From Bacterial Toxin to Therapeutic Agent: The Unexpected Fate of Mycolactone.

"Recognizing a surprising fact is the first step towards discovery." This famous quote from Louis Pasteur is particularly appropriate to describe what led us to study mycolactone, a lipid toxin produced by the human pathogen Mycobacterium ulcerans. M. ulcerans is the causative agent of Buruli ulcer, a neglected tropical disease manifesting as chronic, necrotic skin lesions with a "surprising" lack of inflammation and pain. Decades after its first description, mycolactone has become much more than a mycobacterial toxin. This uniquely potent inhibitor of the mammalian translocon (Sec61) helped reveal the central importance of Sec61 activity for immune cell functions, the spread of viral particles and, unexpectedly, the viability of certain cancer cells. We report in this review the main discoveries that marked our research into mycolactone, and the medical perspectives they opened up. The story of mycolactone is not over and the applications of Sec61 inhibition may go well beyond immunomodulation, viral infections, and oncology.

Novel evidence of Thymosin α1 immunomodulatory properties in SARS-CoV-2 infection: Effect on innate inflammatory response in a peripheral blood mononuclear cell-based in vitro model.

The peculiar property of Thymosin alpha 1 (Tα1) to act as master regulator of immune homeostasis has been successfully defined in different physiological and pathological contexts ranging from cancer to infection. Interestingly, recent papers also demonstrated its mitigating effect on the "cytokine storm" as well as on the T-cell exhaustion/activation in SARS-CoV-2 infected individuals. Nevertheless, in spite of the increasing knowledge on Tα1-induced effects on T cell response confirming the distinctive features of this multifaceted peptide, little is known on its effects on innate immunity during SARS-CoV-2 infection. Here, we interrogated peripheral blood mononuclear cell (PBMC) cultures stimulated with SARS-CoV-2 to disclose Tα1 properties on the main cell players of early response to infection, namely monocytes and myeloid dendritic cells (mDC). Moving from ex vivo data showing an enhancement in the frequency of inflammatory monocytes and activated mDC in COVID-19 patients, a PBMC-based experimental setting reproduced in vitro a similar profile with an increased percentage of CD16+ inflammatory monocytes and mDC expressing CD86 and HLA-DR activation markers in response to SARS-CoV-2 stimulation. Interestingly, the treatment of SARS-CoV-2-stimulated PBMC with Tα1 dampened the inflammatory/activation status of both monocytes and mDC by reducing the release of pro-inflammatory mediators, including TNF-α, IL-6 and IL-8, while promoting the production of the anti-inflammatory cytokine IL-10. This study further clarifies the working hypothesis on Tα1 mitigating action on COVID-19 inflammatory condition. Moreover, these evidence shed light on inflammatory pathways and cell types involved in acute SARS-CoV-2 infection and likely targetable by newly immune-regulating therapeutic approaches.

Sec61 blockade therapy overrides resistance to proteasome inhibitors and immunomodulatory drugs in multiple myeloma.

Multiple Myeloma (MM) is an incurable neoplasm of mature B cells and the second most prevalent hematological malignancy worldwide. While combinations of proteasome inhibitors like bortezomib (Bz) and immunomodulators (IMiDs) like lenalinomide (Len) are generally effective in newly diagnosed patients, some do not respond to this first-line therapy, and all others will eventually become drug resistant. We previously reported that inhibiting the Sec61 translocon with mycolactone synergizes with Bz to induce terminal unfolded protein response in MM cells, irrespective of their resistance to proteasome inhibition. Here, we examined how Sec61 blockade interferes with IMiD action and whether it overrides resistance to Len. With this aim, we knocked out the IMiD target CRBN in the MM1S cell line and a Bz-resistant subclone to generate Len- and Len/Bz-resistant daughters, respectively. Both the Len- and Len/Bz-resistant clones were susceptible to mycolactone toxicity, especially the doubly resistant one. Notably, the synergy between mycolactone and Bz was maintained in these two clones, and mycolactone also synergized with Len in the two Len-susceptible ones. Further, mycolactone enhanced the therapeutic efficacy of the Bz/Len combination in both mice engrafted with parental or double drug resistant MM1S. Together, these data consolidate the interest of Sec61 blockers as new anti-MM agents and reveal their potential for treatment of refractory or relapsed MM.

ERp57 chaperon protein protects neuronal cells from Aß-induced toxicity.

