ИСТИНА

Antibiotic resistant strains of Staphylococcus aureus are one of the major healthcare problems today. One of the possible ways to tackle this problem is the development of antibacterial lysins, which are enzymes capable of hydrolyzing the cell walls of bacteria, including antibiotic resistant strains. The advantages of antibacterial lysins include their high activity, specificity and presumed low propensity to resistance development. On the other hand, a major drawback is fast elimination from systemic circulation. To this end we constructed a recombinant fusion protein consisting of lysostaphin and albumin-binding domain from streptococcal protein G. Lysostaphin is one of the most active and extensively studied anti-staphylococcal lysin. Albumin-binding domain is often used to increase the effective molecular weight of a protein through its interaction with albumin. The increase in effective molecular weight prevents the elimination of the recombinant protein by glomerular filtration in kidneys and increases the residence time in the systemic circulation [1]. The activity of lysostaphin with albumin-binding domain (Lst-AlBD) was decreased. The time to half-clearing of S. aureus ATCC 29213 cell suspension by 1 µg/mL Lst-AlBD was twice that for 1 µg/mL lysostaphin (Lst) – 22.1±1.6 min vs. 11.0±1.0 min. Addition of rat serum albumin to the reaction mixture further decreased the activity of Lst-AlBD by 3.7 times, to 80.4±12.9 min. The pharmacokinetic characteristics of Lst-AlBD were studied in rats. The terminal half-life of Lst was 2.1 h, while that of Lst-AlBD 7.7 h. Moreover, lysostaphin was almost completely eliminated during the first 25 minutes after injection, and the are under the curve (AUC) for Lst-AlBD was almost 90 times greater compared to Lst (385.9 vs 4.3 mg*h/L). To sum up, the addition of albumin-binding domain dramatically increases the residence time of lysostaphin in systemic circulation in rats. On the other hand, the activity of the fusion protein is decreased. However, other approaches to the improvement of pharmacokinetic characteristics such as PEGylation, were shown to fully eliminate the activity [2], thus making Lst-AlBD a promising slow-elimination lysin variant. Further investigation and optimization of lysostaphin with albumin-binding domain is planned. The work was supported by Russian Science Foundation grant № 18-15-00235.