Evaluation of immune protection againstToxoplasma gondiiinfection in mice induced by a multi-antigenic DNA vaccine containing TgGRA24, TgGRA25 and TgMIC6

Abstract

Toxoplasma gondii infection is prevalent in humans and animals worldwide. In this study, recombinant eukaryotic expression plasmids (pVAX-GRA24, pVAX-GRA25 and pVAX-MIC6) were constructed, and then injected into Kunming mice intramuscularly, as cocktailed plasmids or as single-gene plasmids. We evaluated immune protective responses by detecting the titer of antibodies and cytokine production of IFN-γ, IL-2, IL-4, IL-10, IL-12 and IL-23, the percentages of the subclasses of T lymphocytes, as well as the records of the survival time and cyst decrement in the brain of the mouse model after challenge with the T. gondii RH and Pru strains, respectively. Compared with the control groups, antibody and cytokine production were significantly increased, while the survival times of mice in all immunized groups were also prolonged, and the number of T. gondii cysts in their brains were decreased significantly (29.03% for pVAX-GRA24; 40.88% for pVAX-GRA25; 37.70% for pVAX-MIC6; 48.06% for pVAX-GRA24 + pVAX-GRA25; and 55.37% for pVAX-GRA24 + pVAX-GRA25 + pVAX-MIC6). The mouse group immunized with the three-gene cocktail (TgGRA24 + TgGRA25 + TgMIC6) had better performance in each detection index than the mouse groups immunized with the two-gene cocktail of TgGRA24 + TgGRA25, which was better than that in the group immunized with the single gene vaccine of TgGRA24, TgMIC6 or TgGRA25. In conclusion, TgGRA24 or TgGRA25 may be good vaccine candidates against T. gondii infection, but the three-gene cocktail of TgGRA24, TgMIC6 and TgGRA25 may induce the strongest protective immunity. Further studies of multi-antigenic DNA vaccines or cocktailed vaccines against T. gondii infection are necessary.

Protective Immunity Induced by TgMIC5 and TgMIC16 DNA Vaccines Against Toxoplasmosis

“…Therefore, efficient humoral responses are of great significance in limiting the spread of T. gondii tachyzoites (Sayles et al, 2000). In the present study, the significantly increased levels of anti-T. gondii IgG in the mice immunized with the cocktail vaccine may have contributed to limiting the infection with T. gondii tachyzoites, which was in line with the results from DNA immunization with TgROP18, TgROP5, or TgGRA25, TgGRA25, and TgMIC5 (Chen et al, 2015;Xu et al, 2019). Furthermore, DNA immunization with single gene vaccine, especially two-gene cocktail vaccine, significantly increased the levels of IgG2a and IgG1 compared with that in the control groups.…”

“…TgGRA24, TgGRA25, TgROP5, TgROP18, and TgDOC2C, etc.) and they showed effective immunity against T. gondii infection, with inductive Th1 type and CD8+ cytotoxic Tlymphocyte responses, and prolonged survival time in mice after infection with T. gondii Xu et al, 2019;Zhu et al, 2020)., Some microneme proteins (MICs) have also been shown to have immunogenic capabilities (Dodangeh et al, 2019). TgMIC5 is one of a large member of microneme proteins, which can regulate the activity of proteases and it is related to the proteolytic susceptibility of other microneme protein substrates (Susannah et al, 2006).…”

Immunization With a DNA Vaccine Encoding the Toxoplasma gondii’ s GRA39 Prolongs Survival and Reduce Brain Cyst Formation in a Murine Model

“…Similar with previous studies ( Chen et al, 2013 , 2017 ; Gao et al, 2018 ), DNA immunization with a single antigen of TgGRA39 could only induce partial protective immunity in Kunming mice, due to its limited lymphocyte binding sites, leading to a difficulty of mounting an efficient immune response against T. gondii ( Donnelly et al, 2005 ). Although this single DNA immunization with pVAX-GRA39 has elicited similar or different effective immunity in comparison with some other single DNA vaccine candidates, such as TgGRA24, TgGRA25 and TgGRA16 ( Hu et al, 2017 ; Xu et al, 2019 ; Zheng et al, 2019 ), this DNA immunization has evoked Th17 responses, which are commonly directly correlated with mucosa protection, and also considered to be beneficial in limiting the host infection via the gastrointestinal tract ( Gaffen and Moutsopoulos, 2020 ). However, in those previous studies on T. gondii vaccines, detection of Th17 responses was rarely found.…”

“…In previous studies, some DNA vaccine candidates encoding GRA protein of T. gondii , such as GRA6, GRA7, GRA2, GRA15, GRA16, GRA24, and GRA25, have demonstrated some efficacy against T. gondii infection, with their ability of eliciting immunity, particularly cellular immune responses, which is critical for defending against acute and chronic toxoplasmosis in animal models ( Chen et al, 2015 ; Hu et al, 2017 ; Xu et al, 2019 ; Zheng et al, 2019 ). In the present study, we constructed a DNA vaccine expressing TgGRA39, and evaluated its immunogenicity and protective efficacy against infection with the highly virulent T. gondii RH strain and the chronic T. gondii PRU strain.…”

Advances in Toxoplasma gondii Vaccines: Current Strategies and Challenges for Vaccine Development

“…Notably, marginally higher brain cyst reduction was detected from mice immunized with the vaccine expressing all five aforementioned antigens than those expressing only four out of the five antigens [ 31 ]. Consistent with these findings, a multi-antigenic DNA vaccine expressing GRA24, GRA25, and MIC6 induced the highest level of protection compared to the single antigen or GRA24 and GRA25 combined vaccines [ 32 ]. A single dose of hexaplex modified dendrimer nanoparticle vaccine carrying replicons encoding GRA6, ROP2A, ROP18, SAG1, SAG2A, and AMA1 successfully protected mice against a lethal challenge infection with PRUΔ hxgprt strain [ 33 ].…”