Novel high-yield potato protease inhibitor panels block a wide array of proteases involved in viral infection and crucial tissue damage

Viruses critically rely on various proteases to ensure host cell entry and replication. In response to viral infection, the host will induce acute tissue inflammation pulled by granulocytes. Upon hyperactivation, neutrophil granulocytes may cause undue tissue damage through proteolytic degradation of the extracellular matrix. Here, we assess the potential of protease inhibitors (PI) derived from potatoes in inhibiting viral infection and reducing tissue damage. The original full spectrum of potato PI was developed into five fractions by means of chromatography and hydrolysis. Individual fractions showed varying inhibitory efficacy towards a panel of proteases including trypsin, chymotrypsin, ACE2, elastase, and cathepsins B and L. The fractions did not interfere with SARS-CoV-2 infection of Vero E6 cells in vitro. Importantly, two of the fractions fully inhibited elastin-degrading activity of complete primary human neutrophil degranulate. These data warrant further development of potato PI fractions for biomedical purposes, including tissue damage crucial to SARS-CoV-2 pathogenesis. KEY MESSAGES: Protease inhibitor fractions from potato differentially inhibit a series of human proteases involved in viral replication and in tissue damage by overshoot inflammation. Protease inhibition of cell surface receptors such as ACE2 does not prevent virus infection of Vero cells in vitro. Protease inhibitors derived from potato can fully inhibit elastin-degrading primary human neutrophil proteases. Protease inhibitor fractions can be produced at high scale (hundreds of thousands of kilograms, i.e., tons) allowing economically feasible application in lower and higher income countries.

Viral presence and immunopathology in a kidney transplant recipient with fatal COVID-19: a clinical autopsy report

COVID-19 is of special concern to immunocompromised individuals, including organ transplant recipients. However, the exact implications of COVID-19 for the immunocompromised host remain unclear. Existing theories regarding this matter are controversial and mainly based on clinical observations. Here, the postmortem histopathology, immunopathology, and viral presence in various tissues of a kidney transplant recipient with COVID-19 were compared to those of 2 nontransplanted patients with COVID-19 matched for age, sex, length of intensive care unit stay, and admission period in the pandemic. None of the tissues of the kidney transplant recipient demonstrated the presence of SARS-CoV-2. In lung tissues of both controls, some samples showed viral positivity with high Ct values with quantitative reverse transcription polymerase chain reaction. The lungs of the kidney transplant recipient and controls demonstrated similar pathology, consisting of acute fibrinous and organizing pneumonia with thrombosis and an inflammatory response with T cells, B cells, and macrophages. The kidney allograft and control kidneys showed a similar pattern of interstitial lymphoplasmacytic infiltration. No myocarditis could be observed in the hearts of the kidney transplant recipient and controls, although all cases contained scattered lymphoplasmacytic infiltrates in the myocardium, pericardium, and atria. The brainstems of the kidney transplant recipient and controls showed a similar pattern of lymphocytic inflammation with microgliosis. This research report highlights the possibility that, based on the results obtained from this single case, at time of death, the immune response in kidney transplant recipients with long-term antirejection immunosuppression use prior to severe illness is similar to nontransplanted deceased COVID-19 patients.

Causal inference using observational intensive care unit data: a scoping review and recommendations for future practice

This scoping review focuses on the essential role of models for causal inference in shaping actionable artificial intelligence (AI) designed to aid clinicians in decision-making. The objective was to identify and evaluate the reporting quality of studies introducing models for causal inference in intensive care units (ICUs), and to provide recommendations to improve the future landscape of research practices in this domain. To achieve this, we searched various databases including Embase, MEDLINE ALL, Web of Science Core Collection, Google Scholar, medRxiv, bioRxiv, arXiv, and the ACM Digital Library. Studies involving models for causal inference addressing time-varying treatments in the adult ICU were reviewed. Data extraction encompassed the study settings and methodologies applied. Furthermore, we assessed reporting quality of target trial components (i.e., eligibility criteria, treatment strategies, follow-up period, outcome, and analysis plan) and main causal assumptions (i.e., conditional exchangeability, positivity, and consistency). Among the 2184 titles screened, 79 studies met the inclusion criteria. The methodologies used were G methods (61%) and reinforcement learning methods (39%). Studies considered both static (51%) and dynamic treatment regimes (49%). Only 30 (38%) of the studies reported all five target trial components, and only seven (9%) studies mentioned all three causal assumptions. To achieve actionable AI in the ICU, we advocate careful consideration of the causal question of interest, describing this research question as a target trial emulation, usage of appropriate causal inference methods, and acknowledgement (and examination of potential violations of) the causal assumptions.

Mitochondrial protein BNIP3 regulates Chikungunya virus replication in the early stages of infection

Chikungunya virus (CHIKV) is a human pathogen causing outbreaks of febrile illness for which vaccines and specific treatments remain unavailable. Autophagy-related (ATG) proteins and autophagy receptors are a set of host factors that participate in autophagy, but have also shown to function in other unrelated cellular pathways. Although autophagy is reported to both inhibit and enhance CHIKV replication, the specific role of individual ATG proteins remains largely unknown. Here, a siRNA screen was performed to evaluate the importance of the ATG proteome and autophagy receptors in controlling CHIKV infection. We observed that 7 out of 50 ATG proteins impact the replication of CHIKV. Among those, depletion of the mitochondrial protein and autophagy receptor BCL2 Interacting Protein 3 (BNIP3) increased CHIKV infection. Interestingly, BNIP3 controls CHIKV independently of autophagy and cell death. Detailed analysis of the CHIKV viral cycle revealed that BNIP3 interferes with the early stages of infection. Moreover, the antiviral role of BNIP3 was found conserved across two distinct CHIKV genotypes and the closely related Semliki Forest virus. Altogether, this study describes a novel and previously unknown function of the mitochondrial protein BNIP3 in the control of the early stages of the alphavirus viral cycle.

Characterization of soluble TLR2 and CD14 levels during acute dengue virus infection

Dengue virus infection results in a broad spectrum of diseases ranging from mild dengue fever (DF) to severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Hitherto, there is no consensus biomarker for the prediction of severe dengue disease in patients. Yet, early identification of patients who progress to severe dengue is pivotal for better clinical management. We have recently reported that an increased frequency of classical (CD14 ⁺⁺CD16^-) monocytes with sustained high TLR2 expression in acutely infected dengue patients correlates with severe dengue development. Here, we hypothesized that the relatively lower TLR2 and CD14 expression in mild dengue patients is due to the shedding of their soluble forms (sTLR2 and sCD14) and that these could be used as indicators of disease progression. Therefore, using commercial sandwich ELISAs, we evaluated the release of sTLR2 and sCD14 by peripheral blood mononuclear cells (PBMCs) in response to in vitro dengue virus (DENV) infection and assessed their levels in acute-phase plasma of 109 dengue patients. We show that while both sTLR2 and sCD14 are released by PBMCs in response to DENV infection in vitro, their co-circulation in an acute phase of the disease is not always apparent. In fact, sTLR2 was found only in 20% of patients irrespective of disease status. In contrast, sCD14 levels were detected in all patients and were significantly elevated in DF patients when compared to DHF patients and age-matched healthy donors. Altogether, our results suggest that sCD14 may help in identifying patients at risk of severe dengue at hospital admittance.

