Induction of dendritic cell differentiation by IFN-alpha in systemic lupus erythematosus

Dendritic cells (DCs) are important in regulating both immunity and tolerance. Hence, we hypothesized that systemic lupus erythematosus (SLE), an autoimmune disease characterized by autoreactive B and T cells, may be caused by alterations in the functions of DCs. Consistent with this, monocytes from SLE patients' blood were found to function as antigen-presenting cells, in vitro. Furthermore, serum from SLE patients induced normal monocytes to differentiate into DCs. These DCs could capture antigens from dying cells and present them to CD4-positive T cells. The capacity of SLE patients' serum to induce DC differentiation correlated with disease activity and depended on the actions of interferon-alpha (IFN-alpha). Thus, unabated induction of DCs by IFN-alpha may drive the autoimmune response in SLE.

Nucleic acids of mammalian origin can act as endogenous ligands for Toll-like receptors and may promote systemic lupus erythematosus

Raised serum levels of interferon (IFN)-alpha have been observed in systemic lupus erythematosus (SLE) patients, and these levels are correlated with both disease activity and severity. The origin of this IFN-alpha is still unclear, but increasing evidence suggests the critical involvement of activated plasmacytoid predendritic cells (PDCs). In SLE patients, DNA and RNA viruses, as well as immune complexes (ICs), that consist of autoantibodies specific to self-DNA and RNA protein particles can stimulate production of IFN-alpha. We have developed three series of oligonucleotide (ODN)-based inhibitors of Toll-like receptor (TLR) signaling. These ODNs include inhibitors of TLR9, inhibitors of TLR7 but not TLR9, and sequences that inhibit both TLR7 and TLR9. Specificity of these inhibitors is confirmed by inhibition of IFN-alpha production by PDCs in response to DNA or RNA viruses. We show that mammalian DNA and RNA, in the form of ICs, are potent self-antigens for TLR9 and TLR7, respectively, and induce IFN-alpha production by PDCs. This work suggests that TLRs may have a critical role in the promotion of lupus through the induction of IFN-alpha by PDCs. These inhibitors of TLR signaling thus represent novel therapeutic agents with potential for the treatment of lupus.

IFN-alpha and IL-10 induce the differentiation of human type 1 T regulatory cells

CD4(+) T regulatory type 1 (Tr1) cells suppress Ag-specific immune responses in vitro and in vivo. Although IL-10 is critical for the differentiation of Tr1 cells, the effects of other cytokines on differentiation of naive T cells into Tr1 cells have not been investigated. Here we demonstrate that endogenous or exogenous IL-10 in combination with IFN-alpha, but not TGF-beta, induces naive CD4(+) T cells derived from cord blood to differentiate into Tr1 cells: IL-10(+)IFN-gamma(+)IL-2(-/low)IL-4(-). Naive CD4(+) T cells derived from peripheral blood require both exogenous IL-10 and IFN-alpha for Tr1 cell differentiation. The proliferative responses of the Tr1-containing lymphocyte populations, following activation with anti-CD3 and anti-CD28 mAbs, were reduced. Similarly, cultures containing Tr1 cells displayed reduced responses to alloantigens via a mechanism that was partially mediated by IL-10 and TGF-beta. More importantly, Tr1-containing populations strongly suppressed responses of naive T cells to alloantigens. Collectively, these results show that IFN-alpha strongly enhances IL-10-induced differentiation of functional Tr1 cells, which represents a first major step in establishing specific culture conditions to generate T regulatory cells for biological and biochemical analysis, and for cellular therapy to induce peripheral tolerance in humans.

Increased circulating cytokines in patients with myocarditis and cardiomyopathy

OBJECTIVES

To elucidate the potential role of cytokines in the pathogenesis of cardiomyopathy and myocarditis.

BACKGROUND

Experimental studies show that certain cytokines depress myocardial contractility and that tumour necrosis factor-alpha plays an important part in the pathogenesis of myocardial injury in animal models of viral and autoimmune myocarditis.

METHODS

Plasma interleukin 1-alpha, interleukin 1-beta, interleukin-2, interleukin-6, tumour necrosis factor-alpha, tumour necrosis factor-beta, granulocyte-macrophage colony stimulating factor, granulocyte colony stimulating factor, macrophage colony stimulating factor, interferon-alpha and interferon-gamma were measured in 13 patients with acute myocarditis, 23 patients with dilated cardiomyopathy, 51 patients with hypertrophic cardiomyopathy, nine patients with acute myocardial infarction, 18 patients with angina pectoris, 12 patients with essential hypertension and 17 healthy controls.

