Tetravalent Virus-like Particles Engineered To Display Envelope Domain IIIs of Four Dengue Serotypes in Silkworm as Vaccine Candidates

Dengue virus (DENV) causes dengue fever, the leading mosquito-borne viral disease affecting millions globally. Licensed vaccines have their restrictions, and the development of vaccines is in progress to overcome the limitations. In this study, we expressed two types of virus-like particles (VLPs) and four DENV serotype antigens, 1EDIII-4EDIII (tetEDIII), in silkworm larvae and engineered them into tetravalent VLPs (tetVLPs) displaying tetEDIII. Canine parvovirus-like particles (CPV-LPs) were self-assembled <i>in vivo</i> from viral protein VP2 of CPV (CPV-VP2) as heterologous VLPs; dengue virus capsid-like particles (DENV C-LPs) from capsid protein of DENV serotype 2 (DENV-C2) as homologous VLPs. The tetEDIII was displayed on the surface of CPV-LPs and DENV C-LPs through <i>in vitro</i> SpyTag/SpyCatcher (SpT/SpC) covalent ligation. The EDIII display of CPV-LP is better than that of DENV C-LP. Both tetEDIII-displaying tetravalent CPV-LPs (tetCPV-LPs) and tetravalent DENV C-LPs (tetDENV C-LPs) elicited neutralizing antibodies in BALB/c mice assayed through the single-round infectious particles (SRIP) method. The immunogenicity of tetDENV C-LPs for anti-IgG EDIIIs was higher than that of tetCPV-LPs for serotypes 1 and 3. The neutralization activity of tetDENV C-LPs was higher than that of tetCPV-LPs for D1-SRIP, while tetCPV-LPs were higher than that of tetDENV C-LPs for D2- and D4-SRIP. These results suggest that homologous tetDENV C-LPs and heterologous tetCPV-LPs can be suitable vaccine candidates for further evaluation. This result is the first report to display a tetEDIII on the surface of the DENV C-LPs and the CPV-LPs by <i>in vitro</i> bioconjugation.