Most studies evaluating vaccine candidates against visceral leishmaniasis (VL) have used parasite promastigote-expressed antigens; however, Leishmania proteins expressed in the amastigote forms should be considered, since few hours after infection this stage comes into contact with the host immune system and is responsible for the development of the disease. In this context, in the present study, a Leishmania amastigote-specific hypothetical protein, called LiHyJ, was evaluated as a recombinant protein plus saponin as an adjuvant or DNA vaccine to protect against VL. The vaccine effect was evaluated by means of the evaluation of immunological and parasitological analyses performed in BALB/c mice against Leishmania infantum infection. Results showed that rLiHyJ/saponin and DNA LiHyJ induced significantly higher levels of anti-protein and anti-parasite IFN-γ, IL-12, GM-CSF, and IgG2a isotype antibodies, which were associated with a low presence of IL-4 and IL-10. DNA vaccination induced higher IFN-γ production, mainly by CD8⁺ T cells, while rLiHyJ/saponin stimulated the production of this cytokine, mainly by CD4⁺ T cells. The parasite load evaluated in distinct organs showed that both immunization schedules significantly reduced organic parasitism, when compared to the controls. Similar results were found in the immunological and parasitological assays when using the recombinant protein or DNA, although the vaccination with rLiHyJ plus saponin induced a slightly higher Th1 response and lower parasite load, when compared to the use of DNA plasmid. The protein also proved to be immunogenic when peripheral blood mononuclear cells of treated VL patients and healthy subjects were in vitro stimulated, since higher IFN-γ and lower IL-4 and IL-10 levels were found in the culture supernatants. In conclusion, LiHyJ should be considered in future studies as a vaccine candidate to protect against VL.

大多数评估候选疫苗抗内脏利什曼病（VL）的研究都使用了寄生虫前鞭毛体表达的抗原。然而，应考虑以鞭毛体形式表达的利什曼原虫蛋白，因为感染后数小时该阶段与宿主免疫系统接触并导致疾病的发展。在这种情况下，在本研究中，利什曼原虫鞭毛体特异性假说蛋白被称为LiHyJ，被评估为重组蛋白加皂苷作为佐剂或DNA疫苗来预防VL。通过评估BALB / c小鼠对婴儿利什曼原虫的免疫和寄生虫学分析来评估疫苗的作用感染。结果显示，rLiHyJ /皂苷和DNA LiHyJ诱导显着较高水平的抗蛋白和抗寄生虫IFN-γ，IL-12，GM-CSF和IgG2a同型抗体，与IL-4和IL-4含量低相关IL-10。DNA疫苗接种主要通过CD8 ⁺ T细胞诱导更高的IFN-γ产生，而rLiHyJ /皂苷则主要通过CD4 ⁺刺激这种细胞因子的产生。T细胞。在不同器官中评估的寄生虫负荷显示，与对照相比，两种免疫方案均显着减少了有机寄生虫。使用重组蛋白或DNA时，在免疫学和寄生虫学测定中发现了相似的结果，尽管与使用DNA质粒相比，使用rLiHyJ加上皂苷的疫苗接种诱导了更高的Th1反应和更低的寄生虫负荷。当在体外刺激治疗的VL患者和健康受试者的外周血单个核细胞时，该蛋白也被证明具有免疫原性，因为在培养物上清液中发现较高的IFN-γ和较低的IL-4和IL-10水平。总之，在未来的研究中应将LiHyJ视为预防VL的候选疫苗。