RESULTS

Increased concentrations of cytokines were not detected in the controls. In patients with acute myocarditis, interleukin 1-alpha was detected in 23% (mean (SD) 25 (11) pg/ml), tumour necrosis factor-alpha in 46% (61 (31) pg/ml), and macrophage colony stimulating factor was 2.5 (1.8) ng/ml (normal 1.9 (0.4)). In patients with dilated cardiomyopathy, tumour necrosis factor-alpha was detected in 35% (402 (555) pg/ml). In patients with hypertrophic cardiomyopathy, interleukin-2 was detectable in 14% (2318 (4738) pg/ml) and tumour necrosis factor-alpha ws detected in 20% (992 (1517) pg/ml). The concentration of macrophage colony stimulating factor was raised in patients with acute myocardial infarction. Granulocyte colony stimulating factor was often increased in myocarditis, cardiomyopathies, acute myocardial infarction, and angina pectoris--suggesting activation of macrophages and/or endothelial cells--but this increase was not specific to these diseases. Increased concentrations of cytokines were not found in patients with essential hypertension.

CONCLUSION

These results suggest that cytokines may play a part in the pathogenesis of myocardial injury in myocarditis and cardiomyopathies and that further studies to explore the potential pathogenetic role of cytokines in myocardial diseases may be warranted.

Activation of type I interferon system in systemic lupus erythematosus correlates with disease activity but not with antiretroviral antibodies

The objective was to investigate the relation between serum levels of interferon-alpha (IFN-alpha), the activity of an endogenous IFN-alpha inducing factor (SLE-IIF), clinical and immunological disease activity as well as serum levels of antiretroviral antibodies in SLE. Serum levels of IFN-alpha were measured in serial sera from 30 patients sampled at different stages of disease activity (SLEDAI score). The SLE-IIF activity was measured by its ability to induce IFN-alpha production in cultures of normal peripheral blood mononuclear cells. Both serum IFN-alpha and SLE-IIF increased markedly at flare in serially followed patients. The SLEDAI score, levels of anti-dsDNA antibodies and IL-10 correlated positively, and complement components Clq, C3 and leukocytes correlated inversely with serum concentrations of IFN-alpha. The extent of multiple organ involvement correlated with serum IFN-alpha. No relation between concentrations of retroviral peptide binding antibodies and IFN-alpha or SLE-IIF activity was found. The close relationship between disease activity in SLE patients and IFN-alpha serum levels suggests that activation of the type 1 IFN system might be of importance in the disease process.

Cytokines induced during chronic hepatitis B virus infection promote a pathway for NK cell-mediated liver damage

Hepatitis B virus (HBV) causes chronic infection in more than 350 million people worldwide. It replicates in hepatocytes but is non-cytopathic; liver damage is thought to be immune mediated. Here, we investigated the role of innate immune responses in mediating liver damage in patients with chronic HBV infection. Longitudinal analysis revealed a temporal correlation between flares of liver inflammation and fluctuations in interleukin (IL)-8, interferon (IFN)-α, and natural killer (NK) cell expression of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) directly ex vivo. A cross-sectional study confirmed these findings in patients with HBV-related liver inflammation compared with healthy carriers. Activated, TRAIL-expressing NK cells were further enriched in the liver of patients with chronic HBV infection, while their hepatocytes expressed increased levels of a TRAIL death–inducing receptor. IFN-α concentrations found in patients were capable of activating NK cells to induce TRAIL-mediated hepatocyte apoptosis in vitro. The pathogenic potential of this pathway could be further enhanced by the ability of the IFN-α/IL-8 combination to dysregulate the balance of death-inducing and regulatory TRAIL receptors expressed on hepatocytes. We conclude that NK cells may contribute to liver inflammation by TRAIL-mediated death of hepatocytes and demonstrate that this non-antigen–specific mechanism can be switched on by cytokines produced during active HBV infection.

Interferon-alpha and interleukin-12 are induced differentially by Toll-like receptor 7 ligands in human blood dendritic cell subsets

Dendritic cells (DCs) play a crucial role in the immune responses against infections by sensing microbial invasion through toll-like receptors (TLRs). In humans, two distinct DC subsets, CD11c(-) plasmacytoid DCs (PDCs) and CD11c(+) myeloid DCs (MDCs), have been identified and can respond to different TLR ligands, depending on the differential expression of cognate TLRs. In this study, we have examined the effect of TLR-7 ligands on human DC subsets. Both subsets expressed TLR-7 and could respond to TLR-7 ligands, which enhanced the survival of the subsets and upregulated the surface expression of costimulatory molecules such as CD40, CD80, and CD86. However, the cytokine induction pattern was distinct in that PDCs and MDCs produced interferon (IFN)-alpha and interleukin (IL)-12, respectively. In response to TLR-7 ligands, the Th1 cell supporting ability of both DC subsets was enhanced, depending on the cytokines the respective subsets produced. This study demonstrates that TLR-7 exerts its biological effect in a DC subset-specific manner.

