Abstract
Passive immunity can provide immediate protection against infectious pathogens. To date, only a few studies have investigated the effect of passive immunization against Toxoplasma gondii, and the use of immune sera acquired from VLP-vaccinated mice for passive immunity assessment remains unreported. In this study, immune sera were produced by a single immunization with virus-like particles (VLPs) expressing the inner membrane complex (IMC), rhoptry protein 18 (ROP18), and microneme protein 8 (MIC8) of Toxoplasma gondii, with or without a CpG-ODN adjuvant. The passive immunization of immune sera conferred protection in mice, as indicated by their potent parasite-specific antibody response, lessened brain cyst counts, lower bodyweight loss, and enhanced survival. In order to confirm that the immune sera of the VLP-immunized mice were truly protective, the antibody responses and other immunological parameters were measured in the VLP-immunized mice. We found that VLP immunization induced higher levels of parasite-specific IgG, IgG subclass, and IgM antibody responses in the sera and intestines than in the controls. Enhanced Th1 and Th2-associated cytokines in the spleen, diminished brain cyst counts, and lessened body weight loss were found following T. gondii ME49 challenge infection. These results suggest that passive immunization with the immune sera acquired from VLP-vaccinated mice can confer adequate protection against T. gondii infection.
Highlights
Toxoplasma gondii is a notorious intracellular protozoan parasite which infects a wide range of warm-blooded vertebrates such as cats, sheep, mice, and humans
We evaluated the adjuvanted viruslike particles (VLPs) vaccine-induced antibody responses (IgG, IgG1, IgG2a, IgG2b, IgM) and attempted to accurately assess the protection conferred by passively immunizing naïve mice with the sera of VLP-immunized mice through the intravenous route
We evaluated the passive immunity induced by the immune sera of VLP-immunized mice
Summary
Toxoplasma gondii is a notorious intracellular protozoan parasite which infects a wide range of warm-blooded vertebrates such as cats, sheep, mice, and humans. As the causative agent of toxoplasmosis, T. gondii infections in healthy individuals are often asymptomatic, whereas pregnant women and acquired immune deficiency syndrome (AIDS) patients can experience severe life-threatening symptoms such as miscarriage, retinitis, and sight loss upon infection [1,2]. The major routes of human T. gondii infection are the ingestion of uncooked meat containing T. gondii cysts or oocyst-contaminated water [3]. It is estimated that one-third of the world’s population has been infected with T. gondii [4,5]. As of this moment, vaccination remains the most effective method for controlling infectious diseases [6]. Albeit limited to veterinary usage, is the only commercially available
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