Contemporary comparison of infective endocarditis caused by Candida albicans and Candida parapsilosis: a cohort study

Background

Although Candida albicans is the most frequent microorganism causing fungal endocarditis, its incidence has decreased during the last two decades, and that of non-albicans Candida species has risen. Among the last, Candida parapsilosis is of particular interest, representing the second most frequent Candida species causing IE1, 2.

Purpose

To compare the clinical course, imaging findings and outcomes among patients with IE caused by C. albicans (CAIE) and C. parapsilosis (CPIE) in order to identify organism-specific peculiarities.

Methods

From January 1998 to June 2020, all consecutive cases of CAIE and CPIE (n=16), admitted to a hospital network composed of 3 tertiary hospitals and prospectively recruited on a multipurpose database, were retrospectively analysed. All cases were evaluated by the Endocarditis Team (ET) and underwent a thorough diagnostic work-up, including blood cultures at admission, transoesophageal echocardiography (TEE) and culture of the valves extracted at surgery. Other imaging tests, such as PET/CT, were performed at the ET's discretion. Diagnosis of IE was made according to the modified Duke criteria until 20153, and the European Society of Cardiology (ESC) 2015 modified diagnostic criteria thereafter4.

Results

Eight patients were diagnosed with CAIE and 8 with CPIE. Regarding predisposing conditions, a higher prevalence of prosthetic valves was found among CPIE. Other population's baseline information is shown in Table 1. Compared to CAIE, CPIE presented a longer time from the beginning of symptoms to hospital admission (40 vs 7 days; p=0.062), but no differences regarding signs and symptoms were observed. Aortic location was the most frequent infection side in both groups, but prosthetic valve involvement was remarkably more frequent among patients with CPIE (75% vs 37.5%; p=0.315. Figure 1). CPIE also presented a higher rate of positive blood cultures at admission (100% vs 62.5%; p=0.200), persistently blood cultures 48–72 hours after antifungals initiation (100% vs 0%; p=0.021) and positive valve cultures (83.3% vs 57.1%; p=0.569). No differences regarding TEE and other imaging tests findings were observed. All patients but 4 underwent valve replacement surgery. No differences in in-hospital complications or in mortality were observed between CAIE and CPIE, even after adjusting for therapeutic management.

Conclusions

Compared to CAIE, CPIE presented a more frequent involvement of prosthetic valves, a longer course of symptoms before admission and a bigger proportion of persistently positive blood cultures. In-hospital complications and mortality were similar between the two groups.

Funding Acknowledgement

Type of funding sources: None. Table 1. Population characteristicsFigure 1. Valve involvement distribution

Combination of phenotype and polygenic risk score in breast cancer risk evaluation in the Spanish population: a case -control study

Background

In recent years, the identification of genetic and phenotypic biomarkers of cancer for prevention, early diagnosis and patient stratification has been a main objective of research in the field. Different multivariable models that use biomarkers have been proposed for the evaluation of individual risk of developing breast cancer.

Methods

This is a case control study based on a population-based cohort. We describe and evaluate a multivariable model that incorporates 92 Single-nucleotide polymorphisms (SNPs) (Supplementary Table S1) and five different phenotypic variables and which was employed in a Spanish population of 642 healthy women and 455 breast cancer patients.

Results

Our model allowed us to stratify two groups: high and low risk of developing breast cancer. The 9th decile included 1% of controls vs 9% of cases, with an odds ratio (OR) of 12.9 and a p-value of 3.43E-07. The first decile presented an inverse proportion: 1% of cases and 9% of controls, with an OR of 0.097 and a p-value of 1.86E-08.

Conclusions

These results indicate the capacity of our multivariable model to stratify women according to their risk of developing breast cancer. The major limitation of our analysis is the small cohort size. However, despite the limitations, the results of our analysis provide proof of concept in a poorly studied population, and opens up the possibility of using this method in the routine screening of the Spanish population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07584-9.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07584-9.

Inter and intraobserver variability in the echocardiographic measurement of vegetations in infective endocarditis

Introduction and objectives

The indication for surgery to prevent embolism in infective endocarditis includes four clinical scenarios and three different echocardiographic measurements of the maximal vegetation diameter. These cut-off points are completely arbitrary and not evidence-based. Our hypothesis is that the vegetation diameter is not an appropriate surgical criterium. The goal of the study is to analyze the inter and intra-observer variability in this measurement and to compare the surgical indications agreement based on these parameters.

