Afucosylation of HLA-specific IgG1 as a potential predictor of antibody pathogenicity in kidney transplantation

Antibody-mediated rejection (AMR) is the leading cause of graft failure. While donor-specific antibodies (DSAs) are associated with a higher risk of AMR, not all patients with DSAs develop rejection, suggesting that the characteristics of alloantibodies determining their pathogenicity remain undefined. Using human leukocyte antigen (HLA)-A2-specific antibodies as a model, we apply systems serology tools to investigate qualitative features of immunoglobulin G (IgG) alloantibodies including Fc-glycosylation patterns and FcγR-binding properties. Levels of afucosylated anti-A2 antibodies are elevated in seropositive patients, especially those with AMR, suggesting potential cytotoxicity via FcγRIII-mediated mechanisms. Afucosylation of both glycoengineered monoclonal and naturally glycovariant polyclonal serum IgG specific to HLA-A2 drives potentiated binding to, slower dissociation from, and enhanced signaling through FcγRIII, a receptor widely expressed on innate effector cells, and greater cytotoxicity against HLA-A2⁺ cells mediated by natural killer (NK) cells. Collectively, these results suggest that afucosylated DSA may be a biomarker of AMR and contribute to pathogenesis.

Implementation of a three-tiered approach to identify and characterize anti-drug antibodies raised against HIV-specific broadly neutralizing antibodies

The ability to detect, quantify, and interrogate the properties of immune responses raised against biological therapeutics is not only important to our understanding of these molecules, but also to their success in the clinic. A tiered assay approach to identify the presence, specificity, and titer of anti-drug antibody (ADA) responses has been adopted as a gold standard by industry leaders, the FDA, and the EMA. In order to support pre-clinical and clinical trials, these assays must be standardized, and their performance sufficiently characterized to ensure the accuracy and reproducibility of results under relevant testing conditions. Here we present implementation of electrochemiluminiscence assays that fit into the tiered paradigm of ADA testing for five HIV broadly neutralizing antibodies (3BNC117, 3BNC117-LS, 10–1074, PGT121, and PGDM1400) in compliance with Good Clinical Laboratory practices. Assay sensitivities and matrix effects were evaluated and used to inform the development of positivity cut points. Once cut points were established, assay precision, specificity, free-drug tolerance, and robustness were defined. In all cases, assay characteristics met or surpassed recommendations set forth by the FDA. To further evaluate the performance of these assays and the tiered approach, samples from non-human primates that had received a subset of the five therapeutics were evaluated. In sum, this study reports qualification of a set of ADA assays available to the scientific community as pre-clinical and clinical trials of broadly HIV-neutralizing antibodies proceed, and a framework that is easily adapted as new drug products are advanced in the clinic.

Risk factors for degenerative aortic valve disease in India: A case control study

Background

Degenerative aortic valve disease often co-exists with coronary artery disease (CAD) and studies done in western populations have shown that it shares the same risk factors which cause CAD. However little is known in this context among Asian Indians. The current study looks into the risk factors of degenerative aortic valve disease in Asian Indian population.

Methods

Ninety-one consecutive patients with severe aortic stenosis (AS) reporting for left heart catheterization prior to valve replacement surgery at a tertiary care centre were recruited for the study. They were compared with age and sex matched controls selected from a database of 3200 patients referred for elective diagnostic left heart catheterization for suspected CAD. Following traditional cardiovascular risk factors were assessed in all patients: age, gender, family history of CAD, smoking history, presence of diabetes, hypertension and dyslipidemia.

Results

The mean age of the study population was 57.8 ± 8.2 years (range, 40-80 years). Smoking, family history of CAD and hypercholesterolemia were significantly more prevalent in patients with degenerative AS compared to those with normal valves. No significant difference was noted in the presence of diabetes mellitus. On multivariate logistic regression, family history of premature CAD (OR 3.68; CI 1.38-9.78) smoking history (OR, 2.56; CI, 1.21-5.39), and raised LDL levels (OR, 5.55; CI, 2.63-11.69) were independently associated with the aortic stenosis patient cohort.

