulated cells, whereas, IE2, by itself, caused no change in IL-1 CAT activity. These studies show that the IE1 gene of HCMV can regulate IL-1 beta gene expression. The observations further suggest that some of the inflammatory processes associated with HCMV infection may be due to an effect of HCMV IE genes on cell-derived genes, such as the IL-1 beta gene.

Interleukin-1-inhibitory IgG in sera from some patients with rheumatoid arthritis

Inhibition of interleukin-1 alpha (IL-1 alpha) activity was detected in 7 of 41 serum samples from patients with rheumatoid arthritis (RA). These 7 sera inhibited not only IL-1 alpha-induced endothelial cell adherence to neutrophils, but also IL-1 beta-induced endothelial cell adherence, although to a lesser extent. These sera showed no influence on tumor necrosis factor-induced endothelial cell adherence. No inhibitory activity was found in 40 sera from normal control subjects. Studies to further examine these effects included gel filtration analysis of 2 of the RA sera. The inhibitory activity was eluted near Mr 158 kd and above Mr 250 kd. Analysis by protein A affinity chromatography showed that IL-1-inhibitory activity was present in protein A-binding fractions. Purified IgG (by DE-52 column chromatography) from RA patients was found to be as potent an inhibitor as the protein A-binding fractions, which suggests that the major inhibitory activity in RA sera is attributable to IgG molecules. These purified IgG molecules also inhibited IL-1-induced proliferation of mouse thymocytes but did not influence IL-2-dependent proliferation of the CTLL-2 murine T cell line. The 7 patients whose sera showed IL-1-inhibitory activity had mild RA and low titers of rheumatoid factor. The findings, taken together, suggest a possible regulatory role of IL-1-inhibitory IgG in RA disease activity.

Increased monokines in cytomegalovirus infected myelomonocytic cell cultures

In an investigation of the role of monokines in CMV associated immunosuppression we document modulation of both TNF and IL-1 beta in CMV infected THP-1 cells. CMV infected cultures released almost two-fold more IL-1 beta protein and contained significantly higher IL-1 beta mRNA levels than uninfected cultures for 72-96 h after induction. In both CMV infected and uninfected cultures, significant amounts of IL-1 beta protein were not detected until 24 h post induction, while maximum amounts of TNF were detected in culture supernatants by 3 h post induction, suggesting that TNF may play a role in IL-1 beta induction. TNF levels subsequently declined but in infected cultures remained over 2.5-fold higher than controls through 96 h. The CMV alteration in the kinetics and extent of IL-1 beta release must be indirectly mediated by CMV since only 1% of THP-1 cells were infected. Most infected cells expressed CMV immediate early proteins but did not overexpress IL-1. We speculate that CMV infected cells release excess TNF or other stimulatory factors which increase IL-1 beta synthesis. Since IL-1 beta is increased, the decreased IL-1 'activity' described by others as an explanation in part for the immunosuppressive effects of infection may actually reflect alterations of IL-1 inhibitor levels during CMV infection.

Brucella abortus regulates bovine macrophage-T-cell interaction by major histocompatibility complex class II and interleukin-1 expression

