Quantification of Toxoplasma gondii in the tissues of BALB/c mice after immunization with nanoliposomal excretory-secretory antigens using Real-Time PCR

Abstract

Background: Toxoplasmosis is an infectious disease caused by the intracellular parasite Toxoplasma gondii. Although almost 1/3 of the world's population are seropositive, there is no effective vaccine against toxoplasmosis. Therefore, the development of an effective vaccine for control of toxoplasmosis is one of major concerns in parasitology. The aim of this study was to evaluate the efficacy of nano-liposomal excretory-secretory antigens (NLESA) in BALB/c mice.

Materials and methods: Excretory-secretory antigens (ESA) was obtained from tachyzoites, encapsulated in the liposome and studied by scanning electron microscope. BALB/c mice were immunized with NLESA and ESA, sterile phosphate-buffered saline (PBS). Immunization was performed three times at 14-day intervals and challenged with 1 × 10⁴ tachyzoites of T. gondii RH strain four weeks later. The parasite load of mice blood, brain and spleen tissues were determined using quantitative PCR targeted at the repeated element (RE) gene.

Results: The immunization with NLESA and ESA induced a significant increase of anti-Toxoplasma IgG antibody compared with PBS group (P < 0.05). After challenge with tachyzoites, qPCR analyses showed significant reduction of parasite load in NLESA and ESA immunized mice compared with control group (P < 0.05). Also, NLESAs were more effective than ESAs and showed significantly reduced parasite load in blood (P = 0.001) and brain tissue (P = 0.01).

Discussion: The vaccination with NLESA showed more promising results comparing to ESA. Further studies are recommended in order to achieve effectiveness of the vaccine against T. gondii.

Keywords: Excretory-secretory antigens; Liposome; Parasite load; Real-time PCR; Toxoplasma gondii; Vaccine.