Abstract
BackgroundToxoplasma gondii is an obligate intracellular parasite that can infect almost all warm-blooded animals. T. gondii profilin (TgPF) plays a crucial role in parasite motility and host cell invasion, and has shown promise against toxoplasmosis. DNA vaccine was considered to elicit effective humoral and cell-mediated immunity against T. gondii infection. The objective of the present study was to evaluate the immunogenicity of TgPF in mice using a DNA vaccination strategy.MethodsA DNA vaccine (pVAX-PF) encoding TgPF gene was constructed and then was intramuscularly injected into mice with and without a plasmid encoding IL-15 (pVAX-IL-15). The immune responses in immunized Kunming mice including lymphocyte proliferation, levels of cytokines, antibody titers and T lymphocyte subclasses were analyzed. The protective efficacy against chronic T. gondii infection was observed at 4 weeks post-infection with the cyst-forming PRU strain of T. gondii (Genotype II).ResultsEitherpVAX-PF with or without pVAX-IL-15 could elicit higher level of IgG and IgG2a antibodies and produce strong cellular immune responses in the immunized mice. The brain cyst numbers in mice immunized with pVAX-PF + pVAX-IL-15 (1843 ± 215.7) and pVAX-PF (1897 ± 337.8) were reduced 40.82% and 39.08%, respectively, compared to that in mice received nothing (3114 ± 168.8), and the differences were statistically significant (P < 0.0001). However, the T. gondii cyst numbers in mice immunized with pVAX-PF + pVAX-IL-15 were not statistically significantly different compared to that in mice immunized with pVAX-PF alone [t(10) = 0.33, P > 0.05].ConclusionsThe present study indicated that TgPF could be a promising vaccine candidate against chronic toxoplasmosis, which can be further used to develop multi-epitope vaccine formulations in food-producing animals against T. gondii infection.
Highlights
Toxoplasma gondii is an obligate intracellular parasite that can infect almost all warm-blooded animals
Gao et al BMC Infectious Diseases (2018) 18:117 (MIC), dense granule antigens (GRA) and some other proteins playing important roles in the life cycle of T. gondii have been evaluated against T. gondii infection
The complete open reading frame (ORF) of T. gondii profilin (TgPF) gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) using a pair of specific primers, designed according to the corresponding sequence of the ME49 strain (ToxoDB: TGME49_293690), in which the Kpn I and EcoR I restriction sites were introduced and underlined
Summary
Toxoplasma gondii is an obligate intracellular parasite that can infect almost all warm-blooded animals. T. gondii profilin (TgPF) plays a crucial role in parasite motility and host cell invasion, and has shown promise against toxoplasmosis. DNA vaccine was considered to elicit effective humoral and cell-mediated immunity against T. gondii infection. DNA-based vaccines were considered to elicit effective humoral and cell-mediated immunity against T. gondii invasion in animal models, which have been used in many previous studies [11,12,13]. T. gondii profilin (TgPF), one of the ligands of both TLR11 and 12, is essential for the parasite gliding motility, host cell invasion and egress from host cells in mice [17, 19]. Immunization of C57BL/6 mice with TgPF encapsulated in oligomannose-coated liposomes induces protective immunity against infection with T. gondii tachyzoites (PLK strain) [20]
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