T-cell activation is dependent on nominal antigen associated with major histocompatibility complex (MHC) class II molecules and interleukin-1 (IL-1), both provided by antigen-presenting cells. We have studied the effects of Brucella abortus and recombinant bovine gamma interferon (IFN-gamma) on bovine macrophage expression of MHC class II and IL-1 molecules and subsequent T-cell proliferation in response to B. abortus. When peripheral blood mononuclear cells were cocultured with B. abortus and IFN-gamma, increasing amounts of IFN-gamma, from 1 to 100 U/ml, down regulated T-cell proliferation. Expression of MHC class II molecules on macrophages was increased independently by IFN-gamma or B. abortus treatment. Thus, class II molecule expression was not the cause of down regulation of T-cell proliferation as observed in other systems. However, B. abortus-IFN-gamma-treated macrophages obtained from overnight cultures had minimal membrane IL-1 compared with macrophages treated with B. abortus alone. Loss of membrane IL-1 required IFN-gamma and the o-polysaccharide of the lipopolysaccharide. IFN-gamma at 1 U/ml in combination with B. abortus produced a 32% decrease in T-cell response, while IFN-gamma at 100 U/ml added to B. abortus-treated cultures produced an 82% reduction in T-cell response. Membrane IL-1 levels were not altered when recombinant bovine IFN-alpha or the rough strain 45/20 of B. abortus, which lacks the o-polysaccharide, was used. Secreted IL-1 levels were unaffected by IFN-gamma and B. abortus treatment. The addition of recombinant bovine IL-1 beta (0.001 to 0.1 ng/ml) to B. abortus- and IFN-gamma-treated cultures failed to provide a signal necessary for T-cell proliferation. These data suggest that membrane IL-1 has a key role in T-cell activation in response to B. abortus. When the o-polysaccharide of B. abortus lipopolysaccharide is combined with IFN-gamma at an inappropriate time during an immune response, T-cell proliferation is prevented and cannot be restored by the addition of exogenous IL-1.

Human cytomegalovirus induces stage-specific embryonic antigen 1 in differentiating human teratocarcinoma cells and fibroblasts

Cell surface expression of stage specific embryonic antigen 1 (SSEA-1), or Lex (III3 FucnLC4), was induced in differentiated human teratocarcinoma cells and in human diploid fibroblasts 3-6 d after infection with human cytomegalovirus (HCMV). In parallel, fucosylated lactoseries glycolipids bearing the SSEA-1/Lex epitope were readily detected in the infected cells but not in the uninfected cells. HCMV infection also results in altered expression of several glycosyltransferases. SSEA-1/Lex induction is probably a consequence of both increased expression of beta 1----3N-acetylglucosaminyltransferase, which catalyzes the rate-limiting step in lactoseries core chain synthesis, and subtle alterations in the relative competition for common precursor structures at key points in the biosynthetic pathway. Since SSEA-1 has been suggested to play a role in some morphogenetic cell-cell interactions during embryonic development, the induction of this antigen at inappropriate times might provide one mechanism whereby intrauterine infection with HCMV can damage the developing fetal nervous system.

Impairment in T-lymphocyte responses during early infection with the human immunodeficiency virus

Uncertainty has existed as to whether a T-cell deficiency exists in human immunodeficiency virus (HIV) infection different from that inherent in the reduced T-cell numbers characteristic of the disease. Heretofore, methods for measuring T-cell responses in patients have been carried out with systems requiring monocytes as accessory cells. In the presence of high concentrations of interleukin-2, however, highly purified T cells respond in a monocyte-independent fashion to antibody reactive with the CD3 component of the antigen receptor complex Ti/CD3. Highly purified T cells of HIV-infected patients responded subnormally in this anti-CD3/IL-2 system, even in the case of patients who were asymptomatic or had only lymphadenopathy. The defective T-cell responses occurred over a wide range of concentrations of the anti-CD3. Neither poor IL-2 receptor function as reflected by responses to limiting dilutions of IL-2 nor IL-1 receptor function as defined by incremental proliferation when IL-1 is added accounted for this defect, which also correlated poorly with T4 and T8 numbers. These results suggested that the T-cell abnormality was closely related to Ti/CD3 function, was not specifically or restrictively associated with T4 cells, and was not due to defective IL-2- or IL-1-receptor functions. The amount of HIV RNA in 10(5) T lymphocytes from the patients amounted to less than that found in one cell of a standard HIV infected laboratory cell line (CEM), using slot-blot hybridization. Thus the T-cell deficiency we have observed was not likely to be due directly to cell killing by HIV resident in the T4 cells. Other factors may be important in inducing the immunodeficiency, some of which are discussed.