Methods

Two trained echocardiographers have measured the maximal vegetation diameter by transesophageal echocardiogram in 67 consecutive patients with definite infective endocarditis in an off-line workstation. The inter- and intra-observer variability was calculated by the interclass correlation coefficient and with the Bland-Altman analysis. The relationship between the strength of agreement for the cut-off points of 10 and 15 mm was also calculated.

Results

Intra and inter-observer interclass correlation coefficient in the measurement of the maximal longitudinal diameter of the vegetations were 0.872 (0.805–0.917) and 0.757 (0.642–0.839) respectively. The strength of agreement of the intra and inter-observer analysis for the cut-off point of 10 mm were 0.674 (0.485–0.862) and 0.533 (0.327–0.759). For the cut-off point of 15 mm they were 0.696 (0.530–0.862) and 0.475 (0.270–0.679).

Conclusions

The variability in the measurements of the maximal longitudinal diameter by transesophageal echocardiogram between two experimented echocardiographers is good. Nonetheless, surgical indications based on the cut-off points recommended in the European guidelines would have changed in an unacceptable high proportion of patients. Therefore, we suggest that these indications should be revised in the light of our results.

Funding Acknowledgement

Type of funding source: None

The 3 noes right-sided infective endocarditis: a unrecognized type of right-sided endocarditis

Introduction

The “3 noes right-sided infective endocarditis” (3no-RSIE: no left-sided, no drug users, no cardiac devices) was depicted for the first time more than a decade ago. We describe the largest series to date to characterize its clinical, microbiological, echocardiographic and prognostic profile.

Methods

Eight tertiary centers with surgical facilities participated in this study. Patients with right-sided endocarditis without left involvement, absence of antecedents of drug use and no intracardiac electronic devices were retrospectively included in a multipurpose database. A total of 53 variables were analysed in every patient. We performed a univariate analysis of in-hospital mortality to determine variables associated with worse prognosis.

Results

A total of 100 patients (mean age 54.1±20 years, 65% male) with definite 3no-RSIE were included (16.7% of all the right-sided endocarditis of the series). Most of the episodes were community-acquired (72%), congenital cardiopathies were frequent, fever was the main manifestation at admission (85%). The microbiological profile is led by Staphylococci spp. Vegetations were detected in 92% of the patients. Global in-hospital mortality was 19% (5.7% in patients operated and 26% in patients who received only medical treatment, p<0.001). Non community-acquired infection, diabetes mellitus, right heart failure, septic shock and acute renal failure were more common in patients who died.

Conclusions

The clinical profile of 3no-RSIE is closer to other types of RSIE than to LSIE, but mortality is higher than that reported on for other types of RSIE. Surgery plays an important role in improving outcome.

Funding Acknowledgement

Type of funding source: None

Autoimmune rheumatic diseases in the intensive care unit: experience from a tertiary referral hospital and review of the literature

Autoimmune rheumatic diseases (AIRD) are not uncommon in the general population and up to one third of hospitalized patients with AIRD may need admission to intensive care unit (ICU). This paper describes the causes of admission, the clinical features and outcome of 24 AIRD patients admitted to a medical ICU from a third level hospital. Thirteen patients had systemic lupus erythematosus (54.2%), three rheumatoid arthritis (12.5%), three pulmonary renal syndrome (12.5%), two dermatopolymyositis (8.3%), two scleroderma (8.3%) and one antiphospholipid syndrome (4.2%). The main causes for ICU admission were rheumatic disease flare-up (37.5%), infection (37.5%) and complications derived from rheumatic disease (29.1%). Mortality during ICU stay was 16.7% (four patients). Excluding shock requiring vasopressor support, no statistical difference was found between survivors and nonsurvivors; although there was a trend to higher test severity scores (APACHE II, ODIN) in nonsurvivors. Our results reveal a lower mortality rate in AIRD patients admitted to the ICU than reported previously. Severity scores such as APACHE II are predictors of mortality in patients with AIRD in the ICU.

