Protective immunity against acute toxoplasmosis in BALB/c mice induced by a DNA vaccine encoding Toxoplasma gondii elongation factor 1-alpha.

Shuai Wang,Xiangrui Li,Zhenchao Zhang,Xiaokai Song,Xiaoni Sun,Ruofeng Yan,Javaid Ali Gadahi,Yujian Wang,Lixin Xu,Tingqi Liu,Ibrahim Adam Hassan

doi:10.1186/s12879-015-1220-5

Abstract

BackgroundToxoplasma gondii can infect almost all warm-blood animals including human beings. The high incidence and severe damage that can be caused by T. gondii infection clearly indicates the need for the development of a vaccine. T. gondii elongation factor 1-alpha (TgEF-1α) plays an important role in pathogenesis and host cell invasion for this parasite. The aim of this study was to evaluate the immune protective efficacy of a DNA vaccine encoding TgEF-1α gene against acute T. gondii infection in mice.MethodsA DNA vaccine (pVAX-EF-1α) encoding T. gondii EF-1a (TgEF-1α) gene was constructed and its immune response and protective efficacy against lethal challenge in BALB/c mice were evaluated.ResultsMice inoculated with the pVAX-EF-1α vaccine had a high level of specific anti-T. gondii antibodies and produced high levels of IFN-gamma, interleukin (IL)-4, and IL-17. The expression levels of MHC-I and MHC-II molecules as well as the percentages of both CD4+ and CD8+ T cells in mice vaccinated with pVAX-EF-1α were significantly increased (p < 0.05), compared with those in all the mice from control groups (blank control, PBS, and pVAXI). Immunization with pVAX-EF-1α significantly (p < 0.05) prolonged mouse survival time to 14.1 ± 1.7 days after challenge infection with the virulent T. gondii RH strain, compared with mice in the control groups which died within 8 days.ConclusionsDNA vaccination with pVAX-EF-1α triggered strong humoral and cellular responses and induced effective protection in mice against acute T. gondii infection, indicating that TgEF-1α is a promising vaccine candidate against acute toxoplasmosis.

Highlights

Toxoplasma gondii can infect almost all warm-blood animals including human beings
Successful construction of the eukaryotic expression plasmids The DNA vaccine pVAX-EF-1α was constructed as described in the Methods
To test that the construction was successful, an enzyme digestion was performed with BamH I and Xho I, yielding a fragment of the expected size, 1,347 pb (Fig. 1)

Summary

Introduction

Toxoplasma gondii can infect almost all warm-blood animals including human beings. The high incidence and severe damage that can be caused by T. gondii infection clearly indicates the need for the development of a vaccine. T. gondii elongation factor 1-alpha (TgEF-1α) plays an important role in pathogenesis and host cell invasion for this parasite. Toxoplasma gondii, an obligate intracellular protozoan parasite, is responsible for toxoplasmosis in a wide range of hosts including humans, mammals, birds, shellfish and marine mammals [1,2,3,4,5]. T. gondii infection is usually asymptomatic or solely causes mild symptoms but can result in severe disease, such as ocular toxoplasmosis or encephalitis in immunocompromised patients, and it causes congenital birth defects [6, 7]. The only licensed T. gondii vaccine, which is based on the attenuated-live T

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