Partial purification and characterization of a factor produced by mitogen-stimulated sheep mononuclear cells with thymocyte-activating and cartilage-degrading properties

Ovine peripheral blood mononuclear cells stimulated with concanavalin A released a soluble factor capable of inducing cartilage resorption and thymocyte activation in vitro, but not lysis of the murine L929 cell line. The active moiety has a molecular mass of around 15-20 kDa on gel filtration columns, and can be separated into two molecular species with isoelectric points of 6.3 and 4.6 respectively. These two species were partially purified by gel filtration, chromatofocusing, high performance liquid chromatography on hydroxylapatite and anion exchange columns, and SDS-polyacrylamide gel electrophoresis. Both partially purified species showed a major band on gels at 16 kDa. When the band from the acidic factor was excised and eluted from gels it was found to retain some cartilage-degrading and thymocyte-activating properties. The biochemical and biological characteristics of the two factors is consistent with their being members of the interleukin-1 family of cytokines.

Replication of cytomegalovirus in human thymic epithelial cells

Cytomegalovirus (CMV) has often been cited as a cause of immune suppression in children, yet little is known of the mechanisms through which this agent might affect immune function. We have succeeded in using CMV to productively infect cultured human fetal and infantile thymic epithelial (TE) cells. Morphological changes were apparent by 2-4 days after viral inoculation. CMV-related early antigen (EA) and late antigen (LA) were detected by immunofluorescence after 8 days, and progeny infectious CMV was recovered from culture media after 12-17 days. TE cells that reacted with monoclonal antibodies specific for keratin and for GQ ganglioside were predominant throughout the culture period. In contrast, infection by CMV resulted in a significant decrease in numbers of cells reactive with monoclonal antibodies specific for mesoderm-derived components. Inoculation of TE cells with CMV also caused a diminution in levels of detectable interleukin-1 (IL-1)-related antigen by 17 days after infection.

Interleukin-1 production in acute viral hepatitis

The in vitro production of interleukin-1 in 15 children with acute hepatitis A and five children with acute hepatitis B was determined by measuring lymphocyte activating factor secreted by peripheral blood monocytes in a thymocyte proliferation assay. Aluminium hydroxide induced production of lymphocyte activating factor was significantly lower in patients with acute hepatitis A as well as patients with hepatitis B as compared with healthy control subjects. In both forms of acute viral hepatitis production of lymphocyte activating factor was severely depressed during the first week, increased gradually during the further course of the illness, but did not reach normal concentrations within the first three weeks after onset of the acute symptoms of the disease. No correlation could be found between in vitro production of lymphocyte activating factor and the severity of liver disease as estimated by the rise of serum concentrations of transaminases, bilirubin, or several parameters of acute phase reaction (alpha 1 antitrypsin, C reactive protein, erythrocyte sedimentation rate). The reduced production of interleukin-1, as assessed by determination of lymphocyte activating factor, could explain the only moderate acute phase reaction seen during acute viral hepatitis.

Native interleukin 1 inhibitors

Much information has accumulated on the isolation and characterization of a heterogeneous group of molecules that inhibit one or more of the bioactivities of interleukin 1. In this review James Larrick discusses the biological and biochemical data available on several of these native interleukin 1 inhibitors, some of which have additional, unexpected activities.

Interleukin-1 and interleukin-1 inhibitor production by human adherent cells stimulated with periodontopathic bacteria

This study examined the effect of the putative periodontopathic bacteria Bacteroides gingivalis and Fusobacterium nucleatum on the production of interleukin-1 (IL-1) and IL-1 inhibitors by human plastic-adherent mononuclear cells from normal donors. Fusobacterium mortiferum was used as a non-oral, non-pathogenic control organism. Unstimulated adherent cells spontaneously secreted an IL-1 inhibitor, whereas stimulation with B. gingivalis induced the synthesis and secretion of IL-1. With both fusobacteria IL-1 was present in the intracellular environment, whereas the predominant secretory product was either IL-1 or an IL-1 inhibitor. These results suggest that bacteria are capable of modulating cytokine production by monocytes and may thereby alter the local immune response.

