Phage receptor binding protein and Fc fragment fusion enhances phagocytosis of Y. enterocolitica.

Bacteriophage receptor binding proteins (RBPs) belong to a group of proteins that are components of the bacteriophage tail. RBPs are mainly responsible for recognizing receptors on the bacterial host surface and enabling infection and subsequent progeny phage multiplication. Our previous research suggested that recombinant tail fiber gp17 (TFPgp17) protein from Yersinia enterocolitica phage φYeO3-12 recognizes serotype O:3 with high specificity and could be used as a diagnostic tool. In this paper, we study the possibility of using modified TFPgp17 in fusion with IgG1 Fc immunoglobulin fragment (Fc_TFPgp17) to improve the efficacy of pathogen recognition by phagocytic cells, opsonization of bacterial cells, and then phagocytosis by the THP-1 macrophages and the HL-60 neutrophils. We demonstrate that the Fc_TFPgp17 protein can bind both bacterial and phagocytic cells, due to the presence of the RBP domain and the IgG1 Fc fragment, respectively. Additionally, it contributes to the better recognition of bacterial cells and their subsequent phagocytosis by phagocytes. Additionally, we proved that glycosylation of Fc_TFPgp17 which occurred during protein production, harms the ability to recognize Y. enterocolitica O:3. Fc_TFPgp17 is a bispecific protein that possesses two biological functions: (I) recognized Y. enterocolitica O:3 cells via phage RBP (TFPgp17) and (II) recognized phagocytic cells via Fc-fragment IgG1 immunoglobulin. In this work, we demonstrated that the recombined bispecific protein facilitates more effective recognition and opsonization of the pathogenic bacterial cell, leading to its subsequent phagocytosis.