Alzheimer's disease (AD) is a neurodegenerative disorder whose main pathological hallmark is the accumulation of Amyloid-ß peptide (Aß) in the form of senile plaques. Aß can cause neurodegeneration and disrupt cognitive functions by several mechanisms, including oxidative stress. ERp57 is a protein disulfide isomerase involved in the cellular stress response and known to be present in the cerebrospinal fluid of normal individuals as a complex with Aß peptides, suggesting that it may be a carrier protein which prevents aggregation of Aß. Although several studies show ERp57 involvement in neurodegenerative diseases, no clear mechanism of action has been identified thus far. In this work, we gain insights into the interaction of Aß with ERp57, with a special focus on the contribution of ERp57 to the defense system of the cell. Here, we show that recombinant ERp57 directly interacts with the Aß25-35 fragment in vitro with high affinity via two in silico-predicted main sites of interaction. Furthermore, we used human neuroblastoma cells to show that short-term Aß25-35 treatment induces ERp57 decrease in intracellular protein levels, different intracellular localization, and ERp57 secretion in the cultured medium. Finally, we demonstrate that recombinant ERp57 counteracts the toxic effects of Aß25-35 and restores cellular viability, by preventing Aß25-35 aggregation. Overall, the present study shows that extracellular ERp57 can exert a protective effect from Aß toxicity and highlights it as a possible therapeutic tool in the treatment of AD.

Differential plasmacytoid dendritic cell phenotype and type I Interferon response in asymptomatic and severe COVID-19 infection.

SARS-CoV-2 fine-tunes the interferon (IFN)-induced antiviral responses, which play a key role in preventing coronavirus disease 2019 (COVID-19) progression. Indeed, critically ill patients show an impaired type I IFN response accompanied by elevated inflammatory cytokine and chemokine levels, responsible for cell and tissue damage and associated multi-organ failure. Here, the early interaction between SARS-CoV-2 and immune cells was investigated by interrogating an in vitro human peripheral blood mononuclear cell (PBMC)-based experimental model. We found that, even in absence of a productive viral replication, the virus mediates a vigorous TLR7/8-dependent production of both type I and III IFNs and inflammatory cytokines and chemokines, known to contribute to the cytokine storm observed in COVID-19. Interestingly, we observed how virus-induced type I IFN secreted by PBMC enhances anti-viral response in infected lung epithelial cells, thus, inhibiting viral replication. This type I IFN was released by plasmacytoid dendritic cells (pDC) via an ACE-2-indipendent but Neuropilin-1-dependent mechanism. Viral sensing regulates pDC phenotype by inducing cell surface expression of PD-L1 marker, a feature of type I IFN producing cells. Coherently to what observed in vitro, asymptomatic SARS-CoV-2 infected subjects displayed a similar pDC phenotype associated to a very high serum type I IFN level and induction of anti-viral IFN-stimulated genes in PBMC. Conversely, hospitalized patients with severe COVID-19 display very low frequency of circulating pDC with an inflammatory phenotype and high levels of chemokines and pro-inflammatory cytokines in serum. This study further shed light on the early events resulting from the interaction between SARS-CoV-2 and immune cells occurring in vitro and confirmed ex vivo. These observations can improve our understanding on the contribution of pDC/type I IFN axis in the regulation of the anti-viral state in asymptomatic and severe COVID-19 patients.

Visual Function and Ophthalmological Findings in CHARGE Syndrome: Revision of Literature, Definition of a New Clinical Spectrum and Genotype Phenotype Correlation.

CHARGE syndrome (CS) is a rare genetic disease causing multiple anatomical defects and sensory impairment. Visual function is usually reported by caregivers and has never been described with a structured behavioral assessment. Our primary objective was to describe ocular abnormalities, visual function and genotype-ocular-phenotype correlation in CS. A prospective monocentric cohort study was performed on 14 children with CS carrying pathogenic CHD7 variants. All children underwent ophthalmological evaluation and structured behavioral assessment of visual function. The VISIOCHARGE questionnaire was administered to parents. Colobomas were present in 93% of patients. Genotype-phenotype correlation documented mitigated features in a subset of patients with intronic pathogenic variants predicted to affect transcript processing, and severe features in patients with frameshift/nonsense variants predicting protein truncation at the N-terminus. Abnormal visual function was present in all subjects, with different degrees of impairment. A significant correlation was found between visual function and age at assessment (p-value = 0.025). The present data are the first to characterize visual function in CS patients. They suggest that hypomorphic variants might be associated with milder features, and that visual function appears to be related to age. While studies with larger cohorts are required for confirmation, our data indicate that experience appears to influence everyday use of visual function more than ocular abnormalities do.