Properties of the immunosuppressive factor induced by murine cytomegalovirus

Murine cytomegalovirus infection of spleen cultures induced the production of a small (less than 10,000 molecular weight) immunosuppressive factor (VISF), which suppressed concanavalin-A mitogenesis in fresh mouse spleen cells, and in fresh human peripheral blood leukocytes. The factor did not affect the growth of two murine T-cell lines or of mouse fibroblasts. A similar factor was also found in the serum of infected mice, at the time of maximum immune suppression. The properties of VISF indicate that the mechanism of MCMV immune suppression is different from that caused by several other viruses which are important in human and veterinary medicine.

Correlative studies of blastogenic responses and interleukin 1 production by mononuclear cells from patients with zoopathogenic fungal infections

The production of interleukin 1 (IL 1) by adherent peripheral blood mononuclear cells (PBMC) was quantitated in 16 individuals infected with Histoplasma capsulatum or Blastomyces dermatitidis and 16 age-matched controls. In parallel, we measured blastogenic responses to phytohemagglutinin (PHA) by PBMC from patients and controls. Of the 16 patients, six had pulmonary histoplasmosis, six had disseminated histoplasmosis, two had pulmonary blastomycosis, and two had disseminated blastomycosis. At the time of study, none of the patients were receiving immunosuppressive agents or had an underlying debilitating illness. Proliferative responses by PBMC from patients to PHA were significantly (P less than 0.05) less than the mean response by PBMC from an equal number of controls. In the 16 controls, the increase in secretion of IL 1 by lipopolysaccharide (LPS)-stimulated adherent cells over unstimulated cells ranged from 18 to 40 units of IL 1 activity per 10(5) adherent cells. The increment in IL 1 levels between LPS-stimulated adherent PBMC and unstimulated cells was diminished (less than 18 units of IL 1 activity per 10(5) adherent cells) in five of the 16 patients. Diminished IL 1 secretion in response to LPS was associated with impaired PHA responses in four of 10 patients.

The cellular immune response to cell-associated and cell-free cytomegalovirus (CMV) antigens after primary CMV-infection in non-immunocompromised hosts: development and maintenance of CMV-latency and its influence on immunocompetence

Development and maintenance of cellular immunity to cell-associated CMV-antigens (CMVFF) was investigated in non-immunocompromised hosts during the first year (group I, n = 11) and 1 to 5 years (group II, n = 9) after a symptomatic primary CMV infection, as well as in healthy CMV-seropositive controls without a history of CMV disease (group III, n = 28). During the acute phase (0-2 months) of a primary CMV-infection CMVFF-induced lymphocyte proliferation was severely decreased compared to that in the post-illness phase (5-12 months), and to that in groups II and III. After the reconvalescent period (3-4 months) it gradually increased to levels seen in group III. In group II higher responses to CMVFF were found than in group III or during the post-illness phase of a primary infection. In general CMV-virion induced lymphocyte proliferation showed the same pattern of development as the CMVFF-induced lymphocyte response, but during the acute phase (0-2 months) a lack of correlation was observed between lymphocyte proliferation to CMVFF and CMV-virions. Lymphocyte proliferation to PHA, Con A, allogeneic lymphocytes and recall antigens were severely depressed in the acute phase of a primary CMV-infection and restored gradually to levels seen in groups II and III, with the exception of Con A-reactivity. The latter response remained depressed when compared to healthy seropositive controls, not only during the post-illness period, but also later on (group II).

