The Annexin A1 Receptor FPR2 Regulates the Endosomal Export of Influenza Virus

Implication of the Annexin 1/FPR axis in leishmanial exosome-mediated Leishmania major skin hyperpathogenesis

Introduction

Exosomes produced by the protozoan parasite Leishmania (LeishEXO) are well-established drivers of virulence, though mechanisms underlying their exacerbation of experimental leishmaniasis remain elusive. Expression of Annexin A1 (ANXA1), a protein implicated in exosome-mediated pathologies and viral internalization, has been shown to correlate with cutaneous leishmaniasis severity. Given ANXA1's regulation of myeloid cells - the canonical hosts for Leishmania - we studied the potential role of ANXA1 and its receptors FPR1/2 in exerting LeishEXO's effects.

Methods

Murine and in vitro ANXA1-/- models were used to study the generation of protective TH1 responses during experimental L. major infection with and without LeishEXO. Recruitment of inflammatory cells was assessed using a peritoneal cell recruitment assay and immunophenotyping, and production of inflammatory mediators was measured using a cytokine and chemokine array. Treatment of experimental models with FPR2 antagonist WRW4 and FPR1/2 agonist WKYMVm was used to delineate the role of the FPR/ANXA1 axis in LeishEXO-mediated hyperpathogenesis.

Results

We established that ANXA1 deficiency prohibits LeishEXO-mediated pathogenesis and myeloid cell infection, with minimal alterations to adaptive and innate immune phenotypes. FPR2 blockade with WRW4 similarly inhibited leishmanial hyperpathogenesis, while direct activation of FPRs with WKYMVm enhanced infection and recapitulated the LeishEXO-mediated phenotype. This research describes LeishEXO's utilization of the ANXA1/FPR axis to facilitate parasitic internalization and pathogenesis, which may be leveraged in the development of therapeutics for leishmaniasis.

GENIX enables comparative network analysis of single-cell RNA sequencing to reveal signatures of therapeutic interventions

Single-cell RNA sequencing (scRNA-seq) has transformed our understanding of cellular responses to perturbations such as therapeutic interventions and vaccines. Gene relevance to such perturbations is often assessed through differential expression analysis (DEA), which offers a one-dimensional view of the transcriptomic landscape. This method potentially overlooks genes with modest expression changes but profound downstream effects and is susceptible to false positives. We present GENIX (gene expression network importance examination), a computational framework that transcends DEA by constructing gene association networks and employing a network-based comparative model to identify topological signature genes. We benchmark GENIX using both synthetic and experimental datasets, including analysis of influenza vaccine-induced immune responses in peripheral blood mononuclear cells (PBMCs) from recovered COVID-19 patients. GENIX successfully emulates key characteristics of biological networks and reveals signature genes that are missed by classical DEA, thereby broadening the scope of target gene discovery in precision medicine.

Host proteins interact with viral elements and affect the life cycle of highly pathogenic avian influenza A virus H7N9

Host-virus interactions can significantly impact the viral life cycle and pathogenesis; however, our understanding of the specific host factors involved in highly pathogenic avian influenza A virus H7N9 (HPAI H7N9) infection is currently restricted. Herein, we designed and synthesized 65 small interfering RNAs targeting host genes potentially associated with various aspects of RNA virus life cycles. Afterward, HPAI H7N9 viruses were isolated and RNA interference was used to screen for host factors likely to be involved in the life cycle of HPAI H7N9. Moreover, the research entailed assessing the associations between host proteins and HPAI H7N9 proteins. Twelve key host proteins were identified: Annexin A (ANXA)2, ANXA5, adaptor related protein complex 2 subunit sigma 1 (AP2S1), adaptor related protein complex 3 subunit sigma 1 (AP3S1), ATP synthase F1 subunit alpha (ATP5A1), COPI coat complex subunit alpha (COP)A, COPG1, heat shock protein family A (Hsp70) member 1A (HSPA)1A, HSPA8, heat shock protein 90 alpha family class A member 1 (HSP90AA1), RAB11B, and RAB18. Co-immunoprecipitation revealed intricate interactions between viral proteins (hemagglutinin, matrix 1 protein, neuraminidase, nucleoprotein, polymerase basic 1, and polymerase basic 2) and these host proteins, presumably playing a crucial role in modulating the life cycle of HPAI H7N9. Notably, ANXA5, AP2S1, AP3S1, ATP5A1, HSP90A1, and RAB18, were identified as novel interactors with HPAI H7N9 proteins rather than other influenza A viruses (IAVs). These findings underscore the significance of host-viral protein interactions in shaping the dynamics of HPAI H7N9 infection, while highlighting subtle variations compared with other IAVs. Deeper understanding of these interactions holds promise to advance disease treatment and prevention strategies.

