Production of egg yolk antibody (IgY) against a chimeric protein containing IpaD, StxB, and TolC antigens from Shigella: An investigation of its prophylactic effects against Shiga toxin (Stx) and Shigella dysenteriae in vitro and in vivo

Shigella is a major problem in developing countries. Immunoglobulin Y (IgY) can be used for prophylaxis and neutralize bacteria. The aim of this study was to produce IgY against the chimeric protein containing IpaD, StxB, and TolC antigens from Shigella, investigate its prophylactic and neutralizing effects against Stx and Shigella dysenteriae. The nucleotide sequence corresponding to the chimeric protein was cloned into pET28a plasmid and expressed in E. coli BL21 (DE3). Protein expression was confirmed by SDS-PAGE and the recombinant protein was purified by Ni-NTA affinity chromatography. The 150 mu g of chimeric protein was mixed with Freund's adjutant and injected into laying hens (Leghorn). IgY was purified using PEG6000 precipitation. Antibody titer in the serum and egg yolk was evaluated by ELISA. IgY challenge against 1,10 and 50 LD50 of Stx and S. dysenteriae was investigated. A 60.6 kDa recombinant protein was confirmed by SDSPAGE. ELISA showed that the antibody titer was significantly increased. MTT assay [3-(4,5Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] showed that at 16 mu mol/L, IgY protected HeLa cells against Stx. Treatment of mice with 1000 and 1500 mu g IgY leads to complete survival of the mice against 1LD50 toxin and 4000 mu g of IgY led to complete survival against 1LD50, also 70% and 30% survival against 10 and 50 LD50 S. dysenteriae. This study showed that IgY produced against Stx and Shigella virulence factors could cause high protective effects against bacteria and toxins.