Virus-like particle vaccines expressing Toxoplasma gondii rhoptry protein 18 and microneme protein 8 provide enhanced protection

Toxoplasma gondii rhoptry protein 18 (ROP18) and microneme protein 8 (MIC8) are important invasion factors that mediate parasite multiplication. The main objective of this study was to determine the immunogenicity and efficacy by virus-like particle (VLP) vaccines of T. gondii ROP18 VLPs and MIC8 VLPs in combination or individuals. Mice were intranasally immunized with single ROP18 VLPs or MIC8 VLPs, or a combination of ROP18 VLP5 and MIC8 VLPs followed by challenge with T. gondii tachyzoites (GT1) through intraperitoneal injection or challenge with T. gondii (ME49) through oral infection. Vaccination with a combination of ROP18 VLPs and MIC8 VLP5 resulted in more potent effects on inducing parasite neutralizing activity, memory T cell response, and reducing parasite burden compared to single VLP vaccination. Lower levels of inflammatory cytokines (IFN-gamma, IL-6) and apoptosis responses were observed with VLP vaccine combination after challenge. These results suggest that VLP vaccines presenting both T. gondii ROP18 and MIC8 antigens confer enhanced protection compared to a single VLPs vaccine, and VLP platforms could be developed as potential vaccines against toxoplasmosis. (C) 2018 Elsevier Ltd. All rights reserved.