High serum IFN-alpha activity is a heritable risk factor for systemic lupus erythematosus

Interferon alpha (IFN-alpha) levels are elevated in many patients with systemic lupus erythematosus (SLE); however it is not known whether high serum IFN-alpha activity is a cause or a result of the disease. We studied 266 SLE patients and 405 of their healthy relatives, and frequently found high serum IFN-alpha activity in both patients and healthy relatives as compared to healthy unrelated individuals. High IFN-alpha activity was clustered in specific families in both SLE patients and their healthy first-degree relatives, suggesting a heritable trait. Heritability was also supported by quantitative familial correlation of IFN-alpha activity, concordance in affected sib pairs and frequent transmission of the high IFN-alpha activity trait from parents to offspring. Autoantibodies to RNA-binding proteins and double-stranded DNA were associated with high IFN-alpha activity in SLE patients; however these autoantibodies were very uncommon in healthy family members and did not explain the observed familial correlations. The frequency of high IFN-alpha activity was similar across all studied ethnic backgrounds. These data suggest that high serum IFN-alpha activity is a complex heritable trait, which plays a primary role in SLE pathogenesis.

Human asymptomatic Ebola infection and strong inflammatory response

BACKGROUND

Ebola virus is one of the most virulent pathogens, killing a very high proportion of patients within 5-7 days. Two outbreaks of fulminating haemorrhagic fever occurred in northern Gabon in 1996, with a 70% case-fatality rate. During both outbreaks we identified some individuals in direct contact with sick patients who never developed symptoms. We aimed to determine whether these individuals were indeed infected with Ebola virus, and how they maintained asymptomatic status.

METHODS

Blood was collected from 24 close contacts of symptomatic patients. These asymptomatic individuals were sampled 2, 3, or 4 times during a 1-month period after the first exposure to symptomatic patients. Serum samples were analysed for the presence of Ebola antigens, virus-specific IgM and IgG (by ELISA and western blot), and different cytokines and chemokines. RNA was extracted from peripheral blood mononuclear cells, and reverse transcriptase-PCR assays were done to amplify RNA of Ebola virus. PCR products were then sequenced.

FINDINGS

11 of 24 asymptomatic individuals developed both IgM and IgG responses to Ebola antigens, indicating viral infection. Western-blot analysis showed that IgG responses were directed to nucleoprotein and viral protein of 40 kDa. The glycoprotein and viral protein of 24 kDa genes showed no nucleotide differences between symptomatic and asymptomatic individuals. Asymptomatic individuals had a strong inflammatory response characterised by high circulating concentrations of cytokines and chemokines.

INTERPRETATION

This study showed that asymptomatic, replicative Ebola infection can and does occur in human beings. The lack of genetic differences between symptomatic and asymptomatic individuals suggest that asymptomatic Ebola infection did not result from viral mutations. Elucidation of the factors related to the genesis of the strong inflammatory response occurring early during the infectious process in these asymptomatic individuals could increase our understanding of the disease.

Activation of the type I interferon system in primary Sjögren's syndrome: a possible etiopathogenic mechanism

OBJECTIVE

The etiopathogenesis of primary Sjögren's syndrome (SS) is largely unknown. In other autoimmune diseases, type I interferon (IFN) may play a pivotal role by triggering and sustaining the disease process. We therefore aimed to determine whether patients with primary SS had an activated type I IFN system.

METHODS

Salivary gland biopsy specimens and sera from patients with primary SS were investigated for the occurrence of IFNalpha-producing cells and measurable IFNalpha levels, respectively. The ability of primary SS sera together with apoptotic or necrotic cells to induce IFNalpha production in normal peripheral blood mononuclear cells was examined. The IFNalpha inducer was characterized, and IFNalpha-producing cells were identified. Clinical data were correlated with the IFNalpha-inducing capacity of primary SS sera.

RESULTS

Numerous IFNalpha-producing cells were detected in salivary gland biopsy specimens, despite low serum IFNalpha levels. Autoantibodies to RNA-binding proteins, combined with material released by necrotic or late apoptotic cells, were potent inducers of IFNalpha production in plasmacytoid dendritic cells (PDCs). This appeared to be attributable to RNA-containing immune complexes triggering PDCs by means of RNA and interaction with Fcgamma receptor IIa. The IFNalpha-inducing capacity of sera was associated with positive results of a labial salivary gland biopsy (focus score >/=1) and with dermatologic, hematologic, and pulmonary manifestations.

CONCLUSION

Patients with primary SS have an activated type I IFN system. Although virus may initiate the production of IFN, the continued IFNalpha synthesis is caused by RNA-containing immune complexes that activate PDCs to prolong IFNalpha production at the tissue level. This IFNalpha promotes the autoimmune process by a vicious circle-like mechanism, with increased autoantibody production and formation of more endogenous IFNalpha inducers.