Conclusions

The study showed a significant association of cardiovascular risk factors with aortic stenosis independent of age and gender in Asian Indian patients.

Biophysical and Functional Characterization of Rhesus Macaque IgG Subclasses

Antibodies raised in Indian rhesus macaques [Macaca mulatta (MM)] in many preclinical vaccine studies are often evaluated in vitro for titer, antigen-recognition breadth, neutralization potency, and/or effector function, and in vivo for potential associations with protection. However, despite reliance on this key animal model in translation of promising candidate vaccines for evaluation in first in man studies, little is known about the properties of MM immunoglobulin G (IgG) subclasses and how they may compare to human IgG subclasses. Here, we evaluate the binding of MM IgG1, IgG2, IgG3, and IgG4 to human Fc gamma receptors (FcγR) and their ability to elicit the effector functions of human FcγR-bearing cells, and unlike in humans, find a notable absence of subclasses with dramatically silent Fc regions. Biophysical, in vitro, and in vivo characterization revealed MM IgG1 exhibited the greatest effector function activity followed by IgG2 and then IgG3/4. These findings in rhesus are in contrast with the canonical understanding that IgG1 and IgG3 dominate effector function in humans, indicating that subclass-switching profiles observed in rhesus studies may not strictly recapitulate those observed in human vaccine studies.

Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions

The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.

Increased dendritic spine density and tau expression are associated with individual differences in steroidal regulation of male sexual behavior

Male sexual behavior (MSB) is modulated by gonadal steroids, yet this relationship is highly variable across species and between individuals. A significant percentage (~30%) of B6D2F1 hybrid male mice demonstrate MSB after long-term orchidectomy (herein after referred to as "maters"), providing an opportunity to examine the mechanisms that underlie individual differences in steroidal regulation of MSB. Use of gene expression arrays comparing maters and non-maters has provided a first pass look at the genetic underpinnings of steroid-independent MSB. Surprisingly, of the ~500 genes in the medial preoptic area (MPOA) that differed between maters and non-maters, no steroid hormone or receptor genes were differentially expressed between the two groups. Interestingly, best known for their association with Alzheimer's disease, amyloid precursor protein (APP) and the microtubule-associated protein tau (MAPT) were elevated in maters. Increased levels of their protein products (APP and tau) in their non-pathological states have been implicated in cell survival, neuroprotection, and supporting synaptic integrity. Here we tested transgenic mice that overexpress tau and found facilitated mounting and intromission behavior after long-term orchidectomy relative to littermate controls. In addition, levels of synaptophysin and spinophilin, proteins generally enriched in synapses and dendritic spines respectively, were elevated in the MPOA of maters. Dendritic morphology was also assessed in Golgi-impregnated brains of orchidectomized B6D2F1 males, and hybrid maters exhibited greater dendritic spine density in MPOA neurons. In sum, we show for the first time that retention of MSB in the absence of steroids is correlated with morphological differences in neurons.

Small-molecule quinolinol inhibitor identified provides protection against BoNT/A in mice

Botulinum neurotoxins (BoNTs), etiological agents of the life threatening neuroparalytic disease botulism, are the most toxic substances currently known. The potential for the use as bioweapon makes the development of small-molecule inhibitor against these deadly toxins is a top priority. Currently, there are no approved pharmacological treatments for BoNT intoxication. Although an effective vaccine/immunotherapy is available for immuno-prophylaxis but this cannot reverse the effects of toxin inside neurons. A small-molecule pharmacological intervention, especially one that would be effective against the light chain protease, would be highly desirable. Similarity search was carried out from ChemBridge and NSC libraries to the hit (7-(phenyl(8-quinolinylamino)methyl)-8-quinolinol; NSC 84096) to mine its analogs. Several hits obtained were screened for in silico inhibition using AutoDock 4.1 and 19 new molecules selected based on binding energy and Ki. Among these, eleven quinolinol derivatives potently inhibited in vitro endopeptidase activity of botulinum neurotoxin type A light chain (rBoNT/A-LC) on synaptosomes isolated from rat brain which simulate the in vivo system. Five of these inhibitor molecules exhibited IC(50) values ranging from 3.0 nM to 10.0 µM. NSC 84087 is the most potent inhibitor reported so far, found to be a promising lead for therapeutic development, as it exhibits no toxicity, and is able to protect animals from pre and post challenge of botulinum neurotoxin type A (BoNT/A).

