Postoperative delirium is associated with grey matter brain volume loss

Delirium is associated with long-term cognitive dysfunction and with increased brain atrophy. However, it is unclear whether these problems result from or predisposes to delirium. We aimed to investigate preoperative to postoperative brain changes, as well as the role of delirium in these changes over time. We investigated the effects of surgery and postoperative delirium with brain MRIs made before and 3 months after major elective surgery in 299 elderly patients, and an MRI with a 3 months follow-up MRI in 48 non-surgical control participants. To study the effects of surgery and delirium, we compared brain volumes, white matter hyperintensities and brain infarcts between baseline and follow-up MRIs, using multiple regression analyses adjusting for possible confounders. Within the patients group, 37 persons (12%) developed postoperative delirium. Surgical patients showed a greater decrease in grey matter volume than non-surgical control participants [linear regression: B (95% confidence interval) = -0.65% of intracranial volume (-1.01 to -0.29, P < 0.005)]. Within the surgery group, delirium was associated with a greater decrease in grey matter volume [B (95% confidence interval): -0.44% of intracranial volume (-0.82 to -0.06, P = 0.02)]. Furthermore, within the patients, delirium was associated with a non-significantly increased risk of a new postoperative brain infarct [logistic regression: odds ratio (95% confidence interval): 2.8 (0.7-11.1), P = 0.14]. Our study was the first to investigate the association between delirium and preoperative to postoperative brain volume changes, suggesting that delirium is associated with increased progression of grey matter volume loss.

Plasma Kynurenine Predicts Severity and Complications of Heart Failure and Associates with Established Biochemical and Clinical Markers of Disease

BACKGROUND

Kynurenine, a metabolite of the L-tryptophan pathway, plays a pivotal role in neuro-inflammation, cancer immunology, and cardiovascular inflammation, and has been shown to predict cardiovascular events.

OBJECTIVES

It was our objective to increase the body of data regarding the value of kynurenine as a biomarker in chronic heart failure (CHF).

METHODS

We investigated the predictive value of plasma kynurenine in a CHF cohort (CHF, n = 114); in a second cohort of defibrillator carriers with CHF (AICD, n = 156), we determined clinical and biochemical determinants of the marker which was measured by enzyme immunoassay.

RESULTS

In the CHF cohort, both kynurenine and NT-proBNP increased with NYHA class. Univariate binary logistic regression showed kynurenine to predict death within a 6-month follow-up (OR 1.43, 95% CI 1.03-2.00, p = 0.033) whereas NT-proBNP did not contribute significantly. Kynurenine, like NT-proBNP, was able to discriminate at a 30% threshold of left ventricular ejection fraction (LVEF; AUC-ROC, both 0.74). Kynurenine correlated inversely with LVEF (ϱ = -0.394), glomerular filtration fraction (GFR; ϱ = -0.615), and peak VO2 (ϱ = -0.626). Moreover, there was a strong correlation of kynurenine with NT-proBNP (ϱ = 0.615). In the AICD cohort, multiple linear regression analysis demonstrated highly significant associations of kynurenine with GFR, hsCRP, and tryptophan, as well as a significant impact of age.

CONCLUSIONS

This work speaks in favor of kynurenine being a new and valuable biomarker of CHF, with particular attention placed on its ability to predict mortality and reflect exercise capacity.

Increased pericardial adipose tissue and cardiometabolic risk in patients with schizophrenia versus healthy controls

Patients with schizophrenia are at increased risk of diabetes, cardiovascular disease (CVD) and associated mortality versus the general population. Increased intra-abdominal and pericardial adipose tissue are associated with elevated CVD and mortality in the general population, but little is known about these in patients with schizophrenia. This study examined pericardial and intra-abdominal adipose tissue in schizophrenia and compared this to healthy controls. Thirty-one patients with schizophrenia (mean age 41.2 years, 76% males) and 30 healthy volunteers (CTRL) were examined in this study. The primary outcomes were the volumes of pericardial adipose tissue and intra-abdominal adipose tissue, measured using magnetic resonance imaging. Secondary outcomes included diabetes and cardiac event risk assessed by established instruments. Volumes of pericardial adipose tissue were increased in male and female patients with schizophrenia compared to healthy controls after the adjustment of age, sex and body mass index (P < 0.005). The 10-year risk of a cardiac event was significantly higher in patients with schizophrenia. Furthermore, the risk for developing type-2 diabetes mellitus was slightly increased in schizophrenia. Volumes of intra-abdominal adipose tissue were slightly increased in male and female patients with schizophrenia, albeit not statistically significant. This study demonstrates that patients with schizophrenia have increased pericardial adipose tissue versus controls. This increased fat deposit around the heart is highly relevant for understanding the comorbidity between heart disease and schizophrenia. Interventions aiming to reduce pericardial and intra-abdominal adipose tissue, such as exercise, may be essential to reduce the burden of heart disease in schizophrenia.

Plasma Zonulin and its Association with Kidney Function, Severity of Heart Failure, and Metabolic Inflammation

BACKGROUND

The tight junction regulator zonulin has attracted clinical attention as a biomarker of increased gastrointestinal permeability. Recent work also suggests zonulin to represent a general regulator of tissue barriers and a player in metabolic inflammation. Here, we investigated the associations of zonulin with chronic heart failure (CHF), kidney function, and metabolic inflammation.

METHODS

Using multiple linear regression (Generalized Linear Model), this study determined the association of plasma zonulin with different laboratory and clinical parameters in 225 patients carrying automatic implantable cardioverters/defibrillators (AICD) for primary or secondary prevention. In another 115 patients with diastolic or systolic CHF, we investigated a possible relationship between zonulin and CHF severity.

RESULTS

In the AICD cohort, zonulin associated inversely with serum creatinine (p = 0.013), carboxymethyl-lysine calprotectin (p < 0.001), and kynurenine (p = 0.009) and positively with homoarginine (p < 0.001). In the subgroup with type-2 diabetes (T2D) (n = 51), zonulin increased significantly with high-sensitivity CRP (p = 0.014). In the CHF cohort, we found a highly significant rise of NT-proBNP, but not of zonulin with NYHA functional classes I-IV or other parameters of CHF severity.

CONCLUSIONS

The inverse associations of zonulin with creatinine and markers of cardio-vascular risk (high CMLcalprotectin and kynurenine, low homoarginine) are novel findings that need further experimental and clinical clarification. Our study indicates zonulin involvement in metabolic inflammation in T2D, but no association with disease status in CHF.

Homoarginine Associates with Zonulin and Tryptophan - Findings in a High-Risk Cohort of Patients Carrying an AICD

BACKGROUND

Homoarginine (hArg) is known to have an impact on nitric oxide (NO) metabolism. It seems to increase NO generation and/or availability, thereby enhancing endothelial function. In addition, hArg is connected to energy metabolism since the key enzyme, L-arginine-glycine amidinotransferase (AGAT) for hArg synthesis in the kidneys, is also involved in the synthesis of energy metabolites like guanidinoacetate. Former studies indicate that low levels of hArg are linked to cardiovascular disease and increased all-cause mortality.

