Expression of a Zika virus antigen in microalgae: Towards mucosal vaccine development

Zika virus (ZIKV) infection has extended rapidly all over the world in the last decades affecting humans of all ages, inducing severe illness such as the autoimmune Guillain-Barré syndrome as well as fetal neurodevelopmental defects. Despite the epidemiological importance of ZIKV, today there are no commercially available drugs or vaccines to combat or prevent this infection. Microalgae are attractive hosts to produce and deliver vaccines, with some candidates under preclinical evaluation. Herein, algae-based expression was assessed for the production of a new vaccine candidate against ZIKV called ZK. The Algevir technology was applied to express an antigenic protein called ZK comprising the B subunit of the heat labile Escherichia coli enterotoxin along with 3 epitopes from the ZIKV envelope glycoprotein. Efficient expression of the ZK antigen was achieved in Schizochytrium sp. with yields of up to 365 μg g^-1 microalgae fresh weight. Upon oral administration in mice, the microalgae-made ZK protein elicited significant humoral responses at a higher magnitude to those induced upon subcutaneous immunization. The algae-made ZK vaccine represents a promising candidate to formulate attractive vaccines against ZIKV.