Developments in immunotherapy for gastrointestinal cancer

Gastrointestinal (GI) cancers are the most commonly occurring cancer worldwide. Colorectal cancer (CRC) is the second and third most commonly diagnosed cancer in women and men, respectively. Despite the advent of screening and the declining incidence of CRC overall, most patients are not diagnosed at an early, localized stage. Due to resistance to chemotherapy, recurrence, and metastatic disease, those diagnosed with advanced disease have only a 12% 5-year survival rate. Given the overwhelming global impact of CRC, the need for advanced therapy is crucial. Targeted immunotherapy in addition to surgical resection, traditional chemotherapy, and radiation therapy is on the rise. For the purpose of this review, we focused on the advances of immunotherapy, particularly in CRC, with mention of research pertaining to particular advances in immunotherapy for other aspects of the GI system. We review basic immunology and the microenvironment surrounding colorectal tumors that lead to immune system evasion and poor responses to chemotherapy. We also examined the way these obstacles are proving to be the targets of tumor specific immunotherapy. We will present current FDA approved immunotherapies such as monoclonal antibodies (mAb) targeting tumor specific antigens, as well as vaccines, adoptive cell therapy, cytokines, and check-point inhibitors. A summation of prior research, current clinical trials, and prospective therapies in murine models help delineate our current status and future strategies on CRC immunotherapy.

Psychometric field study of the new haemophilia quality of life questionnaire for adults: The 'Hemofilia-QoL'

Although there is a worldwide interest in the assessment of health-related quality-of-life (HRQoL) in haemophilia patients, no non-disease specific instruments (for adults) are readily available. In this paper, a haemophilia-specific quality-of-life assessment measure for adults (the Hemofilia-QoL questionnaire) has been developed and tested for psychometric properties in 121 adults with haemophilia living in Spain. The Hemofilia-QoL questionnaire is a self-report modular instrument that assesses nine relevant HRQoL domains for patients with haemophilia (e.g. physical health, daily activities, joint damage, pain, treatment satisfaction, treatment difficulties, emotional functioning, mental health, relationships and social activity). Psychometric examination involved the assessment of data quality, scaling assumptions, reliability (internal consistency and test-retest) and validity (concurrent; external clinical criterion and sensitivity). The Hemofilia-QoL 36-item version questionnaire had acceptable internal consistency and retest reliability values. The questionnaire shows excellent concurrent validity (with the SF-36 Health Survey) and external clinical criterion validity (haemophilia clinical status) and sensitivity (health status changes) as well. The Hemofilia-QoL is now available for adult assessment and is ready for use in clinical research in Spain.

Smoking and age-related macular degeneration. The POLA Study. Pathologies Oculaires Liées à l'Age

OBJECTIVE

To assess the associations between age-related macular degeneration (ARMD) and smoking.

METHODS

The POLA study is a population-based study taking place in the town of Sète, located on the French Mediterranean Sea border. The presence of early and late ARMD was assessed in 2196 participants on the basis of 50 degrees color fundus photographs using an international classification system.

RESULTS

After adjustment for age and sex, current and former smokers showed an increased prevalence of late ARMD (odds ratio [OR] = 3.6, 95% confidence interval [CI] = 1.1-12.4; OR = 3.2, 95% CI = 1.3-7.7, respectively). An increased risk was present in participants who smoked more than 20 pack-years (OR = 3.0, 95% CI = 0.9-9.5 for 20-39 pack-years; OR = 5.2, 95% CI = 2.0-13.6 for 40 pack-years and more). In addition, the risk of late ARMD remained increased until 20 years after cessation of smoking (OR = 9.0, 95% CI = 3.0-27.0 for 1-9 years; OR = 4.0, 95% CI = 1.3-12.0 for 10-19 years; OR = 1.3, 95% CI = 0.4-4.3 for 20 years and more). Smoking was not significantly associated with early signs of ARMD.

CONCLUSIONS

This study further confirms the adverse effect of tobacco on late ARMD. Former smokers seem to remain at high risk for ARMD.

Dimerization properties of human BAD. Identification of a BH-3 domain and analysis of its binding to mutant BCL-2 and BCL-XL proteins

