The T-cell repertoire of Spanish patients with COVID-19 as a strategy to link T-cell characteristics to the severity of the disease.

BACKGROUND: The architecture and dynamics of T cell populations are critical in orchestrating the immune response to SARS-CoV-2. In our study, we used T Cell Receptor sequencing (TCRseq) to investigate TCR repertoires in 173 post-infection COVID-19 patients. METHODS: The cohort included 98 mild and 75 severe cases with a median age of 53. We amplified and sequenced the TCR ß chain Complementary Determining Region 3 (CDR3b) and performed bioinformatic analyses to assess repertoire diversity, clonality, and V/J allelic usage between age, sex and severity groups. CDR3b amino acid sequence inference was performed by clustering structural motifs and filtering validated reactive CDR3b to COVID-19. RESULTS: Our results revealed a pronounced decrease in diversity and an increase in clonal expansion in the TCR repertoires of severe COVID-19 patients younger than 55 years old. These results reflect the observed trends in patients older than 55 years old (both mild and severe). In addition, we identified a significant reduction in the usage of key V alleles (TRBV14, TRBV19, TRBV15 and TRBV6-4) associated with disease severity. Notably, severe patients under 55 years old had allelic patterns that resemble those over 55 years old, accompanied by a skewed frequency of COVID-19-related motifs. CONCLUSIONS: Present results suggest that severe patients younger than 55 may have a compromised TCR repertoire contributing to a worse disease outcome.

Mutational landscape of risk variants in comorbid depression and obesity: a next-generation sequencing approach.

Major depression (MD) and obesity are complex genetic disorders that are frequently comorbid. However, the study of both diseases concurrently remains poorly addressed and therefore the underlying genetic mechanisms involved in this comorbidity remain largely unknown. Here we examine the contribution of common and rare variants to this comorbidity through a next-generation sequencing (NGS) approach. Specific genomic regions of interest in MD and obesity were sequenced in a group of 654 individuals from the PISMA-ep epidemiological study. We obtained variants across the entire frequency spectrum and assessed their association with comorbid MD and obesity, both at variant and gene levels. We identified 55 independent common variants and a burden of rare variants in 4 genes (PARK2, FGF21, HIST1H3D and RSRC1) associated with the comorbid phenotype. Follow-up analyses revealed significantly enriched gene-sets associated with biological processes and pathways involved in metabolic dysregulation, hormone signaling and cell cycle regulation. Our results suggest that, while risk variants specific to the comorbid phenotype have been identified, the genes functionally impacted by the risk variants share cell biological processes and signaling pathways with MD and obesity phenotypes separately. To the best of our knowledge, this is the first study involving a targeted sequencing approach toward the study of the comorbid MD and obesity. The framework presented here allowed a deep characterization of the genetics of the co-occurring MD and obesity, revealing insights into the mutational and functional profile that underlies this comorbidity and contributing to a better understanding of the relationship between these two disabling disorders.

Endothelial TGF-ß Signaling Regulates Endothelial-Mesenchymal Transition During Arteriovenous Fistula Remodeling in Mice With Chronic Kidney Disease.

BACKGROUND: Arteriovenous fistulae (AVFs) are the preferred vascular access for hemodialysis in patients with end-stage kidney disease. Chronic kidney disease (CKD) is associated with endothelial injury, impaired AVF maturation, and reduced patency, as well as utilization. Because CKD is characterized by multiple pathophysiological processes that induce endothelial-to-mesenchymal transition (EndMT), we hypothesized that CKD promotes EndMT during venous remodeling and that disruption of endothelial TGF (transforming growth factor)-ß signaling inhibits EndMT to prevent AVF failure even in the end-stage kidney disease environment. METHODS: The mouse 5/6 nephrectomy and aortocaval fistula models were used. CKD was created via 5/6 nephrectomy, with controls of no (0/6) or partial (3/6) nephrectomy in C57BL/6J mice. AVFs were created in mice with knockdown of TGF-ßR1/R2 (TGF-ß receptors type 1/2) in either smooth muscle cells or endothelial cells. AVF diameters and patency were measured and confirmed by serial ultrasound examination. AVF, both murine and human, were examined using Western blot, histology, and immunofluorescence. Human and mouse endothelial cells were used for in vitro experiments. RESULTS: CKD accelerates TGF-ß activation and promotes EndMT that is associated with increased AVF wall thickness and reduced patency in mice. Inhibition of TGF-ß signaling in both endothelial cells and smooth muscle cells decreased smooth muscle cell proliferation in the AVF wall, attenuated EndMT, and was associated with reduced wall thickness, increased outward remodeling, and improved AVF patency. Human AVF also showed increased TGF-ß signaling and EndMT. CONCLUSIONS: CKD promotes EndMT and reduces AVF patency. Inhibition of TGF-ß signaling, especially disruption of endothelial cell-specific TGF-ß signaling, attenuates EndMT and improves AVF patency in mouse AVF. Inhibition of EndMT may be a therapeutic approach of translational significance to improve AVF patency in human patients with CKD.