Colocalization of Chikungunya Virus with Its Receptor MXRA8 during Cell Attachment, Internalization, and Membrane Fusion

Arthritogenic alphaviruses, including chikungunya virus (CHIKV), preferentially target joint tissues and cause chronic rheumatic disease that adversely impacts the quality of life of patients. Viruses enter target cells via interaction with cell surface receptor(s), which determine the viral tissue tropism and pathogenesis. Although MXRA8 is a recently identified receptor for several clinically relevant arthritogenic alphaviruses, its detailed role in the cell entry process has not been fully explored. We found that in addition to its localization on the plasma membrane, MXRA8 is present in acidic organelles, endosomes, and lysosomes. Moreover, MXRA8 is internalized into cells without a requirement for its transmembrane and cytoplasmic domains. Confocal microscopy and live cell imaging revealed that MXRA8 interacts with CHIKV at the cell surface and then enters cells along with CHIKV particles. At the moment of membrane fusion in the endosomes, many viral particles are still colocalized with MXRA8. These findings provide insight as to how MXRA8 functions in alphavirus internalization and suggest possible targets for antiviral development. IMPORTANCE The globally distributed arthritogenic alphaviruses have infected millions of humans and induce rheumatic disease, such as severe polyarthralgia/polyarthritis, for weeks to years. Alphaviruses infect target cells through receptor(s) followed by clathrin-mediated endocytosis. MXRA8 was recently identified as an entry receptor that shapes the tropism and pathogenesis for multiple arthritogenic alphaviruses, including chikungunya virus (CHIKV). Nonetheless, the exact functions of MXRA8 during the process of viral cell entry remain undetermined. Here, we have provided compelling evidence for MXRA8 as a bona fide entry receptor that mediates the uptake of alphavirus virions. Small molecules that disrupt MXRA8-dependent binding of alphaviruses or internalization steps could serve as a platform for unique classes of antiviral drugs.

TLR2 axis on peripheral blood mononuclear cells regulates inflammatory responses to non-infectious immature dengue virus particles

Severe dengue virus (DENV) infection is characterized by exacerbated inflammatory responses that lead to endothelial dysfunction and plasma leakage. We have recently demonstrated that Toll-like receptor 2 (TLR2) on blood monocytes senses DENV infection leading to endothelial activation. Here, we report that non-infectious immature DENV particles, which are released in large numbers by DENV-infected cells, drive endothelial activation via the TLR2 axis. We show that fully immature DENV particles induce a rapid, within 6 hours post-infection, inflammatory response in PBMCs. Furthermore, pharmacological blocking of TLR2/TLR6/CD14 and/or NF-kB prior to exposure of PBMCs to immature DENV reduces the initial production of inter alia TNF-α and IL-1β by monocytes and prevents endothelial activation. However, prolonged TLR2 block induces TNF-α production and leads to exacerbated endothelial activation, indicating that TLR2-mediated responses play an important role not only in the initiation but also the resolution of inflammation. Altogether, these data indicate that the maturation status of the virus has the potential to influence the kinetics and extent of inflammatory responses during DENV infection.

Visualization of conformational changes and membrane remodeling leading to genome delivery by viral class-II fusion machinery

Chikungunya virus (CHIKV) is a human pathogen that delivers its genome to the host cell cytoplasm through endocytic low pH-activated membrane fusion mediated by class-II fusion proteins. Though structures of prefusion, icosahedral CHIKV are available, structural characterization of virion interaction with membranes has been limited. Here, we have used cryo-electron tomography to visualize CHIKV's complete membrane fusion pathway, identifying key intermediary glycoprotein conformations coupled to membrane remodeling events. Using sub-tomogram averaging, we elucidate features of the low pH-exposed virion, nucleocapsid and full-length E1-glycoprotein's post-fusion structure. Contrary to class-I fusion systems, CHIKV achieves membrane apposition by protrusion of extended E1-glycoprotein homotrimers into the target membrane. The fusion process also features a large hemifusion diaphragm that transitions to a wide pore for intact nucleocapsid delivery. Our analyses provide comprehensive ultrastructural insights into the class-II virus fusion system function and direct mechanistic characterization of the fundamental process of protein-mediated membrane fusion.

Mediators of Obesity Do Not Influence SARS-CoV-2 Infection or Activation of Primary Human Lung Microvascular Endothelial Cells In Vitro

Clinical observations have shown that obesity is associated with the severe outcome of SARS-CoV-2 infection hallmarked by microvascular dysfunction in the lungs and other organs. Excess visceral fat and high systemic levels of adipose tissue (AT) derived mediators such as leptin and other adipokines have also been linked to endothelial dysfunction. Consequently, we hypothesized that AT-derived mediators may exacerbate microvascular dysfunction during of SARS-CoV-2 infection and tested this in a primary human lung microvascular endothelial (HLMVEC) cell model. Our results indicate that HLMVEC are not susceptible to SARS-CoV-2 infection since no expression of viral proteins and no newly produced virus was detected. In addition, exposure to the virus did not induce endothelial activation as evidenced by a lack of adhesion molecule, E-selectin, VCAM-1, ICAM-1, and inflammatory cytokine IL-6 induction. Incubation of endothelial cells with the pro-inflammatory AT-derived mediator, leptin, prior to virus inoculation, did not alter the expression of endothelial SARS-CoV-2 entry receptors and did not alter their susceptibility to infection. Furthermore, it did not induce inflammatory activation of endothelial cells. To verify if the lack of activated phenotype in the presence of adipokines was not leptin-specific, we exposed endothelial cells to plasma obtained from critically ill obese COVID-19 patients. Plasma exposure did not result in E-selectin, VCAM-1, ICAM-1, or IL-6 induction. Together our results strongly suggest that aberrant inflammatory endothelial responses are not mounted by direct SARS-CoV-2 infection of endothelial cells, even in the presence of leptin and other mediators of obesity. Instead, endothelial activation associated with COVID-19 is likely a result of inflammatory responses initiated by other cells. Further studies are required to investigate the mechanisms regulating endothelial behavior in COVID-19 and the mechanisms driving severe disease in obese individuals.

Vitamin D-induced LL-37 modulates innate immune responses of human primary macrophages during DENV-2 infection

Epidemics of dengue, an acute and potentially severe disease caused by mosquito-borne dengue virus (DENV), pose a major challenge to clinicians and health care services across the sub(tropics). Severe disease onset is associated with a dysregulated inflammatory response to the virus and there are currently no drugs to alleviate disease symptoms. LL-37 is a potent antimicrobial peptide with a wide range of immunoregulatory properties. In this study, we assessed the effect of LL-37 on DENV-2-induced responses in human monocyte-derived macrophages (MDMs). We show that simultaneous exposure of exogenous LL-37 and DENV-2 resulted in reduced replication of the virus in MDMs, while the addition of LL-37 post-exposure to DENV-2 did not. Interestingly, the latter condition reduced the production of IL-6 and increased the expression of genes involved in virus sensing and antiviral response. Finally, we demonstrate that low endogenous levels and limited production of LL-37 in MDMs in response to DENV-2 infection can be increased by differentiating MDMs in the presence of Vitamin D (VitD3). Taken together, this study demonstrates that in addition to its antimicrobial properties, LL-37 has immunomodulatory properties in the curse of DENV infection and its production can be increased by VitD3.

The Impact of Incisional Negative Pressure Wound on Scar Quality and Patient Reported Outcomes: a Within-Patient Controlled, Randomized Trial

Literature provides a moderate level of evidence for the beneficial effects of incisional negative pressure wound therapy (iNPWT) on scar quality. The purpose of this study was to establish if iNPWT results in improved scar outcomes in comparison to the standard of care. Therefore, a within‐patient randomised controlled, open‐label trial was conducted in transgender men undergoing gender‐affirming mastectomies. A unilateral side was randomised to receive iNPWT (PICO™, Smith&Nephew) without suction drains and contrastingly the standard dressing (Steri‐Strips™) with suction drain. Scar quality and questionnaires were bilaterally measured by means of objective assessments and patient‐reported outcome measures (PROM) at 1, 3 and 12 months. Objective scar outcomes were scar pliability (Cutometer®), colouration (DSM‐II) and scar width (3‐D imaging). PROM outcomes were related to scars (POSAS and SCAR‐Q) and body satisfaction (BODY‐Q). From 85 included patients, 80 were included for analyses. No significant difference between treatments was seen in the quantitative outcomes of scar pliability, colour, and width. For qualitative scar outcomes, several significant findings for iNPWT were found for several subscales of the POSAS, SCAR‐Q, and BODY‐Q. These effects could not be substantiated with linear mixed‐model regression, signifying no statically more favourable outcome for either treatment option. In conclusion, this study demonstrated that some PROM outcomes were more favourable for the iNPWT compared to standard treatment. In contrast, the quantitative outcomes showed no beneficial effects of iNPWT on scar outcomes. This suggests that iNPWT is of little benefit as a scar‐improving therapy.