METHODS

This study investigated the dependence of plasma hArg on various biochemical and clinical factors in 229 patients carrying an automatic, implantable cardioverter/defibrillator (AICD) using multiple linear regression analysis (Generalized Linear Model, GLM).

RESULTS

GLM revealed a highly significant, positive association between hArg and zonulin (p < 0.001). hArg was also positively correlated with tryptophan (p = 0.004), BMI (p = 0.02), and body weight (p = 0.02). Patients with hsCRP above 10 mg/L had significantly lower hArg concentrations than patients with hsCRP ≤ 10 mg/L.

CONCLUSIONS

The highly significant positive association of hArg with zonulin is a novel finding which may indicate a different meaning of circulating versus local (gut) zonulin. Therefore, further experimental and clinical investigation is needed to explore this association, focusing on possible pathophysiological pathways and the role of circulating zonulin levels in cardiovascular disease. The positive correlation of hArg and Trp also deserves further research because both amino acids might have a protective effect on cardiovascular disease by inhibition of the enzyme alkaline phosphatase. Eventually, our study associates low hArg concentrations with chronic low-grade inflammation and parameters of malnutrition in cardiovascular high-risk patients.

Cardiac adipose tissue, intra-abdominal adipose tissue, and risk for cardio-metabolic diseases in patients with schizophrenia

Introduction

Schizophrenia is associated with increased physical morbidity and mortality. In particular, cardio-metabolic diseases are more frequent. Several underlying reasons have been discussed, including adverse lifestyle behaviors, or adverse effects of neuroleptic treatment. However, little is known about changes of cardiac and intra-abdominal adipose tissue, both are risk factors for the development of cardio-metabolic diseases.

Objectives/aims

To compare, cardiac and intra-abdominal adipose tissue between patients with schizophrenia and healthy controls.

Methods

Ten physically healthy patients with schizophrenia according to DSM-V were included, and compared to healthy control subjects. Cardiac and intra-abdominal adipose tissue was quantified using magnetic resonance tomography. Further factors assessed comprise the metabolic syndrome, physical activity, smoking behavior, and scores for the assessment of cardio-metabolic diseases (FINDRISK score and modified ESC score).

Results

Cardiac adipose tissue and intra-abdominal adipose tissue was increased in patients with schizophrenia. Further findings were higher diastolic blood pressure, more smoking, less physical activity, and an increase for diabetes and cardiovascular disease risk according to the modified ESC and FINDRISK score.

Conclusions

The new finding in our study is an increase of cardiac adipose tissue, a risk factor for the development of cardiovascular disorders, in physically healthy patients with schizophrenia. Furthermore, the risk for the development of type-2 diabetes mellitus is increased, indicated by higher amount of intra-abdominal adipose tissue, and the results of the FINDRISK score. We conclude that lifestyle alterations, particularly exercise training that has been shown to reduce cardiac and intra-abdominal adipose tissue, should be recommended in patients with schizophrenia.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Relaxin-2 does not ameliorate nephropathy in an experimental model of type-1 diabetes

BACKGROUND/AIMS

In diabetic nephropathy (DN), the current angiotensin-II-blocking pharmacotherapy is frequently failing. For diabetic cardiomyopathy (DC), there is no specific remedy available. Relaxin-2 (Rlx) - an anti-fibrotic, anti-inflammatory, and vasoprotecting peptide – is a candidate drug for both.

METHODS

Low-dose (32 μg/kg/day) and high-dose (320 μg/kg/day) Rlx were tested against vehicle (n = 20 each) and non-diabetic controls (n = 14) for 12 weeks in a model of type-1 diabetes induced in endothelial nitric oxide synthase knock-out (eNOS-KO) mice by intraperitoneal injection of streptozotocin.

RESULTS

Diabetic animals showed normal plasma creatinine, markedly increased albuminuria and urinary malonyldialdehyde, elevated relative kidney weight, glomerulosclerosis, and increased glomerular size, but no relevant interstitial fibrosis. Neither dose of Rlx affected these changes although the drug was active and targeted plasma levels were achieved. Of note, we found no activation of the renal TGF-β pathway in this model. In the hearts of diabetic animals, no fibrotic alterations indicative of DC could be determined which precluded testing of the initial hypothesis.

CONCLUSIONS

We investigated a model showing early DN without overt tubulointerstitial fibrosis and activation of the TGF-β-Smad-2/3 pathway. In this model, Rlx proved ineffective; however, the same may not apply to other models and types of diabetes.

Epitope mapping of the human TSH receptor; structure function studies

With the aid of recombinant DNA technology (PCR/site directed mutagenesis, sequencing) the full length coding region of the human TSH receptor was manipulated to place a specific epitope peptide tag (FLAG epitope sequence) at the carboxyl end of the protein. The resulting construct was cloned into a eukaryotic expression vector and stably transfected into HeLa cells. The expression/translation of the tagged TSH receptor molecule was monitored by immune-precipitation and western blotting of protein lysates, and was found to be expressed at considerable levels using the commercially available antibodies directed towards the FLAG epitope. This analysis revealed two discrete specific bands 90-120 KDa representing, presumably, differently glycosylated forms of the receptor. TSH radio receptor assays demonstrated that the FLAG tagged TSH receptor bound TSH comparable with the wild type receptor. Furthermore TSH stimulated cAMP response in these transfected cells were comparable to the wild type receptor, thus demonstrating that the tagged receptor was functionally identical to the transfected wild type receptor. These cell lines will be of great value when analysing TSH/receptor or receptor/autoantibody interactions considering the availability of well characterized experimental anti-TSH receptor sera.

Autoantibodies against epidermal transglutaminase are a sensitive diagnostic marker in patients with dermatitis herpetiformis on a normal or gluten-free diet

BACKGROUND

Dermatitis herpetiformis (DH) is a cutaneous manifestation of gluten-sensitive enteropathy (celiac disease). Patients with DH demonstrate circulating IgA antibodies against epidermal transglutaminase (eTG) and tissue transglutaminase (tTG). It has been suggested that eTG is the autoantigen of DH.

OBJECTIVE

The purpose of this study was to characterize the autoimmune response to eTG and tTG in patients with DH on a normal or gluten-free diet (GFD).

METHODS

Sera from 52 patients with DH were studied for the presence of IgA antibodies to eTG and tTG by enzyme-linked immunosorbant assay. In 38 patients, serum was obtained before initiation of a GFD, whereas 14 patients had been on a GFD for at least 2 years.

