Abstract
BackgroundToxoplasma gondii has been shown to trigger strong cellular immune responses to heterologous antigens expressed by the parasite in the inbred mouse model [1]. We studied the immune response induced by T. gondii as an effective vaccine vector in chickens and rabbits.ResultsT. gondii RH strain was engineered to express the yellow fluorescent protein (YFP) in the cytoplasm. A subcutaneous injection of the transgenic T. gondii YFP in chickens afforded partial protection against the infection of transgenic E. tenella YFP. T. gondii YFP induced low levels of antibodies to YFP in chickens, suggesting that YFP specific cellular immune response was probably responsible for the protective immunity against E. tenella YFP infection. The measurement of T-cell response and IFN-γ production further confirmed that YFP specific Th1 mediated immune response was induced by T. gondii YFP in immunized chickens. The transgenic T. gondii stimulated significantly higher YFP specific IgG titers in rabbits than in chickens, suggesting greater immunogenicity in a T. gondii susceptible species than in a resistant species. Priming with T. gondii YFP and boosting with the recombinant YFP can induce a strong anti-YFP antibody response in both animal species.ConclusionsOur findings suggest that T. gondii can be used as an effective vaccine vector and future research should focus on exploring avirulent no cyst-forming strains of T. gondii as a live vaccine vector in animals.
Highlights
Toxoplasma gondii has been shown to trigger strong cellular immune responses to heterologous antigens expressed by the parasite in the inbred mouse model [1]
We firstly demonstrated that the transgenic T. gondii yellow fluorescent protein (YFP) elicited YFP-specific immune responses that conferred partial protection against a challenge with YFP-expressing E. tenella
Transgenic T. gondii elicited YFP-specific cytokines expression To further determine the YFP specific immune response induced by transgenic T. gondii YFP, we examined the level of IFN-g (Th1 type) and IL-4 (Th2 type) production by YFP specific T cells using Real-time RT-PCR
Summary
Toxoplasma gondii has been shown to trigger strong cellular immune responses to heterologous antigens expressed by the parasite in the inbred mouse model [1]. The antigen delivering efficiency and the type of immune response of live vaccine vectors depends on their replication at infected sites and in target cells [7]. An effective live vaccine vector should have the capacity to infect a wide range of target cells with high efficiency and present effectively heterologous antigens to T cells. Toxoplasma gondii is an obligate intracellular parasite It can infect any nucleated cells of warm-blood vertebrates [9,10,11,12] and induce strong humoral, mucosal and cellular immune responses, making it an attractive system for delivering heterologous antigens [9]. Avirulent strains of T. gondii have been tested to immunize
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