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 the 21st century, various infectious diseases threaten humans and animals around the world due to ever-increasing global movements of people, animals, and materials [19, 23] . Nonetheless, the most effective way of approaching an epidemic that occurs at unexpected times and or in unexpected places is to rapidly supply vaccines related to the infectious diseases within a limited time [15] . However, during rapid vaccine developments performed to date, there has been little consideration given to establishing a precise protocol for ensuring brain safety. This oversight in the development of general and/or emergent vaccines should be corrected by developing an effective safety protocol that can reduce brain damage risks before distribution of the vaccine. The present study was undertaken to establish a protocol that can be used to determine if a material, such as a vaccine, will damage the brain by breaking down the brain-protective blood-brain barrier (BBB). Since the BBB is a critical morphological structure with selective permeability between blood vessels and brain tissue, it is very important to determine the conditions that can make the BBB vulnerable; for example, exposure to a pyrogenic inflammatory agent such as a lipopolysaccharide (LPS) administered via systemic injection [10] . To ensure the brain safety of newly developed vaccines and to establish positive-control conditions for use in a vaccine safety protocol, we used the specificity of brain anatomical structures to investigate the robustness of the BBB by varying LPS exposure times (0, 2, 4, and 24 h) in two different mouse strains (C57BL/6 and ICR). In this study, we describe an effective positive-control protocol for were tested in two different strains of mice (C57BL/6 [B6] and ICR). The intraperitoneally administered EB (4 mL/kg, 2% [w/v] in phosphate buffered saline [PBS]; pH 7.4) appeared in the homogenized brains following the injection of LPS(S) or LPS(E) in the different mice strains. Compared to the control group administered with vehicle (PBS) only, the amount of EB that penetrated the brain was significantly higher in both mouse strains after injection with both LPSs. Interestingly, for both LPSs the amounts of EB penetrating ICR mouse brains were greater than those of B6 mouse brains, and for both mouse strains the amount of EB penetrance was greater in LPS(S) than in LPS(E). assessing the brain safety of vaccines that will be developed and supplied in the future. The protocol may develop into a complete safety assurance protocol in the future.