RESULTS

Autoantibodies against eTG were detected in 36 of 38 patients (95%) and those against tTG in 30 of 38 patients (79%) with DH on a normal diet. Of 14 patients on a long-term GFD, 7 patients were free of DH lesions and did not require dapsone treatment. None of these patients showed circulating antibodies against eTG or tTG. The remaining 7 patients on a GFD were not able to stop taking dapsone. All these patients demonstrated anti-eTG antibodies, whereas only 3 of them showed additional reactivity against tTG.

LIMITATION

Autoantibody levels against eTG and tTG before and after introduction of a GFD were not examined in the same patients.

CONCLUSION

Our data suggest that antibodies to eTG are the most sensitive serologic marker in treated and untreated patients with DH and confirm the central role of eTG in the pathogenesis of this disease.

Phase I clinical trial of a TGF-beta antisense-modified tumor cell vaccine in patients with advanced glioma

We performed a phase I clinical trial in grade IV astrocytoma to assess the safety of a whole-cell vaccine comprising autologous tumor cells genetically modified by a transforming growth factor-beta2 (TGF-beta2) antisense vector. Blocking secretion of the immunosuppressive molecule TGF-beta in this manner should inhibit one of the major mechanisms by which tumor cells evade immune surveillance and should lead to clinically effective antitumor immunity. Six patients with progressive WHO grade IV astrocytoma were enrolled in the trial. Patients received 2-7 subcutaneous injections of 5 x 10(6)-2 x 10(7) autologous tumor cells per injection. TGF-beta2 secretion by the tumor cells used to vaccinate patients was inhibited by 53-98%. Treatment was well tolerated with only low-grade, transient treatment-related toxicities reported. Two patients had partial regressions and two had stable disease following therapy. The overall median survival was 68 weeks. Median survival of the responding patients was 78 weeks, compared to a historic value of 47 weeks for glioma patients treated conventionally. There were indications of humoral and cellular immunity induced by the vaccine. These findings support further clinical evaluation of vaccines comprised of TGF-beta antisense-modified tumor cells.

Directional atherectomy facilitates the interventional procedure and leads to a low rate of recurrent stenosis in left anterior descending and left circumflex artery ostium stenoses: subgroup analysis of the FLEXI-CUT study

OBJECTIVES

To examine by retrospective analysis of data from the FLEXI-CUT monocentre registry whether atherectomy can effectively simplify complex stent implantation in ostial bifurcation lesions by reducing the procedure to stenting of the left anterior descending (LAD) or left circumflex (LCX) artery ostium alone.

PATIENTS AND METHODS

All patients who had been enrolled in the prospective FLEXI-CUT study (directional atherectomy with adjunctive balloon angioplasty) were retrospectively analysed on the basis of significant LAD or LCX ostial stenosis (>or= 70% stenosis) deriving from an undiseased left main stem. The primary combined end point was the rate of target lesion revascularisation (TLR) and binary restenosis; secondary end points were procedural success and major adverse cardiac events (MACE) at the six-month follow up.

RESULTS

Of 30 patients enrolled with significant LAD or LCX ostium stenosis, 29 were effectively treated with directional atherectomy (96.7% procedural success). All patients underwent single-vessel stenting procedures of solely the LAD or LCX ostium. At follow up, binary stenosis was 25% (6 of 24), TLR (angiographic plus clinical) 10.3% (3 of 29) and total MACE 6.9% (2 of 29).

CONCLUSIONS

Directional atherectomy with single-vessel stenting procedures facilitates the interventional treatment of LAD and LCX ostium stenosis, and leads to remarkably low TLR and binary stenosis at follow up.

Two cases of severe sepsis due to Vibrio vulnificus wound infection acquired in the Baltic Sea

Two severe cases of Vibrio vulnificus wound infection with secondary septicemia occurred during 1 week in August 2003 on the German island of Usedom in the southwestern Baltic Sea. In both cases, pre-existing wounds were inoculated by wading in contaminated sea water. One of the patients died from septic multiorgan failure. To the best of our knowledge, this is the first fatality due to a V. vulnificus infection to have occurred in Germany. Microbiological analysis revealed high concentrations of V. vulnificus in sea water along the coastline, following a period when water temperature exceeded 20 degrees C for more than 2 weeks.

Prediction of pathology and survival by FDG PET in gliomas

OBJECTIVES

Despite being in use for nearly two decades, the utility of [18F]2-fluoro-2deoxy-D-glucose positron emission tomography (FDG PET) in the evaluation and treatment of brain tumors remains controversial. We retrospectively analyzed all patients with histologically proven gliomas, between the years 1990 and 2000, who underwent FDG PET studies at various stages of their treatment and who were followed till either death or for a minimum period of 1 year in an attempt to bring resolution to this controversy.

METHODS

All PET scans prior to 1997 were acquired on an ECAT 951/31 scanner in 2D. Scans since 1997 were obtained on a Siemens HR+ scanner in 3D mode. The majority of FDG PET scans were co-registered with the magnetic resonance imaging (MRI) scans to aid in diagnosis and therapy. Based on independent visual inspection, two board certified nuclear medicine physicians graded the highest activity level of the tumor using the metabolic grading: 0 = no uptake; 1 = uptake less or equal to normal white matter; 2 = uptake greater than normal white matter and less than gray matter; 3 = uptake equal to or greater than gray mater. The measure of association of lambda (lambda) was used to measure the strength of predictive ability of FDG PET for pathological grading of the gliomas. The Cox proportional hazards regression model was used to assess the significance of grade of uptake on survival.

RESULTS

A total of 331 patients were analyzed of which 137 had a PET scan prior to histological diagnosis and therapeutic intervention (mean age = 46.5 years; M:F = 1.7:1). Eighty six percent (143/166) of the patients with low uptake (metabolic scores 0,1) had low-grade gliomas (grade I,II) and 14% (23/166) high-grade gliomas (grade III,IV) on histologic examination. Ninety four percent (154/165) of the patients with high uptake (metabolic scores 2,3) on PET had high-grade gliomas and 7% (11/165) had low-grade gliomas on histologic examination. The grade of uptake had increasing significance on survival as the level increased from 'low' to 'high' (P = 0.0009). Ninety four percent (156/166) of the patients with low uptake survived for > 1 year (median survival of 28 months) and 19% survived for > 5 years. Only 29% (48/165) of patients with high uptake survived for > 1 year, (median survival of 11 months) and none survived for > 5 years. Irrespective of when the scan showed a high uptake of FDG, before or after intervention, the prognosis following that scan was poor.

CONCLUSIONS

Our observations confirm the utility of FDG PET as a prognostic tool for the histological grading and survival in patients with gliomas and appears to more than complement pathological grading.