Beeswax Alcohol Prevents Low-Density Lipoprotein Oxidation and Demonstrates Antioxidant Activities in Zebrafish Embryos and Human Subjects: A Clinical Study.

Oxidative stress is one of the primary instigators of the onset of various human ailments, including cancers, cardiovascular diseases, and dementia. Particularly, oxidative stress severely affects low-density lipid & protein (LDL) oxidation, leading to several detrimental health effects. Therefore, in this study, the effect of beeswax alcohol (BWA) was evaluated in the prevention of LDL oxidation, enhancement of paraoxonase 1 (PON-1) activity of high-density lipid & protein (HDL), and zebrafish embryo survivability. Furthermore, the implication of BWA consumption on the oxidative plasma variables was assessed by a preliminary clinical study on middle-aged and older human subjects (n = 50). Results support BWA augmentation of PON-1 activity in a dose-dependent manner (10-30 µM), which was significantly better than the effect exerted by coenzyme Q10 (CoQ10). Moreover, BWA significantly curtails LDL/apo-B oxidation evoked by CuSO4 (final 0.5 µM) and a causes a marked reduction in lipid peroxidation in LDL. The transmission electron microscopy (TEM) analysis revealed a healing effect of BWA towards the restoration of LDL morphology and size impaired by the exposure of Cu2+ ions (final 0.5 µM). Additionally, BWA counters the toxicity induced by carboxymethyllysine (CML, 500 ng) and rescues zebrafish embryos from development deformities and apoptotic cell death. A completely randomized, double-blinded, placebo-controlled preliminary clinical study on middle- and older-aged human subjects (n = 50) showed that 12 weeks of BWA (100 mg/day) supplementation efficiently diminished serum malondialdehyde (MDA) and total hydroperoxides and enhanced total antioxidant status by 25%, 27%, and 22%, respectively, compared to the placebo-control and baseline values. Furthermore, the consumption of BWA did not exhibit any noteworthy changes in physical variables, lipid profile, glucose levels, and biomarkers pertinent to kidney and liver function, thus confirming the safety of BWA for consumption. Conclusively, in vitro, BWA prevents LDL oxidation, enhances PON-1 activity in HDL, and positively influences oxidative variables in human subjects.

Association of Socioeconomic Status, Sex, Racial, and Ethnic Identity With Sustained and Cultivated Careers in Surgery.

OBJECTIVE: Examine the association between sex, race, ethnicity, and family income, and the intersectionality between these identities, and sustained or cultivated paths in surgery in medical school. METHODS: This retrospective cohort study examines US medical students who matriculated in academic years 2014-2015 and 2015-2016. Data were provided by the Association of American Medical Colleges, including self-reported sex, race, ethnicity, family income, interest in surgery at matriculation, and successful placement into a surgical residency at graduation. This study examined 2 outcomes: (1) sustained path in surgery between matriculation and graduation for students who entered medical school with an interest in surgery and (2) cultivated path in surgery for students who entered medical school not initially interested in surgery and who applied to and were successfully placed into a surgical residency at graduation. RESULTS: Among the 5074 students who reported interest in surgery at matriculation, 2108 (41.5%) had sustained path in surgery. Compared to male students, female students were significantly less likely to have sustained path in surgery [adjusted relative risk (aRR): 0.92 (0.85-0.98)], while Asian (aRR: 0.82, 95% CI: 0.74-0.91), Hispanic (aRR: 0.70, 95% CI: 0.59-0.83), and low-income (aRR: 0.85, 95% CI: 0.78-0.92) students were less likely to have a sustained path in surgery compared to their peers. Among the 17,586 students who reported an initial interest in a nonsurgical specialty, 1869 (10.6%) were placed into a surgical residency at graduation. Female students, regardless of race/ethnic identity and income, were significantly less likely to have cultivated paths in surgery compared to male students, with underrepresented in medicine female students reporting the lowest rates. CONCLUSIONS AND RELEVANCE: This study demonstrates the significant disparity in sustained and cultivated paths in surgery during undergraduate medical education. Innovative transformation of the surgical learning environment to promote surgical identity development and belonging for females, underrepresented in medicine, and low-income students is essential to diversify the surgical workforce.

