Antibody agonists trigger immune receptor signaling through local exclusion of receptor-type protein tyrosine phosphatases.

Antibodies can block immune receptor engagement or trigger the receptor machinery to initiate signaling. We hypothesized that antibody agonists trigger signaling by sterically excluding large receptor-type protein tyrosine phosphatases (RPTPs) such as CD45 from sites of receptor engagement. An agonist targeting the costimulatory receptor CD28 produced signals that depended on antibody immobilization and were sensitive to the sizes of the receptor, the RPTPs, and the antibody itself. Although both the agonist and a non-agonistic anti-CD28 antibody locally excluded CD45, the agonistic antibody was more effective. An anti-PD-1 antibody that bound membrane proximally excluded CD45, triggered Src homology 2 domain-containing phosphatase 2 recruitment, and suppressed systemic lupus erythematosus and delayed-type hypersensitivity in experimental models. Paradoxically, nivolumab and pembrolizumab, anti-PD-1-blocking antibodies used clinically, also excluded CD45 and were agonistic in certain settings. Reducing these agonistic effects using antibody engineering improved PD-1 blockade. These findings establish a framework for developing new and improved therapies for autoimmunity and cancer.

Comparative supragenomic analyses among the pathogens Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae using a modification of the finite supragenome model.

BACKGROUND: Staphylococcus aureus is associated with a spectrum of symbiotic relationships with its human host from carriage to sepsis and is frequently associated with nosocomial and community-acquired infections, thus the differential gene content among strains is of interest. RESULTS: We sequenced three clinical strains and combined these data with 13 publically available human isolates and one bovine strain for comparative genomic analyses. All genomes were annotated using RAST, and then their gene similarities and differences were delineated. Gene clustering yielded 3,155 orthologous gene clusters, of which 2,266 were core, 755 were distributed, and 134 were unique. Individual genomes contained between 2,524 and 2,648 genes. Gene-content comparisons among all possible S. aureus strain pairs (n = 136) revealed a mean difference of 296 genes and a maximum difference of 476 genes. We developed a revised version of our finite supragenome model to estimate the size of the S. aureus supragenome (3,221 genes, with 2,245 core genes), and compared it with those of Haemophilus influenzae and Streptococcus pneumoniae. There was excellent agreement between RAST's annotations and our CDS clustering procedure providing for high fidelity metabolomic subsystem analyses to extend our comparative genomic characterization of these strains. CONCLUSIONS: Using a multi-species comparative supragenomic analysis enabled by an improved version of our finite supragenome model we provide data and an interpretation explaining the relatively larger core genome of S. aureus compared to other opportunistic nasopharyngeal pathogens. In addition, we provide independent validation for the efficiency and effectiveness of our orthologous gene clustering algorithm.

A probabilistic model for predicting the probability of no-show in hospital appointments.

The number of no-shows has a significant impact on the revenue, cost and resource utilization for almost all healthcare systems. In this study we develop a hybrid probabilistic model based on logistic regression and empirical Bayesian inference to predict the probability of no-shows in real time using both general patient social and demographic information and individual clinical appointments attendance records. The model also considers the effect of appointment date and clinic type. The effectiveness of the proposed approach is validated based on a patient dataset from a VA medical center. Such an accurate prediction model can be used to enable a precise selective overbooking strategy to reduce the negative effect of no-shows and to fill appointment slots while maintaining short wait times.

Controlled molecular organization of surface macromolecular assemblies based on stimuli-responsive polypeptide brushes.