Lipopeptide particles as the immunologically active component of CTL inducing vaccines

Using a bipalmitoylated lipopeptide consisting of an ovalbumin helper T-cell epitope covalently linked to an influenza virus cytotoxic T-lymphocyte (CTL) epitope, we addressed possible factors that may be critical for CTL induction. Antigen processing of lipopeptide appears to be required for T-cell induction since there was virtually no in vitro binding of lipopeptide to purified MHC molecules. A major portion of lipopeptide immunogenicity was due to its particulate nature inasmuch as CTL induction in mice correlated with insoluble lipopeptide constructs, whereas more soluble analogs were significantly less immunogenic. Immunohistological analysis of tissue from immunized animals revealed that lipopeptide migration from the s.c. injection site to the spleen could be detected as early as 1 h after immunization and cell-associated lipopeptide was observed on macrophages and dendritic cells, implicating both cell populations in the processing and presentation of lipopeptide particles to CTLs.

IcePick: a flexible surface-based system for molecular diversity

IcePick is a system for computationally selecting diverse sets of molecules. It computes the dissimilarity of the surface-accessible features of two molecules, taking into account conformational flexibility. Then, the intrinsic diversity of an entire set of molecules is calculated from a spanning tree over the pairwise dissimilarities. IcePick's dissimilarity measure is compared against traditional 2D topological approaches, and the spanning tree diversity measure is compared against commonly used variance techniques. The method has proven easy to implement and is fast enough to be used in selection of reactants for numerous production-sized combinatorial libraries.

Automatic identification and representation of protein binding sites for molecular docking

Molecular docking is a popular way to screen for novel drug compounds. The method involves aligning small molecules to a protein structure and estimating their binding affinity. To do this rapidly for tens of thousands of molecules requires an effective representation of the binding region of the target protein. This paper presents an algorithm for representing a protein's binding site in a way that is specifically suited to molecular docking applications. Initially the protein's surface is coated with a collection of molecular fragments that could potentially interact with the protein. Each fragment, or probe, serves as a potential alignment point for atoms in a ligand, and is scored to represent that probe's affinity for the protein. Probes are then clustered by accumulating their affinities, where high affinity clusters are identified as being the "stickiest" portions of the protein surface. The stickiest cluster is used as a computational binding "pocket" for docking. This method of site identification was tested on a number of ligand-protein complexes; in each case the pocket constructed by the algorithm coincided with the known ligand binding site. Successful docking experiments demonstrated the effectiveness of the probe representation.

Hammerhead: fast, fully automated docking of flexible ligands to protein binding sites

BACKGROUND

Molecular docking seeks to predict the geometry and affinity of the binding of a small molecule to a given protein of known structure. Rigid docking has long been used to screen databases of small molecules, because docking techniques that account for ligand flexibility have either been too slow or have required significant human intervention. Here we describe a docking algorithm, Hammerhead, which is a fast, automated tool to screen for the binding of flexible molecules to protein binding sites.

RESULTS

We used Hammerhead to successfully dock a variety of positive control ligands into their cognate proteins. The empirically tuned scoring function of the algorithm predicted binding affinities within 1.3 log units of the known affinities for these ligands. Conformations and alignments close to those determined crystallographically received the highest scores. We screened 80 000 compounds for binding to streptavidin, and biotin was predicted as the top-scoring ligand, with other known ligands included among the highest-scoring dockings. The screen ran in a few days on commonly available hardware.

CONCLUSIONS

Hammerhead is suitable for screening large databases of flexible molecules for binding to a protein of known structure. It correctly docks a variety of known flexible ligands, and it spends an average of only a few seconds on each compound during a screen. The approach is completely automated, from the elucidation of protein binding sites, through the docking of molecules, to the final selection of compounds for assay.

Human CTL epitopes encoded by human papillomavirus type 16 E6 and E7 identified through in vivo and in vitro immunogenicity studies of HLA-A*0201-binding peptides

Human papillomavirus type 16 (HPV16) is strongly associated with cervical carcinogenesis. The HPV16 E6 and E7 oncoproteins are constitutively expressed in the majority of cervical tumor cells and are, therefore, attractive targets for CTL-mediated immunotherapy. In mice, the outgrowth of a lethal dose of HPV16-induced tumor cells has been prevented by vaccination with a CTL epitope encoded by HPV16 E7, indicating the feasibility of peptide immunization to obtain antitumor CTL responses. In the present study, the immunogenicity of 9 HLA-A*0201-binding peptides encoded by HPV16 E6 and E7 was analyzed in vivo in HLA-A*0201Kb transgenic mice and in vitro in CTL cultures induced from PBMC of HLA-A*0201+ healthy donors. Four peptides with a good binding affinity were immunogenic in HLA-A*0201Kb transgenic mice, and three of them were also highly immunogenic in CTL induction experiments with PBMC of HLA-A*0201+ healthy donors. Human CTL clones specific for these three peptides were capable of lysing the HPV16 E7-containing HLA-A*0201+ cervical carcinoma cell line CaSki. These E7-derived peptides (11-20, YMLDLQPETT; 82-90, LLMGTLGIV; 86-93, TLGIVCPI), therefore, are likely to represent naturally processed human CTL epitopes of HPV16. Additionally, these three HPV16-encoded peptides have the highest affinity of binding to the HLA-A*0201 molecule. In this study, peptides with a lower binding affinity were less immunogenic. Therefore, our data illustrate that the HLA-binding affinity of a peptide has a major impact on its immunogenicity. In conclusion, we have identified immunogenic peptides encoded by HPV16 E6 and E7 that could be used in vaccines for the prevention and treatment of cervical carcinoma.

Human CTL epitopes encoded by human papillomavirus type 16 E6 and E7 identified through in vivo and in vitro immunogenicity studies of HLA-A*0201-binding peptides

Human papillomavirus type 16 (HPV16) is strongly associated with cervical carcinogenesis. The HPV16 E6 and E7 oncoproteins are constitutively expressed in the majority of cervical tumor cells and are, therefore, attractive targets for CTL-mediated immunotherapy. In mice, the outgrowth of a lethal dose of HPV16-induced tumor cells has been prevented by vaccination with a CTL epitope encoded by HPV16 E7, indicating the feasibility of peptide immunization to obtain antitumor CTL responses. In the present study, the immunogenicity of 9 HLA-A*0201-binding peptides encoded by HPV16 E6 and E7 was analyzed in vivo in HLA-A*0201Kb transgenic mice and in vitro in CTL cultures induced from PBMC of HLA-A*0201+ healthy donors. Four peptides with a good binding affinity were immunogenic in HLA-A*0201Kb transgenic mice, and three of them were also highly immunogenic in CTL induction experiments with PBMC of HLA-A*0201+ healthy donors. Human CTL clones specific for these three peptides were capable of lysing the HPV16 E7-containing HLA-A*0201+ cervical carcinoma cell line CaSki. These E7-derived peptides (11-20, YMLDLQPETT; 82-90, LLMGTLGIV; 86-93, TLGIVCPI), therefore, are likely to represent naturally processed human CTL epitopes of HPV16. Additionally, these three HPV16-encoded peptides have the highest affinity of binding to the HLA-A*0201 molecule. In this study, peptides with a lower binding affinity were less immunogenic. Therefore, our data illustrate that the HLA-binding affinity of a peptide has a major impact on its immunogenicity. In conclusion, we have identified immunogenic peptides encoded by HPV16 E6 and E7 that could be used in vaccines for the prevention and treatment of cervical carcinoma.