Disturbed flow in the juxta-anastomotic area of an arteriovenous fistula correlates with endothelial loss, acute thrombus formation, and neointimal hyperplasia.

Clinical failure of arteriovenous neointimal hyperplasia (NIH) fistulae (AVF) is frequently due to juxta-anastomotic NIH (JANIH). Although the mouse AVF model recapitulates human AVF maturation, previous studies focused on the outflow vein distal to the anastomosis. We hypothesized that the juxta-anastomotic area (JAA) has increased NIH compared with the outflow vein. AVF was created in C57BL/6 mice without or with chronic kidney disease (CKD). Temporal and spatial changes of the JAA were examined using histology and immunofluorescence. Computational techniques were used to model the AVF. RNA-seq and bioinformatic analyses were performed to compare the JAA with the outflow vein. The jugular vein to carotid artery AVF model was created in Wistar rats. The neointima in the JAA shows increased volume compared with the outflow vein. Computational modeling shows an increased volume of disturbed flow at the JAA compared with the outflow vein. Endothelial cells are immediately lost from the wall contralateral to the fistula exit, followed by thrombus formation and JANIH. Gene Ontology (GO) enrichment analysis of the 1,862 differentially expressed genes (DEG) between the JANIH and the outflow vein identified 525 overexpressed genes. The rat jugular vein to carotid artery AVF showed changes similar to the mouse AVF. Disturbed flow through the JAA correlates with rapid endothelial cell loss, thrombus formation, and JANIH; late endothelialization of the JAA channel correlates with late AVF patency. Early thrombus formation in the JAA may influence the later development of JANIH.NEW & NOTEWORTHY Disturbed flow and focal endothelial cell loss in the juxta-anastomotic area of the mouse AVF colocalizes with acute thrombus formation followed by late neointimal hyperplasia. Differential flow patterns between the juxta-anastomotic area and the outflow vein correlate with differential expression of genes regulating coagulation, proliferation, collagen metabolism, and the immune response. The rat jugular vein to carotid artery AVF model shows changes similar to the mouse AVF model.

Nucleo-Cytoplasmic Transport of ZIKV Non-Structural 3 Protein Is Mediated by Importin-α/ß and Exportin CRM-1.

Flaviviruses have a cytoplasmic replicative cycle, and crucial events, such as genome translation and replication, occur in the endoplasmic reticulum. However, some viral proteins, such as C, NS1, and NS5 from Zika virus (ZIKV) containing nuclear localization signals (NLSs) and nuclear export signals (NESs), are also located in the nucleus of Vero cells. The NS2A, NS3, and NS4A proteins from dengue virus (DENV) have also been reported to be in the nucleus of A549 cells, and our group recently reported that the NS3 protein is also located in the nucleus of Huh7 and C636 cells during DENV infection. However, the NS3 protease-helicase from ZIKV locates in the perinuclear region of infected cells and alters the morphology of the nuclear lamina, a component of the nuclear envelope. Furthermore, ZIKV NS3 has been reported to accumulate on the concave face of altered kidney-shaped nuclei and may be responsible for modifying other elements of the nuclear envelope. However, nuclear localization of NS3 from ZIKV has not been substantially investigated in human host cells. Our group has recently reported that DENV and ZIKV NS3 alter the nuclear pore complex (NPC) by cleaving some nucleoporins. Here, we demonstrate the presence of ZIKV NS3 in the nucleus of Huh7 cells early in infection and in the cytoplasm at later times postinfection. In addition, we found that ZIKV NS3 contains an NLS and a putative NES and uses the classic import (importin-α/ß) and export pathway via CRM-1 to be transported between the cytoplasm and the nucleus. IMPORTANCE Flaviviruses have a cytoplasmic replication cycle, but recent evidence indicates that nuclear elements play a role in their viral replication. Viral proteins, such as NS5 and C, are imported into the nucleus, and blocking their import prevents replication. Because of the importance of the nucleus in viral replication and the role of NS3 in the modification of nuclear components, we investigated whether NS3 can be localized in the nucleus during ZIKV infection. We found that NS3 is imported into the nucleus via the importin pathway and exported to the cytoplasm via CRM-1. The significance of viral protein nuclear import and export and its relationship with infection establishment is highlighted, emphasizing the development of new host-directed antiviral therapeutic strategies.

