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 Dual Role of CCR5 in the Course of Influenza Infection: Exploring Treatment Opportunities

Influenza is one of the most relevant respiratory viruses to human health causing annual epidemics, and recurrent pandemics. Influenza disease is principally associated with inappropriate activation of the immune response. Chemokine receptor 5 (CCR5) and its cognate chemokines CCL3, CCL4 and CCL5 are rapidly induced upon influenza infection, contributing to leukocyte recruitment into the airways and a consequent effective antiviral response. Here we discuss the existing evidence for CCR5 role in the host immune responses to influenza virus. Complete absence of CCR5 in mice revealed the receptor’s role in coping with influenza via the recruitment of early memory CD8+ T cells, B cell activation and later recruitment of activated CD4+ T cells. Moreover, CCR5 contributes to inflammatory resolution by enhancing alveolar macrophages survival and reprogramming macrophages to pro-resolving phenotypes. In contrast, CCR5 activation is associated with excessive recruitment of neutrophils, inflammatory monocytes, and NK cells in models of severe influenza pneumonia. The available data suggests that, while CCL5 can play a protective role in influenza infection, CCL3 may contribute to an overwhelming inflammatory process that can harm the lung tissue. In humans, the gene encoding CCR5 might contain a 32-base pair deletion, resulting in a truncated protein. While discordant data in literature regarding this CCR5 mutation and influenza severity, the association of CCR5delta32 and HIV resistance fostered the development of different CCR5 inhibitors, now being tested in lung inflammation therapy. The potential use of CCR5 inhibitors to modulate the inflammatory response in severe human influenza infections is to be addressed.

Pro-resolving therapies as potential adjunct treatment for infectious diseases: Evidence from studies with annexin A1 and angiotensin-(1-7)

Infectious diseases, once believed to be an eradicable public health threat, still represent a leading cause of death worldwide. Environmental and social changes continuously favor the emergence of new pathogens and rapid dissemination around the world. The limited availability of anti-viral therapies and increased antibiotic resistance has made the therapeutic management of infectious disease a major challenge. Inflammation is a primordial defense to protect the host against invading microorganisms. However, dysfunctional inflammatory responses contribute to disease severity and mortality during infections. In recent years, a few studies have examined the relevance of resolution of inflammation in the context of infections. Inflammation resolution is an active integrated process transduced by several pro-resolving mediators, including Annexin A1 and Angiotensin-(1-7). Here, we examine some of the cellular and molecular circuits triggered by pro-resolving molecules and that may be beneficial in the context of infectious diseases.

The Annexin A1/FPR2 pathway controls the inflammatory response and bacterial dissemination in experimental pneumococcal pneumonia

Streptococcus pneumoniae is a major cause of community-acquired pneumonia leading to high mortality rates. Inflammation triggered by pneumococcal infection is necessary for bacterial clearance but must be spatially and temporally regulated to prevent further tissue damage and bacterial dissemination. Annexin A1 (AnxA1) mainly acts through Formyl Peptide Receptor 2 (FPR2) inducing the resolution of inflammation. Here, we have evaluated the role of AnxA1 and FPR2 during pneumococcal pneumonia in mice. For that, AnxA1, Fpr2/3 knockout (KO) mice and wild-type (WT) controls were infected intranasally with S pneumoniae. AnxA1 and Fpr2/3 KO mice were highly susceptible to infection, displaying uncontrolled inflammation, increased bacterial dissemination, and pulmonary dysfunction compared to WT animals. Mechanistically, the absence of AnxA1 resulted in the loss of lung barrier integrity and increased neutrophil activation upon S pneumoniae stimulation. Importantly, treatment of WT or AnxA1 KO-infected mice with Ac2-26 decreased inflammation, lung damage, and bacterial burden in the airways by increasing macrophage phagocytosis. Conversely, Ac2-26 peptide was ineffective to afford protection in Fpr2/3 KO mice during infection. Altogether, these findings show that AnxA1, via FPR2, controls inflammation and bacterial dissemination during pneumococcal pneumonia by promoting host defenses, suggesting AnxA1-based peptides as a novel therapeutic strategy to control pneumococcal pneumonia.

Altered intracellular signaling cascades in peripheral blood mononuclear cells from BD patients

Bipolar disorder (BD) is a severe psychiatric disorder of complex physiopathology that has been associated with a pro-inflammatory state. The aim of the present study was to investigate intracellular pathways associated with inflammatory signaling, assessing the phosphorylation levels of transcription factor nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPKs) in peripheral blood mononuclear cells of euthymic BD patients and healthy controls. Fifteen BD euthymic type I patients, and 12 healthy controls matched by age and gender were enrolled in this study. All subjects were assessed by the Mini-International Neuropsychiatry Interview and the patients also by the Young Mania Rating Scale and the Hamilton Depression Rating Scale. Phosphorylation levels of p65 NF-κB subunit, and MAPK ERK1/2, and p38 were assessed by Western blot and flow cytometry. Plasma cytokines (IL-2, IL-4, IL6, IL-10, IFN-γ, TNF-α, and IL-17A) were measured using cytometric bead arrays. Western blot and flow cytometry analyses showed increased phosphorylation levels of p65 NF-κB subunit, and MAPKs ERK1/2, and p38 in BD patients in euthymia in comparison with controls. BD patients presented increased pro-inflammatory cytokines levels in comparison with controls, and TNF-α correlated with the levels of phosphorylated p65 NF-κB. The present study found increased activation of MAPK and NF-κB pathways in BD patients, which is in line with a pro-inflammatory status.