The relationship between class I binding affinity and immunogenicity of potential cytotoxic T cell epitopes

The relationship between binding affinity for HLA class I molecules and immunogenicity of discrete peptide epitopes has been analyzed in two different experimental approaches. In the first approach, the immunogenicity of potential epitopes ranging in MHC binding affinity over a 10,000-fold range was analyzed in HLA-A*0201 transgenic mice. In the second approach, the antigenicity of approximately 100 different hepatitis B virus (HBV)-derived potential epitopes, all carrying A*0201 binding motifs, was assessed by using PBL of acute hepatitis patients. In both cases, it was found that an affinity threshold of approximately 500 nM (preferably 50 nM or less) apparently determines the capacity of a peptide epitope to elicit a CTL response. These data correlate well with class I binding affinity measurements of either naturally processed peptides or previously described T cell epitopes. Taken together, these data have important implications for the selection of epitopes for peptide-based vaccines, and also formally demonstrate the crucial role of determinant selection in the shaping of T cell responses. Because in most (but not all) cases, high affinity peptides seem to be immunogenic, our data also suggest that holes in the functional T cell repertoire, if they exist, may be relatively rare.

The relationship between class I binding affinity and immunogenicity of potential cytotoxic T cell epitopes

The relationship between binding affinity for HLA class I molecules and immunogenicity of discrete peptide epitopes has been analyzed in two different experimental approaches. In the first approach, the immunogenicity of potential epitopes ranging in MHC binding affinity over a 10,000-fold range was analyzed in HLA-A*0201 transgenic mice. In the second approach, the antigenicity of approximately 100 different hepatitis B virus (HBV)-derived potential epitopes, all carrying A*0201 binding motifs, was assessed by using PBL of acute hepatitis patients. In both cases, it was found that an affinity threshold of approximately 500 nM (preferably 50 nM or less) apparently determines the capacity of a peptide epitope to elicit a CTL response. These data correlate well with class I binding affinity measurements of either naturally processed peptides or previously described T cell epitopes. Taken together, these data have important implications for the selection of epitopes for peptide-based vaccines, and also formally demonstrate the crucial role of determinant selection in the shaping of T cell responses. Because in most (but not all) cases, high affinity peptides seem to be immunogenic, our data also suggest that holes in the functional T cell repertoire, if they exist, may be relatively rare.

Development of high potency universal DR-restricted helper epitopes by modification of high affinity DR-blocking peptides

Pan DR-binding peptides engineered by introducing anchor residues for different DR motifs within a polyalanine backbone bound 10 of 10 DR molecules tested, with affinities, in most cases, in the nanomolar range. Because of the small methyl group exposed for T cell recognition, these peptides were poor immunogens but effective blockers of DR-restricted antigen presentation. Introduction of bulky and charged residues at positions accessible for T cell recognition yielded extremely powerful Pan DR epitope peptides (PADRE). These peptides elicited powerful responses in vitro from human peripheral blood mononuclear cells (PBMC). Because these cells also cross-react on certain mouse class II alleles, we could also demonstrate that PADRE peptides are active in vivo. In one example of their capacity to elicit T help, they were approximately 1000 times more powerful than natural T cell epitopes. We propose that PADRE peptides may be useful in the development of subunit vaccines.

Peptide binding to the most frequent HLA-A class I alleles measured by quantitative molecular binding assays

Quantitative assays to measure the binding of defined synthetic antigenic peptides and purified MHC class I molecules are described for several common human HLA-A alleles (A1, A2.1, A3, A11 and A24). Under appropriate conditions, the binding of radiolabeled peptides to purified MHC class I molecules is very effective, highly specific, and appears to be dependent on the specific sequence motif of the peptide as defined by critical anchor residue positions. Establishment and optimization of the assay reveals that a relatively high fraction of the MHC class I molecules isolated from EBV transformed B cell line sources is capable of binding exogenously added peptide. Scatchard analysis for all alleles yields 5-10% occupancy values. There is a stringent peptide size requirement that is reflected by the direct influence of peptide length on the binding affinity. The peptide-MHC class I interactions demonstrate remarkable similarity to peptide-MHC class II interactions, both in overall affinity and kinetic behavior. The immunological relevance of the peptide-MHC class I binding assay is also demonstrated by measuring the affinity of a panel of previously described HLA restricted peptides for their HLA restriction element. In 91% (10/11) of the cases, the peptides bound with affinities of 50 nM or less, and in the remaining 9% (1/11) of the cases, in the 50 to 500 nM range. Thus, these data provide the first quantitative estimate of what level of HLA-A binding affinity is associated with a diverse panel of immunodominant CTL epitopes in man.

Class I MHC-peptide interaction: structural and functional aspects

The structural requirements for the interaction between antigens and class I molecules was investigated through the use of a quantitative assay to measure peptide binding to different MHC class I alleles. We determined the permissiveness of the main anchors reported by Rammensee and his group for peptide binding and defined an extended motif for peptides binding to the HLA-A2.1 allele, including the role of non-anchor positions. It was found that the main anchors were necessary, but not sufficient, for good binding. Certain non-anchor positions contributed significantly to overall binding and were referred to a secondary anchors. This finding allowed a better prediction of high affinity binding peptides selected from libraries of different viral and tumor proteins. Furthermore, our data allowed correlation of the structural requirements for binding of peptides with crystallographic data of the MHC molecule. In order to characterize allele-specific motifs for a larger number of alleles, the HLA-A alleles A1, A3, A11, and A24, which represent some of the most common alleles found in different ethnic populations, were chosen. Here, most motifs were found to be highly exclusive; however, HLA-A3 and A11 shared a common motif. The defined motifs were validated further by using naturally processed peptides. Those peptides were also synthesized and tested for binding to the appropriate HLA alleles, giving a binding affinity from 0.3 to 200 nM for sequences of naturally processed peptides. Finally, a set of all possible 9-mer peptides from HPV 16 proteins were synthesized and tested for binding to the five class I alleles. For each allele, high affinity binders were identified, thus allowing for selection of possible peptide candidates for a CTL based vaccine.