Handcrafted versus non-handcrafted (self-supervised) features for the classification of antimicrobial peptides: complementary or redundant?

Antimicrobial peptides (AMPs) have received a great deal of attention given their potential to become a plausible option to fight multi-drug resistant bacteria as well as other pathogens. Quantitative sequence-activity models (QSAMs) have been helpful to discover new AMPs because they allow to explore a large universe of peptide sequences and help reduce the number of wet lab experiments. A main aspect in the building of QSAMs based on shallow learning is to determine an optimal set of protein descriptors (features) required to discriminate between sequences with different antimicrobial activities. These features are generally handcrafted from peptide sequence datasets that are labeled with specific antimicrobial activities. However, recent developments have shown that unsupervised approaches can be used to determine features that outperform human-engineered (handcrafted) features. Thus, knowing which of these two approaches contribute to a better classification of AMPs, it is a fundamental question in order to design more accurate models. Here, we present a systematic and rigorous study to compare both types of features. Experimental outcomes show that non-handcrafted features lead to achieve better performances than handcrafted features. However, the experiments also prove that an improvement in performance is achieved when both types of features are merged. A relevance analysis reveals that non-handcrafted features have higher information content than handcrafted features, while an interaction-based importance analysis reveals that handcrafted features are more important. These findings suggest that there is complementarity between both types of features. Comparisons regarding state-of-the-art deep models show that shallow models yield better performances both when fed with non-handcrafted features alone and when fed with non-handcrafted and handcrafted features together.

Do deep learning models make a difference in the identification of antimicrobial peptides?

In the last few decades, antimicrobial peptides (AMPs) have been explored as an alternative to classical antibiotics, which in turn motivated the development of machine learning models to predict antimicrobial activities in peptides. The first generation of these predictors was filled with what is now known as shallow learning-based models. These models require the computation and selection of molecular descriptors to characterize each peptide sequence and train the models. The second generation, known as deep learning-based models, which no longer requires the explicit computation and selection of those descriptors, started to be used in the prediction task of AMPs just four years ago. The superior performance claimed by deep models regarding shallow models has created a prevalent inertia to using deep learning to identify AMPs. However, methodological flaws and/or modeling biases in the building of deep models do not support such superiority. Here, we analyze the main pitfalls that led to establish biased conclusions on the leading performance of deep models. Also, we analyze whether deep models truly contribute to achieve better predictions than shallow models by performing fair studies on different state-of-the-art benchmarking datasets. The experiments reveal that deep models do not outperform shallow models in the classification of AMPs, and that both types of models codify similar chemical information since their predictions are highly similar. Thus, according to the currently available datasets, we conclude that the use of deep learning could not be the most suitable approach to develop models to identify AMPs, mainly because shallow models achieve comparable-to-superior performances and are simpler (Ockham's razor principle). Even so, we suggest the use of deep learning only when its capabilities lead to obtaining significantly better performance gains worth the additional computational cost.

Gastrointestinal dysmotility is associated with proton pump inhibitor refractory esophagitis in patients with systemic sclerosis.

OBJECTIVES: Patients with systemic sclerosis present with severe gastroesophageal reflux disease, often refractory to proton-pump inhibitors (PPI) treatment. The aim of the present study was to identify factors associated with PPI-refractory esophagitis. METHODS: We performed a cross-sectional study in a single-center cohort of patients diagnosed with systemic sclerosis. We included patients who underwent an esophagogastroduodenoscopy while on PPI treatment. Patients with PPI-refractory erosive esophagitis were compared with those with endoscopically normal esophageal mucosa. RESULTS: A total of 69 patients were included, from these, 23 patients (33%) had PPI-refractory esophagitis (Grade A, n = 11; Grade B, n = 7; Grade C, n = 2; Grade D, n = 3) and 46 (67%) had an endoscopically normal esophageal mucosa. On univariate analysis, patients with PPI-refractory esophagitis were more frequently diffuse SSc subset (43% vs 17%; p= 0.041). Evaluating gastrointestinal motility tests, neither absent esophageal contractility (39% vs 25%, p= 0.292) nor hypotensive lower esophageal sphincter (47% vs 44%, p= 0.980) were significantly associated with PPI-refractory esophagitis. Gastrointestinal dysmotility, defined as abnormal gastric emptying and/or small bowel dilated loops, was significantly associated with PPI-refractory esophagitis (66 vs 8%, p = <0.001). On a multivariate regression model to evaluate the association between motility test results adjusted for the diffuse subset, gastrointestinal dysmotility (ß = 0.751, p= 0.010) was independently associated with PPI-refractory esophagitis, while absent esophageal contractility (ß = 0.044, p= 0.886) or a hypotensive LES were not (ß=-0.131, p= 0.663). CONCLUSIONS: Our findings suggest that gastric and small intestinal motor dysfunction may be an important contributor to the development of PPI-refractory esophagitis in patients with systemic sclerosis.

