Partial protection to respiratory syncytial virus (RSV) elicited in mice by intranasal immunization using live staphylococci with surface-displayed RSV-peptides

A live bacterial vaccine-delivery system based on the food-grade bacterium Staphylococcus carnosus was used for delivery of peptides from the G glycop rotein of human respiratory syncytial virus, subtype A (RSV-A). Three pepti des, corresponding to the G protein amino acids, 144-159 (denoted G5), 190- 203 (G9) and 171-188 (G4 S), the latter with four cysteine residues substit uted for serines, were expressed by recombinant means as surface-exposed on three different bacteria, and their surface accessibility on the bacteria was verified by fluorescence-activated cell sorting (FACS). Intranasal immu nization of mice with the live recombinant staphylococci elicited significa nt anti-peptide as well as anti-virus serum IgG responses of balanced IgG1/ IgG2a isotype profiles, and upon viral challenge with 10(5) tissue culture infectious doses(50) (TCID50), lung protection was demonstrated for approxi mately half of the mice in the G9 and G4 S immunization groups. To our know ledge, this is the first study in which protective immunity to a viral path ogen has been evoked using food-grade bacteria as vaccine-delivery vehicles . (C) 2000 Elsevier Science Ltd. All rights reserved.