Objectives. The increasing prevalence of antibiotic-resistant Staphylococcus aureus, besides the inadequate numbers of effective antibiotics, emphasises the need to find new therapeutic agents against this lethal pathogen. Methods. In this study, to obtain antibody fragments against S. aureus, a human single-chain fragment variable (scFv) library was enriched against living methicillin-resistant S. aureus (MRSA) cells, grown in three different conditions, that is human peripheral blood mononuclear cells with plasma, whole blood and biofilm. The antibacterial activity of scFvs was evaluated by the growth inhibition assay in vitro. Furthermore, the therapeutic efficacy of anti-S. aureus scFvs was appraised in a mouse model of bacteraemia. Results. Three scFv antibodies, that is MEH63, MEH158 and MEH183, with unique sequences, were found, which exhibited significant binding to S. aureus and reduced the viability of S. aureus in in vitro inhibition assays. Based on the results, MEH63, MEH158 and MEH183, in addition to their combination, could prolong the survival rate, reduce the bacterial burden in the blood and prevent inflammation and tissue destruction in the kidneys and spleen of mice with MRSA bacteraemia compared with the vehicle group (treated with normal saline). Conclusion. The combination therapy with anti-S. aureus scFvs and conventional antibiotics might shed light on the treatment of patients with S. aureus infections.

SARS-CoV-2 entrance to the host cells is started by the interaction between receptor binding domain (RBD) of the spike (S) protein on the virus with the angiotensin-converting enzyme 2 (ACE2) receptor which is very important in the onset of viral infection. Interference with this interaction can be a promising way to prevent Covid-19 infection. In this study, a novel potential therapeutic peptide was designed in silico based on the key interacting amino acids of ACE2 against SARS-CoV-2 S protein. In our computational analysis, a peptide consisting of residues 19–48 of ACE2 was chosen as the wild-type peptide. Based on this peptide, six mutant peptides (Mu_P1-6) were designed and then assessed in term of interaction with S protein. The result of protein-peptide docking by HADDOCK web server and then immunological analysis by SVMTriP epitope prediction tool leads to choose Mu_P3 as the best mutant. Molecular dynamics simulations of wild-type peptide-S protein complex and Mu_P3-S protein complex, showed Mu_P3 has better interaction with S protein than wild type peptide (interaction energies [Formula: see text] vs. [Formula: see text] (kJ/mol)) which can be a potential therapeutic peptide for Covid-19 pandemic.

Background: Plants are among promising and suitable platform systems for production of recombinant biopharmaceutical proteins due to several features such as safety, no need for fermentation, inexpensive investment, and fast and easy scale-up. Human insulin is one of the most widely used medicines in the world. Up to now different expression systems including Escherichia coli, yeast and CHO have been exploited for producing recombinant human insulin and a variety of different recombinant insulin are extensively used. Objectives: This study reports on the transformation and expression of proinsulin gene in tomato plants for the first time in Iran. Materials and Methods: This study reports the cloning, transformation and expression of proinsulin gene in tomato plants. Specific primers were designed and used for PCR amplification and cloning of the proinsulin gene in the plant expression vector pCAMBIA1304. The recombinant construct was transferred into Agrobacterium tumefaciens strain LBA4404, and used for Agrobacterium mediated stable transformation of tomato plants. Presence of the desired gene in transgenic lines was confirmed through colony PCR and sequencing. The expression of the protein in transgenic lines was confirmed by immunodot blot assay. Results: The presence of the proinsulin gene in the genomic DNA of transgenic tomato was confirmed by PCR. Also total protein of transgenic tomato was extracted and the expression of proinsulin was detected using dotblot assay. Conclusions: This survey addresses the possibility of proinsulin gene transfer and expression in tomato transgenic lines. This study can be used as a basis for future researches to produce human proinsulin in tomato and other candidate plants.

Background Staphylococcal superantigens are virulence factors that help the pathogen escape the immune system and develop an infection. Toxic shock syndrome toxin (TSST)-1 is one of the most studied superantigens whose role in toxic shock syndrome and some particular disorders have been demonstrated. Inhibiting TSST-1 production with antibiotics and targeting TSST-1 with monoclonal antibodies might be one of the best strategies to prevent TSST-1-induced cytokines storm followed by lethality. Results A novel single-chain variable fragment (scFv), MS473, against TSST-1 was identified by selecting an scFv phage library on the TSST-1 protein. The MS473 scFv showed high affinity and specificity for TSST-1. Moreover, MS473 could significantly prevent TSST-1-induced mitogenicity (the IC50 value: 1.5 µM) and cytokine production. Conclusion Using traditional antibiotics with an anti-TSST-1 scFv as a safe and effective agent leads to deleting the infection source and preventing the detrimental effects of the toxin disseminated into the whole body.