Pentoxifylline ameliorates subclinical atherosclerosis progression in patients with type 2 diabetes and chronic kidney disease: a randomized pilot trial.

BACKGROUND: Diabetic kidney disease (DKD) is associated with a higher risk of cardiovascular disease (CVD). Pentoxifylline (PTF), a nonselective phosphodiesterase inhibitor with anti-inflammatory, antiproliferative, and antifibrotic actions, has demonstrated renal benefits in both clinical trials and meta-analyses. The present work aimed to study the effects of PTF on the progression of subclinical atherosclerosis (SA) in a population of patients with diabetes and moderate to severe chronic kidney disease (CKD). METHODS: In this open-label, randomized controlled, prospective single-center pilot study the evolution of carotid intima-media thickness (CIMT) and ankle-brachial index (ABI) were determined in 102 patients with type 2 diabetes mellitus and CKD assigned to PTF, aspirin or control groups during 18 months. We also determined the variations in the levels of inflammatory markers and Klotho (KL), a protein involved in maintaining cardiovascular health, and their relationship with the progression of SA. RESULTS: Patients treated with PTF presented a better evolution of CIMT, increased KL mRNA levels in peripheral blood cells (PBCs) and reduced the inflammatory state. The progression of CIMT values was inversely related to variations in KL both in serum and mRNA expression levels in PBCs. Multiple regression analysis demonstrated that PTF treatment and variations in mRNA KL expression in PBCs, together with changes in HDL, were significant determinants for the progression of CIMT (adjusted R2 = 0.24, P < 0.001) independently of traditional risk factors. Moreover, both variables constituted protective factors against a worst progression of CIMT [OR: 0.103 (P = 0.001) and 0.001 (P = 0.005), respectively]. CONCLUSIONS: PTF reduced SA progression assessed by CIMT variation, a beneficial effect related to KL gene expression in PBCs. TRIAL REGISTRATION: The study protocol code is PTF-AA-TR-2009 and the trial was registered on the European Union Drug Regulating Authorities Clinical Trials (EudraCT #2009-016595-77). The validation date was 2010-03-09.

Analyzing the role of ACE2, AR, MX1 and TMPRSS2 genetic markers for COVID-19 severity.

BACKGROUND: The use of molecular biomarkers for COVID-19 remains unconclusive. The application of a molecular biomarker in combination with clinical ones that could help classifying aggressive patients in first steps of the disease could help clinician and sanitary system a better management of the disease. Here we characterize the role of ACE2, AR, MX1, ERG, ETV5 and TMPRSS2 for trying a better classification of COVID-19 through knowledge of the disease mechanisms. METHODS: A total of 329 blood samples were genotyped in ACE2, MX1 and TMPRSS2. RNA analyses were also performed from 258 available samples using quantitative polymerase chain reaction for genes: ERG, ETV5, AR, MX1, ACE2, and TMPRSS2. Moreover, in silico analysis variant effect predictor, ClinVar, IPA, DAVID, GTEx, STRING and miRDB database was also performed. Clinical and demographic data were recruited from all participants following WHO classification criteria. RESULTS: We confirm the use of ferritin (p < 0.001), D-dimer (p < 0.010), CRP (p < 0.001) and LDH (p < 0.001) as markers for distinguishing mild and severe cohorts. Expression studies showed that MX1 and AR are significantly higher expressed in mild vs severe patients (p < 0.05). ACE2 and TMPRSS2 are involved in the same molecular process of membrane fusion (p = 4.4 × 10-3), acting as proteases (p = 0.047). CONCLUSIONS: In addition to the key role of TMPSRSS2, we reported for the first time that higher expression levels of AR are related with a decreased risk of severe COVID-19 disease in females. Moreover, functional analysis demonstrates that ACE2, MX1 and TMPRSS2 are relevant markers in this disease.