Moxidectin and Ivermectin Inhibit SARS-CoV-2 Replication in Vero E6 Cells but Not in Human Primary Bronchial Epithelial Cells

Antiviral therapies are urgently needed to treat and limit the development of severe COVID-19 disease. Ivermectin, a broad-spectrum anti-parasitic agent, has been shown to have anti-SARS-CoV-2 activity in Vero cells at a concentration of 5 μM. These limited in vitro results triggered the investigation of ivermectin as a treatment option to alleviate COVID-19 disease. However, in April 2021, the World Health Organization stated the following: "The current evidence on the use of ivermectin to treat COVID-19 patients is inconclusive." It is speculated that the in vivo concentration of ivermectin is too low to exert a strong antiviral effect. Here, we performed a head-to-head comparison of the antiviral activity of ivermectin and the structurally related, but metabolically more stable moxidectin in multiple in vitro models of SARS-CoV-2 infection, including physiologically relevant human respiratory epithelial cells. Both moxidectin and ivermectin exhibited antiviral activity in Vero E6 cells. Subsequent experiments revealed that these compounds predominantly act on the steps following virus cell entry. Surprisingly, however, in human-airway-derived cell models, both moxidectin and ivermectin failed to inhibit SARS-CoV-2 infection, even at concentrations of 10 μM. These disappointing results call for a word of caution in the interpretation of anti-SARS-CoV-2 activity of drugs solely based on their activity in Vero cells. Altogether, these findings suggest that even using a high-dose regimen of ivermectin, or switching to another drug in the same class, is unlikely to be useful for treatment of SARS-CoV-2 in humans.

Posaconazole inhibits multiple steps of the alphavirus replication cycle

Repurposing drugs is a promising strategy to identify therapeutic interventions against novel and re-emerging viruses. Posaconazole is an antifungal drug used to treat invasive aspergillosis and candidiasis. Recently, posaconazole and its structural analog, itraconazole were shown to inhibit replication of multiple viruses by modifying intracellular cholesterol homeostasis. Here, we show that posaconazole inhibits replication of the alphaviruses Semliki Forest virus (SFV), Sindbis virus and chikungunya virus with EC₅₀ values ranging from 1.4 μM to 9.5 μM. Posaconazole treatment led to a significant reduction of virus entry in an assay using a temperature-sensitive SFV mutant, but time-of-addition and RNA transfection assays indicated that posaconazole also inhibits post-entry stages of the viral replication cycle. Virus replication in the presence of posaconazole was partially rescued by the addition of exogenous cholesterol. A transferrin uptake assay revealed that posaconazole considerably slowed down cellular endocytosis. A single point mutation in the SFV E2 glycoprotein, H255R, provided partial resistance to posaconazole as well as to methyl-β-cyclodextrin, corroborating the effect of posaconazole on cholesterol and viral entry. Our results indicate that posaconazole inhibits multiple steps of the alphavirus replication cycle and broaden the spectrum of viruses that can be targeted in vitro by posaconazole, which could be further explored as a therapeutic agent against emerging viruses.

Tomatidine reduces Chikungunya virus progeny release by controlling viral protein expression

Tomatidine, a natural steroidal alkaloid from unripe green tomatoes has been shown to exhibit many health benefits. We recently provided in vitro evidence that tomatidine reduces the infectivity of Dengue virus (DENV) and Chikungunya virus (CHIKV), two medically important arthropod-borne human infections for which no treatment options are available. We observed a potent antiviral effect with EC50 values of 0.82 μM for DENV-2 and 1.3 μM for CHIKV-LR. In this study, we investigated how tomatidine controls CHIKV infectivity. Using mass spectrometry, we identified that tomatidine induces the expression of p62, CD98, metallothionein and thioredoxin-related transmembrane protein 2 in Huh7 cells. The hits p62 and CD98 were validated, yet subsequent analysis revealed that they are not responsible for the observed antiviral effect. In parallel, we sought to identify at which step of the virus replication cycle tomatidine controls virus infectivity. A strong antiviral effect was seen when in vitro transcribed CHIKV RNA was transfected into Huh7 cells treated with tomatidine, thereby excluding a role for tomatidine during CHIKV cell entry. Subsequent determination of the number of intracellular viral RNA copies and viral protein expression levels during natural infection revealed that tomatidine reduces the RNA copy number and viral protein expression levels in infected cells. Once cells are infected, tomatidine is not able to interfere with active RNA replication yet it can reduce viral protein expression. Collectively, the results delineate that tomatidine controls viral protein expression to exert its antiviral activity. Lastly, sequential passaging of CHIKV in presence of tomatidine did not lead to viral resistance. Collectively, these results further emphasize the potential of tomatidine as an antiviral treatment towards CHIKV infection.

Chikungunya fever is a debilitating disease caused by the mosquito-borne Chikungunya virus. Over the past two decades the geographical spread of the virus and its mosquito vector has drastically increased thereby causing millions of infections. To date there is no antiviral drug and no vaccine available to treat/prevent Chikungunya virus infection. We recently showed that the natural steroidal alkaloid tomatidine has potent antiviral activity towards Chikungunya virus at submicromolar concentrations. In this study we dissected how tomatidine reduces the production of Chikungunya virus particles. We show that tomatidine lowers viral protein expression and we hypothesize that the effect of tomatidine on viral protein translation hampers the production of progeny viral RNA copies / number of infected cells thereby leading to a reduced production of secreted virus particles. Also, we show that Chikungunya virus does not readily become resistant to tomatidine. Collectively, we deciphered the mechanism by which tomatidine exerts antiviral activity to Chikungunya virus and our results strengthen the potential of tomatidine as an antiviral treatment strategy towards Chikungunya virus.

Left atrial appendage size is a marker of atrial fibrillation recurrence after radiofrequency catheter ablation in patients with persistent atrial fibrillation

Background

Catheter ablation is an established therapy for rhythm control in patients with drug-refractory atrial fibrillation (AF), however, recurrence is frequent particularly in persistent AF. There are no consistently confirmed predictors of AF recurrence after catheter ablation. The left atrial appendage (LAA) potentially plays an important role in AF recurrence, although the exact mechanism and pathophysiology are still unclear.

Purpose

We aimed to study whether LAA volume (LAAV) and function influence the long-term recurrence of AF after point-by-point radiofrequency catheter ablation, depending on AF type.

Methods

AF patients who underwent point-by-point radiofrequency catheter ablation after preprocedural cardiac computed tomography (CT) and transthoracic and transesophageal echocardiography (TEE) were included in this retrospective analysis. LAAV and LAA orifice area were measured by CT and LAA flow velocity assessed by TEE and was used as a surrogate marker of LAA function. Uni- and multivariable Cox proportional hazard regression models were performed to determine the predictors of AF recurrence.

Results

In total, 561 AF patients (61.9±10.2 years, 34.9% females) were included in the study. Recurrence of AF was detected in 40.8% of the cases (34.6% in patients with paroxysmal and 53.5% in those with persistent AF) with a median recurrence-free time of 22.7 [9.3–43.1] months. Patients with AF recurrence had significantly higher body surface area-indexed left atrial volume (iLAV), LAAV and LAA orifice area, as compared to those without recurrence. Moreover, patients with persistent AF had significantly higher iLAV, LAAV, LAA orifice area and lower LAA flow velocity, than those with paroxysmal AF. After adjustment for the main cardiovascular risk factors and comorbidities left ventricular ejection fraction (LVEF) <50% (HR=2.17; 95% CI=1.38–3.43; p<0.001) and LAAV (HR=1.06; 95% CI=1.01–1.12; p=0.029) were independently associated with AF recurrence in persistent AF, while no independent predictors could be identified in paroxysmal AF.

Conclusions

The current study demonstrates that beyond left ventricular systolic dysfunction, LAA enlargement is associated with higher rate of AF recurrence after catheter ablation in persistent AF, but not in patients with paroxysmal AF. Our results suggest that preprocedural assessment of LVEF and LAAV might contribute to optimal patient selection and aid to improve long-term results of ablation procedures in patients with persistent AF.

Funding Acknowledgement

Type of funding sources: None.