Antigen analogs/MHC complexes as specific T cell receptor antagonists

Recent studies demonstrated that antigen analogs can act as powerful and specific inhibitors of T cell activation, leading to the formulation of the concept that antigen analog/MHC complexes may act as antagonists of the T cell receptor (TCR). TCR antagonism appears to be associated with engagement of the TCR below a crucial affinity threshold necessary for full T cell activation. Studies addressing the molecular mechanism of this effect suggest that TCR antagonists could act by interfering with membrane-related events (such as proper receptor clustering) that might precede intracellular signaling. Discovery of the TCR antagonism phenomenon also suggested a possible rational approach to antigen-specific immunointervention in allergies and autoimmune diseases. The feasibility of such an approach is now being actively investigated. Finally, TCR antagonist peptides may provide a useful tool to probe TCR-peptide/MHC interactions involved in the process of thymic education.

TCR antagonism and T cell tolerance can be independently induced in a DR-restricted, hemagglutinin-specific T cell clone

The outcome of TCR engagement with peptide-MHC is of central importance for the immune response of the host. TCR antagonism is one phenomenon known which is characterized by selective inhibition of T cell responses by non-stimulatory antigen analogs. T cell anergy is another state resulting in T cell unresponsiveness, generally characterized by lack of proliferation and lymphokine production. In the present study, the relationship between TCR antagonism and T cell anergy was examined by using protocols known to induce either phenomenon. Re-isolation experiments demonstrated that antagonized T cells were not tolerized, in that they were fully capable of responding to a subsequent antigen challenge. Conversely, while high doses of soluble antigen could efficiently induce T cell tolerance, TCR antagonists, either alone or in conjunction with suboptimal antigen doses, could not. Taken together, these data demonstrate that TCR antagonism and T cell tolerance are phenomena independent of each other.

Prominent role of secondary anchor residues in peptide binding to HLA-A2.1 molecules

The functional determinants of histocompatibility leukocyte antigen (HLA)-A2.1-peptide interactions have been detailed by the use of quantitative molecular binding assays and a chemically synthesized library of naturally occurring epitopes. The importance of hydrophobic anchor residues in position 2 and the C-terminus was confirmed. These anchors are necessary, but not sufficient, for high affinity binding, as the predictions based solely on these anchors are only about 30% accurate. Prominent roles for several other positions (1, 3, and 7) were also demonstrated. The location of these residues within the peptides matches secondary A2.1 pockets previously demonstrated by X-ray crystallography. From a functional standpoint, similar dominant negative effects on binding were observed for charged residues in both nonamers and decamers, while positive effects differed between nonamers and decamers. An extended motif taking into account secondary anchors increased the predictability of A2.1-binding epitopes to a level of 70%, underscoring the practical usefulness of extended motifs.

Effect of T-cell receptor antagonism on interaction between T cells and antigen-presenting cells and on T-cell signaling events

T-cell receptor (TCR) antagonism induced by complexes of antigen analogue with major histocompatibility complex (MHC) molecules results in efficient inhibition of antigen-dependent T-cell responses. We have investigated some of the possible mechanisms by which TCR antagonists bound to the MHC molecules of antigen-presenting cells (APCs) can inhibit T-cell activation. Using a nonstimulatory analogue of the antigenic peptide influenza hemagglutinin-(307-319), we showed that MHC/antagonist complexes completely inhibit very early intracellular events of antigen-dependent T-cell activation, such as inositol phosphate turnover and Ca2+ influx. In a parallel series of experiments, the effect of TCR antagonist peptide on membrane-related activation events was also investigated. It was found that MHC/antagonist complexes on the surface of APCs did not induce stable conjugates with T cells and, most interestingly, did not inhibit antigen-induced conjugate formation. Thus, our data suggest that antagonistic peptides do not interfere with the cellular events that are required for stable T-cell/APC conjugate formation but do inhibit early biochemical events required for T-cell proliferation. The data are discussed with respect to the role of surface receptor clustering in TCR antagonism.

Antigen analogues as antagonists of the T cell receptor

Complexes of antigen analogues and major histocompatibility complexes have been demonstrated to function as effective antagonists of the T cell receptor (TCR). It was observed that modification of any of the major T cell contact residues can create powerful TCR antagonists. Increasing similarity of antagonist to antigen structure resulted in increased capacity to act as a TCR antagonist up to a point beyond which the analogues themselves showed antigenicity. These data strongly suggested that peptide: TCR interaction with a certain low affinity may still be sufficient for engagement of the receptor but not for signalling, thus resulting in antagonism. It was found that the presentation of antagonistic peptides alone did not induce the formation of stable conjugates between antigen presenting cells and T cells, but rather that presentation of antigen was required to induce the initial interaction of APC with T cells in cell:cell conjugates. This antigen-dependent conjugate formation was not affected by the antagonist, while very early intracellular biochemical events such as PI turnover and CA2+ flux were inhibited.

Down-regulation and release of CD14 on human monocytes by IL-4 depends on the presence of serum or GM-CSF

IL-4 induces down-regulation of CD14 expression on human monocytes only when the cells are cultured with serum. In serum-free cultures we failed to down-regulate CD14 by IL-4. Instead of serum, GM-CSF was required as a co-factor to restore the regulatory effect of IL-4 on CD14-expression. After 4 days of culture human monocytes were quantitatively CD14-negative as determined by flow-cytometry. On day 6, high amounts of CD14 molecules were detected in the SUP of these cultures, whereas intracellular immunofluorescence staining revealed no detectable CD14 in cytokine-treated monocytes. Thus, CD14 is lost by down-regulation (as shown by others) as well as by delivery into the medium. We previously hypothesized that dendritic cells may originate from monocytes. Our present finding support that one of the key markers, distinguishing monocytes/macrophages from dendritic cells, can be lost upon physiological stimuli.

Functional consequences of engagement of the T cell receptor by low affinity ligands

The mechanisms involved in TCR antagonism by Ag analog/MHC have been analyzed. A detailed structure-activity relationship study indicated that modification of any of the major T cell contact residues of the peptide molecule can yield a powerful antagonist. It was also shown that as the analog structure increased in similarity to the Ag, the capacity to antagonize Ag-TCR interaction increased up to the point that the analogs themselves became antigenic. These data strongly suggest an affinity-related mechanism whereby a certain affinity is required for signaling through the TCR, and that below this level there can be sufficient affinity to engage the receptor such that triggering does not occur and antagonism can be detected. Taking advantage of this information, antagonist peptides active down to the 10 nM range were engineered. Thus, this approach demonstrates for the first time a rational approach to designing effective, selective low m.w. compounds with high potential in treatment of allergies and autoimmune diseases.

Functional consequences of engagement of the T cell receptor by low affinity ligands

The mechanisms involved in TCR antagonism by Ag analog/MHC have been analyzed. A detailed structure-activity relationship study indicated that modification of any of the major T cell contact residues of the peptide molecule can yield a powerful antagonist. It was also shown that as the analog structure increased in similarity to the Ag, the capacity to antagonize Ag-TCR interaction increased up to the point that the analogs themselves became antigenic. These data strongly suggest an affinity-related mechanism whereby a certain affinity is required for signaling through the TCR, and that below this level there can be sufficient affinity to engage the receptor such that triggering does not occur and antagonism can be detected. Taking advantage of this information, antagonist peptides active down to the 10 nM range were engineered. Thus, this approach demonstrates for the first time a rational approach to designing effective, selective low m.w. compounds with high potential in treatment of allergies and autoimmune diseases.