Predictors of first hospitalization due to disease activity and infections in systemic lupus erythematosus patients.

OBJECTIVES: To identify the predictive factors of first hospitalization and associated variables to the main causes of hospitalizations in lupus patients from a Latin American cohort. METHODS: The first hospitalization after entry into the cohort during these patients' follow-up due to either lupus disease activity and/or infection was examined. Clinical and therapeutic variables were those occurring prior to the first hospitalization. Descriptive statistical tests, multivariable logistic, and Cox regression models were performed. RESULTS: 1341 individuals were included in this analysis; 1200 (89.5%) were women. Their median and interquartile range (IQR) age at diagnosis were 27 (20-37) years and their median and IQR follow up time were 27.5 (4.7-62.2) months. A total of 456 (34.0%) patients were hospitalized; 344 (75.4%), 85 (18.6%) and 27 (5.9%) for disease activity, infections, or both, respectively. The predictors of the first hospitalization regardless of its cause were: medium (HR 2.03(1.27-3.24); p = 0.0028) and low (HR 2.42(1.55-3.79); p < 0.0001) socioeconomic status, serosal (HR 1.32(1.07-1.62); p = 0.0074) and renal (HR 1.50(1.23-1.82); p < 0.0001) involvement. Antimalarial (AM) use (HR 0.61(0.50-0.74); p < 0.0001) and achieving remission (HR 0.80(0.65-0.97); p = 0.0300) were negative predictors. CONCLUSIONS: The first hospitalization was associated with worse socioeconomic status and serosal and renal involvement. Conversely, AM use and achieving remission were associated with a lower risk of hospitalizations.

Recolonization of secondary forests by a locally extinct Caribbean anole through the lens of range expansion theory.

Disturbance and recovery dynamics are characteristic features of many ecosystems. Disturbance dynamics are widely studied in ecology and conservation biology. Still, we know less about the ecological processes that drive ecosystem recovery. The ecological processes that mediate ecosystem recovery stand at the intersection of many theoretical frameworks. Range expansion theory is one of these complementary frameworks that can provide unique insights into the population-level processes that mediate ecosystem recovery, particularly fauna recolonization. Although the biodiversity patterns that follow the fauna recolonization of recovering forests have been well described in the literature, the ecological processes at the population level that drive these patterns remain conspicuously unknown. In this study, we tested three fundamental predictions of range expansion theory during the recolonization of recovering forests in Puerto Rico by a shade specialist anole, Anolis gundlachi. Range expansion theory predicts that individuals at the early stages of recolonization (i.e., younger forests) would have a high prevalence of dispersive traits, experience less density dependence, and suffer less parasitism. To test these predictions, we conducted a chronosequence study applying space-for-time substitution where we compared phenotypic traits (i.e., body size, body condition, and relative limb size), population density, population growth rates, and Plasmodium parasitism rates among lizard populations living in young (<30 years), mid (~40-70 years), and old-growth forests (>75 years). Lizard populations in younger forests had lower densities, higher population growth rates, and lower rates of Plasmodium parasitism compared with old-growth forests. Still, while we found that individuals had larger body sizes, and longer forelimbs in young forests in one site, this result was not consistent among sites. This suggests a potential trade-off between the traits that provide a dispersal advantage during the initial stages of recolonization and those that are advantageous to establish in novel environmental conditions. Overall, our study emphasizes the suitability of range expansion theory to describe fauna recolonization but also highlights that the ecological processes that drive recolonization are time-dependent, complex, and nuanced.

Differentiation of isobaric cross-linked peptides prepared via maleimide chemistry using MALDI-MS and MS/MS.

