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A J Puren

Publications and source records attributed to A J Puren.

15 recordsLinked to original sources
PubMed2002

The HIV-1 epidemic in South Africa.

The first reported cases of HIV-1 infection in South Africa occurred in 1982. Two distinct HIV-1 epidemic patterns were recognized. Initially the infection was prevalent in white males who had sex with males. The HIV-1 clade B was associated with this group. By 1989, the second epidemic was recognized primarily in the black population. Infections in this case were mainly heterosexual in origin. The HIV-1 clade involved was mainly C. The national HIV-1 sero-prevalence in antenatal attendees was less than 1% in 1990 and by 1994 this figure had risen to 7.5%. The most recent antenatal surveillance for HIV-1 sero-prevalence in 1999 revealed the following. The national prevalence rate for 1999 was 22.4% compared with the 1998 rate of 22.8%. The data highlighted the profound effect the epidemic had and will have on the disease burden in South Africa and by extension on the social and economic fronts. This view was emphasised by the impact HIV-1 infection had on tuberculosis. For example, sentinel surveys have attributed 44% of tuberculosis cases to HIV-1 infection. Moreover, the high prevalence of sexually transmitted infections will certainly exacerbate the HIV-1 epidemic.

AIDS-Related Opportunistic Infections↗
PubMed2000

A short course of oral aspirin increases IL-18-induced interferon-gamma production in whole blood cultures.

The effect of aspirin on whole blood cytokine production was studied in six healthy volunteers. Four days after cessation of a 3-day regimen of 650 mg of oral aspirin, there was a 70% increase in interferon-gamma (IFN-gamma) production, stimulated by a combination of interleukin-18 (IL-18) plus lipopolysaccharide (p < 0.05). At this time, there was a 4-fold increase in the production of tumor necrosis factor-alpha (TNF-alpha) compared to pre-aspirin levels (p < 0.03). TNF-alpha and IFN-gamma production returned to pre-aspirin levels one month after the discontinuation of aspirin. Short-term aspirin treatment induces a significant increase in the production of these cytokines, probably through inhibition of prostaglandins. These data suggest a novel pathway through which long aspirin use reduces the risk of colon cancer, and may explain the effects of aspirin in inflammatory bowel disease.

Administration, Oral↗
PubMed2000

Rethinking globally relevant vaccine strategies to human immunodeficiency virus type-1.

According to the latest UNAIDS figures for 1999 there were an estimated 30.6 million people living with HIV-1, with 16,000 new HIV infections per day. The only global strategy of combating new HIV infections is to make a vaccine that is affordable to developing countries, where greater than 90% of new infections occur, and that has enough efficacy to interrupt high rates of transmission. This review critically examines: 1) important immune parameters that should be considered which will allow an understanding of preventative vaccine design and 2) the mechanisms underlying immune destruction during HIV-1 infection that will facilitate design of therapeutic vaccines. A realistic goal of a preventative vaccine is to elicit protective immune responses in vaccinees that would prevent HIV-1 from replicating extensively in the host. Components of protective immunity are thought to include neutralizing antibodies (NAB) and cytotoxic T lymphocytes (CTL). Rethinking vaccine strategies has to take into account that HIV-1 vaccines must elicit primary cellular and humoral immunity via dendritic cell and Langerhan cell priming. It is only under these conditions that boosting immunity with subsequent vaccinations will allow high enough CTL effector cells and NAB titres to impede or to prevent HIV-1 replication. Success of therapeutic vaccine strategies, has to take into consideration the pathology of persistent immune stimulation by chronic HIV-1 infection. To re-stimulate immunity and re-direct immune responses, chronic immune stimulation by HIV-1 has to be alleviated by reducing high levels of viral antigen presentation by suppressing virus with antiretroviral agents. Such treatment courses may only have to be transient, long enough for immunity to respond to an immunogenic stimulus. Short-course drug therapy may then be an affordable option for many countries already carrying a high burden of HIV-1/AIDS.

AIDS Vaccines↗
PubMed1999

Gene expression, synthesis, and secretion of interleukin 18 and interleukin 1beta are differentially regulated in human blood mononuclear cells and mouse spleen cells.

