Lu Gang, Zhou Aihua, Meng Min, Wang Lin, Han Yali, Guo Jingjing, Zhou Huaiyu, Cong Hua, Zhao Qunli, Zhu Xing-Quan, He Shenyi
Department of Parasitology, Shandong University School of Medicine, Jinan, Shandong Province, 250012, Peoples Republic of China.
Department of Pediatrics, Provincial Hospital Affiliated to Shandong University, Shandong University School of Medicine, Jinan, Shandong Province, 250021, Peoples Republic of China.
BMC Infect Dis. 2014 Dec 20;14:3862. doi: 10.1186/s12879-014-0706-x.
Toxoplasmosis caused by the intracellular parasite Toxoplasma gondii (T. gondii) is a global epidemic parasitic disease. DNA vaccines play an important role in preventing the spread of toxoplasmosis. SAG family genes encoding particular surface proteins of T. gondii are the best candidates of DNA vaccine. As a member of SAG family genes, SAG5 gene has been proved to have better antigenic than SAG1. In addition, alpha-Galactosylceramide (α-GalCer) was used to be an adjuvant in malaria vaccine and received positive results. In this study, the effect of the DNA vaccine enhanced by α-GalCer was evaluated by immunizing BALB/c mice.
In the present study, SAG5D gene of T. gondii was cloned, sequenced, and biologically characterized. BALB/c mice were randomly divided into five groups, including three experimental groups (pEGFP-C1-SAG5D, α-GalCer and α-GalCer/pEGFP-C1-SAG5D) and two control groups (PBS and pEGFP-C1), and were immunized intramuscularly three times. The levels of IgG antibodies and cytokine productions in mouse sera were determined by enzyme-linked immunosorbent assays (ELISA). Two weeks after the last immunization, all mice were challenged intraperitoneally with 1 × 10(4) tachyzoites of T. gondii and the survival time of mice was recorded.
A significant level of increase of IgG response against the soluble tachyzoite antigens (STAg) was detected by ELISA in experimental group. It revealed relatively high level of IFN-γ production by the spleen cells. There were higher productions of interleukin-4 (IL-4) in α-GalCer treated groups compared to control groups. Challenge experiment showed a longer survival period (11 days compared with 5 days in control) in SAG5D DNA vaccinated mice was found after a lethal challenge with T. gondii RH strain.
The present study suggested that T. gondii SAG5D was a novel and positive DNA vaccine candidate against toxoplasmosis. In addition, the adjuvant (α-GalCer) enhanced the body's cellular immune response and prolonged the survival time of mice after challenge.
由细胞内寄生虫刚地弓形虫（T. gondii）引起的弓形虫病是一种全球性流行的寄生虫病。DNA疫苗在预防弓形虫病传播方面发挥着重要作用。编码刚地弓形虫特定表面蛋白的SAG家族基因是DNA疫苗的最佳候选基因。作为SAG家族基因的一员，SAG5基因已被证明比SAG1具有更好的抗原性。此外，α-半乳糖神经酰胺（α-GalCer）曾被用作疟疾疫苗的佐剂并取得了阳性结果。在本研究中，通过免疫BALB/c小鼠评估了α-GalCer增强的DNA疫苗的效果。
在本研究中，克隆、测序并对刚地弓形虫的SAG5D基因进行生物学特性分析。将BALB/c小鼠随机分为五组，包括三个实验组（pEGFP-C1-SAG5D、α-GalCer和α-GalCer/pEGFP-C1-SAG5D）和两个对照组（PBS和pEGFP-C1），并进行三次肌肉注射免疫。通过酶联免疫吸附测定（ELISA）测定小鼠血清中IgG抗体水平和细胞因子产生情况。最后一次免疫两周后，所有小鼠腹腔注射1×10⁴个刚地弓形虫速殖子，并记录小鼠的存活时间。
通过ELISA在实验组中检测到针对可溶性速殖子抗原（STAg）的IgG反应显著升高。脾脏细胞产生的IFN-γ水平相对较高。与对照组相比，α-GalCer处理组中白细胞介素-4（IL-4）的产生更高。攻毒实验显示，用刚地弓形虫RH株进行致死性攻毒后，接种SAG5D DNA疫苗的小鼠存活期更长（与对照组的5天相比为11天）。
本研究表明，刚地弓形虫SAG5D是一种新型且有效的抗弓形虫病DNA疫苗候选物。此外，佐剂（α-GalCer）增强了机体的细胞免疫反应并延长了攻毒后小鼠的存活时间。
