Li-Chen Yen, Yi-Ling Lin, Hwei-Jen Lee, Jia-Teh Liao and Ching-Len Liao
National Institute of Infectious Diseases and Vaccinology, Taiwan
The NS1 is the only nonstructural protein that enters the lumen of ER, where NS1 is glycosylated, forms dimer, and subsequently is secreted during flavivirus replication as hexamers, which appear to be highly antigenic to the infected host as protective immunity can be elicited against homologous flavivirus infections. Here, by using trans-complementation assay, we identified the C-terminal of NS1 derived from Japanese encephalitis virus (JEV) that was more plastic than other regions for housing foreign epitopes without significant impact on virus replication. Such mapped flexible region is located in the conserved tip of core β-ladder domain of multimeric NS1 crystal structure also known to reside certain linear epitopes readily triggering specific antibody responses from the host. Despite becoming attenuated, recombinant JEV with insertion of neutralizing epitope derived from Enterovirus-71 (EV71) into the C-terminal of NS1 could not only be normally released from the infected cells but also induce dual protective immunity for the host to counteract the lethal challenge of either JEV or EV71 in neonatal mice. These results indicate that the secreted multimeric NS1 of flaviviruses may serve as a nature protein carrier to make epitopes of interest more immunogenic in its C-terminus of core β-ladder domain.
Keywords: Flaviviral NS1 fusion proteins, β-ladder domain, dimer, hexamer, JEV/EV-71 recombinants.