Production of highly immunogenic and safe Triton X-100 produced bacterial ghost vaccine against Shigella fexneri 2b serotype

Abstract

Background Bacterial ghost cells (BGCs) are cells were drained of their genetic and cytoplasmic components. This work aimed to develop vaccine candidates against the Shigella fexneri (S. fexneri) 2b serotype using the BGCs approach. For the frst time, (S. fexneri) 2b serotype BGCs vaccine was prepared by incubation with Triton X-100 (TX100) for only 12 h. Its safety and immunogenicity were compared to another vaccine produced using a previously used surfactant, namely Tween 80 (TW80). Scanning electron microscopy (SEM), cellular DNA, protein contents meas- urements, and ghost cell re-cultivation were used to confrm the successful generation of the BGCs. Immunogenic- ity was assessed through mice’s intraperitoneal (IP) immunization followed by infection with S. fexneri ATCC 12022. Finally, histopathological examination was carried out. Results Viable colony forming units (CFUs) of S. fexneri were counted from stool samples as well as homogenized colon tissues of the non-immunized challenged group. Immunized mice sera showed a signifcant increase in serum bactericidal activity of both preparations (TX100=40% and TW80=56%) compared to the non-immunized chal- lenged group (positive control). The IgG levels of the bacterial ghost-vaccinated groups were four and three times greater for the TX100 and TW80 ghost vaccines, respectively, compared to that of the positive control; both bac- terial ghost vaccines (BGVs) were safe and efective, according to the results of the safety check tests and histopatho- logical analysis. Conclusions When comparing the BGVs prepared using TX100 and TW80 methods, the use of TX100 as a new chemical treating agent for BGC production attained robust results in terms of shorter incubation time with the tar- geted cells and a strong immune response against S. fexneri 2b serotype ATCC 12022 in the IP challenge test. How- ever, a clinical study is needed to confrm the efcacy and total safety of this novel vaccine.