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The immune response is crucial for coronavirus disease 19 (COVID-19) progression, with the participation of proinflammatory cells and cytokines, inducing lung injury and loss of respiratory function. CLEC5A expression on monocytes can be triggered by viral and bacterial infections, leading to poor outcomes. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is able to induce neutrophil activation by CLEC5A and Toll-like receptor 2, leading to an aggressive inflammatory cascade, but little is known about the molecular interactions between CLEC5A and SARS-CoV-2 proteins. Here, we aimed to explore how CLEC5A expression could be affected by SARS-CoV-2 infection using immunological tools with in vitro, in vivo, and in silico assays. The findings revealed that high levels of CLEC5A expression were found in monocytes from severe COVID-19 patients in comparison with mild COVID-19 and unexposed subjects, but not in vaccinated subjects who developed mild COVID-19. In hamsters, we detected CLEC5A gene expression during 3-15 days of Omicron strain viral challenge. Our results also showed that CLEC5A can interact with SARS-CoV-2, promoting inflammatory cytokine production, probably through an interaction with the receptor-binding domain in the N-acetylglucosamine binding site (NAG-601). The high expression of CLEC5A and high levels of proinflammatory cytokine production were reduced in vitro by a human CLEC5A monoclonal antibody. Finally, CLEC5A was triggered by spike glycoprotein, suggesting its involvement in COVID-19 progression; therapy with a monoclonal antibody could be a good strategy for COVID-19 treatment, but vaccines are still the best option to avoid hospitalization/deaths.

The severe acute respiratory syndrome caused by the new coronavirus (SARS-CoV-2), termed COVID-19, has been highlighted as the most important infectious disease of our time, without a vaccine and treatment available until this moment, with a big impact on health systems worldwide, and with high mortality rates associated with respiratory viral disease. The medical and scientific communities have also been confronted by an urgent need to better understand the mechanism of host-virus interaction aimed at developing therapies and vaccines. Since this viral disease can trigger a strong innate immune response, causing severe damage to the pulmonary tract, immunotherapies have also been explored as a means to verify the immunomodulatory effect and improve clinical outcomes, whilst the comprehensive COVID-19 immunology still remains under investigation. In this review, both cellular and molecular immunopathology as well as hemostatic disorders induced by SARS-CoV-2 are summarized. The immunotherapeutic approaches based on the most recent clinical and nonclinical studies, emphasizing their effects for the treatment of COVID-19, are also addressed. The information presented elucidates helpful insights aiming at filling the knowledge gaps around promising immunotherapies that attempt to control the dysfunction of host factors during the course of this infectious viral disease.

The cellular immune response plays an important role in COVID-19, caused by SARS-CoV-2. This feature makes use of in vitro models’ useful tools to evaluate vaccines and biopharmaceutical effects. Here, we developed a two-step model to evaluate the cellular immune response after SARS-CoV-2 infection-induced or spike protein stimulation in peripheral blood mononuclear cells (PBMC) from both unexposed and COVID-19 (primo-infected) individuals (Step1). Moreover, the supernatants of these cultures were used to evaluate its effects on lung cell lines (A549) (Step2). When PBMC from the unexposed were infected by SARS-CoV-2, cytotoxic natural killer and nonclassical monocytes expressing inflammatory cytokines genes were raised. The supernatant of these cells can induce apoptosis of A549 cells (mock vs. Step2 [mean]: 6.4% × 17.7%). Meanwhile, PBMCs from primo-infected presented their memory CD4+ T cells activated with a high production of IFNG and antiviral genes. Supernatant from past COVID-19 subjects contributed to reduce apoptosis (mock vs. Step2 [ratio]: 7.2 × 1.4) and to elevate the antiviral activity (iNOS) of A549 cells (mock vs. Step2 [mean]: 31.5% × 55.7%). Our findings showed features of immune primary cells and lung cell lines response after SARS-CoV-2 or spike protein stimulation that can be used as an in vitro model to study the immunity effects after SARS-CoV-2 antigen exposure.

Introduction Melanoma is a skin neoplasia originated from transformed melanocytes, which may acquire the capacity of invasion through dermis. Despite of its low incidence (232.000 cases globally), it is one of the most lethal cancers (55.500 deaths, GLOBOCAN 2012). One of the factors that correlates with its malignant phenotype is the presence of Protease-Activated Receptor 1 (PAR1), which is overexpressed in melanoma and metastatic lesions. PAR1 can be activated in two different ways: 1) the canonical pathway (CP) – when the receptor is cleaved by thrombin at Arg41; and 2) the non-canonical pathway (NCP) – when other proteases cleave a distinct peptide bond in the PAR1 N-terminal region. The CP activation leads to an increased secretion of pro-angiogenic factors by tumour cells as well as pro-inflammatory effects in models of inflammation. On the other hand, the NCP activation by Activated Protease C (APC), in endothelial cells, evoke in vitro and in vivo antitumor effects. There are no studies describing the direct effects of NCP activation in melanoma cells. The aim of this work was to stablish an in vitro model to evaluate the effects of the NCP activation of PAR1 in cultured melanoma cells. Material and methods In order to establish representative models, the lineages A375 (harbouring an activating BRAF -V600E mutation) and FM-6 (wild-type BRAF) were used. The agonists TR41 (SFLLRNPN-NH2) and TR47 (NPNDKYEP-NH2) were used to mimic CP and NCP PAR1 cleavages, respectively. PAR1 expression was evaluated by qPCR and flow cytometry. The effects of PAR1 activation were evaluated by p-ERK detection, cell proliferation assays, analysis of IL-8, VEGF and MMP-9 expression and migration assays. Results and discussions Both lineages expressed high levels of PAR1. A transient reduction in the ERK-p was observed upon treatment of either A375 or FM-6 with TR47, while no effects were observed for TR41. Treatment with TR41 increased the proliferation of both cell lines after 24 or 48 hour. A slight decrease in proliferation and transient reduction in VEGF expression were observed when both lineages were incubated with TR47. Finally, it was observed that treatment with TR47 for 18 hs reduced the migratory properties of A375 but not FM-6. Conclusion Taken together, our preliminary results show, for the first time in melanoma cell lines, that the NCP PAR1 agonist might modulate cultured tumour cells. However further studies are necessary to establish the role of NCP activation of PAR1 in cancer models and its possible utility in a therapeutic way.

Yellow Fever vaccine is one of the most efficacious human vaccines ever made. The vaccine (YF 17D) virus induces polyvalent immune responses, with a mixed TH1/TH2 CD4(+) cell profile, which results in robust T CD8(+) responses and high titers of neutralizing antibody. In recent years, it has been suggested that early events after yellow fever vaccination are crucial to the development of adequate acquired immunity. We have previously shown that primary immunization of humans and monkeys with YF 17D virus vaccine resulted in the early synthesis of IFN-γ. Herein we have demonstrated, for the first time that early IFN-γ production after yellow fever vaccination is a feature also of murine infection and is much more pronounced in the C57BL/6 strain compared to the BALB/c strain. Likewise, in C57BL/6 strain, we have observed the highest CD8(+) T cells responses as well as higher titers of neutralizing antibodies and total anti-YF IgG. Regardless of this intense IFN-γ response in mice, it was not possible to see higher titers of IgG2a in relation to IgG1 in both mice lineages. However, IgG2a titers were positively correlated to neutralizing antibodies levels, pointing to an important role of IFN-γ in eliciting high quality responses against YF 17D, therefore influencing the immunogenicity of this vaccine.