Immune mechanisms in congenital cytomegalovirus infection: activation of CMV-specific T helper cells (CMV-Th) by exogenous IL-2

Infants with congenital CMV infection have a specific defect in CMV-induced lymphocyte proliferation, providing a model for investigation of mechanisms of viral immune recognition and immune response. In the present study the possible role of a defect in lymphokine activation of CMV-specific T helper cells (Th) was examined. IL-1 activity was detected in supernatants of patient mononuclear cell (MNC) cultures stimulated with CMV. In contrast, no IL-2 activity could be detected in supernatants of CMV-stimulated MNC cultures, whereas PHA induced normal IL-2 production. Addition of low concentrations of either crude TCGF or recombinant IL-2 (rIL-2) resulted in 2-4 fold augmentation of CMV-specific lymphocyte proliferation; exogenous IL-2 had no effect on MNC responses to HSV. CMV-specific Th lines/clones were established from three congenital CMV patients by initial stimulation of MNCs with CMV antigen and 0.1 U/ml rIL-2, followed by repeated stimulation with CMV, HLA-matched allogeneic feeder cells and 10% TCGF. The resulting CMV Th lines/clones proliferated specifically in response to stimulation with CMV antigen and produced endogenous IL-2. Thus, the immune deficiency associated with congenital CMV may either be due to an intrinsic defect in CMV-Th activation or CMV-specific suppressor cell activity.

A human urine-derived interleukin 1 inhibitor. Homology with deoxyribonuclease I

We have previously reported that the urine of febrile humans contained large quantities of an inhibitor of IL-1-induced murine thymocyte proliferation that was a glycoprotein between 30 and 40 kD in size. In the present study this factor has been purified to homogeneity using a sequence of eight purification steps (ammonium sulfate precipitation, ion exchange chromatography, molecular sieve chromatography, hydrophobic affinity chromatography, hydroxylapatite chromatography, fast protein liquid chromatography, and two HPLC steps). SDS-PAGE analysis indicates that the purified material is a 38-kD molecule. Evidence based on a partial amino acid sequence analysis as well as enzyme studies indicates that this inhibitor is a type of human DNase I.

Impaired interleukin 1 and interleukin 2 production following in vitro abortive infection of murine spleen mononuclear cells by Semliki Forest virus

The effect of Semliki Forest virus (SFV) infection of murine spleen mononuclear cells was investigated in vitro. A small percentage of spleen macrophages expressed viral antigens, but no infectious virus particles were released, indicating an abortive-type infection. Wild-type SFV infected a higher percentage of macrophages than the attenuated, demyelinating mutant A7. The proliferation of spleen mononuclear cells under Con A stimulation was inhibited by the viral infection. The supernatant (SN) harvested from infected and Con A-stimulated spleen adherent cells could not stimulate thymocytes in an interleukin 1 (IL-1) assay and indomethacin treatment of infected cultures had no effect. The stimulatory effect of SN from noninfected cultures in the IL-1 assay was reduced when SN from infected cultures was added, suggesting the presence of an IL-1 inhibitor. Interleukin 2 (IL-2) production by splenocytes also decreased after viral infection, but exogenous IL-2 restored the response to Con A stimulation of infected spleen cells. This study demonstrates that abortive SFV infection of spleen macrophages has an immunosuppressive effect which may lead to an aberrant immune regulation.

Cytomegalovirus infection of peripheral blood mononuclear cells: effects on interleukin-1 and -2 production and responsiveness

Cytomegalovirus suppresses the proliferative response of peripheral blood mononuclear cells to phytohemagglutinin. In these experiments, we identified which mononuclear cell subpopulation might be responsible for the suppression. We found that prior infection of either lymphocytes or monocytes followed by reconstitution with monocytes or lymphocytes, respectively, would abrogate the proliferative response in a subsequent culture with phytohemagglutinin. Infection of either cell type also reduced both the production of interleukin-1 (IL-1) and IL-2 and the proliferative response to exogenously supplied IL-1 or IL-2. We did not find evidence for an IL-2 antagonist. These experiments suggest that cytomegalovirus causes a metabolic derangement in lymphocytes and monocytes and impairs their ability both to produce and to respond to physiological mediators of the immune response.