Reduced blood CD123+ (lymphoid) and CD11c+ (myeloid) dendritic cell numbers in primary HIV-1 infection

Successful immunologic control of HIV infection is achieved only in rare individuals. Dendritic cells (DCs) are required for specific antigen presentation to naive T lymphocytes and for antiviral, type I interferon secretion. Two major blood DC populations are found: CD11c+ (myeloid) DCs, which secrete IL-12, and CD123+ (IL-3-receptor+) DCs (lymphoid), which secrete type I interferons in response to viral stimuli. The authors have previously found a decreased proportion of blood CD11c+ DCs in chronic HIV+ patients. In this study, 26 to 57 days after infection and before treatment, CD123+ and CD11c+ DC numbers were dramatically reduced in 13 HIV+ patients compared with 13 controls (P =.0002 and P =.001, respectively). After 6 to 12 months of highly active antiretroviral therapy, DC subpopulation average numbers remained low, but CD123+ DC numbers increased again in 5 of 13 patients. A strong correlation was found between this increase and CD4 T-cell count increase (P =.0009) and plasma viral load decrease (P =.009). Reduced DC numbers may participate in the functional impairment of HIV-specific CD4+ T cells and be responsible for the low type I interferon responsiveness already known in HIV infection. The restoration of DC numbers may be predictive of immune restoration and may be a goal for immunotherapy to enhance viral control in a larger proportion of patients.

Phase I clinical trial: T-cell therapy for prostate cancer using autologous dendritic cells pulsed with HLA-A0201-specific peptides from prostate-specific membrane antigen

BACKGROUND

Conventional treatment for metastatic prostate cancer have failed to demonstrate curative potential in all patients. Investigations involving the role of T-cell immunity in the clearance of neoplastic cells are now available. Development of T-cell immunotherapy may give a new approach to the treatment of advanced metastatic prostate cancer.

METHODS

A phase I clinical trial assessing the administration of autologous dendritic cells (DC) pulsed with HLA-A0201-specific prostate-specific membrane antigen (PSMA) peptides were conducted. Participants were divided into five groups receiving four or five infusions of peptides alone (PSM-P1 or PSM-P2; groups 1 and 2, respectively), autologous DC (group 3), or DC pulsed with PSM-P1 or P2 (groups 4 and 5, respectively).

RESULTS

No significant toxicity was observed in all five groups. Cellular response against PSM-P1 and -P2 was observed in HLA-A2+ patients infused with DC pulsed with PSM-P1 or -P2 (groups 4 and 5), respectively. An average decrease in PSA was detected only in group 5. Seven partial responders were identified based on NPCP criteria + PSA.

CONCLUSIONS

Infusions of test substances were well tolerated by all study participants. Detection of cellular response and decrease in PSA level in some patients who received DC pulsed with PSM-P2 indicate this method's potential in prostate cancer therapy.

Symptom pathogenesis during acute influenza: interleukin-6 and other cytokine responses

In experimental human influenza infection initiated by nasal inoculation, the magnitude of viral replication, fever, and symptoms correlate with nasopharyngeal lavage fluid levels of various cytokines. Our aim was to assess these relationships in patients with naturally occurring acute influenza. Patients with culture-positive influenza illness of less than 36 hr of duration were studied. Nasopharyngeal washing were collected at enrollment and on Day 2, 4, 6 and 8 for quantitative virus isolation and IL-6, TNF-alpha, INF-alpha, INF-gamma and IL-10 determinations. Blood samples collected at entry and on Day 2 and 6 were processed to assess plasma cytokines and circulating influenza RNA. Patients received either oseltamivir or placebo for 5 days. We assessed the correlation between nasopharyngeal lavage fluid or blood levels of cytokines before treatment and viral titers, symptom severity and fever. Sixteen adult subjects (median age of 22 years) were studied. In this small group of patients no significant differences between placebo and oseltamivir patients were found in viral replication or measures of cytokines. Thus the data for all 16 subjects were pooled for analysis. At entry, influenza A viruses were cultured from nasopharyngeal washes at a median titer of 4.8 log(10)TCID(50)/ml of wash. Viral titers correlated positively with symptom score (P = 0.006) and temperature values (P < 0.001). Viral titers, fever and symptoms were highest at enrollment and fell in parallel during the subsequent days. RT-PCR assays failed to detect influenza RNA in the white blood cells from any patient. We observed a significant release, in both nasopharyngeal lavage fluid and in plasma, of IL-6, TNF-alpha, INF-alpha, INF-gamma and IL-10. At entry high IL-6 levels were detected in the nasopharyngeal lavage fluid (median 10.3 pg/ml) and plasma (median 5.1 pg/ml) of all patients. We found a positive correlation between plasma IL-6 levels and both symptom scores and temperature values (P < 0.05), as well as a positive correlation between nasopharyngeal lavage fluid levels of IL-6 and TNF-alpha and temperature (P < 0.05). We did not find significant associations between symptoms, fever and levels of INF-alpha, INF-gamma or IL-10. The magnitude of early decrease in viral titers correlated with initial levels of INF-gamma in nasopharyngeal lavage fluid (P < 0.05). Significant production of IL-6, TNF-alpha, INF-alpha, INF-gamma and IL-10 occurs in response to community acquired influenza A illness. As in experimental influenza, symptoms and fever in natural acute influenza correlate with the release of IL-6.