Bad, an inducer of programmed cell death, was recently isolated from a mouse cDNA library by its ability to bind to the anti-apoptotic protein BCL-2. Sequence analysis suggested that Bad was a member of the BCL-2 gene family that encodes both inducers and inhibitors of programmed cell death. To further analyze the role of BAD in the network of homo- and heterodimers formed by the BCL-2 family, we have cloned the human homologue of BAD and assessed its biological activity and its interactions with wild type and mutant BCL-2 family proteins. Our results indicate that the human BAD protein, like its mouse homologue, is able to induce apoptosis when transfected into mammalian cells. Furthermore, in yeast two-hybrid assays as well as quantitative in vitro interaction assays, human Bad interacted with BCL-2 and BCL-XL. Sequence alignments of human BAD revealed the presence of a BH-3 homology domain as seen in other BCL-2 family proteins. Peptides derived from this domain were able to completely inhibit the dimerization of BAD with BCL-XL. Thus, as previously shown for BAX, BAK, BCL-2, and BCL-XL, the BH3 domain of BAD is required for its dimerization with other BCL-2 family proteins. BAD was further analyzed for its ability to bind to various mutants of BCL-2 and BCL-XL that have lost the ability to bind BAX and BAK, some of which retain biological activity and some of which do not. Surprisingly, all of the mutated BCL-2 and BCL-XL proteins analyzed strongly interacted with human BAD. Our data thus indicate that mutations in BCL-2 and BCL-XL can differentially affect the heterodimeric binding of different death-promoting proteins and have implications concerning the relationship between heterodimerization and biological activity.

Structural and functional complementation of an inactive Bcl-2 mutant by Bax truncation

Interactions among proteins in the Bcl-2 family regulate the onset of programmed cell death. Previous work has shown that the death-inhibiting family members Bcl-2 and Bcl-xL form heterodimers with the death-promoting homologue Bax and that certain site-directed mutants of Bcl-2 and Bcl-xL lose both biological activity and the ability to bind Bax. To better understand the structural basis of heterodimer formation, we have used a yeast two-hybrid assay to screen for mutants of Bax that regain the ability to bind to these inactive Bcl-2(G145A) and Bcl-xL(G138A) mutants. This screen identified a series of C-terminally truncated Bax molecules that contain complete BH3 (Bcl-2 homology domain 3) domains but that have lost BH1 and BH2 sequences. These results indicate that while the Bcl-2 and Bcl-xL mutants fail to bind full-length Bax, they still retain a binding site for the critical BH3 domain. This suggests that conformational constraints in full-length Bax regulate its ability to bind to other Bcl-2 family members. Furthermore, we demonstrate that the normally inert Bcl-2(G145A) mutant effectively blocks apoptosis induced by a C-terminally truncated Bax molecule, but does not block apoptosis induced by wild-type Bax. This demonstrates that cell protection can be effected by directly binding pro-apoptotic members of the Bcl-2 family.

A common binding site mediates heterodimerization and homodimerization of Bcl-2 family members

Bcl-2 inhibits apoptosis induced by a wide variety of stimuli. In contrast, the Bcl-2 homologue, Bax, antagonizes Bcl-2's death protecting function. Bcl-2 forms protein-protein homodimers with itself and heterodimers with Bax, and previous experiments have shown that point mutations in Bcl-2 can abrogate Bax binding while leaving homodimerization intact. These mutagenesis results can be interpreted to suggest that Bcl-2 has separate binding sites that are responsible for homodimer and heterodimer formation. Results from yeast two-hybrid studies have also suggested that homodimerization and heterodimerization reflect distinct modes of interaction. However, using quantitative plate binding assays, we now show that Bax as well as peptides derived from the BH3 domains of Bax and Bak block both Bcl-2/Bax binding and Bcl-2/Bcl-2 binding. Similar assays demonstrate that Bcl-xL can form both homodimers and heterodimers and that these interactions are also inhibited by Bax and the BH3-derived peptides. These results demonstrate that the same binding motifs are responsible for both homodimerization and heterodimerization of Bcl-2 family members.

Tyloxapol inhibits NF-kappa B and cytokine release, scavenges HOCI, and reduces viscosity of cystic fibrosis sputum

Cystic fibrosis (CF) patients develop progressive cytokine-mediated inflammatory lung disease, with abundant production of thick, tenacious, protease- and oxidant-rich purulent airway secretions that are difficult to clear even with physiotherapy. In the search for a potential treatment, we have tested tyloxapol, an alkylaryl polyether alcohol polymer detergent previously used as a mucolytic agent in adult chronic bronchitis. Tyloxapol inhibits activation of the transcription factor nuclear factor-kappa B (NK-kappa B), reduces resting secretion of the cytokine interleukin-8 (IL-8) in cultured human monocytes, and inhibits lipopolysaccharide (LPS)-stimulated release of tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and the eiconsanoids thromboxane A2 and leukotriene B4 (LTB4). We have previously shown that tyloxapol is a potent antioxidant for hydroxyl radicals ( OH). Tyloxapol (0.05 to 0.1% wt/vol) effectively scavenges the oxidant hypochlorous acid (HOCl; 1 to 7.5 mM) in vitro, and protects from HOCl-mediated lung injury in rats. Tyloxapol also reduces the viscosity of CF sputum (from 463 +/- 133 to 128 +/- 52 centipoise). We conclude that tyloxapol is potentially useful as a new antiinflammatory therapy for CF lung disease, and could possibly promote clearance of secretions in the CF airway.