RATIONALE: The thiosuccinimide linker is widely used in the synthesis of bioconjugates. However, it is susceptible to hydrolysis and is transformed into its hydrolyzed and/or the isobaric thiazine forms, the latter of which is a fairly common product in a conjugate that contains a cysteinyl peptide. Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and matrix-assisted laser desorption/ionization-tandem mass spectrometry (MALDI-MS/MS) are useful for differentiating these isobaric species. METHODS: Four cross-linked peptides with thiosuccinimide linkers were synthesized. Analogs with linkers that were transformed into thiazine and/or the hydrolyzed thiosuccinimide linkers were then synthesized by incubating the samples at neutral or basic pH. All the cross-linked peptides were purified using RP-HPLC (reversed-phase high-performance liquid chromatography) and differentiated using MALDI-MS, MALDI-MS/MS, and ultraviolet photodissociation. RESULTS: A cysteinyl peptide-containing conjugate, the thiosuccinimide form, was largely transformed into the hydrolyzed or thiazine forms after incubation at neutral or basic pH. MALDI-MS allowed the three forms to be differentiated: the thiosuccinimide and its hydrolysis product yielded two constituent peptides after reductive cleavage between the Cys and succinimide moieties; no fragment ions were produced from the thiazine form. In addition, MALDI-MS/MS of the thiosuccinimide form yielded two pairs of complementary fragment ions via 1,4-elimination: Cys-SH and maleimide, and dehydro-alanine and thiosuccinimide, which are different from those produced via reductive cleavage in MALDI-MS. The thiazine form yielded fragment ions resulting from the cleavage of the newly formed amide bond in the linker that resulted from thiazine formation. CONCLUSIONS: The thiosuccinimide (but not thiazine) form of the cross-linked peptide yielded individual constituent peptides using MALDI-MS and MALDI-MS/MS, showing specific 1,4-elimination for the thiosuccinimide form and cleavage at the newly formed peptide bond via transcyclization for the thiazine form.

A hydrolyzed N-propionylthiosuccinimide linker is cleaved by metastable fragmentation, increasing reliability of conjugation site identification in conjugate vaccines.

RATIONALE: Conjugation sites are a quality attribute of conjugate vaccines. Proteolysis of bioconjugates synthesized by maleimide-thiol chemistry generates type 2 peptides with a hydrolyzed thiosuccinimide linker containing information on the conjugation sites. A mass spectrometry (MS)-cleavable linker could make the identification of conjugation sites by MS more reliable. METHODS: Four synthetic type 2 peptides with a hydrolyzed thiosuccinimide linker were analyzed by matrix-assisted laser desorption ionization (MALDI) MS/MS with and without collision gas. These peptides were also partially labeled with 18O in the linker to confirm the proposed fragmentation mechanism. A conjugate vaccine with the hydrolyzed thiosuccinimide linker was reduced and S-alkylated, digested with trypsin and analyzed by liquid chromatography-MS/MS using collision-induced dissociation (CID) and higher-energy collisional dissociation (HCD) fragmentation methods at a normalized collision energy of 30. RESULTS: A metastable fragmentation preferentially cleaves the newly formed pseudopeptide bond within the hydrolyzed thiosuccinimide linker of type 2 peptides to yield P + 71 and C + 98 ions. These ions make the assignment of conjugation sites more reliable. Partial 18O-labeling and MS/MS analysis confirmed the proposed structures. CID produces these ions as the two most intense signals more favorably than HCD. The latter also yields these ions, guarantees better sequence coverage and promotes other fragmentations in the linker. CONCLUSIONS: Hydrolyzed thiosuccinimide linker is cleavable in MALDI and electrospray ionization MS/MS analysis by a gas-phase metastable fragmentation. The resulting fragment ions (P + 71 and C + 98) make the identification of conjugation sites more reliable. These results could be extended to self-hydrolyzing maleimides, which efficiently stabilize the thiosuccinimide linker upon hydrolysis, in antibody-drug conjugates.

Pd8 Cluster: Too Small to Melt? A BOMD Study.

The question of whether a solid-liquid phase transition occurs in small clusters poses a fundamental challenge. In this study, we attempt to elucidate this phenomenon through a thorough examination of the thermal behavior and structural stability of Pd8 clusters employing ab initio simulations. Initially, a systematic global search is carried out to identify the various isomers of the Pd8 cluster. This is accomplished by employing an ab initio basin-hopping algorithm and using the PBE/SDD scheme integrated in the Gaussian code. The resulting isomers are further refined through reoptimization using the deMon2k package. To ensure the structural firmness of the lowest-energy isomer, we calculated normal modes. The structural stability as a function of temperature is analyzed through the Born-Oppenheimer molecular dynamics (BOMD) approach. Multiple BOMD trajectories at distinct simulated temperatures are examined with data clustering analysis to determine cluster isomers. This analysis establishes a connection between the potential energy landscape and the simulated temperature. To address the question of cluster melting, canonical parallel-tempering BOMD runs are performed and analyzed with the multiple-histogram method. A broad maximum in the heat capacity curve indicates a melting transition between 500 and 600 K. To further examine this transition, the mean-squared displacement and the pair-distance distribution function are calculated. The results of these calculations confirm the existence of a solid-liquid phase transition, as indicated by the heat capacity curve.