Detection of interferon alpha protein reveals differential levels and cellular sources in disease

Type I interferons (IFNs) are essential mediators of antiviral responses. These cytokines have been implicated in the pathogenesis of autoimmunity, most notably systemic lupus erythematosus (SLE), diabetes mellitus, and dermatomyositis, as well as monogenic type I interferonopathies. Despite a fundamental role in health and disease, the direct quantification of type I IFNs has been challenging. Using single-molecule array (Simoa) digital ELISA technology, we recorded attomolar concentrations of IFNα in healthy donors, viral infection, and complex and monogenic interferonopathies. IFNα protein correlated well with functional activity and IFN-stimulated gene expression. High circulating IFNα levels were associated with increased clinical severity in SLE patients, and a study of the cellular source of IFNα protein indicated disease-specific mechanisms. Measurement of IFNα attomolar concentrations by digital ELISA will enhance our understanding of IFN biology and potentially improve the diagnosis and stratification of pathologies associated with IFN dysregulation.

Markedly elevated levels of interferon (IFN)-gamma, IFN-alpha, interleukin (IL)-2, IL-10, and tumor necrosis factor-alpha associated with fatal Ebola virus infection

The role of immune mechanisms in the pathogenesis of Ebola hemorrhagic fever (EHF) remains to be elucidated. In this report, the serum cytokine levels of patients who died of EHF were compared with those of patients who recovered and those of control patients. A marked elevation of interferon (IFN)-gamma levels (>100 pg/mL) was observed in sequential serum samples from all fatal EHF cases compared with patients who recovered or controls. Markedly elevated serum levels of interleukin (IL)-2, IL-10, tumor necrosis factor (TNF)-alpha, and IFN-alpha were also noted in fatal EHF cases; however, they had a greater degree of variability. No differences were noted in serum levels of IL-4 and IL-6. mRNA quantitation from blood clots of the same patients showed relatively elevated levels of TNF-alpha and IFN-alpha in samples from EHF patients. Taken together, these results suggest that a high degree of immune activation accompanies and potentially contributes to a fatal outcome in EHF patients.

Comparison of procalcitonin with C-reactive protein, interleukin 6 and interferon-alpha for differentiation of bacterial vs. viral infections

BACKGROUND

Procalcitonin (PCT) concentration increases in bacterial infections but remains low in viral infections and inflammatory diseases. The change is rapid and the molecule is stable, making it a potentially useful marker for distinguishing between bacterial and viral infections.

METHODS

PCT concentration was determined with an immunoluminometric assay on plasma collected at admission in 360 infants and children hospitalized for bacterial or viral infection. It was compared with C-reactive protein (CRP), interleukin 6 and interferon-alpha measured on the same sample.

RESULTS

The mean PCT concentration was 46 microg/l (median, 17.8) in 46 children with septicemia or bacterial meningitis. PCT concentration was > 1 microg/l in 44 of 46 in this group and in 59 of 78 children with a localized bacterial infection who had a negative blood culture (sensitivity, 83%). PCT concentration was > 1 microg/l in 16 of 236 children with a viral infection (specificity, 93%). PCT concentration was low in 9 of 10 patients with inflammatory disease and fever. A CRP value > or =20 mg/l was observed in 61 of 236 patients (26%) with viral infection and in 105 of 124 patients (86%) with bacterial infection. IL-6 was > 100 pg/ml in 14% of patients infected with virus and in 53% with bacteria. A secretion of interferon-alpha was found in serum in 77% of viral infected patients and in 8.6% of bacterial infected patients.

CONCLUSIONS

In this study a PCT value of 1 microg/l or greater had better specificity, sensitivity and predictive value than CRP, interleukin 6 and interferon-alpha in children for distinguishing between viral and bacterial infections. PCT values are higher in invasive bacterial infections, but the cutoff value of 1 microg/l indicates the severity of the disease in localized bacterial infection and helps to decide antibiotic treatment in emergency room. PCT may be useful in an emergency room for differentiation of bacterial vs. viral infections in children and for making decisions about antibiotic treatments.