Interleukin (IL)-18, formerly called interferon gamma (IFN-gamma)-inducing factor, is biologically and structurally related to IL-1beta. A comparison of gene expression, synthesis, and processing of IL-18 with that of IL-1beta was made in human peripheral blood mononuclear cells (PBMCs) and in human whole blood. Similar to IL-1beta, the precursor for IL-18 requires processing by caspase 1. In PBMCs, mature but not precursor IL-18 induces IFN-gamma; in whole human blood stimulated with endotoxin, inhibition of caspase 1 reduces IFN-gamma production by an IL-1beta-independent mechanism. Unlike the precursor for IL-1beta, precursor for IL-18 was expressed constitutively in PBMCs and in fresh whole blood from healthy human donors. Western blotting of endotoxin-stimulated PBMCs revealed processed IL-1beta in the supernatants via an caspase 1-dependent pathway. However, in the same supernatants, only unprocessed precursor IL-18 was found. Unexpectedly, precursor IL-18 was found in freshly obtained PBMCs and constitutive IL-18 gene expression was present in whole blood of healthy donors, whereas constitutive IL-1beta gene expression is absent. Similar to human PBMCs, mouse spleen cells also constitutively contained the preformed precursor for IL-18 and expressed steady-state IL-18 mRNA, but there was no IL-1beta protein and no spontaneous gene expression for IL-1beta in these same preparations. We conclude that although IL-18 and IL-1beta are likely members of the same family, constitutive gene expression, synthesis, and processing are different for the two cytokines.

Animals↗
PubMed1998

Interleukin 18 stimulates HIV type 1 in monocytic cells.

The cytokine interleukin (IL) 18 (formerly interferon gamma-inducing factor) induces the T helper type 1 response. In the present studies, IL-18 increased HIV type 1 (HIV-1) production from 5- to 30-fold in the chronically infected U1 monocytic cell line. Inhibition of tumor necrosis factor (TNF) activity by the addition of TNF-binding protein reduced IL-18-stimulated HIV-1 production by 48%. In the same cultures, IL-18-induced IL-8 was inhibited by 96%. Also, a neutralizing anti-IL-6 mAb reduced IL-18-induced HIV-1 by 63%. Stimulation of U1 cells with IL-18 resulted in increased production of IL-6, and exogenous IL-6 added to U1 cells increased HIV-1 production 4-fold over control. A specific inhibitor of the p38 mitogen-activated protein kinase reduced IL-18-induced HIV-1 by 73%, and a 50% inhibition was observed at 0.05 microM. In the same cultures, IL-8 was inhibited by 87%. By gel-shift and supershift analyses, increased binding activity of the transcription factor NF-kappaB was measured in nuclear extracts from U1 cells 1 h after exposure to IL-18. These results demonstrate induction of HIV-1 by IL-18 in a monocyte target associated with an intermediate role for TNF and IL-6, activation of p38 mitogen-activated protein kinase, and nuclear translocation of NF-kappaB.

Base Sequence↗
PubMed1998

Interleukin-18 regulation of interferon gamma production and cell proliferation as shown in interleukin-1beta-converting enzyme (caspase-1)-deficient mice.

Interleukin-18 (IL-18) is a costimulatory factor for interferongamma (IFNgamma) production. Processing of pro-IL-18 by IL-1beta-converting enzyme (ICE) leads to the release of bioactive IL-18. Compared with wild-type (WT) mice, splenocytes from ICE-deficient mice produced low IFNgamma after lipopolysaccharide (LPS) or zymosan (50% and 80% reduction). In contrast, IFNgamma production was unimpaired in ICE-deficient mice using Concanavalin A (Con A). Comparable results were obtained when endogenous IL-18 was blocked with a neutralizing antibody. LPS-induced IFNgamma was also reduced by an ICE inhibitor. Exogenous IL-18 augmented zymosan-induced IFNgamma production in WT mice. In ICE-deficient cells, IFNgamma production was only partially restored by IL-18. The reduced levels of IFNgamma in ICE-deficient mice were not due to a lack of IL-12, because zymosan induced IL-12 equally in WT and in ICE-deficient mice. IFNgamma is an important regulator of cell proliferation. In accordance, splenocytes from ICE-deficient mice proliferated more when stimulated with LPS, but not with Con A. Furthermore, in ovalbumin-sensitized ICE-deficient mice, proliferation of lymph node cells in response to the specific antigen was not altered. Exogenous IFNgamma inhibited, whereas blockade of endogenous IFNgamma or IL-18 increased, LPS induced splenocyte proliferation both in WT and in ICE-deficient mice. Our results show that IL-18 is an IL-12-independent regulator of IFNgamma production and of cell proliferation induced by microbial stimuli. However, ICE-dependent processing of IL-18 is not needed for response to mitogens or antigens.