T-lymphocyte lines specific for glutamic acid decarboxylase (GAD) the 64K beta-cell antigen of IDDM

Insulin-dependent diabetes mellitus (IDDM) is viewed as a thymus-dependent autoimmune disease, although the specific beta-cell autoantigen or autoantigens remain unknown. The recent identification of the beta-cell 64K antigen as the enzyme glutamic acid decarboxylase (GAD) permits investigation of GAD as a candidate for the autoantigen associated with beta-cell destruction, mediated by T-lymphocytes, in susceptible individuals. In this study, we describe the isolation of GAD-specific T-lymphocyte lines from BB rats, an animal model of IDDM. GAD (Escherichia coli) was inoculated into the footpads of diabetes-resistant BB rats, and after 10 days, a popliteal lymph node cell culture suspension was prepared. GAD-specific T lymphocytes were obtained by culture with interleukin 2 and repeated stimulation with GAD in the presence of BB rat thymic antigen-presenting cells. Four stable, CD4+, MHC (RT1u)-restricted T-lymphocyte lines were isolated. They proliferate selectively in the presence of GAD and secrete interleukin 2 and interferon-gamma. T-lymphocyte lines such as these could be important in the definition of pathogenetic epitopes associated with GAD.

Synergistic effects of kinship, sex and rank in the behavioural interactions of captive stump-tailed macaques

In almost all non-human primate species kinship, sex and rank bias the patterning of interactions among subjects, seemingly in a way that favours the individual's fitness. A number of studies have been done in order to study separately the effects of these variables, concluding that an adequate model of interactions cannot be developed assuming preponderance of a single variable. The 'willingness' of one animal to interact with another can be explained as the result of assessing the possible outcomes (proximate and/or ultimate) of the interaction. The interrelationship of variables such as kinship, sex and rank, among others, provides the actors with a basis for deciding their rates of social interactions. The following study was done to assess whether kinship, rank and sex exerted independent, additive effects in the within-group distributions of eight social behaviour categories of captive groups of stump-tailed macaques. We found that the three variables synergistically affected the patterning of all behavioural categories. This suggests that the pay-offs of social interactions do not vary linearly, being intrinsically correlated with the actors' attributes so that uncertainty in the choice of a potential partner is minimized.

The relationship between insulin autoantibodies and islet cell histology in the diabetes prone BB rat

The relationship between insulin autoantibodies (IAA) and pancreatic islet cell histology was examined in 71 diabetes prone BB rats from the Toronto colony. Twenty-seven of the 71 became diabetic and of these, 18 (67%) were IAA positive by ELISA. IAA were also detected in 39/44 (89%) which did not develop diabetes, but in none of six control animals at 50-140 days of age. All 27 which became diabetic showed some evidence of lymphocytic infiltration scored + to ++++ histometrically and 26/27 evidence of beta cell degranulation. The frequency of diabetes increased with both intensity of insulitis and degree of beta cell degranulation, but there was no correlation between either and IAA. IAA are a marker for the BB strain of Wistar rat, but do not correlate with islet cell histology and do not predict clinical diabetes.

Delayed disappearance of human compared to porcine insulin in a patient with the insulin autoimmune syndrome

The insulin autoimmune syndrome is characterised by high titres of autoantibody to insulin, a high circulating concentration of total insulin and later, reactive hypoglycaemia. We have studied a patient with this syndrome whose insulin autoantibody bound exclusively human insulin. This permitted us to investigate the disappearance of bound (human) and unbound (porcine) insulin in the same patient, using i.v. injections of 0.075 U/g of each insulin on separate days. The peak plasma free insulin concentration following porcine insulin was four times greater than that following the same dose of human insulin. The plasma disappearance half-time of porcine insulin following injection was 11 min compared with 32 min following human insulin injection, and the area beneath the disappearance curve of free insulin during the 120 min of sampling was greater for porcine insulin by a factor of 3.15. The nadir in plasma glucose occurred at 45 min following porcine insulin and at 90 min following human insulin injection. The restoration of basal glucose concentration was correspondingly slower following human insulin, but the absolute fall in glucose achieved was no different. There was no evidence of insulin resistance. Insulin autoantibodies can seriously disturb the kinetics and effect of free insulin.