An interdomain helix in IRE1α mediates the conformational change required for the sensor's activation.

The unfolded protein response plays an evolutionarily conserved role in homeostasis, and its dysregulation often leads to human disease, including diabetes and cancer. IRE1α is a major transducer that conveys endoplasmic reticulum stress via biochemical signals, yet major gaps persist in our understanding of how the detection of stress is converted to one of several molecular outcomes. It is known that, upon sensing unfolded proteins via its endoplasmic reticulum luminal domain, IRE1α dimerizes and then oligomerizes (often visualized as clustering). Once assembled, the kinase domain trans-autophosphorylates a neighboring IRE1α, inducing a conformational change that activates the RNase effector domain. However, the full details of how the signal is transmitted are not known. Here, we describe a previously unrecognized role for helix αK, located between the kinase and RNase domains of IRE1α, in conveying this critical conformational change. Using constructs containing mutations within this interdomain helix, we show that distinct substitutions affect oligomerization, kinase activity, and the RNase activity of IRE1α differentially. Furthermore, using both biochemical and computational methods, we found that different residues at position 827 specify distinct conformations at distal sites of the protein, such as in the RNase domain. Of importance, an RNase-inactive mutant, L827P, can still dimerize with wildtype monomers, but this mutation inactivates the wildtype molecule and renders leukemic cells more susceptible to stress. We surmise that helix αK is a conduit for the activation of IRE1α in response to stress.

Human plasmacytoid dendritic cells at the crossroad of type I interferon-regulated B cell differentiation and antiviral response to tick-borne encephalitis virus.

The Tick-borne encephalitis virus (TBEV) causes different disease symptoms varying from asymptomatic infection to severe encephalitis and meningitis suggesting a crucial role of the human host immune system in determining the fate of the infection. There is a need to understand the mechanisms underpinning TBEV-host interactions leading to protective immunity. To this aim, we studied the response of human peripheral blood mononuclear cells (PBMC) to the whole formaldehyde inactivated TBEV (I-TBEV), the drug substance of Encepur, one of the five commercially available vaccine. Immunophenotyping, transcriptome and cytokine profiling of PBMC revealed that I-TBEV generates differentiation of a sub-population of plasmacytoid dendritic cells (pDC) that is specialized in type I interferon (IFN) production. In contrast, likely due to the presence of aluminum hydroxide, Encepur vaccine was a poor pDC stimulus. We demonstrated I-TBEV-induced type I IFN together with Interleukin 6 and BAFF to be critical for B cell differentiation to plasmablasts as measured by immunophenotyping and immunoglobulin production. Robust type I IFN secretion was induced by pDC with the concerted action of both viral E glycoprotein and RNA mirroring previous data on dual stimulation of pDC by both S. aureus and influenza virus protein and nucleic acid that leads to a type I IFN-mediated sustained immune response. E glycoprotein neutralization or high temperature denaturation and inhibition of Toll-like receptor 7 signalling confirmed the importance of preserving the functional integrity of these key viral molecules during the inactivation procedure and manufacturing process to produce a vaccine able to stimulate strong immune responses.

Neurodevelopmental outcomes in very preterm infants: The role of severity of Bronchopulmonary Dysplasia.

OBJECTIVE: Bronchopulmonary dysplasia is a chronic respiratory disease that still affects preterm neonates; its association with neurodevelopmental (ND) impairment is already known. Different studies investigated neurodevelopmental outcomes in infants with BPD, often using the old dichotomous definition (BPD vs Non-BPD). This retrospective study aims to evaluate the role of different BPD severity grades on ND outcomes at 24 months of corrected age (CA). METHODS: All preterm infants born between 2011 and 2015 in the study hospital with a gestational age (GA) ≤ 30 weeks and discharged from our NICU were included and were divided in infants with and without BPD. Infants with BPD were divided into three severity groups as defined by NICHD/NHLBI Workshop in 2001, and were compared to their Non-BPD peers, matching them according to the same GA and year of birth. At 24 months postmenstrual age, we assessed general outcomes (growth and hospital readmissions) and neurodevelopmental outcomes (motor, developmental and sensory outcomes) with a standardized assessment. RESULTS: We enrolled 89 patients affected by BPD of different grades of severity and a control group of 89 preterm infants without BPD. Infants with Moderate and Severe BPD showed a significantly higher corrected odds ratio (OR) for cognitive impairment compared to controls. Within the group of infants without severe disability (regarding Griffiths' scales), infants with Moderate and Severe BPD as well as infants with Mild BPD showed a significantly higher risk of a lower total Developmental Quotient (DQ) score, even after correction for confounding factors. CONCLUSIONS: Our study evidenced that not only Severe BPD infants, but also Moderate ones showed a higher risk of overall cognitive impairment at 24 months CA. Within the group of infants without severe disability, also those with Mild BPD had lower Griffiths DQ scores than those without. This would suggest that infants with BPD, regardless of severity, warrant neurodevelopmental follow-up.