Unveiling the fungal color palette: pigment analysis of Fusarium solani species complex and Curvularia verruculosa clinical isolates.

Fungal species in the Nectriaceae, such as Fusarium spp. (Hypocreales: Nectriaceae), are etiologic agents of hyalohyphomycosis capable of producing violaceous or yellowish pigments under certain conditions, while Curvularia spp. (Pleosporales: Pleosporaceae) are agents of phaeohyphomycosis and typically produce melanin in their cell walls. In nectriaceous and pleosporaceous fungi, these pigments are mainly constituted by polyketides (e.g., azaphilones, naphthoquinones, and hydroxyanthraquinones). Considering the importance of pigments synthesized by these genera, this work focused on the selective extraction of pigments produced by eight Fusarium solani species complex and one Curvularia verruculosa isolate recovered from dermatomycosis specimens, their separation, purification, and posterior chemical analysis. The pigments were characterized through spectral and acid-base analysis, and their maximum production time was determined. Moreover, spectral identification of isolates was carried out to approach the taxonomic specificity of pigment production. Herein we describe the isolation and characterization of three acidic pigments, yellowish and pinkish azaphilones (i.e., coaherin A and sclerotiorin), and a purplish xanthone, reported for the first time in the Nectriaceae and Pleosporaceae, which appear to be synthesized in a species-independent manner, in the case of fusaria.

Drug repositioning identifies histone deacetylase inhibitors that promote innate immunity in non-tuberculous mycobacterial infection.

Non-tuberculosis infections in immunocompromised patients represent a cause for concern, given the increased risks of infection, and limited treatments available. Herein, we report that molecules for binding to the catalytic site of histone deacetylase (HDAC) inhibit its activity, thus increasing the innate immune response against environmental mycobacteria. The action of HDAC inhibitors (iHDACs) was explored in a model of type II pneumocytes and macrophages infection by Mycobacterium aurum. The results show that the use of 1,3-diphenylurea increases the expression of the TLR-4 in M. aurum infected MDMs, as well as the production of defb4, IL-1ß, IL-12, and IL-6. Moreover, we observed that aminoacetanilide upregulates the expression of TLR-4 together with TLR-9, defb4, CAMP, RNase 6, RNase 7, IL-1ß, IL-12, and IL-6 in T2P. Results conclude that the tested iHDACs selectively modulate the expression of cytokines and antimicrobial peptides that are associated with reduction of non-tuberculous mycobacteria infection.

Immune Response to the Recombinant Apa Protein from Mycobacterium tuberculosis Expressed in Streptomyces lividans After Intranasal Administration in Mice. Induction of Protective Response to Tubercle Bacillus Aerosols Exposure.

Identifying and evaluating potential vaccine candidates has become one of the main objectives to combat tuberculosis. Among them, mannosylated Apa antigen from Mycobacterium tuberculosis and the non-mannosylated protein expressed in Escherichia coli, have been studied. Although both proteins can induce a protective response in mice, it has been considered that native protein can be dispensed. In this work, we study the protective response induced by Apa expressed in E. coli and in Streptomyces lividans. The latter, like native is secreted as a double band of 45/47 kDa, however, only its 47 kDa band is mannosylated. Both antigens and BCG were intranasal administrated in mice, and animals were then challenged by aerosol with M. tuberculosis H37Rv. The results showed that both, Apa from S. lividans and E. coli conferred statistically significantly protection to animals compared to controls. The cytokine immune response was studied by an immunoassay after animals' immunization, revealing that Apa from S. lividans induced a statistically significant proliferation of T cell, as well as the expression of IFN-γ, IL-1ß, IL-17 and IL-10. In contrast, non-proliferation was obtained with non-mannosylated protein, but induction of IL-12 and IL-17 was observed. Together, these results demonstrate that both proteins were able to modulate a specific immune response against M. tuberculosis, that could be driven by different mechanisms possibly associated with the presence or not of mannosylation. Furthermore, stimulation of cells from BCG-vaccinated animals with the proteins could be an important tool, to help define the use of a given subunit-vaccine after BCG vaccination.