We investigated whether
eyedrop vaccination using modified outer membrane vesicles (mOMVs) is effective for protecting against
hemolytic uremic syndrome (HUS) caused by enterohemorrhagic E. coli (EHEC) O157:H7
infection. Modified OMVs and waaJ-mOMVs were prepared from cultures of MsbB- and
Shiga toxin A subunit (STxA)-deficient EHEC O157:H7 bacteria with or without an additional waaJ mutation. BALB/c mice were immunized by
eyedrop mOMVs, waaJ-mOMVs, and mOMVs plus
polymyxin B (PMB). Mice were boosted at 2 weeks, and challenged peritoneally with wild-type OMVs (wtOMVs) at 4 weeks. As parameters for evaluation of the OMV-mediated immune protection, serum and mucosal
immunoglobulins,
body weight change and blood
urea nitrogen (BUN)/Creatinin (Cr) were tested, as well as histopathology of renal tissue. In order to confirm the safety of mOMVs for
eyedrop use,
body weight and ocular histopathological changes were monitored in mice. Modified OMVs having
penta-acylated
lipid A moiety did not contain STxA subunit
proteins but retained non-toxic
Shiga toxin B (STxB) subunit. Removal of the polymeric
O-antigen of O157 LPS was confirmed in waaJ-mOMVs. The mice group vaccinated with mOMVs elicited greater humoral and mucosal immune responses than did the waaJ-mOMVs and PBS-treated groups.
Eyedrop vaccination of mOMVs plus PMB reduced the level of humoral and mucosal immune responses, suggesting that intact O157 LPS
antigen can be a critical component for enhancing the immunogenicity of the mOMVs. After challenge, mice vaccinated with mOMVs were protected from a lethal dose of wtOMVs administered intraperitoneally, conversely mice in the PBS control group were not. Collectively, for the first time, EHEC O157-derived mOMV
eyedrop vaccine was experimentally evaluated as an efficient and safe means of
vaccine development against EHEC O157:H7
infection-associated HUS.