Resolution pharmacology and the treatment of infectious diseases

Inflammation is elicited by the host in response to microbes, and is believed to be essential for protection against infection. However, we have previously hypothesized that excessive or misplaced inflammation may be a major contributor to tissue dysfunction and death associated with viral and bacterial infections. The resolutive phase of inflammation is a necessary condition to achieve homeostasis after acute inflammation. It is possible that targeting inflammation resolution may be beneficial for the host during infection. In this review, we summarize the evidence demonstrating the expression, roles and effects of the best described pro-resolving molecules in the context of bacterial and viral infections. Pro-resolving molecules play a pivotal role in modulating a spectrum of pathways associated with tissue inflammation and damage during both viral and bacterial infections. These molecules offer a blend of anti-inflammatory, pro-resolving and sometimes anti-infective benefits, all the while circumventing the undesired and immune-suppressive unwanted effects associated with glucocorticoids. Whether these beneficial effects will translate into benefits to patients clearly deserve further investigation.

The Multifaceted Role of Annexin A1 in Viral Infections

Dysregulated inflammatory responses are often correlated with disease severity during viral infections. Annexin A1 (AnxA1) is an endogenous pro-resolving protein that timely regulates inflammation by activating signaling pathways that culminate with the termination of response, clearance of pathogen and restoration of tissue homeostasis. Harnessing the pro-resolution actions of AnxA1 holds promise as a therapeutic strategy to control the severity of the clinical presentation of viral infections. In contrast, AnxA1 signaling might also be hijacked by viruses to promote pathogen survival and replication. Therefore, the role of AnxA1 during viral infections is complex and dynamic. In this review, we provide an in-depth view of the role of AnxA1 during viral infections, from pre-clinical to clinical studies. In addition, this review discusses the therapeutic potential for AnxA1 and AnxA1 mimetics in treating viral infections.

The role and mechanism of the annexin A1 peptide Ac2-26 in rats with cardiopulmonary bypass lung injury

The main causes of lung injury after cardiopulmonary bypass (CPB) are systemic inflammatory response syndrome (SIRS) and pulmonary ischaemia‐reperfusion injury (IR‐I). SIRS and IR‐I are often initiated by a systemic inflammatory response. The present study investigated whether the annexin A1 (ANX‐A1) peptidomimetic Ac2‐26 by binding to formyl peptide receptors (FPRs) inhibit inflammatory cytokines and reduce lung injury after CPB. Male rats were randomized to the following five groups (n = 6, each): sham, exposed to pulmonary ischaemic‐reperfusion (IR‐I), IR‐I plus Ac2‐26, IR‐I plus the FPR antagonist, BoC2 (N‐tert‐butyloxycarbonyl‐Phe‐Leu‐Phe‐Leu‐Phe) and IR‐I plus Ac2‐26 and BoC2. Treatment with Ac2‐26 improved the oxygenation index, an effect blocked by BoC2. Histopathological analysis of the lung tissue revealed that the degree of lung injury was significantly less (P < 0.05) in the Ac2‐26‐treated rats compared to the other experimental groups exposed to IR‐I. Ac2‐26 treatment reduced the levels of the inflammatory cytokines TNF‐α, IL‐1β, ICAM‐1 and NF‐κB‐p65 (P < 0.05) compared to the vehicle‐treated group exposed to IR‐I. In conclusion, the annexin A1 (ANX‐A1) peptidomimetic Ac2‐26 by binding to formyl peptide receptors inhibit inflammatory cytokines and reduce ischaemic‐reperfusion lung injury after cardiopulmonary bypass.

Techniques and Strategies for Potential Protein Target Discovery and Active Pharmaceutical Molecule Screening in a Pandemic

Viruses remain a major challenge in the fierce fight against diseases. There have been many pandemics caused by various viruses throughout the world over the years. Recently, the global outbreak of COVID-19 has had a catastrophic impact on human health and the world economy. Antiviral drug treatment has become another essential means to overcome pandemics in addition to vaccine development. How to quickly find effective drugs that can control the development of a pandemic is a hot issue that still needs to be resolved in medical research today. To accelerate the development of drugs, it is necessary to target the key target proteins in the development of the pandemic, screen active molecules, and develop reliable methods for the identification and characterization of target proteins based on the active ingredients of drugs. This article discusses key target proteins and their biological mechanisms in the progression of COVID-19 and other major epidemics. We propose a model based on these foundations, which includes identifying potential core targets, screening potential active molecules of core targets, and verifying active molecules. This article summarizes the related innovative technologies and methods. We hope to provide a reference for the screening of drugs related to pandemics and the development of new drugs.

Reduced Annexin A3 in schizophrenia

The cellular and molecular mechanisms underlying onset and development of schizophrenia have not yet been completely elucidated, but the association of disturbed neuroplasticity and inflammation has gained particular relevance recently. These mechanisms are linked to annexins functions. ANXA3, particularly, is associated to inflammation and membrane metabolism cascades. The aim was to determine the ANXA3 levels in first-onset drug-naïve psychotic patients. We investigated by western blot the protein expression of annexin A3 in platelets of first-onset, drug-naïve psychotic patients (diagnoses according to DSM-IV: 28 schizophrenia, 27 bipolar disorder) as compared to 30 age- and gender-matched healthy controls. Annexin A3 level was lower in schizophrenia patients as compared to healthy controls (p < 0.001) and to bipolar patients (p < 0.001). Twenty out of 28 schizophrenic patients had undetectable annexin A3 levels, as compared to none from the bipolar and none from the control subjects. ANXA3 was reduced in drug-naïve patients with schizophrenia. ANXA3 affects neuroplasticity, inflammation and apoptosis, as well as it modulates membrane phospholipid metabolism. All these processes have been discussed in regard to the biology of schizophrenia. In face of these data, we feel that further studies with larger samples are warranted to investigate the possible role of reduced ANXA3 as a possible risk marker for schizophrenia.

