AUTHOR=Sun Hong-Chao , Huang Jing , Fu Yuan , Hao Li-Li , Liu Xin , Shi Tuan-Yuan 

TITLE=Enhancing Immune Responses to a DNA Vaccine Encoding Toxoplasma gondii GRA7 Using Calcium Phosphate Nanoparticles as an Adjuvant

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.787635

DOI=10.3389/fcimb.2021.787635

ISSN=2235-2988

ABSTRACT=<p><italic>Toxoplasma gondii</italic> infects almost all warm-blooded animals, including humans. DNA vaccines are an effective strategy against <italic>T. gondii</italic> infection, but these vaccines have often been poorly immunogenic due to the poor distribution of plasmids or degradation by lysosomes. It is necessary to evaluate the antigen delivery system for optimal vaccination strategy. Nanoparticles (NPs) have been shown to modulate and enhance the cellular humoral immune response. Here, we studied the immunological properties of calcium phosphate nanoparticles (CaPNs) as nanoadjuvants to enhance the protective effect of <italic>T. gondii</italic> dense granule protein (GRA7). BALB/c mice were injected three times and then challenged with <italic>T. gondii</italic> RH strain tachyzoites. Mice vaccinated with GRA7-pEGFP-C2+nano-adjuvant (CaPNs) showed a strong cellular immune response, as monitored by elevated levels of anti-<italic>T. gondii</italic>-specific immunoglobulin G (IgG), a higher IgG2a-to-IgG1 ratio, elevated interleukin (IL)-12 and interferon (IFN)-γ production, and low IL-4 levels. We found that a significantly higher level of splenocyte proliferation was induced by GRA7-pEGFP-C2+nano-adjuvant (CaPNs) immunization, and a significantly prolonged survival time and decreased parasite burden were observed in vaccine-immunized mice. These data indicated that CaPN-based immunization with <italic>T. gondii</italic> GRA7 is a promising approach to improve vaccination.</p>