Influenza Virus-Like Particles Presenting both Toxoplasma gondii ROP4 and ROP13 Enhance Protection against T. gondii Infection

Abstract

Rhoptry organelle proteins (ROPs) secreted by Toxoplasma gondii (T. gondii) play a critical role during parasite invasion into host cells. In this study, virus-like particles (VLPs) vaccines containing ROP4 and/or ROP13 together with influenza M1 were generated. ROP4+ROP13 VLPs were produced by combining ROP4 VLPs with ROP13 VLPs, and ROP(4 + 13) VLPs by co-infecting insect cells with recombinant baculovirus expressing ROP4 or ROP13. Mice intranasally immunized with ROP(4 + 13) VLPs showed significantly higher levels of IgG, IgG1, IgG2a and IgA antibody responses in sera compared to ROP4+ROP13VLPs. Upon challenge infection by oral route, mice immunized with ROP(4 + 13) VLPs elicited higher levels of IgG and IgA antibody responses in fecal, urine, intestine and vaginal samples as well as CD4+ T, CD8+ T cells, and germinal center B cell responses compared to other type of vaccines, ROP4 VLPs, ROP13 VLPs, and ROP4+ROP13 VLPs. ROP(4 + 13) VLPs vaccination showed a significant decrease in the size and number of cyst in the brain and less body weight loss compared to combination ROP4+ROP13 VLPs upon challenge infection with T. gondii ME49. These results indicated that the ROP(4 + 13) VLPs vaccination provided enhanced protection against T. gondii infection compared to ROP4+ROP13 VLPs, providing an important insight into vaccine design strategy for T. gondii VLPs vaccines.

Toxoplasma gondii virus‐like particle vaccination alleviates inflammatory response in the brain upon T gondii infection

“…ROP4 or ROP13 VLPs vaccination has shown a significant reduction of cyst counts in the brain in our previous study 9,12 . Thus, in this study, we investigated the inflammatory responses induced by ROP4 or ROP13 VLPs immunization and its correlation with the reduced cyst counts, IgG and IgA antibody responses in the brains.…”

“…Toxoplasma gondii RH was obtained from mice and total RNA of T gondii was extracted using RNeasy Mini Kit (Qiagen, Valencia, CA, USA). The cDNAs of ROP4, ROP13 and M1 were acquired as previously described 9 . ROP4, ROP13 and M1 recombinant bacmids were prepared and transfected into the SF9 cells as previously described 9 .…”

“…The cDNAs of ROP4, ROP13 and M1 were acquired as previously described 9 . ROP4, ROP13 and M1 recombinant bacmids were prepared and transfected into the SF9 cells as previously described 9 . SF9 cells were co‐infected with influenza M1 rBV and either ROP4 or ROP13 rBV for VLPs production as described previously 9 .…”

“…ROP4, ROP13 and M1 recombinant bacmids were prepared and transfected into the SF9 cells as previously described 9 . SF9 cells were co‐infected with influenza M1 rBV and either ROP4 or ROP13 rBV for VLPs production as described previously 9 . Expressions of ROP4 and ROP13 VLPs were confirmed by Western blot and transmission electron microscopy (TEM) 9,13 …”

“…In spite of these efforts, vaccine incorporating the aforementioned strategies failed to provide sufficient protection in mice. Contrastingly, our previous works have demonstrated that virus‐like particles (VLPs) vaccines expressing various T gondii proteins could provide adequate protection against T gondii ME49 in murine models 9‐11 . However, reduced inflammatory responses in the brain induced by VLPs immunization upon T gondii ME49 infection has not been investigated in any of the previous works.…”