Regulation of innate immune responses in macrophages differentiated in the presence of vitamin D and infected with dengue virus 2

A dysregulated or exacerbated inflammatory response is thought to be the key driver of the pathogenesis of severe disease caused by the mosquito-borne dengue virus (DENV). Compounds that restrict virus replication and modulate the inflammatory response could thus serve as promising therapeutics mitigating the disease pathogenesis. We and others have previously shown that macrophages, which are important cellular targets for DENV replication, differentiated in the presence of bioactive vitamin D (VitD3) are less permissive to viral replication, and produce lower levels of pro-inflammatory cytokines. Therefore, we here evaluated the extent and kinetics of innate immune responses of DENV-2 infected monocytes differentiated into macrophages in the presence (D3-MDMs) or absence of VitD3 (MDMs). We found that D3-MDMs expressed lower levels of RIG I, Toll-like receptor (TLR)3, and TLR7, as well as higher levels of SOCS-1 in response to DENV-2 infection. D3-MDMs produced lower levels of reactive oxygen species, related to a lower expression of TLR9. Moreover, although VitD3 treatment did not modulate either the expression of IFN-α or IFN-β, higher expression of protein kinase R (PKR) and 2'-5'-oligoadenylate synthetase 1 (OAS1) mRNA were found in D3-MDMs. Importantly, the observed effects were independent of reduced infection, highlighting the intrinsic differences between D3-MDMs and MDMs. Taken together, our results suggest that differentiation of MDMs in the presence of VitD3 modulates innate immunity in responses to DENV-2 infection.

Resveratrol and Pterostilbene Inhibit SARS-CoV-2 Replication in Air-Liquid Interface Cultured Human Primary Bronchial Epithelial Cells

The current COVID-19 pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has an enormous impact on human health and economy. In search for therapeutic options, researchers have proposed resveratrol, a food supplement with known antiviral, anti-inflammatory, and antioxidant properties as an advantageous antiviral therapy for SARS-CoV-2 infection. Here, we provide evidence that both resveratrol and its metabolically more stable structural analog, pterostilbene, exhibit potent antiviral properties against SARS-CoV-2 in vitro. First, we show that resveratrol and pterostilbene antiviral activity in African green monkey kidney cells. Both compounds actively inhibit virus replication within infected cells as reduced virus progeny production was observed when the compound was added at post-inoculation conditions. Without replenishment of the compound, antiviral activity was observed up to roughly five rounds of replication, demonstrating the long-lasting effect of these compounds. Second, as the upper respiratory tract represents the initial site of SARS-CoV-2 replication, we also assessed antiviral activity in air-liquid interface (ALI) cultured human primary bronchial epithelial cells, isolated from healthy volunteers. Resveratrol and pterostilbene showed a strong antiviral effect in these cells up to 48 h post-infection. Collectively, our data indicate that resveratrol and pterostilbene are promising antiviral compounds to inhibit SARS-CoV-2 infection. Because these results represent laboratory findings in cells, we advocate evaluation of these compounds in clinical trials before statements are made whether these drugs are advantageous for COVID-19 treatment.

Within-patient randomized clinical trial comparing incisional negative-pressure wound therapy with suction drains in gender-affirming mastectomies

BACKGROUND

Incisional negative-pressure wound therapy (iNPWT) is widely adopted by different disciplines for multiple indications. Questions about the most appropriate uses and value of iNPWT have been raised.

METHODS

An open-label within-patient RCT was conducted in transgender men undergoing gender-affirming mastectomies. The objective was to determine the effect of iNPWT as a substitute for standard dressing and suction drains on wound healing complications. One chest side was randomized to receive the iNPWT intervention, and the other to standard dressing with suction drain. The primary endpoints were wound healing complications (haematoma, seroma, infection, and dehiscence) after three months. Additional outcomes were pain according to a numerical rating scale and patient satisfaction one week after surgery.

RESULTS

Eighty-five patients were included, of whom 81 received both the iNPWT and standard treatment. Drain removal criteria were met within 24 h in 95 per cent of the patients. No significant decrease in wound healing complications was registered on the iNPWT side, but the seroma rate was significantly increased. In contrast, patients experienced both significantly less pain and increased comfort on the iNPWT side. No medical device-related adverse events were registered.

CONCLUSION

Substituting short-term suction drains with iNPWT in gender-affirming mastectomies increased the seroma rates and did not decrease the amount of wound healing complications. Registration number: NTR7412 (Netherlands Trial Register).

Recent advances in antiviral drug development towards dengue virus

Despite the high disease burden of dengue virus, there is no approved antiviral treatment or broadly applicable vaccine to treat or prevent dengue virus infection. In the last decade, many antiviral compounds have been identified but only few have been further evaluated in pre-clinical or clinical trials. This review will give an overview of the direct-acting and host-directed antivirals identified to date. Furthermore, important parameters for further development that is, drug properties including efficacy, specificity and stability, pre-clinical animal testing, and combinational drug therapy will be discussed.

Chikungunya virus requires an intact microtubule network for efficient viral genome delivery

Chikungunya virus (CHIKV) is a re-emerging mosquito-borne alphavirus, which has rapidly spread around the globe thereby causing millions of infections. CHIKV is an enveloped virus belonging to the Togaviridae family and enters its host cell primarily via clathrin-mediated endocytosis. Upon internalization, the endocytic vesicle containing the virus particle moves through the cell and delivers the virus to early endosomes where membrane fusion is observed. Thereafter, the nucleocapsid dissociates and the viral RNA is translated into proteins. In this study, we examined the importance of the microtubule network during the early steps of infection and dissected the intracellular trafficking behavior of CHIKV particles during cell entry. We observed two distinct CHIKV intracellular trafficking patterns prior to membrane hemifusion. Whereas half of the CHIKV virions remained static during cell entry and fused in the cell periphery, the other half showed fast-directed microtubule-dependent movement prior to delivery to Rab5-positive early endosomes and predominantly fused in the perinuclear region of the cell. Disruption of the microtubule network reduced the number of infected cells. At these conditions, membrane hemifusion activity was not affected yet fusion was restricted to the cell periphery. Furthermore, follow-up experiments revealed that disruption of the microtubule network impairs the delivery of the viral genome to the cell cytosol. We therefore hypothesize that microtubules may direct the particle to a cellular location that is beneficial for establishing infection or aids in nucleocapsid uncoating.

Chikungunya virus (CHIKV) is an alphavirus that is transmitted to humans by infected mosquitoes. Disease symptoms can include fever, rash, myalgia, and long-lasting debilitating joint pains. Unfortunately, there is currently no licensed vaccine or antiviral treatment available to combat CHIKV. Understanding the virus:host interactions during the replication cycle of the virus is crucial for the development of effective antiviral therapies. In this study we elucidated the trafficking behavior of CHIKV particles early in infection. During cell entry, CHIKV virions require an intact microtubule network for efficient delivery of the viral genome into the host cell thereby increasing the chance to productively infect a cell.

Serotonergic Drugs Inhibit Chikungunya Virus Infection at Different Stages of the Cell Entry Pathway

Chikungunya virus (CHIKV) is an important reemerging human pathogen transmitted by mosquitoes. The virus causes an acute febrile illness, chikungunya fever, which is characterized by headache, rash, and debilitating (poly)arthralgia that can reside for months to years after infection. Currently, effective antiviral therapies and vaccines are lacking. Due to the high morbidity and economic burden in the countries affected by CHIKV, there is a strong need for new strategies to inhibit CHIKV replication. The serotonergic drug 5-nonyloxytryptamine (5-NT) was previously identified as a potential host-directed inhibitor for CHIKV infection. In this study, we determined the mechanism of action by which the serotonin receptor agonist 5-NT controls CHIKV infection. Using time-of-addition and entry bypass assays, we found that 5-NT predominantly inhibits CHIKV in the early phases of the replication cycle, at a step prior to RNA translation and genome replication. Intriguingly, however, no effect was seen during virus-cell binding, internalization, membrane fusion and genomic RNA (gRNA) release into the cell cytosol. In addition, we show that the serotonin receptor antagonist methiothepin mesylate (MM) also has antiviral properties toward CHIKV and specifically interferes with the cell entry process and/or membrane fusion. Taken together, pharmacological targeting of 5-HT receptors may represent a potent way to limit viral spread and disease severity.IMPORTANCE The rapid spread of mosquito-borne viral diseases in humans puts a huge economic burden on developing countries. For many of these infections, including those caused by chikungunya virus (CHIKV), there are no specific treatment possibilities to alleviate disease symptoms. Understanding the virus-host interactions that are involved in the viral replication cycle is imperative for the rational design of therapeutic strategies. In this study, we discovered an antiviral compound, elucidated its mechanism of action, and propose serotonergic drugs as potential host-directed antivirals for CHIKV.

