Establishment of minimal positive-control conditions to ensure brain safety during rapid development of emergency vaccines

Baek, Hyekyung; Kim, Kwang Ho; Park, Min Young; Kim, Kyeongryun; Ko, Bokyeong; Seo, Hyung Seok; Kim, Byoung Soo; Hahn, Tae-Wook; Yi, Sun Shin

In that protocol, to assure that the alterations to occludin or ZO-1 mRNA levels actually result in damage to the BBB's selective permeability function, EB assays were performed. In that assay, EB penetrates into brain parenchymal tissues and an EB ratio (brain/blood EB content) is calculated. A high permeated EB ratio indicates a significantly damaged BBB structure. We used LPS from two sources (S. enterica and E. coli) and two strains of mice (B6 and ICR mice). Interestingly, the results from each LPS and mouse strain showed different trends. The BBB protective permeability of ICR mice was more intensely impaired than that of B6 mice, and LPS derived from S. enterica penetrated the brain more effectively than that derived from E. coli. It has been reported that LPS consists of three different structures; O-antigen, core polysaccharide, and lipid A. In particular, the composition of the O-chain varies notably from strain to strain and the O-chain is a recognizable target of host antibodies, as O-antigen. Therefore, it is possible that LPSs of different bacterial origins can produce different degrees of BBB permeability damage. As the purpose of this study was to establish an effective BBB safety verification positive-control protocol, we selected the LPS type that had the highest damage effect on BBB permeability. In addition, the EB results from the two mouse strains showed that a more sensitive positive-control protocol could be established by using ICR mice instead of B6 mice.