Systematic variation and differences in insulin-autoantibody measurements

Insulin autoantibodies (IAAs) are currently the subject of intensive investigation as potential markers for autoimmune insulitis. However, the results of different reports vary widely. In an attempt to elucidate the reasons for the discrepant reports and to initiate standardization procedures, the International Diabetes Workshop (IDW) undertook two studies in which 22 centers worldwide measured IAA in coded samples. The variance in binding signal from the 49 sera in study 1 was considerable, even when results were standardized, but was largely systematic and attributable to basic differences in assay type (liquid phase versus solid phase) and to differences in the ligand used (human vs. nonhuman insulin). In study 2, 5 sera were prepared and presented blindly to compare dilution curves, insulin-species specificity, interference from irrelevant serum proteins, precision, and dose-dependent displaceability. Many assays, both liquid and solid phase, were influenced by marked and unpredictable nonspecific binding, revealed by loss of parallelism between dilution curves in pooled normal serum and buffer, by variable binding signals with different normal sera, and by difficulty in distinguishing human insulin-specific from cross-reactive IAA sera. It was concluded from the experience of both studies that variance could probably be reduced by using a standard curve with derived common units, a single species of ligand, and methodology to minimize the effect of nonspecific binding. Variation related to assay type was probably due to liquid- versus solid-phase systems being differentially more sensitive to certain aspects of antigen-antibody binding; this issue will be addressed in future serum exchanges and workshops.

The time course of insulin autoantibodies (IAA) in the diabetes prone BB rat

The BB rat is a widely used animal model for the study of insulin dependent diabetes. An enzyme linked immunosorbent assay, using purified rat insulin, was used to measure serial insulin autoantibodies (IAA) levels in coded sera from the BB/W/D rat colony in order to establish the time course of IAA. The animals included 26 diabetes-prone BB rats, six diabetes-resistant BB rats and six Wistar controls. There was an increase in both IAA frequency and titre with time in the diabetes-prone group: none were positive at 45 days, 17/19 (89%) were positive by day 90 and all were positive thereafter. Similar results were observed in the diabetes-resistant BB group (0/6 positive at day 51, 6/6 positive at day 90). None of the Wistar controls were positive at 105 days, although occasional positive sera were observed at 120 days. IAA seem to be acquired early on in the majority of BB rats, both diabetes-prone and diabetes-resistant, and much later, if at all, in controls. A clear homology of the MHC genes exists in both BB rat sublines, thus IAA appear to be a strain related phenomenon rather than a marker for IDDM.

Behavioral effect of scopolamine in cats

An ethological study was performed on a colony of cats. Their spontaneous behavior was observed following the chronic administration of scopolamine hydrobromide (0.3 mg/kg/day). Forty-four behavioral units grouped under four categories--resting postures, individual actions, grooming and social interactions--were coded. A general decrease of the frequency of the tested behaviors was observed; this was particularly true of those behaviors in response to individual or social stimulus of an affiliative or agonistic type. The results were consistent with former reports in other species suggesting the changes in attention underlie this lack of response.

Effect of iodination site on binding of radiolabeled ligand by insulin antibodies and insulin autoantibodies

Four human insulins and four porcine insulins, each monoiodinated to the same specific activity at one of the four tyrosine residues (A14, A19, B16, B26) and purified by reversed-phase liquid chromatography, were tested in a radiobinding assay against a panel of insulin-antibody (IA)-positive sera from 10 insulin-treated diabetics and insulin-autoantibody-positive (IAA) sera from 10 nondiabetics. Of the 10 IAA-positive sera, five were fully cross reactive with both insulin species, and five were specific for human insulin. The rank order of binding of sera with the four ligands from each species was random for IA (mean rank values of 1.9 for A14, 2.0 for A19, 2.5 for B16, and 3.6 for B26 from a possible ranking range of 1 to 4), but more consistent for non-human-insulin-specific IAA (mean rank values 1.3 for A14, 3.8 for A19, 1.7 for B16, and 3.2 for B26 for labeled human insulins; 1.2 for A14, 4.0 for A19, 1.8 for B16, and 3.0 for B26 for labeled porcine insulins). The rank order of binding was virtually uniform for human-insulin-specific IAA (mean values 1.2 for A14, 3.0 for A19, 1.8 for B16, and 4.0 for B26). The influence of iodination site on the binding of labeled insulin appears to be dependent on the proximity of the labeled tyrosine to the antibody binding site and the clonal diversity, or restriction, of insulin-binding antibodies in the test serum. When IA and IAA are measured, the implications of this study regarding the choice of assay ligand may be important.