2'-O-methyl-modified RNAs act as TLR7 antagonists

RNA molecules such as single-stranded RNA (ssRNA) and small interfering RNA (siRNA) duplexes induce Toll-like receptor (TLR)-mediated immune stimulation after intracellular delivery. We have previously shown that selective incorporation of 2'-O-methyl (2'OMe) residues into siRNA abrogates cytokine production without reduction of gene silencing activity. Here we show that 2'OMe-modified RNA acts as a potent inhibitor of RNA-mediated cytokine induction in both human and murine systems. This activity does not require the direct incorporation of 2'OMe nucleotides into the immunostimulatory RNA or that the 2'OMe nucleotide-containing RNA be annealed as a complementary strand to form a duplex. Our results indicate that 2'OMe RNA acts as a potent antagonist of immunostimulatory RNA. We further show that 2'OMe RNA is able significantly to reduce both interferon-alpha (IFN-alpha) and interleukin-6 (IL-6) induction by the small-molecule TLR7 agonist loxoribine in human peripheral blood mononuclear cells (human PBMCs), in murine Flt3L dendritic cells (Flt3L DCs), and in vivo in mice. These results indicate that 2'OMe-modified RNA may have utility as an inhibitor of TLR7 with potential applications in the treatment of inflammatory and autoimmune diseases that involve TLR7-mediated immune stimulation.

Lipids, lipoproteins, triglyceride clearance, and cytokines in human immunodeficiency virus infection and the acquired immunodeficiency syndrome

Infection causes disturbances in lipid metabolism that may be mediated by cytokines. Therefore we studied plasma lipids, lipoproteins, triglyceride (TG) metabolism, and serum cytokines in three groups: patients with the acquired immunodeficiency syndrome (AIDS) without active secondary infection, patients with evidence of human immunodeficiency virus infection but without clinical AIDS (HIV+), and controls. Plasma TGs and FFA were increased in AIDS, while plasma cholesterol, high density lipoprotein (HDL) cholesterol, apolipoprotein-A-1 (Apo-A-1), low density lipoprotein (LDL) cholesterol, and Apo-B-100 levels were decreased. Increased TG levels in AIDS were primarily due to increases in very low density lipoprotein of normal composition; in addition, LDL and HDL were TG enriched. In HIV+, TGs and FFA were not increased, but total cholesterol, HDL cholesterol, Apo-A-1, and Apo-B-100 were significantly decreased. Interferon-alpha (IFN alpha) and C-reactive protein levels were increased in AIDS, but tumor necrosis factor and haptoglobin levels were not. There was a significant correlation between plasma TGs and IFN alpha levels (r = 0.477; P less than 0.01), but not between TGs and tumor necrosis factor, C-reactive protein, haptoglobin, or P-24 antigen. In addition, there was no relationship between circulating IFN alpha levels and plasma cholesterol, HDL cholesterol, Apo-A-1, LDL cholesterol, Apo-B-100, or FFA. TG clearance time and postheparin lipase were significantly decreased in AIDS and HIV+. There was a strong correlation between serum IFN alpha levels and TG clearance time in AIDS and HIV+ (r = 0.783; P less than 0.001). In summary, decreases in cholesterol and cholesterol containing lipoproteins (including HDL) in both AIDS and HIV+ precede the appearance of hypertriglyceridemia and are not related to IFN alpha or TG levels. Our data raise the possibility that with development of AIDS, subsequent increases in IFN alpha may contribute to increases in plasma TG levels in part by decreasing the clearance of TG.

Malaria Blood Stage Parasites Activate Human Plasmacytoid Dendritic Cells and Murine Dendritic Cells through a Toll-Like Receptor 9-Dependent Pathway

A common feature of severe Plasmodium falciparum infection is the increased systemic release of proinflammatory cytokines that contributes to the pathogenesis of malaria. Using human blood, we found that blood stage schizonts or soluble schizont extracts activated plasmacytoid dendritic cells (PDCs) to up-regulate CD86 expression and produce IFN-alpha. IFN-alpha production was also detected in malaria-infected patients, but the levels of circulating PDCs were markedly reduced, possibly because of schizont-stimulated up-regulation of CCR7, which is critical for PDC migration. The schizont-stimulated PDCs elicited a poor T cell response, but promoted gamma delta T cell proliferation and IFN-gamma production. The schizont immune stimulatory effects could be reproduced using murine DCs and required the Toll-like receptor 9 (TLR9)-MyD88 signaling pathway. Although the only known TLR9 ligand is CpG motifs in pathogen DNA, the activity of the soluble schizont extract was far greater than that of schizont DNA, and it was heat labile and precipitable with ammonium sulfate, unlike the activity of bacterial DNA. These results demonstrate that schizont extracts contain a novel and previously unknown ligand for TLR9 and suggest that the stimulatory effects of this ligand on PDCs may play a key role in immunoregulation and immunopathogenesis of human falciparum malaria.