Tomatidine, a natural steroidal alkaloid shows antiviral activity towards chikungunya virus in vitro

In recent decades, chikungunya virus (CHIKV) has re-emerged, leading to outbreaks of chikungunya fever in Africa, Asia and Central and South America. The disease is characterized by a rapid onset febrile illness with (poly)arthralgia, myalgia, rashes, headaches and nausea. In 30 to 40% of the cases, CHIKV infection causes persistent (poly)arthralgia, lasting for months or even years after initial infection. Despite the drastic re-emergence and clinical impact there is no vaccine nor antiviral compound available to prevent or control CHIKV infection. Here, we evaluated the antiviral potential of tomatidine towards CHIKV infection. We demonstrate that tomatidine potently inhibits virus particle production of multiple CHIKV strains. Time-of -addition experiments in Huh7 cells revealed that tomatidine acts at a post-entry step of the virus replication cycle. Furthermore, a marked decrease in the number of CHIKV-infected cells was seen, suggesting that tomatidine predominantly acts early in infection yet after virus attachment and cell entry. Antiviral activity was still detected at 24 hours post-infection, indicating that tomatidine controls multiple rounds of CHIKV replication. Solasodine and sarsasapogenin, two structural derivatives of tomatidine, also showed strong albeit less potent antiviral activity towards CHIKV. In conclusion, this study identifies tomatidine as a novel compound to combat CHIKV infection in vitro.

Role of autophagy during the replication and pathogenesis of common mosquito-borne flavi- and alphaviruses

Arboviruses that are transmitted to humans by mosquitoes represent one of the most important causes of febrile illness worldwide. In recent decades, we have witnessed a dramatic re-emergence of several mosquito-borne arboviruses, including dengue virus (DENV), West Nile virus (WNV), chikungunya virus (CHIKV) and Zika virus (ZIKV). DENV is currently the most common mosquito-borne arbovirus, with an estimated 390 million infections worldwide annually. Despite a global effort, no specific therapeutic strategies are available to combat the diseases caused by these viruses. Multiple cellular pathways modulate the outcome of infection by either promoting or hampering viral replication and/or pathogenesis, and autophagy appears to be one of them. Autophagy is a degradative pathway generally induced to counteract viral infection. Viruses, however, have evolved strategies to subvert this pathway and to hijack autophagy components for their own benefit. In this review, we will focus on the role of autophagy in mosquito-borne arboviruses with emphasis on DENV, CHIKV, WNV and ZIKV, due to their epidemiological importance and high disease burden.

Short-term cost-effectiveness of one-stage implant-based breast reconstruction with an acellular dermal matrix versus two-stage expander-implant reconstruction from a multicentre randomized clinical trial

Background

Implant‐based breast reconstruction (IBBR) is the most commonly performed reconstructive procedure and its economic impact is significant. This study aimed to analyse whether a direct one‐stage IBBR with use of an acellular dermal matrix (ADM) is more cost‐effective than two‐stage (expander‐implant) breast reconstruction.

Methods

The BRIOS (Breast Reconstruction In One Stage) study was an open‐label multicentre RCT in which women scheduled for skin‐sparing mastectomy and immediate IBBR were randomized between one‐stage IBBR with ADM or two‐stage IBBR. Duration of surgery and hospital stay, and visits for the primary surgery, unplanned and cosmetic procedures were recorded. Costs were estimated at an institutional level. Health status was assessed by means of the EuroQol Five Dimensions 5L questionnaire.

Results

Fifty‐nine patients (91 breasts) underwent one‐stage IBBR with ADM and 62 patients (92 breasts) two‐stage IBBR. The mean(s.d.) duration of surgery in the one‐stage group was significantly longer than that for two‐stage IBBR for unilateral (2·52(0·55) versus 2·02(0·35) h; P < 0·001) and bilateral (4·03(1·00) versus 3·25(0·58) h; P = 0·017) reconstructions. Costs were higher for one‐stage compared with two‐stage IBBR for both unilateral (€12 448 (95 per cent c.i. 10 722 to 14 387) versus €9871 (9373 to 10 445) respectively; P = 0·025) and bilateral (€16 939 (14 887 to 19 360) versus €13 383 (12 414 to 14 669); P = 0·002) reconstructions. This was partly related to the use of relatively expensive ADM. There was no difference in postoperative health status between the groups.

Conclusion

One‐stage IBBR with ADM was associated with higher costs, but similar health status, compared with conventional two‐stage IBBR. Registration number: NTR5446 ( http://www.trialregister.nl).

Tomatidine, a novel antiviral compound towards dengue virus

Dengue is the most common arboviral disease worldwide with 96 million symptomatic cases annually. Despite its major impact on global human health and huge economic burden there is no antiviral drug available to treat the disease. The first tetravalent dengue virus vaccine was licensed in 2015 for individuals aged 9 to 45, however, most cases are reported in infants and young children. This, together with the limited efficacy of the vaccine to dengue virus (DENV) serotype 2, stresses the need to continue the search for compounds with antiviral activity to DENV. In this report, we describe tomatidine as a novel compound with potent antiviral properties towards all DENV serotypes and the related Zika virus. The strongest effect was observed for DENV-2 with an EC50 and EC90 value of 0.82 and 1.61 μM, respectively, following infection of Huh7 cells at multiplicity of infection of 1. The selectivity index is 97.7. Time-of-drug-addition experiments revealed that tomatidine inhibits virus particle production when added pre, during and up to 12 h post-infection. Subsequent experiments show that tomatidine predominantly acts at a step after virus-cell binding and membrane fusion but prior to the secretion of progeny virions. Tomatidine was found to control the expression of the cellular protein activating transcription factor 4 (ATF4), yet, this protein is not solely responsible for the observed antiviral effect. Here, we propose tomatidine as a candidate for the treatment of dengue given its potent antiviral activity.

Predictors of complications after direct-to-implant breast reconstruction with an acellular dermal matrix from a multicentre randomized clinical trial

BACKGROUND

In the multicentre randomized trial BRIOS (Breast Reconstruction In One Stage), direct-to-implant (DTI) breast reconstruction with an acellular dermal matrix (ADM) was associated with a markedly higher postoperative complication rate compared with two-stage tissue expander/implant breast reconstruction. This study aimed to identify factors that contribute to the occurrence of complications after DTI ADM-assisted breast reconstruction.

METHODS

Data were obtained from the BRIOS study, including all patients treated with DTI ADM-assisted breast reconstruction. Logistic regression analyses were performed to identify factors predictive of postoperative complications.

RESULTS

Fifty-nine patients (91 breasts) were included, of whom 27 (35 breasts) developed a surgical complication. Reoperations were performed in 29 breasts (32 per cent), with prosthesis removal in 22 (24 per cent). In multivariable analyses, mastectomy weight was associated with complications (odds ratio (OR) 1·94, 95 per cent c.i. 1·33 to 2·83), reoperations (OR 1·70, 1·12 to 2·59) and removal of the implant (OR 1·55, 1·11 to 2·17). Younger patients (OR 1·07, 1·01 to 1·13) and those who received adjuvant chemotherapy (OR 4·83, 1·15 to 20·24) more frequently required reoperation. In univariable analyses, adjuvant radiotherapy showed a trend towards more complications (OR 7·23, 0·75 to 69·95) and removal of the implant (OR 5·12, 0·76 to 34·44), without reaching statistical significance.

CONCLUSION

Breast size appeared to be the most significant predictor of complications in DTI ADM-assisted breast reconstruction. The technique should preferably be performed in patients with small to moderate sized breasts. Registration number: NTR5446 ( http://www.trialregister.nl).