Effect of iodination site on binding of radiolabeled ligand by insulin antibodies and insulin autoantibodies

Four human insulins and four porcine insulins, each monoiodinated to the same specific activity at one of the four tyrosine residues (A14, A19, B16, B26) and purified by reversed-phase liquid chromatography, were tested in a radiobinding assay against a panel of insulin-antibody (IA)-positive sera from 10 insulin-treated diabetics and insulin-autoantibody-positive (IAA) sera from 10 nondiabetics. Of the 10 IAA-positive sera, five were fully cross reactive with both insulin species, and five were specific for human insulin. The rank order of binding of sera with the four ligands from each species was random for IA (mean rank values of 1.9 for A14, 2.0 for A19, 2.5 for B16, and 3.6 for B26 from a possible ranking range of 1 to 4), but more consistent for non-human-insulin-specific IAA (mean rank values 1.3 for A14, 3.8 for A19, 1.7 for B16, and 3.2 for B26 for labeled human insulins; 1.2 for A14, 4.0 for A19, 1.8 for B16, and 3.0 for B26 for labeled porcine insulins). The rank order of binding was virtually uniform for human-insulin-specific IAA (mean values 1.2 for A14, 3.0 for A19, 1.8 for B16, and 4.0 for B26). The influence of iodination site on the binding of labeled insulin appears to be dependent on the proximity of the labeled tyrosine to the antibody binding site and the clonal diversity, or restriction, of insulin-binding antibodies in the test serum. When IA and IAA are measured, the implications of this study regarding the choice of assay ligand may be important.

Spontaneous hypoglycemia associated with autoimmunity specific to human insulin

A 55-yr-old woman with a history of Graves' disease experienced attacks of postprandial hypoglycemia for 6 yr. An insulinoma could not be confirmed by repeated fasting tests and by surgical pancreas revision. Extracted pancreatic insulin was chemically normal. Fasting plasma total insulin (1.22 nM = 183 microU/ml) and proinsulin (0.48 nM) were elevated and greatly increased after oral glucose. Glucose-clamp studies revealed delayed insulin clearance. Plasma free-insulin levels were normal. Insulin-binding antibodies were detected by enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay with human insulin as ligand but not with pork or beef insulins. Analysis with a modified ELISA suggested a monotypic and monoclonal human insulin autoantibody, which showed a restriction to the lambda-light chain. T-lymphocytes (predominantly helper) demonstrated increased responsiveness to beef, pork, and human insulins by proliferation assay. A T-lymphocyte line showed exclusively human insulin specificity. All this indicated cellular and humoral anti-human insulin autoimmunities. Clinically, the cause of hypoglycemia associated with elevated total insulin and proinsulin was misdiagnosed as atypical insulinoma. The study of total and free plasma insulin levels and sensitive antibody assays specific to human insulin were necessary to correctly diagnose autoimmune hypoglycemia.

Differences in epitope restriction of autoantibodies to native human insulin (IAA) and antibodies to heterologous insulin (IA)

The binding profiles of insulin autoantibodies (IAA) and insulin antibodies (IA) to highly purified species variants and fragments of insulin were studied in direct immunospecific enzyme-linked immunosorbent assay (ELISA) and indirect absorption experiments with insulins covalently coupled to Sepharose beads. Five of 10 IAA-containing sera from insulin-naive nondiabetics that bound whole human (H) insulin did not bind whole porcine (P) or whole bovine (B) insulins. These sera bound H insulin B-chain but not P B-chain or desalanated P insulin, suggesting they were dependent on the presence of threonine B30. The other 5 IAA-containing sera bound H, P, B, and desalanated porcine insulins, but only 1 bound isolated B-chains. All 10 IA-containing sera from insulin-treated diabetics bound H, P, B, and desalanated P insulins, but only 1 bound to human (and porcine) B-chain. Further binding studies with ovine, rabbit, rat, and guinea pig insulins confirmed the H (threonine B30) specificity of the 5 IAA-containing sera. B30 residues do not appear to be dominant, however, when insulin is administered exogenously. Instead, IA bind predominantly to A-chain or conformational determinants involving both chains. Scatchard analysis of a representative H insulin-specific IAA serum suggested that it contained a single binding affinity, whereas analysis of a representative IA-diabetic serum suggested it contained several different affinities.