Animals↗
PubMed1998

Interleukin-18 (IFNgamma-inducing factor) induces IL-8 and IL-1beta via TNFalpha production from non-CD14+ human blood mononuclear cells.

IL-18 is synthesized as a precursor molecule without a signal peptide but requires the IL-1beta converting enzyme (ICE, caspase-1) for cleavage into a mature peptide. Human precursor IL-18 was expressed, purified, and cleaved by ICE into a 18-kD mature form. Mature IL-18 induced IL-8, macrophage inflammatory protein-1alpha, and monocyte chemotactic protein-1 in human peripheral blood mononuclear cells in the absence of any co-stimuli. Blocking IL-1 with IL-1 receptor antagonist resulted in a 50% reduction in IL-8. Neutralization of TNF with TNF binding protein resulted in a 66% reduction in IL-1beta, an 80% reduction of IL-8, and an 88% reduction in mean TNFalpha mRNA. In purified CD14+ cells but not CD3+/CD4+, IL-18 induced gene expression and synthesis of IL-8 and IL-1beta. TNFalpha production was induced in the non-CD14+ population and there was no induction of TNFbeta by IL-18. In purified natural killer cells, IL-18 induced IL-8 that was also inhibited by TNF binding protein. IL-18 did not induce antiinflammatory cytokines, IL-1Ra, or IL-10, although IL-18 induction of TNFalpha was inhibited by IL-10. In the presence of IFNgamma, IL-18-induced TNFalpha was enhanced and there was an increase in the mature form of IL-1beta. We conclude that IL-18 possesses proinflammatory properties by direct stimulation of gene expression and synthesis of TNFalpha from CD3+/CD4+ and natural killer cells with subsequent production of IL-1beta and IL-8 from the CD14+ population.

CD3 Complex↗
PubMed1998

Interleukin-18 enhances lipopolysaccharide-induced interferon-gamma production in human whole blood cultures.

Interleukin-18 (IL-18) is a newly described cytokine, formerly called interferon-gamma (IFN-gamma)-inducing factor. In a simple 24-h human whole blood culture, IFN-gamma was produced by the combination of lipopolysaccharide (LPS) plus IL-18. To liberate cytokines in the leukocyte and red cell compartments, the detergent Triton X-100 was added to the entire blood culture. The combination of low concentrations of LPS plus IL-18 induced a 3- to 5-fold greater production of IFN-gamma than did either stimulant alone. Tumor necrosis factor-alpha (TNF-alpha), IL-6, and IL-8 were also produced. The presence of IL-10 completely suppressed the production of IFN-gamma and reduced that of TNF-alpha, IL-6, and IL-8. Thus, IFN-gamma, TNF-alpha, IL-8, and IL-6 are produced in a single whole blood culture, making correlations in the synthesis of a T helper type 1 cytokine and proinflammatory cytokines with disease activity possible in a single culture.

Adult↗
PubMed1998

Spontaneous and inducible cytokine responses in healthy humans receiving a single dose of IFN-alpha2b: increased production of interleukin-1 receptor antagonist and suppression of IL-1-induced IL-8.

The present study was to determine whether the administration of a single dose of interferon-alpha2B (IFN-alpha2B) to healthy humans affects endogenous (or basal level) or inducible cytokines in a whole blood, ex vivo culture. Twenty-four healthy volunteers received an s.c. injection of IFN-alpha2b (3 x 10(6)U), and 4 volunteers received the vehicle as placebo. The study was blinded. Blood was drawn before and 3, 6, 12, and 24 h after the injection and incubated in the presence or absence of lipopolysaccharide (LPS) or interleukin-1beta (IL-1beta). After 24 hs, the plasma was assayed for tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, IL-1beta, IL-1 receptor antagonist (IL-1Ra), and IL-8. Treatment with IFN-alpha2b was associated with a 4.8-fold increase in the endogenous production of IL-1Ra in cultured blood sustained over 24 hs. In contrast, no change in endogenous IL-1Ra production was detected in the controls. A significant suppression (75%, p < 0.001) of IL-1beta-induced IL-8 production 3 and 6 h after IFN-alpha2b compared with control subjects was observed. These effects were also observed when IFN-alpha2b was added directly to whole blood cultures in vitro. In contrast to IL-1 stimulation, LPS stimulation of blood from IFN-alpha2b-treated subjects resulted in enhanced IL-1beta and TNF-alpha production. These results suggest that a single dose of IFN-alpha2b induces an anti-inflammatory state for endogenous stimuli but a proinflammatory state for exogenous endotoxin.