MicroRNA profiling of human primary macrophages exposed to dengue virus identifies miRNA-3614-5p as antiviral and regulator of ADAR1 expression

Background

Due to the high burden of dengue disease worldwide, a better understanding of the interactions between dengue virus (DENV) and its human host cells is of the utmost importance. Although microRNAs modulate the outcome of several viral infections, their contribution to DENV replication is poorly understood.

Methods and principal findings

We investigated the microRNA expression profile of primary human macrophages challenged with DENV and deciphered the contribution of microRNAs to infection. To this end, human primary macrophages were challenged with GFP-expressing DENV and sorted to differentiate between truly infected cells (DENV-positive) and DENV-exposed but non-infected cells (DENV-negative cells). The miRNAome was determined by small RNA-Seq analysis and the effect of differentially expressed microRNAs on DENV yield was examined. Five microRNAs were differentially expressed in human macrophages challenged with DENV. Of these, miR-3614-5p was found upregulated in DENV-negative cells and its overexpression reduced DENV infectivity. The cellular targets of miR-3614-5p were identified by liquid chromatography/mass spectrometry and western blot. Adenosine deaminase acting on RNA 1 (ADAR1) was identified as one of the targets of miR-3614-5p and was shown to promote DENV infectivity at early time points post-infection.

Conclusion/Significance

Overall, miRNAs appear to play a limited role in DENV replication in primary human macrophages. The miRNAs that were found upregulated in DENV-infected cells did not control the production of infectious virus particles. On the other hand, miR-3614-5p, which was upregulated in DENV-negative macrophages, reduced DENV infectivity and regulated ADAR1 expression, a protein that facilitates viral replication.

Dengue is the most common mosquito-borne disease worldwide and it is an increasing global concern for public health as its etiological agent, dengue virus (DENV), keeps spreading around the globe. Currently there are no specific antiviral therapies available to treat the disease. Macrophages are important target cells during natural DENV infection of humans. Here, we unraveled the importance of miRNAs in DENV replication in human primary macrophages. The expression profile of miRNAs was determined in truly DENV-infected cells and cells that were exposed but not productively infected by the virus by RNA sequencing. We revealed that only five miRNAs are regulated in primary macrophages challenged with DENV. These results show that miRNAs do not play a major role in DENV replication. Unexpectedly, we did identify a miRNA with moderate yet significant antiviral properties to DENV. Moreover, miRNA-3614-5p was found to not only decrease DENV but also West Nile virus infectivity. Mass spectrometry and bioinformatics analysis identified adenosine deaminase acting on RNA 1 (ADAR1) as one of the targets. Moreover, ADAR1 was observed to promote the early stages of DENV replication. Collectively, our study broadens the knowledge of the contribution of human miRNAs in shaping the network of interactions between DENV and its human host cells.

Human macrophages differentiated in the presence of vitamin D3 restrict dengue virus infection and innate responses by downregulating mannose receptor expression

Background

Severe dengue disease is associated with high viral loads and overproduction of pro-inflammatory cytokines, suggesting impairment in the control of dengue virus (DENV) and the mechanisms that regulate cytokine production. Vitamin D₃ has been described as an important modulator of immune responses to several pathogens. Interestingly, increasing evidence has associated vitamin D with decreased DENV infection and early disease recovery, yet the molecular mechanisms whereby vitamin D reduces DENV infection are not well understood.

Methods and principal findings

Macrophages represent important cell targets for DENV replication and consequently, they are key drivers of dengue disease. In this study we evaluated the effect of vitamin D₃ on the differentiation of monocyte-derived macrophages (MDM) and their susceptibility and cytokine response to DENV. Our data demonstrate that MDM differentiated in the presence of vitamin D₃ (D₃-MDM) restrict DENV infection and moderate the classical inflammatory cytokine response. Mechanistically, vitamin D₃-driven differentiation led to reduced surface expression of C-type lectins including the mannose receptor (MR, CD206) that is known to act as primary receptor for DENV attachment on macrophages and to trigger of immune signaling. Consequently, DENV bound less efficiently to vitamin D₃-differentiated macrophages, leading to lower infection. Interestingly, IL-4 enhanced infection was reduced in D₃-MDM by restriction of MR expression. Moreover, we detected moderate secretion of TNF-α, IL-1β, and IL-10 in D₃-MDM, likely due to less MR engagement during DENV infection.

Conclusions/Significance

Our findings reveal a molecular mechanism by which vitamin D counteracts DENV infection and progression of severe disease, and indicates its potential relevance as a preventive or therapeutic candidate.

Dengue represents a major worldwide concern for public health. Clinical complications rely on vascular leak of fluids and molecules from the bloodstream that leads to a potentially fatal hemodynamic compromise. Disease progression has been related to poor control of dengue virus (DENV) dissemination and excessive production of pro-inflammatory mediators that affect the endothelial function. Vitamin D has been shown to modulate immune responses and to alleviate dengue disease. Here, we studied how addition of vitamin D during macrophage differentiation modulates the functional features of these cells in the context of DENV infection. We observed that vitamin D reduced susceptibility of these cells to DENV infection and down-regulated the virus-induced cytokine response. This phenotype was attributed to downregulation of MR, a molecule hijacked by the virus to gain entry into the cells and a key receptor of the MR/CLEC5A complex that links binding and immune activation during DENV infection. Our study sheds light on the mechanism by which vitamin D can restrict DENV dissemination and the cytokine response in macrophages, indicating the potential relevance of this hormone as a preventive and therapeutic candidate.

Accuracy and reproducibility of fast fractional flow reserve computation from invasive coronary angiography

Fractional flow reserve (FFR) guided percutaneous coronary intervention (PCI) is associated with favourable outcome compared with revascularization based on angiographic stenosis severity alone. The feasibility of the new image-based quantitative flow ratio (QFR) assessed from 3D quantitative coronary angiography (QCA) and thrombolysis in myocardial infarction (TIMI) frame count using three different flow models has been reported recently. The aim of the current study was to assess the accuracy, and in particular, the reproducibility of these three QFR techniques when compared with invasive FFR. QFR was derived (1) from adenosine induced hyperaemic coronary angiography images (adenosine-flow QFR [aQFR]), (2) from non-hyperemic images (contrast-flow QFR [cQFR]) and (3) using a fixed empiric hyperaemic flow [fixed-flow QFR (fQFR)]. The three QFR values were calculated in 17 patients who prospectively underwent invasive FFR measurement in 20 vessels. Two independent observers performed the QFR analyses. Mean difference, standard deviation and 95% limits of agreement (LOA) between invasive FFR and aQFR, cQFR and fQFR for observer 1 were: 0.01 ± 0.04 (95% LOA: -0.07; 0.10), 0.01 ± 0.05 (95% LOA: -0.08; 0.10), 0.01 ± 0.04 (95% LOA: -0.06; 0.08) and for observer 2: 0.00 ± 0.03 (95% LOA: -0.06; 0.07), -0.01 ± 0.03 (95% LOA: -0.07; 0.05), 0.00 ± 0.03 (95% LOA: -0.06; 0.05). Values between the 2 observers were (to assess reproducibility) for aQFR: 0.01 ± 0.04 (95% LOA: -0.07; 0.09), for cQFR: 0.02 ± 0.04 (95% LOA: -0.06; 0.09) and for fQFR: 0.01 ± 0.05 (95% LOA: -0.07; 0.10). In a small number of patients we showed good accuracy of three QFR techniques (aQFR, cQFR and fQFR) to predict invasive FFR. Furthermore, good inter-observer agreement of the QFR values was observed between two independent observers.