Functional and Morphologic Findings at Four Years After Intravitreal Bevacizumab or Laser for Type 1 ROP.

BACKGROUND AND OBJECTIVE: To compare morphologic and functional status at age 4 years for patients treated in one eye with laser photocoagulation and the other eye with intravitreal bevacizumab (IVB) injection for Type 1 retinopathy of prematurity (ROP). PATIENTS AND METHODS: In this single-center, randomized, controlled trial, best-corrected visual acuity (BCVA) in logMAR was obtained along with spherical equivalent refraction (SER), fluorescein angiography (FA), optical coherent tomography (OCT), and OCT angiography (OCTA). RESULTS: Eighteen babies (36 eyes) were selected for this study. BCVA and SER were similar in the two groups, but six patients had anisometropia of 4 diopters or more. IVB-treated eyes tended to have thinner foveal thickness than laser-treated eyes (mean difference: -5.33 pixels; 95% confidence interval, -9.62 to -1.05). CONCLUSION: Although the differences found here are minimal between the IVB-treated and laser-treated groups, further long-term evaluation of not only FA, but also OCT and OCTA, are needed in larger studies. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:180-186.].

Follow-up to Age 4 Years of Treatment of Type 1 Retinopathy of Prematurity Intravitreal Bevacizumab Injection versus Laser: Fluorescein Angiographic Findings.

PURPOSE: To compare structural outcome at age 4 years of eyes treated with intravitreal injection of bevacizumab with fellow eyes treated with conventional laser photoablation in type 1 retinopathy of prematurity (ROP). DESIGN: Single, randomized, controlled trial. PARTICIPANTS: All inborn babies with type 1 zone 1 ROP at the Neonatal Intensive Care Unit of the Catholic University, Rome, from September 1, 2009, to March 31, 2012. METHODS: In 21 infants (42 eyes), 1 eye was randomized to receive an intravitreal injection of 0.5 mg bevacizumab; the fellow eye underwent conventional laser photoablation. Digital retinal imaging and fluorescein angiography (FA) were performed at an average of 4 years after treatment in follow-up after these studies performed at treatment and 9 months. MAIN OUTCOME MEASURES: Fluorescein angiograms were examined by 2 experts to document retinal and choroidal findings. RESULTS: Among the 20 bevacizumab-treated eyes available at 4 years of age, all showed abnormalities at the periphery (avascular area, vessel leakage, shunts, abnormal vessel branching, and tangles) or the posterior pole (hyperfluorescent lesions, absence of foveal avascular zone). These lesions were not observed in the majority of the lasered eyes. Among the 19 laser-treated eyes, leakage was noted in 1 eye, shunts and tangles were noted in 3 eyes, and macular abnormalities were noted in 3 eyes. CONCLUSIONS: Fluorescein angiography has shown potentially serious and long-term ocular effects that are present more commonly after treatment with bevacizumab for acute-phase ROP than after laser.

Green tea catechins can bind and modify ERp57/PDIA3 activity.

