A rapid strategy for constructing novel simian adenovirus vectors with high viral titer and expressing highly antigenic proteins applicable for vaccine development

Abstract

Adenoviral vectors have been widely used for the development of infectious disease vaccines. However, the challenge of human adenoviral vector rooted from the predominant adenovirus serotype 5 strain limiting its usefulness by the widespread pre-existing neutralizing antibodies in recipients. To circumvent this obstacle, we generated an ad-hoc adenovirus vector in human or primates. Here, a chimeric simian adenoviral vector Sad23 was constructed consisting in deleting of E1 and E3 regions of the full-length simian adenovirus serotype 23 genome (SAdV23) by Gibson assembly. To improve Sad23 virus propagating efficiency, the E4 region open reading frame 6 (orf6) was replaced by the corresponding element of human adenovirus type 5 (Ad5), designated Sad23L. The procedure for cloning this novel vector took a single week, and recombinant adenovirus was packaged with high titer in HEK293 cells. To verify the ability of this novel adenoviral vector to deliver foreign genes, Zika virus (ZIKV) prM-E genes were used as target genes for antigen expression. Recombinant adenoviruses Sad23L-prM-E, Sad23-prM-E and Ad5-prM-E were intramuscularly inoculated into Ad5-eGFP none pre-exposed or pre-exposed mice, and the immune response to ZIKV prM-E was compared between vectors. Sad23L-prM-E induced a fairly robust immune response and maintained immunogenicity in Ad5 pre-exposed mice, which suggested that Ad5 pre-existing immunity did not affect Sad23L-prM-E immunization. These preliminary results suggest that the proposed rapid strategy was effective in constructing a new adenoviral vector platform (Sad23 L) usable for the development of human vaccines.

Keywords: Gibson assembly; High titer; Novel adenoviral vector; Simian adenovirus type 23; Vaccine candidate.