Cytomegalovirus-infected adherent cells interact synergistically and antagonistically with Staphylococcus aureus protein A in vitro

Cytomegalovirus (CMV) has been shown to exert suppressive effects on the immune response but also to have mitogenic properties. A bacterial product, protein A from Staphylococcus aureus (SpA) was chosen to study possible interactions in vitro between bacterial products and adherent cells incubated with infectious CMV and ultraviolet light (UV)-inactivated CMV. Small amounts of infectious CMV potentiated SpA-induced DNA synthesis and Ig secretion measured by induction of plaque-forming cells (PFC). The reason for this may be that CMV in small amounts may act in synergism with the non-specific mitogen SpA. UV-inactivated CMV did not influence these responses except for a markedly enhanced PFC induction with SpA in lymphocytes from seronegative individuals. This remarkable synergism with SpA was also seen in enriched B cells. No synergism was seen in lymphocytes from seropositive donors. Large amounts of infectious CMV markedly reduced SpA-induced immune responses. Preliminary data suggest that the immunosuppressive effects are mediated by an interleukin 1 inhibitory factor. CMV was not shown to be a polyclonal B-cell activator but may, possibly in small amounts, act as such together with bacterial products, which would explain certain autoimmune phenomena. To conclude, CMV could in interaction with a bacterial product generate both synergistic and suppressive effects on immune response.

Infection of human thymic epithelial cells by human cytomegalovirus and other viruses: effect on secretion of interleukin 1-like activity

Cultures of human thymic epithelial (TE) cells are able to produce a interleukin 1 (IL-1) like activity. This IL-1 activity can be detected either using mouse thymocytes in a traditional IL-1 assay, or using thymic lymphocytes obtained from cases of pediatric cardio-vascular surgery. Production of IL-1 activity by TE cells was found to be maximal between 3 and 4 weeks after culture initiation. Human thymocytes worked best as targets in an IL-1 assay, when these cells were derived from donors younger than 1 year of age. Infection of human TE cells by any of human cytomegalovirus, herpes simplex virus type 2, adenovirus 7, Coxsackie B1, and respiratory syncytial virus led to marked reductions in the ability of these cells to secrete measurable IL-1 activity. In the case of TE cells infected by cytomegalovirus, respiratory syncytial virus, and Coxsackie B1, this abrogation of production of IL-1 activity occurred in the absence of any obvious virus-induced cytopathic effect.

Effect of co-incubation with cytomegalovirus on growth of interleukin 2-dependent lymphocytes

We have tested the ability of human cytomegalovirus (CMV) to interfere with the interleukin-2 (IL-2)-dependent proliferation of T lymphocytes in long-term tissue culture. The results indicate that CMV was able to establish an apparently abortive infection in approximately 40% of such cells, although productive viral replication could not be detected, and was able to impede cellular proliferation almost completely. The addition of high concentrations of exogenous IL-2 to cultures of CMV co-incubated cells was not readily able to overcome the anti-proliferation inhibitory effect induced by this virus. Exposure to CMV led to an approximate 50% decrease in the number of cells which expressed Tac Ag, or IL-2 receptor, at the cell surface.

The status of CMV as a human pathogen

Cytomegalovirus (CMV) is a common infectious agent which is well adapted to its host. Following primary infection, which is almost always asymptomatic in people with normal immunity, the virus establishes latency at sites which are unknown. The virus is probably maintained in this latent state by immune surveillance mechanisms since immunosuppression frequently leads to reactivation of virus.

Cytomegalovirus has been identified in most anatomical areas of the human body. The aim of this article is to define criteria for pathogenicity so that clinical and experimental data can be reviewed to determine if CMV is likely to cause disease at these various clinical sites. Thus, patients have been shown to die frequentlywithCMV but do they diefromit?