This work describes the isolation of a lectin (CasuL) from the leaf pinnulae of Calliandra surinamensis and the evaluation of its cytotoxic, antimicrobial and antibiofilm properties. Proteins from pinnulae extract were precipitated with ammonium sulphate (60% saturation) and submitted to Sephadex G-75 chromatography, which yielded isolated CasuL (purification factor: 113). Native CasuL is an acidic protein (pI 5.82) with a relative molecular mass of 48kDa. This lectin is also an oligomeric protein composed of three subunits and mass spectrometry revealed similarities with a Sorghum bicolor protein. CasuL did not undergo unfolding when heated but changes in conformation and hemagglutinating activity were detected at basic pH. CasuL did not reduce the viability of human peripheral blood mononuclear cells but was toxic to leukemic K562 cells (IC 67.04±5.78μg/mL) and breast cancer T47D cells (IC: 58.75±2.5μg/mL). CasuL (6.25-800μg/mL) only showed bacteriostatic effect but was able to reduce biofilm formation by Staphylococcus saprophyticcus and Staphylococcus aureus (non-resistant and oxacillin-resistant isolates). CasuL showed antifungal activity against Candida krusei causing alterations in cell morphology and damage to cell wall. In conclusion, the pinnulae of C. surinamensis leaves contain a thermo-stable lectin with biotechnological potential as cytotoxic, antibiofilm, and antifungal agent.

WSMoL promotes immunomodulation in human PBMC inducing a potential wound healing profile and, in future in vivo assays, can be evaluated as adjuvant in immunosuppressive diseases and wound repair.

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In this study, we report the purification and characterization of a multifunctional lectin (MvFL) from Microgramma vacciniifolia fronds as well as its immunomodulatory properties on human peripheral blood mononuclear cells (PBMCs). MvFL (pI 4.51; 54kDa) is a glycoprotein able to inhibit trypsin activity and that has sequence similarities (32% coverage) with a plant RNA-binding protein. Hemagglutinating activity of MvFL was not altered by heating at 100°C for 30min, but was reduced in alkaline pH (8.0 and 9.0). Fluorimetric analyses showed that this lectin did not undergo marked conformational changes when heated. However, the MvFL conformation changed depending on the pH. MvFL at 6.25-25μg/mL was not cytotoxic to lymphocytes present among PBMCs. The PBMCs incubated for 24h with the lectin (12.5μg/mL) showed increased TNF-α, IFN-γ, IL-6, IL-10, and nitric oxide production. MvFL also stimulated T lymphocytes from PBMCs to differentiate into CD8 cells. The activation (indicated by CD28 expression) of these cells was also stimulated. In conclusion, MvFL is a heat-stable and multifunctional protein, with both lectin and trypsin inhibitor activities, and capable of inducing predominantly a Th1 response in human PBMCs as well as activation and differentiation of T lymphocytes.

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Coronaviruses (CoVs) are a broad group of spherical and enveloped viruses that cause diseases in humans and animals. CoVs have become a major threat to public health in the past two decades, exemplified by epidemics of acute respiratory syndromes and, most recently, the coronavirus disease 2019 pandemic. The envelope of CoVs contains spike (S) proteins, which are transmembrane proteins with a crown-like shape involved in cell attachment, cell‒cell fusion, host tropism, and pathogenesis. The receptors for spike proteins in host cells can be glycans and proteins. This review approaches the structural and functional aspects of the S protein of CoVs. Several issues are presented, including the structure‒function relationship, examples of host receptors, S protein-host cell connection, and its role in the entry of the virus into host cells. The S protein is one of the main targets of studies on the evolutionary relationships between CoVs, mapping of cross-host transmission events, changes in virulence, variations in disease severity level, and the development of therapeutic strategies and vaccines.

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