End-tethered cationic polypeptide brushes of poly(L-lysine) (t-PLL) were combined with three anionic polymers, poly(acrylic acid) (PAA), poly(L-glutamic acid) (PLGA), and poly(L-aspartic acid) (PLAA), to form reversible polyelectrolyte complex films at surfaces at neutral pH. The polyelectrolyte complex formation was confirmed by an in situ zeta-potential study and by positive fluorescent images after adding prelabeled anionic polymers. The secondary conformations of the t-PLL complex films depend upon the specific polyelectrolyte with which t-PLL was coupled as studied by circular dichroism and FTIR. Specifically, the random coil chain configuration of the t-PLL film was converted to an alpha-helical, beta-sheet, or random coil structure after forming complexes with PAA, PLGA, or PLAA, respectively. Each of these complexes could be returned to the original random coil t-PLL structure by a dilute acid rinse. Additional thickness and morphological studies from ellipsometry and atomic force microscopy have further shown that the corresponding film thicknesses of the individual solvated films were affected more by the secondary structures in films than by the adsorbed mass or surface net charges. The solvated thickness was reduced significantly after the random coil t-PLL film was coupled with polyanions in forming compact regulated structures in films. This biomimetic approach provides a new opportunity for controlling the molecular organization in surface macromolecular assemblies and may provide a model for structural study of protein complexes on a chip.

Comparative genomic analyses of seventeen Streptococcus pneumoniae strains: insights into the pneumococcal supragenome.

The distributed-genome hypothesis (DGH) states that pathogenic bacteria possess a supragenome that is much larger than the genome of any single bacterium and that these pathogens utilize genetic recombination and a large, noncore set of genes as a means of diversity generation. We sequenced the genomes of eight nasopharyngeal strains of Streptococcus pneumoniae isolated from pediatric patients with upper respiratory symptoms and performed quantitative genomic analyses among these and nine publicly available pneumococcal strains. Coding sequences from all strains were grouped into 3,170 orthologous gene clusters, of which 1,454 (46%) were conserved among all 17 strains. The majority of the gene clusters, 1,716 (54%), were not found in all strains. Genic differences per strain pair ranged from 35 to 629 orthologous clusters, with each strain's genome containing between 21 and 32% noncore genes. The distribution of the orthologous clusters per genome for the 17 strains was entered into the finite-supragenome model, which predicted that (i) the S. pneumoniae supragenome contains more than 5,000 orthologous clusters and (ii) 99% of the orthologous clusters ( approximately 3,000) that are represented in the S. pneumoniae population at frequencies of >or=0.1 can be identified if 33 representative genomes are sequenced. These extensive genic diversity data support the DGH and provide a basis for understanding the great differences in clinical phenotype associated with various pneumococcal strains. When these findings are taken together with previous studies that demonstrated the presence of a supragenome for Streptococcus agalactiae and Haemophilus influenzae, it appears that the possession of a distributed genome is a common host interaction strategy.

Thalidomide-induced sinus bradycardia.

OBJECTIVE: To report a case of thalidomide-induced sinus bradycardia in an elderly man. CASE SUMMARY: A 72-year-old white man, with transfusion-dependent refractory anemia with ringed sideroblasts and hypertension treated with atenolol, was started on thalidomide 100 mg at bedtime. During the dose titration period (maximum dose 400 mg/d), his heart rate decreased from a baseline of 63 beats/min to as low as 44 beats/min with positive electrocardiogram findings of sinus bradycardia. After discontinuation of atenolol, the patient's heart rate increased to 68 beats/min, but symptoms of bradycardia persisted. Due to the patient's continued dizziness and lightheadedness, thalidomide was discontinued. In the 3 months following discontinuation of thalidomide, the patient's heart rate increased to an average of 74 beats/min. DISCUSSION: Clinical trials and postmarketing surveillance suggest that the incidence of thalidomide-induced bradycardia is low. The mechanism of this effect is unknown. Concurrent medications affecting the heart rate may also increase the risk of thalidomide-induced bradycardia. Following titration of thalidomide to a maximum dose of 400 mg/d, our patient's heart rate decreased markedly, resulting in intermittent symptoms of lightheadedness and dizziness. He may have been at higher risk of thalidomide-induced bradycardia because of concurrent administration of atenolol. An objective causality assessment revealed that the adverse event was probable. CONCLUSIONS: Despite the low incidence of thalidomide-induced bradycardia, it appears to be an important adverse effect, particularly in patients with comorbidities or concurrent medications that decrease heart rate. Therefore, providers should monitor these patients closely for signs and symptoms of bradycardia during the administration of thalidomide.