Percutaneous Closure of Perimembranous Ventricular Septal Defect with Amplatzer Device

BACKGROUND

The Amplatzer perimembranous ventricular septal occluder is an innovative device for percutaneous closure of perimembranous ventricular septal defects (PMVSD). In appropriately selected cases this procedure is safe and effective.

METHODS

Fourteen patients with the mean age 10.53 years (range 18 months to 55 years) and mean body weight 20.64 kg (range 6 to 52 kg) underwent PMVSD closure.

RESULT

The PMVSD mean diameter was 5.28 mm (range from 4 to 9 mm). Implantation was successful in 92% of the cases and all patients had complete occlusion of the shunt within three months.

CONCLUSION

Device orientation was excellent in all cases. Device-related aortic insufficiency, tricuspid insufficiency or left ventricular dysfunction was not observed. One patient had embolisation of the device and another had complete heart block which required a permanent pacemaker implantation. The excellent short term results need to be confirmed over long-term follow-up.

Coronary Artery Revascularisation : Past, Present and Future

The high prevalence of coronary artery disease has inspired the development of technologies and techniques for coronary revascularisation, including coronary artery bypass grafting (CABG) and percutaneous coronary interventions (PCI). PCI have witnessed the impact of innovation with newer hardware and drug eluting stents (DES). DES have indisputably reduced restenosis, however there is an emerging concern over the risk of late stent thrombosis associated with their use. We discuss the limitations of the current generation DES and review advances in the stent technology. The technology used in CABG has improved, resulting in off-pump coronary artery bypass (OPCAB), endoscopic, video-assisted, and robot-assisted CABG with automated one-shot distal anastomotic devices being used increasingly. The difference in adverse outcomes between CABG and PCI continues to decline and the future may witness a close collaboration between the two.

Congenital atresia of left main coronary artery

We report a rare case of congenital atresia of left main coronary artery in an elderly male presenting with angina and positive stress thallium test. Coronary angiogram showed absence of left main coronary artery in the left aortic sinus. Collaterals from right coronary artery supplied left anterior descending artery and left circumflex artery territories. Despite collaterals, the left anterior descending and left circumflex arteries were rudimentary. Poor size of left-sided arteries precluded any surgical revascularization which is the treatment of choice in this rare entity.

Techniques in Cardiology : PDA Closure in Children

BACKGROUND

Transcatheter closure of patent ductus arteriosus (PDA) with various devices has been evaluated worldwide and in selected cases can be performed successfully, thus avoiding the morbidity associated with surgical closure.

METHODS AND RESULTS

A 2 year old female child presented with PDA and aortic angiography showed large PDA (tubular). This defect can be closed nonsurgically by coils and devices. The coil used are normally 0.038" having delivery system called Flipper, but this child had a large PDA and so was closed by thicker coil 0.052" using a coil-Bioptome-sheath system, which is the first reported case from the Armed Forces.

CONCLUSIONS

We report the initial experience at our center of closure of PDA with a new coil-Bioptome-sheath system.

Bone sarcoidosis

Sarcoidosis is a disease that exhibits extremely heterogeneous clinical manifestations. Although the lungs are the most commonly involved organs, the extension of the granulomatous process may also affect the bones. Almost any bone can be involved; curiously, the small bones of the hands and feet are most frequently affected. Diagnosis and recognition of osseous sarcoidosis is easy, but the therapy is disappointing. Corticosteroids and antimalarials may control pain and swelling, but usually do not influence the course of osseous sarcoidosis.