BACKGROUND: Green tea is a rich source of polyphenols, mainly catechins (flavanols), which significantly contribute to the beneficial health effects of green tea in the prevention and treatment of various diseases. In this study the effects of four green tea catechins on protein ERp57, also known as protein disulfide isomerase isoform A3 (PDIA3), have been investigated in an in vitro model. METHODS: The interaction of catechins with ERp57 was explored by fluorescence quenching and surface plasmon resonance techniques and their effect on ERp57 activities was investigated. RESULTS: A higher affinity was observed for galloylated cathechins, which bind close to the thioredoxin-like redox-sensitive active sites of the protein, with a preference for the oxidized form. The effects of these catechins on ERp57 properties were also investigated and a moderate inhibition of the reductase activity of ERp57 was observed as well as a strong inhibition of ERp57 DNA binding activity. CONCLUSIONS: Considering the high affinity of galloylated catechins for ERp57 and their capability to inhibit ERp57 binding to other macromolecular ligands, some effects of catechins interaction with this protein on eukaryotic cells may be expected. GENERAL SIGNIFICANCE: This study provides information to better understand the molecular mechanisms underlying the biological activities of catechins and to design new polyphenol-based ERp57-specific inhibitors.

Dystroglycan is associated to the disulfide isomerase ERp57.

Dystroglycan (DG) is an extracellular receptor composed of two subunits, α-DG and ß-DG, connected through the α-DG C-terminal domain and the ß-DG N-terminal domain. We report an alanine scanning of all DG cysteine residues performed on DG-GFP constructs overexpressed in 293-Ebna cells, demonstrating that Cys-669 and Cys-713, both located within the ß-DG N-terminal domain, are key residues for the DG precursor cleavage and trafficking, but not for the interaction between the two DG subunits. In addition, we have used immunprecipitation and confocal microscopy showing that ERp57, a member of the disulfide isomerase family involved in glycoprotein folding, is associated and colocalizes immunohistochemically with ß-DG in the ER and at the plasma membrane of 293-Ebna cells. The ß-DG-ERp57 complex also included α-DG. DG mutants, unable to undergo the precursor cleavage, were still associated to ERp57. ß-DG and ERp57 were also co-immunoprecipitated in rat heart and kidney tissues. In vitro, a mutant ERp57, mimicking the reduced form of the wild-type protein, interacts directly with the recombinant N-terminal domain of both α-DG and ß-DG with apparent dissociation constant values in the micromolar range. ERp57 is likely to be involved in the DG processing/maturation pathway, but its association to the mature DG complex might also suggest some further functional role that needs to be investigated.

Cognitive profile of disorders associated with dysregulation of the RAS/MAPK signaling cascade.

Mutations in genes coding for transducers participating in the RAS/MAPK pathway have been identified as the molecular cause underlying a group of clinically related developmental disorders with cognitive deficits of variable severity. To determine the spectrum of cognitive defects associated with dysregulation of this signal cascade, we studied the profile of cognitive abilities in patients with mutations affecting the PTPN11, SOS1, HRAS, KRAS, BRAF, RAF1, and MEK1 genes and phenotype-genotype correlations. Our findings support the observation that heterogeneity in cognitive abilities can be at least partially ascribed to the individual affected genes and type of mutation involved. While mutations affecting transducers upstream of RAS were less frequently associated with mental retardation, mutations in downstream components of the pathway were generally associated with a more severe cognitive impairment. Among patients with a heterozygous PTPN11 mutation, the T468M substitution was associated with a mean IQ significantly higher compared to that of individuals carrying the N308D change. Our study provides insights on the range of cognitive abilities in patients with gene mutations causing dysregulation of RAS signaling suggesting that the presence and severity of cognitive involvement can be predicted in part by the gene involved.

Thalamic atrophy in infants with PVL and cerebral visual impairment.

The aim of this retrospective study was to establish the presence and severity of cerebral visual impairment in preterm infants with PVL. We also wished to establish whether abnormalities of visual function are related to brain MRI findings and more specifically not only to the involvement of optic radiations and occipital cortex but also to changes in the thalami, that are often affected in infants with PVL. Twelve infants with cystic PVL were assessed at 1 year (+2) corrected age with a battery of tests specifically designed to assess various aspects of visual function in infancy, such as ocular movements, visual acuity, visual fields and fixation shift. All infants also had a brain MRI. Eleven of the 12 had involvement of the optic radiations: all had some abnormalities of visual function and visual impairment was more severe in infants with more extensive involvement of the optic radiations. The child with normal optic radiations had normal visual function. Six of the 12 infants also had obvious signs of atrophy of the thalami and all had severe and wide-ranging abnormalities of visual function in all testing domains. Two children had equivocal atrophy of the thalami, both had some abnormalities of visual function. Four children had normal thalami and had normal visual function or only minor abnormalities on one of the visual tests. Our results suggest that the atrophy of the thalami may play an additional role in the abnormal development of visual function in infants with PVL and abnormal optic radiations.