Adult↗
PubMed1998

Overview of interleukin-18: more than an interferon-gamma inducing factor.

Initially described in 1989 as interferon-gamma (IFN-gamma) inducing factor (IGIF), interleukin-18 (IL-18) is a novel pro-inflammatory cytokine that is clearly more than an inducer of IFN-gamma. The cytokine possesses several biological properties such as activation of nuclear factor-kappaB (NF-kappaB), Fas ligand expression, the induction of both CC and CXC chemokines, and increased production of competent human immunodeficiency virus. Most activities are due to a receptor complex that recruits the IL-1 receptor-activating kinase (IRAK), leading to translocation of NF-kappaB. This property and others support the concept that IL-18 is related to the IL-1 family. Indeed, one of the IL-18 receptor chains is the IL-1 receptor-related protein, a member of the IL-1R family. In addition, IL-18 is structurally similar to IL-1beta and like IL-1beta is first synthesized as a leaderless precursor requiring the IL-1beta converting enzyme for cleavage into an active molecule. The biology of IL-18 is reviewed in the overview and the implication for a role for this cytokine in disease is presented.

Animals↗
PubMed1995

Patterns of cytokine expression in community-acquired pneumonia.

BACKGROUND: Pneumonia continues to be a major cause of disease and death among patients worldwide. Aspects of the host response to infection, such as the release of cytokines, may be contributing to the persistent morbidity and mortality. METHODS: Plasma levels of cytokines interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) were measured in critically ill patients with pneumonia (ICUP; n = 12) and less severely ill patients with pneumonia (NONICUP; n = 8), and in 2 additional control groups of patients, viz, severely ill postoperative patients without evidence of infection (POSTOP; n = 11) and less severely ill patients with nonpneumonia infections (NONP; n = 9). All four groups of patients were studied in a multivariate one-way analysis of variance using the parameter vector: plasma IL-1 beta, IL-6, TNF-alpha, systolic blood pressure, diastolic blood pressure, plasma urea, creatinine, and temperature. Thereafter the significance of individual parameters were assessed by univariate analysis and pairwise comparisons. RESULTS: All cytokine concentrations were highest in the ICUP group. In the case of IL-1 beta, levels were significantly higher in the ICUP group when compared with the noninfected POSTOP group. The acute physiology and chronic health evaluation (APACHE) II scores were identical in these two groups (17 +/- 3 [SD] and 10 +/- 1, respectively, not significantly different). Intermediate levels were found in those groups with intermediate levels of infection. The IL-6 levels were not significantly different between the groups and in particular, the levels in the ICUP and POSTOP groups were similar. The TNF-alpha levels tended to mimic those of IL-1 beta, although the significant difference found was between the ICUP and NONICUP groups which had significantly different APACHE II scores (17 +/- 3 vs 4.4 +/- 1, respectively). No association between cytokine levels and patient mortality was demonstrated. CONCLUSION: Among the cytokines, IL-1 beta appeared to be associated with the severity of infection, IL-6 appears to reflect severity of stress whether of infection or noninfective origin, and TNF-alpha may be a marker of severity of pneumonia.

APACHE↗
PubMed1992

Interleukin-1 from baboon peripheral blood monocytes: altered response to endotoxin (lipopolysaccharide) and Staphylococcus aureus stimulation compared with human monocytes.