The inducible CXCR3 ligands control plasmacytoid dendritic cell responsiveness to the constitutive chemokine stromal cell-derived factor 1 (SDF-1)/CXCL12

The recruitment of selected dendritic cell (DC) subtypes conditions the class of the immune response. Here we show that the migration of human plasmacytoid DCs (pDCs), the blood natural interferon alpha-producing cells, is induced upon the collective action of inducible and constitutive chemokines. Despite expression of very high levels of CXCR3, pDCs do not respond efficiently to CXCR3 ligands. However, they migrate in response to the constitutive chemokine stromal cell-derived factor 1 (SDF-1)/CXCL12 and CXCR3 ligands synergize with SDF-1/CXCL12 to induce pDC migration. This synergy reflects a sensitizing effect of CXCR3 ligands, which, independently of a gradient and chemoattraction, decrease by 20-50-fold the threshold of sensitivity to SDF-1/CXCL12. Thus, the ability of the constitutive chemokine SDF-1/CXCL12 to induce pDC recruitment might be controlled by CXCR3 ligands released during inflammation such as in virus infection. SDF-1/CXCL12 and the CXCR3 ligands Mig/CXCL9 and ITAC/CXCL1 display adjacent expression both in secondary lymphoid organs and in inflamed epithelium from virus-induced pathologic lesions. Because pDCs express both the lymph node homing molecule l-selectin and the cutaneous homing molecule cutaneous lymphocyte antigen, the cooperation between inducible CXCR3 ligands and constitutive SDF-1/CXCL12 may regulate recruitment of pDCs either in lymph nodes or at peripheral sites of inflammation.

Altered type II interferon precedes autoantibody accrual and elevated type I interferon activity prior to systemic lupus erythematosus classification

OBJECTIVES

The relationship of immune dysregulation and autoantibody production that may contribute to systemic lupus erythematosus (SLE) pathogenesis is unknown. This study evaluates the individual and combined contributions of autoantibodies, type I interferon (IFN-α) activity, and IFN-associated soluble mediators to disease development leading to SLE.

METHODS

Serial serum specimens from 55 individuals collected prior to SLE classification (average timespan=4.3 years) and unaffected healthy controls matched by age (±5 years), gender, race and time of sample procurement were obtained from the Department of Defense Serum Repository. Levels of serum IFN-α activity, IFN-associated mediators and autoantibodies were evaluated and temporal relationships assessed by growth curve modelling, path analysis, analysis of covariance and random forest models.

RESULTS

In cases, but not matched controls, autoantibody specificities and IFN-associated mediators accumulated over a period of years, plateauing near the time of disease classification (p<0.001). Autoantibody positivity coincided with or followed type II IFN dysregulation, preceding IFN-α activity in growth curve models, with elevated IFN-α activity and B-lymphocyte stimulator levels occurring shortly before SLE classification (p≤0.005). Cases were distinguished by multivariate random forest models incorporating IFN-γ, macrophage chemoattractant protein (MCP)-3, anti-chromatin and anti-spliceosome antibodies (accuracy 93% >4 years pre-classification; 97% within 2 years of SLE classification).

CONCLUSIONS

Years before SLE classification, enhancement of the type II IFN pathway allows for accumulation of autoantibodies and subsequent elevations in IFN-α activity immediately preceding SLE classification. Perturbations in select immunological processes may help identify at-risk individuals for further clinical evaluation or participation in prospective intervention trials.

Two subsets of dendritic cells are present in human cerebrospinal fluid

Little is known about the presence of dendritic cells in the human CNS. To investigate the occurrence of dendritic cells in the CSF, paired blood/CSF samples from patients with multiple sclerosis, acute optic neuritis, Lyme neuroborreliosis, other inflammatory neurological diseases and non-inflammatory neurological diseases were examined using flow cytometry. Almost all CSF samples contained myeloid (lin-CD11c+HLA-DR++CD123(dim)) and plasmacytoid (lin-CD11c-HLA-DR+CD123(high)) dendritic cells. In non-inflammatory neurological diseases, dendritic cells of either subset only constituted up to 1% of CSF mononuclear cells. Myeloid CSF dendritic cells were elevated in optic neuritis, neuroborreliosis and other inflammatory neurological disorders, while plasmacytoid dendritic cells were elevated in all neuroinflammatory conditions studied, with especially high numbers in neuroborreliosis. Numbers of CSF dendritic cells correlated with the common parameters of CNS inflammation. The myeloid dendritic cells in CSF expressed higher levels of HLA-DR, CD86, CD80 and CD40 than those in blood, whereas expression of these molecules by plasmacytoid dendritic cells was equal in blood and CSF. Both CSF and blood dendritic cells expressed the chemokine receptor CCR5. This is the first demonstration that dendritic cells are present in human CSF and that plasmacytoid dendritic cells are present in a non-lymphoid compartment. Myeloid and plasmacytoid dendritic cells in CSF may contribute to orchestration of the local immune responses.