Signals required for differentiating dendritic cells from human monocytes in vitro

Human peripheral blood monocytes (Mo) can quantitatively be differentiated into potent accessory cells which exhibit dendritic cell (DC) function and phenotype. This alternative differentiation of Mo into DC rather than into macrophages (M phi) will be triggered when signals leading to M phi differentiation are omitted from the culture. Serum contains such stimulatory signals and was therefore omitted from the cultures. The cells were cultured on solid agarose surfaces. This newly developed technique allows for the attachment-free differentiation of DC. In the absence of signals, Mo do not survive in culture. IL-1 and IL-6 are endogenously produced by Mo and create an autokrine stimulatory milieu which increases the accessory function. However, also mature Mph will respond by an increased accessory activity upon stimulation by these cytokines. Cyclic AMP is the most likely second messenger to trigger an increase in accessory activity. IL-4 plus GM-CSF further act to upregulate dendritic cell properties and function. By action of these mediators, virtually all markers and functions of Mo/M phi are lost, and the cells convert to the phenotype and function of dendritic cells.

Human blood dendritic cells exhibit a distinct T-cell-stimulating mechanism and differentiation pattern

In this study, the mechanisms underlying stimulation of T-cell proliferation by human blood dendritic cells (BDC) and their differentiation have been defined with a panel of monoclonal antibodies (MoAbs). It was found that the MoAbs against LFA-1 (CD11a), CD11c, LFA-3 (CD58), ICAM-1 (CD54) or HLA-DR could significantly suppress T-cell proliferation in an allogeneic mixed lymphocyte reaction (P < 0.05), while being unable to inhibit clustering of BDC with T cells. Addition of anti-CD18 or CD45 MoAbs increased the size of clusters after 18 h of culture, but had no effect on the proliferation of T cells (P < 0.05). The suppressive effect of the MoAbs may be viewed not as an inhibition of contact between BDC and T cells, but rather as a blocking of co-stimulatory signals for T-cell activation, which are mediated by interaction of the adhesion molecules. After depleting the BDC preparations of monocytes, we used a double staining in FACS analysis to demonstrate that BDC do not express specific T (CD3), B (CD20 and CD21) and myeloid cell markers (CD11b, CD13 and CD14), but abundant class II antigens. This pattern remained unaltered after 8 days of culture in the presence of 100 U/ml GM-CSF, although a threefold increase of HLA-DQ and ICAM-1 molecules on the cultured cells was observed.

Inhibition of human immunodeficiency virus-1 proliferation by liposome-encapsulated sense DNA to the 5' tat splice acceptor site

A liposome formulation containing a distearoylphosphatidylethanolamine analog was developed that was endocytosed by both lymphocytes and monocytes. This formulation was used to encapsulate sense and antisense 20-mer oligodeoxynucleotides to the 5' tat splice acceptor site of human immunodeficiency virus type 1. At a DNA concentration of 140 nM, the liposome-encapsulated sense DNA inhibited p24 production by as much as 84% in human peripheral blood leukocytes infected with "wild-type" virus. This treatment also reduced the number of peripheral blood leukocytes producing intracellular viral antigen by 71%. Of interest, no reduction in either parameter was observed for the antisense-containing liposomes. The results demonstrate the promise of a new liposomal delivery vehicle to inhibit human immunodeficiency virus replication by an entrapped oligodeoxynucleotide.

IL-4 decreases the expression of the monocyte differentiation marker CD14, paralleled by an increasing accessory potency

IL-4 has been found to affect the phenotype and a variety of functions of human monocytes and macrophages and has been discussed as a monocyte activating protein along with other cytokines, such as IL-1 and IL-6. In this study we compared the effects of the cytokines IL-1, IL-6, IL-4, and a combination of IL-1 and IL-6 on the expression of the CD14 antigen, the FcIIIg receptor molecule CD16 and the MHC-class II molecules HLA-DR and HLA-DP. These molecules represent characteristic monocyte surface markers. Furthermore, the CD14 molecule has been described as a surface antigen of high in vivo relevance representing an indirect receptor for LPS. We further analyzed the effect of IL-4 on monocytes and macrophages with respect to their accessory function to initiate T-lymphocyte proliferation. Human peripheral blood monocytes strongly express the antigen CD14 and maintain it as a stable surface molecule during their differentiation to macrophages. Flow cytometry analysis of cultured monocytes demonstrated that cells incubated in the presence of IL-4, but not IL-1 and/or IL-6 revealed a reduced expression of the CD14 antigen in a dose- and time-dependent manner. After 3 days IL-4 treated cells were virtually CD14-negative. At the same time the expression of the CD16 antigen (FcRIIIg) was also strongly reduced, whereas the treatment with IL-4 led to an increased expression of MHC class II antigens such as HLA-DR and HLA-DP. The spontaneous low expression of HLA-DQ antigen on monocytes was not affected by any of the cytokines. Functionally, IL-4 treated CD14-negative monocytes exhibited a more than 2-fold higher activity to stimulate an accessory cell-dependent T cell proliferation. This was found in a mitogenic assay and in MLC when compared to monocytes cultured in the absence of IL-4. These observations provide further evidence that IL-4 is a major modulator of monocyte surface antigen expression. Moreover, IL-4 has an enhancer-effect on monocytes as accessory cells and therefore may be of considerable importance as a regulatory factor during monocyte development to accessory cells. Inasmuch as the CD14 molecule functions as a receptor for LPS-binding protein, our results suggest that IL-4 might also play an important regulatory role in processes initiated by bacterial lipopolysaccharides during inflammation and sepsis.

Accessory cell function during monocyte/macrophage differentiation: relation to interleukin-1 (IL-1 beta) production and release

Human peripheral blood monocytes (Mo) can differentiate into highly active accessory cells and approach the phenotype and function of dendritic cells instead of developing into macrophages (Mph). Here we report that monocyte-derived accessory cells (m-AC), but not Mph, spontaneously synthesize and release high amounts of interleukin-1 (IL-1 beta). Furthermore, m-AC retained a high T-cell stimulatory activity and a non-macrophagic phenotype for at least 12 days in culture. They were shown to be weakly adherent, non-phagocytic, and most of them were negative for nonspecific esterase. In contrast, Mo differentiating into mature Mph only transiently showed an elevated accessory function but at no time appeared to release intracellular IL-1 beta into the supernatant when cultured in the absence of exogenous triggers. Additionally, they gained a high phagocytic capacity and a strong expression of Fc-receptors within 4 days. Addition of lipopolysaccharides (LPS) to Mph stimulated IL-1 beta release but concomitantly led to a strong reduction of the Mph-phenotype. Thus, the release of IL-1 beta from monocyte-derived cells negatively correlated with the expression of the Mph phenotype but did not necessarily correlate with their accessory function. These observations may reflect an antagonistic regulation of Mph phenotype and cytokine release in cells of the monocytic lineage and suggest that IL-1 beta release is not essential for accessory activity but might serve rather as an autocrine signal to prolong the accessory function of m-AC.