Comparison of liquid phase radiobinding assay and solid phase ELISA for the measurement of insulin antibodies and insulin autoantibodies in serum

Sera containing insulin antibodies from 20 insulin-treated diabetic patients, sera containing insulin autoantibodies from 20 insulin-naive non-diabetic patients, and from 10 normal controls, were tested at 1:20 dilution in three different radioimmunoassays (RIA) and an enzyme linked immunosorbent assay (ELISA), using a highly purified human insulin ligand. The RIA using insulin radiolabelled at multiple sites detected insulin antibodies in 17/20 and insulin autoantibodies in 13/20 sera. The same RIA using A-14-monoiodinated insulin was sensitive to antibodies and autoantibodies in all the sera. The same RIA using sera after insulin extraction detected only 13/20 diabetic sera and 9/20 autoimmune sera as positive, owing to a substantial rise in non-specific binding of the control sera. ELISA was sensitive to insulin antibodies and autoantibodies in every case. When binding curves for ELISA and the most sensitive RIA were compared using serial dilutions of four insulin antibody containing sera and four insulin autoantibody containing sera, antibody titres varied from 1.1 to 3.8 times higher in ELISA, and autoantibody titres from 10.6 to 28.6 times higher in ELISA. These studies indicate that ELISA is more sensitive than RIA to insulin antibodies, and in particular to insulin autoantibodies.

Value of insulin autoantibodies as serum markers for insulin-dependent diabetes mellitus

Insulin autoantibodies (IAA) were studied in newly diagnosed insulin-dependent diabetics before the start of insulin treatment and in unaffected identical twins of insulin-dependent diabetics. In 15 of the 40 (38%) diabetics and 27 of the 58 (47%) twins IAA levels exceeded those of 100 controls. Frequency of IAA in unaffected twins was not related to duration of diabetes in their affected twin. In 11 unaffected twins, IAA levels differed in two samples taken 1-12 years apart; IAA were detected at least once in all twins and in one on both occasions. IAA in the twins were not related to the presence of islet-cell antibodies or to HLA-DR 3 or 4. As the unaffected twins of longstanding diabetics are unlikely to develop diabetes, these observations suggest that IAA do not always presage diabetes and are probably not a consequence of the disease; they may reflect an inherited autoimmune tendency to diabetes.

Antigenic variation during infection with Neisseria gonorrhoeae: detection of antibodies to surface proteins in sera of patients with gonorrhea

Neisseria gonorrhoeae were cultured from the urethra of male patients and from the cervix and urethra of female contacts. Isolates from a given group of individuals were of the same strain but differed considerably in terms of the molecular weight of both protein II and pili. Radioimmunoprecipitation assays showed that most patients produced serum antibodies to protein I. Antibodies to pili, when present, showed limited cross-reactivity with the different pili produced by a single strain. Antibodies to protein II were highly specific, reacting with only one of the protein II-types produced by a single strain; this observation suggested that the host immune response may be an important factor in antigenic variation. Several sera also contained antibodies to a common surface protein with a molecular weight of 43,000 that was present in all strains tested.

Antigenic variation of outer membrane protein II in colonial variants of Neisseria gonorrhoeae P9

Antibodies were detected by an enzyme-linked immunosorbent assay (ELISA) in sera from rabbits immunized wtih outer membranes from colonial opacity variants in Neisseria gonorrhoeae P9. ELISA-inhibition experiments with purified antigens revealed approximately equal proportions of antibodies directed against each of the three major surface antigens, lipopolysaccharide, the major outer membrane protein (protein I) and protein II, the variable protein associated with colonial opacity. Inhibition experiments with intact gonococci showed considerable antigenic diversity which could be correlated with differences between the protein II species present. Despite their considerable structural homology, different protein II species from colonial variants of the same strain showed little cross-reactivity with specific anti-protein II sera, thus demonstrating the considerable variation in that part of the antigen which is exposed on the surface of the gonococcus and is closely involved in pathogenic mechanisms.