Efficacy of the farnesyl transferase inhibitor R115777 in chronic myeloid leukemia and other hematologic malignancies

We investigated the clinical activity of the farnesyl transferase inhibitor R115777 in 22 patients with chronic myelogenous leukemia (CML) in chronic, accelerated, or blastic phase and in 8 patients with myelofibrosis (MF) and 10 patients with multiple myeloma (MM). R115777 was administered at 600 mg orally twice daily for 4 weeks every 6 weeks. Seven patients with CML (6 in chronic phase, 1 in advanced phase) achieved complete or partial hematologic response. Four of them had a minor cytogenetic response. Responses were transient, with a median duration of 9 weeks (range, 3-23 weeks). Two patients discontinued therapy because of toxicity while in complete hematologic response. Two MF patients had a significant decrease in splenomegaly, one had normalization of white blood cell count and differential, and one became transfusion independent. One patient with MM had a reduction in monoclonal protein of 34%. Adverse events included nausea in 22 patients (55%; all grade 2 or lower) and fatigue in 19 (48%; grade 3 or higher in 1). Other grade 3 or 4 toxicities included skin rash (4 patients, 10%), peripheral neuropathy (2 patients, 5%), and liver toxicity (2 patients, 5%). Patients who responded to therapy had significantly higher plasma vascular endothelial growth factor (VEGF) concentrations prior to treatment than nonresponders. Plasma concentrations decreased significantly during therapy among responders. R115777 showed clinical activity in patients with CML and MF. The effect on VEGF needs to be further investigated to determine whether this might be a possible mechanism of action of R115777.

Presence of cutaneous interferon-alpha producing cells in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) patients have increased levels of interferon-alfa (IFN-alpha) in the circulation but a reduced number of functionally intact natural IFN-alpha producing cells (IPC) in peripheral blood. In search for tissue localisation of activated IPC, we investigated skin biopsies from SLE patients for the occurrence of such cells. Eleven SLE patients with inflammatory skin lesions and six healthy controls were biopsied. An immunohistochemical technique (IH) and in situ hybridisation (ISH) were used to detect intracellular IFN-alpha protein and IFN-alpha mRNA, respectively. In all 11 biopsies from SLE lesions, a high number of IPC were detected by IH. In the nonlesional SLE biopsies we could also demonstrate IPC in 10/11 patients. In 6/11 SLE patients, IFN-alpha mRNA containing cells could be detected in the specimens. A low number of IPC were detected in 1/6 healthy controls by IH, but no ISH positive cells were seen. Our results demonstrate that SLE patients have active IPC in both dermal lesions and in noninflammatory skin. A recruitment of IPC from blood to peripheral tissues may explain the low number of circulating natural IPC in SLE patients. Because the type I IFN system is involved in the SLE disease process, these results are of interest for the understanding of the pathogenesis in SLE.

Viral Double-Stranded RNA Aggravates Lupus Nephritis through Toll-Like Receptor 3 on Glomerular Mesangial Cells and Antigen-Presenting Cells

How viral infections trigger autoimmunity is poorly understood. A role for Toll-like receptor 3 (TLR3) was hypothesized in this context as viral double-stranded RNA (dsRNA) activates dendritic cells to secrete type I interferons and cytokines that are known to be associated with the disease activity in systemic lupus erythematosus (SLE). Immunostaining of nephritic kidney sections of autoimmune MRL(lpr/lpr) mice revealed TLR3 expression in infiltrating antigen-presenting cells as well as in glomerular mesangial cells. TLR3-positive cultured mesangial cells that were exposed to synthetic polyinosinic-cytidylic acid (pI:C) RNA in vitro produced CCL2 and IL-6. pI:C RNA activated macrophages and dendritic cells, both isolated from MRL(lpr/lpr) mice, to secrete multiple proinflammatory factors. In vivo, a single injection of pI:C RNA increased serum IL-12p70, IL-6, and IFN-alpha levels. A course of 50 microg of pI:C RNA given every other day from weeks 16 to 18 of age aggravated lupus nephritis in pI:C-treated MRL(lpr/lpr) mice. Serum DNA autoantibody levels were unaltered upon systemic exposure to pI:C RNA in MRL(lpr/lpr) mice, as pI:C RNA, in contrast to CpG-DNA, failed to induce B cell activation. It therefore was concluded that viral dsRNA triggers disease activity of lupus nephritis by mechanisms that are different from those of bacterial DNA. In contrast to CpG-DNA/TLR9 interaction, pI:C RNA/TLR3-mediated disease activity is B cell independent, but activated intrinsic renal cells, e.g., glomerular mesangial cells, to produce cytokines and chemokines, factors that can aggravate autoimmune tissue injury, e.g., lupus nephritis.