IL-6 and IL-1 enhance the accessory activity of human blood monocytes during differentiation to macrophages

The role of IL-6 and IL-1 in the regulation of accessory activity and differentiation in the human monocyte/macrophage (Mo/Mph) system was investigated. IL-6 combined with IL-1 had a strong effect on the accessory activity of Mo-derived cells dependent on their state of differentiation in vitro. Fresh Mo prepared from peripheral blood differentiated into potent accessory cells in vitro within 24 h in the absence of exogenous triggers in serum-containing and serum-free medium. Mo cultured for 2 days in the presence of the cytokines IL-6 and IL-1 did not significantly increase their spontaneous accessory activity. However, the simultaneous addition of antibodies against IL-6 and IL-1 to accessory Mo cultures significantly diminished their T cell stimulatory capacity. These findings suggest an important positive feedback role of IL-6 and IL-1, secreted by Mo at this early state of differentiation. In marked contrast, untreated mature Mph generated in vitro from Mo exhibited a low spontaneous accessory potency. However, when these cells were subjected to IL-6 and/or IL-1, we observed a strong dose dependent increase in their potency to stimulate a T cell response. Parameters indicating the differentiation of Mo to Mph, such as acid phosphatase and 5' nucleotidase, were not influenced by the addition of IL-1, IL-6, or a mixture of both and confirmed the presence of mature Mph after 6 days of culture. Based on these observations, we conclude that the monocyte-derived cytokines IL-6 and IL-1 not only directly act on T cells but may also function as a signal for accessory activity during Mo/Mph differentiation.

Differentiation of human monocytes into CD14 negative accessory cells: do dendritic cells derive from the monocytic lineage?

Human peripheral-blood monocytes, when cultured in the absence of serum, are prevented to differentiate to macrophages (M phi). Instead, they develop into accessory cells which by various properties resemble dendritic cells. Signals that control development either into M phi or monocyte-derived accessory cells (m-AC) have been investigated by us. By applying such triggers, m-AC phenotypes and functions approached those known from lymphoid dendritic cells. Only the monocyte marker CD14, which is absent from dendritic cells, remained positive on m-AC as a last indicator of the monocytic origin of the cells. We now report that this most stable marker of the monocyte/M phi lineage can completely be down-regulated by combining tissue culture techniques with the inductive property of interleukin-4. Evidence has also been obtained by us that the conversion of monocytes into both m-AC and M phi represents a true differentiation, as demonstrated by the expression of the nuclear marker lamin A/C.

IL-6 and IL-1 enhance the accessory activity of human blood monocytes during differentiation to macrophages

The role of IL-6 and IL-1 in the regulation of accessory activity and differentiation in the human monocyte/macrophage (Mo/Mph) system was investigated. IL-6 combined with IL-1 had a strong effect on the accessory activity of Mo-derived cells dependent on their state of differentiation in vitro. Fresh Mo prepared from peripheral blood differentiated into potent accessory cells in vitro within 24 h in the absence of exogenous triggers in serum-containing and serum-free medium. Mo cultured for 2 days in the presence of the cytokines IL-6 and IL-1 did not significantly increase their spontaneous accessory activity. However, the simultaneous addition of antibodies against IL-6 and IL-1 to accessory Mo cultures significantly diminished their T cell stimulatory capacity. These findings suggest an important positive feedback role of IL-6 and IL-1, secreted by Mo at this early state of differentiation. In marked contrast, untreated mature Mph generated in vitro from Mo exhibited a low spontaneous accessory potency. However, when these cells were subjected to IL-6 and/or IL-1, we observed a strong dose dependent increase in their potency to stimulate a T cell response. Parameters indicating the differentiation of Mo to Mph, such as acid phosphatase and 5' nucleotidase, were not influenced by the addition of IL-1, IL-6, or a mixture of both and confirmed the presence of mature Mph after 6 days of culture. Based on these observations, we conclude that the monocyte-derived cytokines IL-6 and IL-1 not only directly act on T cells but may also function as a signal for accessory activity during Mo/Mph differentiation.

Accessory phenotype and function of macrophages induced by cyclic adenosine monophosphate

Mature macrophages (Mph) differentiated in culture from normal human peripheral blood monocytes (Mo) exhibit low activity as accessory cells (antigen-presenting cells) in T lymphocyte stimulation. A test system was established based on mitogenicity to quantitate the accessory activity of Mph-derived cells and to follow its changes for several days. The system used accessory cells treated with the oxidative mitogen, sodium periodate. The cells were subsequently co-cultured with pooled human lymphocytes from a cryopreserved stock. DNA synthesis in these cells was used as an indicator of accessory activity. Mph could be converted within 5-6 days into highly active accessory cells if a continuous stimulus of exogenously added dibutyryl cyclic AMP (db-cAMP) was provided. Mph treated by db-cAMP retained a high degree of HLA-DR expression but typical Mph markers such as non-specific esterase, phagocytosis, and expression of Fc-receptors were down-regulated. Acid phosphatase and myeloperoxidase underwent only slight changes, while the monocyte marker 5'-nucleotidase remained undetectable. Morphologically, the cells rounded up and developed veils and dendritiform elongations. In contrast to dendritic cells, Mph-derived accessory cells retained the CD14 antigen characteristic of monocytes and Mph. It is concluded that Mph are able to respond to exogenous stimuli and to convert into a highly active accessory cell. This contrasts to the well-known state of the 'activated Mph' with respect to markers and function. Both states appear to be antagonistically controlled by intracellular second messengers, as the accessory cell phenotype is positively correlated with intracellular cyclic AMP increase, whereas Mph activation correlates with cyclic GMP increase.

The Escherichia coli biotin biosynthetic enzyme sequences predicted from the nucleotide sequence of the bio operon

The nucleotide sequence of the biotin (bio) biosynthetic operon of Escherichia coli has been determined. The 5.8-kilobase region contains the five biotin operon genes, bioA, B, F, C, and D. and an open reading frame of unknown function. The operon is negatively regulated and divergently transcribed from a control region between the bioA and bioB genes. The product of the bioA gene, 7,8-diaminopelargonic acid aminotransferase, was discovered to be related to ornithine aminotransferase. The product of the bioF gene, 7-keto-8-aminopelargonic acid synthetase, was found to be similar to 5-aminolevulinic acid synthetase.