Toxoplasma gondii is an obligate intracellular protozoan that belongs to the phylum Apicomplexa, and can infect a wide range of warm-blood animals. Most of toxoplasmosis is asymptomatic, however, it may cause severe opportunistic disease in individuals with immunosuppressive conditions (Elsheikha, 2008). Since the infection causes abortion and congenital disorders in humans and animals, managing the transmission and effects of this parasite is important in public health and livestock husbandry (Tenter et al., 2000). If infection with T. gondii recognized timely, it can be successfully controlled and managed. Unfortunately, the chemical drugs currently recommended for the infection, cannot completely eliminate the protozoa due to the form of tissue cysts (Lopes-Mori et al., 2011; Rajapakse et al., 2013). In addition, chemical drugs prompting the development of drug resistance, and have some side effects such as low neutrophil count (neutropenia), severe drop of platelet count (thrombocytopenia), low white blood cell count (leukopenia) and hypersensitivity reactions(Montazeri et al., 2015; Rajapakse et al., 2013). Although several types of new vaccines have been developed and tested against toxoplasmosis, due to safety concerns or poor efficacy only few have been licensed for use (Darcy et al., 1992; Innes and Vermeulen, 2006; Wang et al., 2007). Therefore, the development of an effective and safe vaccine is urgently needed.

In the past few years, a large number of studies have been carried out to find new T. gondii vaccines based on parasite antigens (Verma and Khanna, 2013; Zhang et al., 2013). T. gondii has various antigens that play a major role in the pathogenesis of this parasite, and to avoid the clearance by humoral immunity(Couvreur et al., 1988). T. gondii secretory and surface antigens have been shown to play a critical role in stimulating the host immune response. Various antigens such as GRA, SAG, ROP, MAG, MICs, BAG, AMA, and ROM have been synthesized from different strains of T. gondii and their protective effects have been reported in various animal models studies in different vaccine platforms (Lee et al., 2018; Khorshidvand et al., 2022; Mamaghani et al., 2022; Zhang et al., 2019). The dense granule molecules (GRA) are major protective antigens which are the main components of execratory secretory antigens (ESAs). ESAs secreted by T. gondii and have been shown to be involved in the intracellular maintenance of the parasite (Arab-Mazar et al., 2016). The main surface antigens (SAGs) are a family of antigens which help parasite to anchor to the cell membrane. In addition, SAGs induce both cellular and humoral immune responses (Khorshidvand et al., 2022). Microneme antigens (MICs) which are secreted by the microneme, play a major role in gliding motility of parasites, and invasion of parasites into host cells during the invasion process(Ghaffarifar et al., 2019). Bradyzoite Antigen 1 (BAG1) is a 28/30 kDa bradyzoite cytoplasmic antigen which has homology to small heat shock proteins. Recent studies suggest that the bradyzoite formation is a stress-induced response that is associated with increased heat shock proteins levels and induction of BAG1 expression (Di Cristina et al., 2004). Apical membrane antigen 1 (AMA1) is another important antigen used by apicomplexan parasites to invade host cells (Kim et al., 2020). Vaccination with only some of the antigens leads to stage-limited protection, and these vaccines are weakly immunogenic (Alexander et al., 1996). Therefore, in new vaccines a complex of different antigens is used together(Donnelly et al., 2005). The aim of present study was to evaluate a novel multi-antigenic DNA vaccine encoding SAG1, SAG3, MIC4, GRA5, GRA7, AMA1and BAG1 against T. gondii in BALB/c mice.