A new platform for creating anti-coronavirus epitope vaccines has been developed. Two loop-like epitopes with lengths of 22 and 42 amino acid residues were selected from the receptor-binding motif of the Spike protein from the SARS‑CoV‑2 virus that participate in a large number of protein-protein interactions in the complexes with ACE2 and neutralizing antibodies. Two types of hybrid proteins, including one of the two selected epitopes, were constructed. To fix conformation of the selected epitopes, an approach using protein scaffolds was used. The homologue of Rop protein from the Escherichia coli ColE1 plasmid containing helix-turn-helix motif was used as an epitope scaffold for the convergence of C- and N-termini of the loop-like epitopes. Loop epitopes were inserted into the turn region. The conformation was additionally fixed by a disulfide bond formed between the cysteine residues present within the epitopes. For the purpose of multimerization, either aldolase from Thermotoga maritima , which forms a trimer in solution, or alpha-helical trimerizer of the Spike protein from SARS‑CoV‑2, was attached to the epitopes incorporated into the Rop-like protein. To enable purification on the heparin-containing sorbents, a short fragment from the heparin-binding hemagglutinin of Mycobacterium tuberculosis was inserted at the C-terminus of the hybrid proteins. All the obtained proteins demonstrated high level of immunogenicity after triplicate parenteral administration to mice. Sera from the mice immunized with both aldolase-based hybrid proteins and the Spike protein SARS‑CoV‑2 trimerizer-based protein with a longer epitope interacted with both the inactivated SARS‑CoV‑2 virus and the Spike protein receptor-binding domain at high titers. Supplementary information The online version contains supplementary material available at 10.1134/S0006297921100096.

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Bacteriophage MS2 was employed for targeted delivery of an apoptosis-inducing agent, Tl+, into a tumor tissue. The targeted delivery was ensured by iRGD peptide, a ligand of integrins presumably located on the surface of endotheliocytes of the tumor tissue neovasculature and certain tumor cells. The synthesized peptide was conjugated to MS2 capsid proteins. Tl+ ions from TlNO3 penetrated the phage particles and tightly bound to phage RNA. Peptide-modified MS2 preparations filled with Tl+ caused cell death in two types of cultivated human breast cancer cells and effected necrosis of these tumor xenografts in mice. Neither peptide-conjugated bacteriophage MS2 without Tl+ nor the phage filled with Tl+ but without the peptide or the same phage with the non-conjugated peptide in solution produced such effects. The preparation exhibited no acute toxicity at a therapeutic dose.

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Synthesis of catabolite-sensitive enzymes is repressed in mutants defective in the general proteins (enzyme I and HPr) of the Escherichia coli phosphoenolpyruvate-dependent phosphotransferase system (ptsl and ptsH mutations). To elucidate the mechanism of this phenomenon we constructed isogenic strains carrying pts mutations as well as different lesions of regulation of the lac operon or mutations affecting adenylate cyclase activity (cyu mutation) and synthesis of cyclic-AMP-receptor protein (crp mutation) Measurements of the differential rate of 1-galactosidase synthesis in these strains showed that the repressive effect of pts mutations was revealed in luc', l a d , luc0" and cyu bacteria, but it was lost in lucP and crp strains.It was concluded that mutational damage to the general components of the phosphoenolpyruvatedependent phosphotransferase system diminishes activity of the lac promoter.The results obtained led to the conclusion that pts gene products (apparently phospho -HPr) are necessary for the initiation of transcription of catabolite-sensitive operons in E. coli.The phosphoenolpyruvate : carbohydrate phosphotransferase system of Escherichia coli carries out the phosphorylation of many carbohydrates [ 1 -41. This process involves the activities of several protein components. Enzyme I catalyzes the transfer of the phosphoryl group from phosphoenolpyruvate to a small histidine-containing heat-stable protein HPr. The phospho -HPr generated serves as a donor of the phosphoryl moiety in the phosphotransferase reaction catalysed by the enzyme 11 which is specfic for a certain carbohydrate or its analogue. Enzyme I and HPr are designated the general proteins of the system since they are required for the phosphorylation of all sugar substrates of the phosphotransferase system. These two components are constitutive soluble proteins ; their synthesis is determined by theptsl (for enzyme I) and ptsH (for HPr) genes [3]. At present it is well established that the phosphotransferase system is necessary for the transport and metabolism of carbohydrates of D-gluco and u-munno configuration [2,4]. Transport of the sugar is catalyzed concomitantly with phosphorylation of the carbohydrate at the expense of phosphoenolpyruvate. Sugars that have an obligatory requirement for phosphorylation during transfer are called phosphotransferase sugars. Non-phosphotransferase substrates are those transported into bacterial cell via their specific systems [2].Mutational damage to the general proteins of the phosphotransferase system (ptsl, ptsI,H and ptsH mutations) leads to severe disturbance of transport of the phosphotransferase sugars into E. coli cells and these mutants are unable to grow in media containing these sugars as the sole source of carbon [5-1.51.Some properties of the p t s mutants indicate that the products of the p t s genes are relevant to the regulation of the synthesis of catabolite-sensitive enzymes. As was demonstrated in our laboratory, pts