The baboon Papio ursinus does not elicit a febrile response upon injection with endotoxin, but fever is produced when injected with Staphylococcus aureus particles (Zurowsky, Y., H. Laburn, D. Mitchell, Can. J. Physiol. Pharmacol. 65, 1402-1407 (1987)). We address the question whether baboon peripheral blood monocytes produce interleukin-1 (IL-1) when stimulated with endotoxin or S. aureus particles in culture. Results show that little IL-1 biological activity was produced from endotoxin-stimulated baboon peripheral blood monocytes, compared with S. aureus-stimulated cells. Measurements of IL-1 beta by radioimmunoassay supported these data. This is contrary to data from human monocytes, which show greater sensitivity to endotoxin. Examination of IL-1 beta mRNA from endotoxin-stimulated and S. aureus-stimulated baboon monocytes, however, showed that more mRNA for IL-1 beta was present in endotoxin-stimulated monocytes than in cells stimulated with S. aureus. This illustrates the possibility that the production and/or the secretion of IL-1 beta is not as efficient in baboon monocytes as it is in human monocytes.

Animals↗
PubMed1989

Studies on IL-1 receptors on D10S T-helper cells: demonstration of two molecularly and antigenically distinct IL-1 binding proteins.

Receptor binding studies were performed on the interleukin-1 (IL-1) sensitive T-helper cell line D10S, a stable line which proliferates to subfemtomolar concentrations of IL-1 in the absence of mitogens. IL-1 binds in a specific and saturable manner and Scatchard analysis at 4 degrees C reveals one class of binding affinity. On D10S cells, the Kd for IL-1 is 227 pM +/- 80, with 11,000 (range 3,300 to 23,800) sites per cell. EL4.6.1 cells, which are less sensitive to IL-1, bind with a single class of high affinity sites (55 pM; 4,000 sites). D10S cells incubated 18 h with IL-1 display reduced IL-1 receptor (IL-1R) numbers and affinities, consistent with reduced (75%, p less than 0.005) proliferation to subsequent IL-1; preincubation with IL-4 increases the number of IL-1R which is associated with increased (200%, p less than 0.001) proliferation to IL-1. The molecular mass of the major (80 kD) IL-1R binding [125I]IL-1 alpha on D10S cells was consistently observed at 73 kD as compared to the 80 kD molecule on the EL4 cells. On the other hand, crosslinking studies with [125I]IL-1 beta on D10S cells revealed a novel 46 kD band on gradient SDS-PAGE corresponding to a binding protein of 29 to 30 kD, which is antigenically distinct from the 80 kD IL-1R. Crosslinking of D10S or EL4 cells at 4 degrees C in the presence of phytohemagglutinin (PHA) and labeled IL-1 enhanced the appearance of the 30 kD IL-1 binding protein. The findings are consistent with a two-chain model for the IL-1R, although Scatchard analysis did not consistently indicate two classes of affinities. IL-1 binding to the 80 kD protein may form a heteroduplex with the 30 kD IL-1R which could account for the presence of the 120 to 130 kD IL-1 crosslinked proteins observed by several investigators.

Animals↗
PubMedDate not supplied

Interleukin 1 receptors and biological responses.

Interleukin 1 (IL-1) is a polypeptide which possesses a wide variety of biological properties. IL-1 was originally studied as "endogenous pyrogen" and "leukocytic endogenous mediator" and more recently as "lymphocyte activating factor." Within a few minutes after intravenous injection into experimental animals, IL-1 triggers events in the hypothalamus to initiate fever, slow-wave sleep, and the release of a variety of neuropeptides. The nature of the IL-1 receptors (IL-1R) is important to the understanding of IL-1's multiple action in mediating both neural and non-neural events. In this paper, the data are reviewed on the physical nature of the dominant, high-binding 80 kDa IL-1R isolated from murine T cells. In addition, newer studies demonstrate the existence of other IL-1 binding proteins which may participate as functional IL-1 receptors. These are a 68-75 kDa binding protein found on B cells and a 26-30 kDa binding protein found on T cells and mesangial cells. There is a considerable discrepancy between the number and affinities of the 80 kDa IL-1R and biological responses. Little is known about the relationship of the 68-75 or 26-30 kDa IL-R's biological responses. It is possible that, similar to neurotransmitter receptors, multiple chains of different binding proteins participate in the signal transduction of IL-1. The hydrolysis of non-phosphatidyl inositol membrane phospholipids plays an important role in responses to IL-1.

Animals↗