Suppression of chikungunya virus replication and differential innate responses of human peripheral blood mononuclear cells during co-infection with dengue virus

Dengue and chikungunya are viral diseases transmitted to humans by infected Aedes spp. mosquitoes. With an estimated 390 million infected people per year dengue virus (DENV) currently causes the most prevalent arboviral disease. During the last decade chikungunya virus (CHIKV) has caused large outbreaks and has expanded its territory causing millions of cases in Asia, Africa and America. The viruses share a common mosquito vector and during the acute phase cause similar flu-like symptoms that can proceed to more severe or debilitating symptoms. The growing overlap in the geographical distribution of these mosquito-borne infections has led to an upsurge in reported cases of DENV/CHIKV co-infections. Unfortunately, at present we have little understanding of consequences of the co-infections to the human host. The overall aim of this study was to define viral replication dynamics and the innate immune signature involved in concurrent DENV and CHIKV infections in human peripheral blood mononuclear cells (PBMCs). We demonstrate that concomitant infection resulted in a significant reduction of CHIKV progeny and moderate enhancement of DENV production. Remarkably, the inhibitory effect of DENV on CHIKV infection occurred independently of DENV replication. Furthermore, changes in type I IFN, IL-6, IL-8, TNF-α, MCP-1 and IP-10 production were observed during concomitant infections. Notably, co-infections led to a significant increase in the levels of TNF-α and IL-6, cytokines that are widely considered to play a crucial role in the early pathogenesis of both viral diseases. In conclusion, our study reveals the interplay of DENV/CHIKV during concomitant infection and provides a framework to investigate viral interaction during co-infections.

Mechanism and role of MCP-1 upregulation upon chikungunya virus infection in human peripheral blood mononuclear cells

Monocyte chemoattractant protein-1 (MCP-1/CCL2)-mediated migration of monocytes is essential for immunological surveillance of tissues. During chikungunya virus (CHIKV) infection however, excessive production of MCP-1 has been linked to disease pathogenesis. High MCP-1 serum levels are detected during the viremic phase of CHIKV infection and correlate with the virus titre. In vitro CHIKV infection was also shown to stimulate MCP-1 production in whole blood; yet the role and the mechanism of MCP-1 production upon infection of human peripheral blood mononuclear cells remain unknown. Here we found that active CHIKV infection stimulated production of MCP-1 in monocytes. Importantly however, we found that communication with other leukocytes is crucial to yield MCP-1 by monocytes upon CHIKV infection. Indeed, blocking interferon-α/β receptor or the JAK1/JAK2 signalling downstream of the receptor abolished CHIKV-mediated MCP-1 production. Additionally, we show that despite the apparent correlation between IFN type I, CHIKV replication and MCP-1, modulating the levels of the chemokine did not influence CHIKV infection. In summary, our data disclose the complexity of MCP-1 regulation upon CHIKV infection and point to a crucial role of IFNβ in the chemokine secretion. We propose that balance between these soluble factors is imperative for an appropriate host response to CHIKV infection.

How antibodies alter the cell entry pathway of dengue virus particles in macrophages

Antibody-dependent enhancement of dengue virus (DENV) infection plays an important role in the exacerbation of DENV-induced disease. To understand how antibodies influence the fate of DENV particles, we explored the cell entry pathway of DENV in the absence and presence of antibodies in macrophage-like P388D1 cells. Recent studies unraveled that both mature and immature DENV particles contribute to ADE, hence, both particles were studied. We observed that antibody-opsonized DENV enters P388D1 cells through a different pathway than non-opsonized DENV. Antibody-mediated DENV entry was dependent on FcγRs, pH, Eps15, dynamin, actin, PI3K, Rab5, and Rab7. In the absence of antibodies, DENV cell entry was FcγR, PI3K, and Rab5-independent. Live-cell imaging of fluorescently-labeled particles revealed that actin-mediated membrane protrusions facilitate virus uptake. In fact, actin protrusions were found to actively search and capture antibody-bound virus particles distantly located from the cell body, a phenomenon that is not observed in the absence of antibodies. Overall, similar results were seen for antibody-opsonized standard and antibody-bound immature DENV preparations, indicating that the maturation status of the virus does not control the entry pathway. Collectively, our findings suggest that antibodies alter the cell entry pathway of DENV and trigger a novel mechanism of initial virus-cell contact.

Altered immune response of immature dendritic cells following dengue virus infection in the presence of specific antibodies

Dengue virus (DENV) replication is known to prevent maturation of infected dendritic cells (DCs) thereby impeding the development of adequate immunity. During secondary DENV infection, dengue-specific antibodies can suppress DENV replication in immature DCs (immDCs), however how dengue-antibody complexes (DENV-IC) influence the phenotype of DCs remains elusive. Here, we evaluated the maturation state and cytokine profile of immDCs exposed to DENV-ICs. Indeed, DENV infection of immDCs in the absence of antibodies was hallmarked by blunted upregulation of CD83, CD86 and the major histocompatibility complex molecule HLA-DR. In contrast, DENV infection in the presence of neutralizing antibodies triggered full DC maturation and induced a balanced inflammatory cytokine response. Moreover, DENV infection under non-neutralizing conditions prompted upregulation of CD83 and CD86 but not HLA-DR, and triggered production of pro-inflammatory cytokines. The effect of DENV-IC was found to be dependent on the engagement of FcγRIIa. Altogether, our data show that the presence of DENV-IC alters the phenotype and cytokine profile of DCs.

Complex interaction between dengue virus replication and expression of miRNA-133a

Background

Dengue virus (DENV) is the most common vector-borne viral infection worldwide with approximately 390 million cases and 25,000 reported deaths each year. MicroRNAs (miRNAs) are small non-coding RNA molecules responsible for the regulation of gene expression by repressing mRNA translation or inducing mRNA degradation. Although miRNAs possess antiviral activity against many mammalian-infecting viruses, their involvement in DENV replication is poorly understood.

Methods

Here, we explored the relationship between DENV and cellular microRNAs using bioinformatics tools. We overexpressed miRNA-133a in Vero cells to test its role in DENV replication and analyzed its expression using RT-qPCR. Furthermore, the expression of polypyrimidine tract binding protein (PTB), a protein involved in DENV replication, was analyzed by western blot. In addition, we profiled miRNA-133a expression in Vero cells challenged with DENV-2, using Taqman miRNA.

Results

Bioinformatic analysis revealed that the 3' untranslated region (3'UTR) of the DENV genome of all four DENV serotypes is targeted by several cellular miRNAs, including miRNA-133a. We found that overexpression of synthetic miRNA-133a suppressed DENV replication. Additionally, we observed that PTB transcription , a miRNA-133a target, is down-regulated during DENV infection. Based in our results we propose that 3'UTR of DENV down-regulates endogenous expression of miRNA-133a in Vero cells during the first hours of infection.

Conclusions

miRNA-133a regulates DENV replication possibly through the modulation of a host factor such as PTB. Further investigations are needed to verify whether miRNA-133a has an anti-DENV effect in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1364-y) contains supplementary material, which is available to authorized users.

Broadly Neutralizing Alphavirus Antibodies Bind an Epitope on E2 and Inhibit Entry and Egress

We screened a panel of mouse and human monoclonal antibodies (MAbs) against chikungunya virus and identified several with inhibitory activity against multiple alphaviruses. Passive transfer of broadly neutralizing MAbs protected mice against infection by chikungunya, Mayaro, and O'nyong'nyong alphaviruses. Using alanine-scanning mutagenesis, loss-of-function recombinant proteins and viruses, and multiple functional assays, we determined that broadly neutralizing MAbs block multiple steps in the viral lifecycle, including entry and egress, and bind to a conserved epitope on the B domain of the E2 glycoprotein. A 16 Å resolution cryo-electron microscopy structure of a Fab fragment bound to CHIKV E2 B domain provided an explanation for its neutralizing activity. Binding to the B domain was associated with repositioning of the A domain of E2 that enabled cross-linking of neighboring spikes. Our results suggest that B domain antigenic determinants could be targeted for vaccine or antibody therapeutic development against multiple alphaviruses of global concern.

The Complexity of a Dengue Vaccine: A Review of the Human Antibody Response

Dengue is the most prevalent mosquito-borne viral disease worldwide. Yet, there are no vaccines or specific antivirals available to prevent or treat the disease. Several dengue vaccines are currently in clinical or preclinical stages. The most advanced vaccine is the chimeric tetravalent CYD-TDV vaccine of Sanofi Pasteur. This vaccine has recently cleared Phase III, and efficacy results have been published. Excellent tetravalent seroconversion was seen, yet the protective efficacy against infection was surprisingly low. Here, we will describe the complicating factors involved in the generation of a safe and efficacious dengue vaccine. Furthermore, we will discuss the human antibody responses during infection, including the epitopes targeted in humans. Also, we will discuss the current understanding of the assays used to evaluate antibody response. We hope this review will aid future dengue vaccine development as well as fundamental research related to the phenomenon of antibody-dependent enhancement of dengue virus infection.