The involvement of annexin A1 in human placental response to maternal Zika virus infection

The association of Zika virus infection (ZIKV) with congenital malformation and neurological sequelae brought a significant global concern. Recent studies have shown that maternal viral infection leads to inflammation in the placental tissue. In this context, the antiinflammatory protein annexin 1 (ANXA1) has a major determination of the resolution of inflammation and it has been positively associated with antiparasitic activity in infected placental explants. Although these effects have been explored to some degree, ANXA1 expression and potential properties have not yet been fully elucidated in placentas infected with ZIKV. This study was conducted to evaluate the histopathology, inflammatory process and elucidate if ANXA1 were differently expressed in placentas of ZIKV-infected mothers. Three classification groups were used in this study: Neg/Neg (mother and placenta negative for the virus), Pos/Neg (infected mother, but no virus detected in placenta) and Pos/Pos (mother and placenta infected with ZIKV). ANXA1 was expressed in syncytiotrophoblast cells of all studied groups, and its expression was decreased in Pos/Neg group, which displayed also an increase of the inflammatory response, as evinced from the recruitment of inflammatory cells, increased levels of placenta cytokines, and evidence of impaired tissue repair. The presence of ZIKV in placentas of Pos/Pos group shows structural alterations, including detachment and disorganization of the trophoblastic epithelium. In summary, our results suggest that maternal infection with ZIKV, even without direct tissue infection, leads to a placental inflammatory response probably related to the modulation of ANXA1. After placental infection, structural changes - including inflammatory cells influx - are observed leading to placental dysfunction and reduced fetal weight. Our study sheds additional light on the outcomes of ZIKV infection in trophoblast and reveals a potential involvement of ANXA1 in the placental biology.

The annexin A1/FPR2 signaling axis expands alveolar macrophages, limits viral replication, and attenuates pathogenesis in the murine influenza A virus infection model

Pattern recognition receptors (PRRs) are key elements in the innate immune response. Formyl peptide receptor (FPR) 2 is a PRR that, in addition to proinflammatory, pathogen-derived compounds, also recognizes the anti-inflammatory endogenous ligand annexin A1 (AnxA1). Because the contribution of this signaling axis in viral infections is undefined, we investigated AnxA1-mediated FPR2 activation on influenza A virus (IAV) infection in the murine model. AnxA1-treated mice displayed significantly attenuated pathology upon a subsequent IAV infection with significantly improved survival, impaired viral replication in the respiratory tract, and less severe lung damage. The AnxA1-mediated protection against IAV infection was not caused by priming of the type I IFN response but was associated with an increase in the number of alveolar macrophages (AMs) and enhanced pulmonary expression of the AM-regulating cytokine granulocyte-M-CSF (GM-CSF). Both AnxA1-mediated increase in AM levels and GM-CSF production were abrogated when mouse (m)FPR2 signaling was antagonized but remained up-regulated in mice genetically deleted for mFPR1, an mFPR2 isoform also serving as AnxA1 receptor. Our results indicate a novel protective function of the AnxA1-FPR2 signaling axis in IAV pathology via GM-CSF–associated maintenance of AMs, expanding knowledge on the potential use of proresolving mediators in host defense against pathogens.—Schloer, S., Hübel, N., Masemann, D., Pajonczyk, D., Brunotte, L., Ehrhardt, C., Brandenburg, L.-O., Ludwig, S., Gerke, V., Rescher, U. The annexin A1/FPR2 signaling axis expands alveolar macrophages, limits viral replication, and attenuates pathogenesis in the murine influenza A virus infection model.

Annexins in Influenza Virus Replication and Pathogenesis

Influenza A viruses (IAVs) are important human respiratory pathogens which cause seasonal or periodic endemic infections. IAV can result in severe or fatal clinical complications including pneumonia and respiratory distress syndrome. Treatment of IAV infections is complicated because the virus can evade host immunity through antigenic drifts and antigenic shifts, to establish infections making new treatment options desirable. Annexins (ANXs) are a family of calcium and phospholipid binding proteins with immunomodulatory roles in viral infections, lung injury, and inflammation. A current understanding of the role of ANXs in modulating IAV infection and host responses will enable the future development of more effective antiviral therapies. This review presents a comprehensive understanding of the advances made in the field of ANXs, in particular, ANXA1 and IAV research and highlights the importance of ANXs as a suitable target for IAV therapy.