Immunogenicity and protective activity of recombinant influenza viruses expressing fragments of ScaAB lipoprotein of group B streptococci in a mouse model

Abstract

Group B streptococci (GBS) cause a number of serious diseases in humans. The development of an effective vaccine against GBS requires special approaches. In the present study, three recombinant influenza viruses were constructed on the backbone of H7N9 live attenuated influenza vaccine (LAIV) strain expressing fragments of the ScaAB lipoprotein of Streptococcus agalactiae, fused to the surface protein of the virus, hemagglutinin, using a flexible linker. Recombinant viruses with ScaAB inserts of 85, 141, and 200 amino acids were successfully rescued by the means of reverse genetics. The recombinant strains were able to grow in developing chicken embryos and MDCK cells and retained the temperature-sensitive phenotype attributable to the LAIV viruses. Studies of immunogenicity and protective activity of the vaccine candidates in BALB/c mice revealed that the most promising strain was a strain with an insert of 141 amino acids: this variant had optimal immunogenicity against influenza and GBS and had a protective effect against both pathogens. These data indicate that further studies of the recombinant vectored vaccine H7-ScaAB-141 as a combined viral-bacterial vaccine capable of protection against both influenza virus and bacterial infections caused by group B streptococci are warranted.