Antibodies against immature virions are not a discriminating factor for dengue disease severity

Humoral immunity plays an important role in controlling dengue virus (DENV) infection. Antibodies (Abs) developed during primary infection protect against subsequent infection with the same dengue serotype, but can enhance disease following secondary infection with a heterologous serotype. A DENV virion has two surface proteins, envelope protein E and (pre)-membrane protein (pr)M, and inefficient cleavage of the prM protein during maturation of progeny virions leads to the secretion of immature and partially immature particles. Interestingly, we and others found that historically regarded non-infectious prM-containing DENV particles can become highly infectious in the presence of E- and prM-Abs. Accordingly, we hypothesized that these virions contribute to the exacerbation of disease during secondary infection. Here, we tested this hypothesis and investigated the ability of acute sera of 30 DENV2-infected patients with different grades of disease severity, to bind, neutralize and/or enhance immature DENV2. We found that a significant fraction of serum Abs bind to the prM protein and to immature virions, but we observed no significant difference between the disease severity groups. Furthermore, functional analysis of the Abs did not underscore any specific correlation between the neutralizing/enhancing activity towards immature DENV2 and the development of more severe disease. Based on our analysis of acute sera, we conclude that Abs binding to immature virions are not a discriminating factor in dengue pathogenesis.

The four serotypes of the mosquito-borne dengue virus (DENV) cause an estimated 390 million human infections per annum. Symptomatic infection can manifest itself as a self-limiting febrile illness, dengue fever (DF), or as more severe and potentially life-threatening dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS). Severe disease development is usually associated with the presence of pre-existing Abs that enhance DENV infection rather than neutralize it. Antibody-dependent enhancement of infection is believed to contribute to high viral loads that prelude the development of severe disease. Indeed, Abs binding to the DENV surface glycoproteins E and prM are known to enhance infection. Here, we studied the role of prM Abs and prM-containing immature virions in the pathogenesis of severe disease. We analyzed the ability of acute sera of DF, DHF and DSS patients to bind, neutralize and/or enhance immature DENV infection. We found that a significant fraction of Abs bind to prM protein of DENV2; however, there was no difference between the disease severity groups. Moreover, we did not observed any specific correlation between the neutralizing/enhancing activity towards immature DENV2 and disease presentation. Based on these data we inferred that prM Abs and immature virions are not a discriminating factor in dengue pathogenesis. These findings are important for the understanding of dengue pathogenesis and the development of new vaccines.

Immature dengue virus is infectious in human immature dendritic cells via interaction with the receptor molecule DC-SIGN

Background

Dengue Virus (DENV) is the most common mosquito-borne viral infection worldwide. Important target cells during DENV infection are macrophages, monocytes, and immature dendritic cells (imDCs). DENV-infected cells are known to secrete a large number of partially immature and fully immature particles alongside mature virions. Fully immature DENV particles are considered non-infectious, but antibodies have been shown to rescue their infectious properties. This suggests that immature DENV particles only contribute to the viral load observed in patients with a heterologous DENV re-infection.

Methodology/Principal findings

In this study, we re-evaluated the infectious properties of fully immature particles in absence and presence of anti-DENV human serum. We show that immature DENV is infectious in cells expressing DC-SIGN. Furthermore, we demonstrate that immature dendritic cells, in contrast to macrophage-like cells, do not support antibody-dependent enhancement of immature DENV.

Conclusions/Significance

Our data shows that immature DENV can infect imDCs through interaction with DC-SIGN, suggesting that immature and partially immature DENV particles may contribute to dengue pathogenesis during primary infection. Furthermore, since antibodies do not further stimulate DENV infectivity on imDCs we propose that macrophages/monocytes rather than imDCs contribute to the increased viral load observed during severe heterotypic DENV re-infections.

Antibody-dependent enhancement of dengue virus infection is inhibited by SA-17, a doxorubicin derivative

Antibody-dependent enhancement (ADE) is thought to play a critical role in the exacerbation of dengue virus (DENV)-induced disease during a heterologous re-infection. Despite ADE's clinical impact, only a few antiviral compounds have been assessed for their anti-ADE activity. We reported earlier that SA-17, a doxorubicin derivative, efficiently inhibits the in vitro infection of DENV and yellow fever virus. Here we explored SA-17's mechanism of inhibition and investigated if the compound is active against ADE of DENV infection. Since enhanced infectivity stimulated by antibodies has been observed with standard and immature DENV, both types of virions were included in the study. We observed that SA-17 (i) inhibits DENV infection by preventing binding/entry to the cell and (ii) interferes with antibody-mediated infection of both standard and immature DENV2. SA-17 markedly reduced the infectivity of DENV2 in ADE conditions, with IC50s ranging from 0.26 to 2.89μM. The compound exerted its activity when added before, during, and after antibody-opsonization of standard and immature virus. Thus, molecules with the characteristics of SA-17 may be attractive antiviral agents since they can be used both to block DENV2 entry during primary and secondary infection and to inhibit ADE of standard and immature virus.

Arthropod-borne flaviviruses and RNA interference: seeking new approaches for antiviral therapy

Flaviviruses are the most prevalent arthropod-borne viruses worldwide, and nearly half of the 70 Flavivirus members identified are human pathogens. Despite the huge clinical impact of flaviviruses, there is no specific human antiviral therapy available to treat infection with any of the flaviviruses. Therefore, there is a continued search for novel therapies, and this review describes the current knowledge on the usage of RNA interference (RNAi) in combating flavivirus infections. RNAi is a process of sequence-specific gene silencing triggered by double-stranded RNA. Antiviral RNAi strategies against arthropod-borne flaviviruses have been reported and although several hurdles must be overcome to employ this technology in clinical applications, they potentially represent a new therapeutic tool.

Development of a highly protective combination monoclonal antibody therapy against Chikungunya virus

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes global epidemics of a debilitating polyarthritis in humans. As there is a pressing need for the development of therapeutic agents, we screened 230 new mouse anti-CHIKV monoclonal antibodies (MAbs) for their ability to inhibit infection of all three CHIKV genotypes. Four of 36 neutralizing MAbs (CHK-102, CHK-152, CHK-166, and CHK-263) provided complete protection against lethality as prophylaxis in highly susceptible immunocompromised mice lacking the type I IFN receptor (Ifnar^−/−) and mapped to distinct epitopes on the E1 and E2 structural proteins. CHK-152, the most protective MAb, was humanized, shown to block viral fusion, and require Fc effector function for optimal activity in vivo. In post-exposure therapeutic trials, administration of a single dose of a combination of two neutralizing MAbs (CHK-102+CHK-152 or CHK-166+CHK-152) limited the development of resistance and protected immunocompromised mice against disease when given 24 to 36 hours before CHIKV-induced death. Selected pairs of highly neutralizing MAbs may be a promising treatment option for CHIKV in humans.

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes outbreaks of polyarthritis in humans, and is currently a threat to spread to the United States due to the presence of its mosquito vector, Aedes albopictus. At present, there is no licensed human vaccine or therapeutic available to protect against CHIKV infection. The primary goal of this study was to develop an antibody-based therapeutic agent against CHIKV. To do this, we developed a panel of 230 new mouse anti-CHIKV MAbs and tested them for their ability to neutralize infection of different CHIKV strains in cell culture. We identified 36 MAbs with broad neutralizing activity, and then tested several of these for their ability to protect immunocompromised Ifnar^−/− mice against lethal CHIKV infection. In post-exposure therapeutic trials, administration of a single dose of a combination of two neutralizing MAbs limited the development of resistance and protected Ifnar^−/− mice against disease even when given just 24 to 36 hours before CHIKV-induced death. Analogous protection against CHIKV-induced arthritis was seen in a disease model in wild type mice. Our data suggest that pairs of highly neutralizing MAbs may be a therapeutic option against CHIKV infection.