Chagas disease is an endemic chronic parasitosis in Latin America affecting more than 7 million people. Around 100 million people are currently at risk of acquiring the infection; however, no effective vaccine has been developed yet. Trypanosoma cruzi is the etiological agent of this parasitosis and as an intracellular protozoan it can reside within different tissues, mainly muscle cells, evading host immunity and allowing progression towards the chronic stage of the disease. Considering this intracellular parasitism triggers strong cellular immunity that, besides being necessary to limit infection, is not sufficient to eradicate the parasite from tissues, a differential immune response is required and new strategies for vaccines against Chagas disease need to be explored. In this work, we designed, cloned and expressed a chimeric molecule, named NCz-SEGN24A, comprising a parasite antigen, the N-terminal domain of the major cysteine protease of T. cruzi, cruzipain (Nt-Cz), and a non-toxic form of the staphylococcal superantigen (SAg) G, SEG, with the residue Asn24 mutated to Ala (N24A). The mutant SAg SEGN24A, retains its ability to trigger classical activation of macrophages without inducing T cell apoptosis. To evaluate, as a proof of concept, the immunogenicity and efficacy of the chimeric immunogen vs. its individual antigens, C3H mice were immunized intramuscularly with NCz-SEGN24A co-adjuvanted with CpG-ODN, or the recombinant proteins Nt-Cz plus SEGN24A with the same adjuvant. Vaccinated mice significantly produced Nt-Cz-specific IgG titers after immunization and developed higher IgG2a than IgG1 titers. Specific cell-mediated immunity was assessed by in-vivo DTH and significant responses were obtained. To assess protection, mice were challenged with trypomastigotes of T. cruzi. Both schemes reduced the parasite load throughout the acute phase, but only mice immunized with NCz-SEGN24A showed significant differences against control; moreover, these mice maintained 100% survival. These results encourage testing mutated superantigens fused to specific antigens as immune modulators against pathogens.

恰加斯病是拉丁美洲的一种地方性慢性寄生虫病，影响了超过700万人。目前大约有1亿人有感染这种病毒的风险；但是，尚未开发出有效的疫苗。克氏锥虫是寄生虫病的病原体，作为细胞内的原生动物，它可以驻留在不同的组织（主要是肌肉细胞）中，从而逃避宿主的免疫力，并可以朝疾病的慢性阶段发展。考虑到这种细胞内寄生虫会触发强大的细胞免疫力，除了限制感染所必需的免疫力之外，还不足以从组织中清除寄生虫，因此需要有不同的免疫应答，因此需要探索针对南美锥虫病疫苗的新策略。在这项工作中，我们设计，克隆并表达了一种名为NCz-SEGN24A的嵌合分子，该分子包含一个寄生虫抗原，即主要的半胱氨酸蛋白酶的N端结构域。克鲁斯，crupzipin（Nt-Cz）和无毒形式的葡萄球菌超抗原（SAg）G，SEG，其中Asn24残基突变为Ala（N24A）。突变体SAg SEGN24A保留了其触发巨噬细胞经典激活而不诱导T细胞凋亡的能力。为了评估嵌合免疫原相对于其单个抗原的免疫原性和功效，使用CzG-ODN佐剂联合NCz-SEGN24A肌肉注射C3H小鼠，或使用CpG-ODN佐剂联合重组蛋白Nt-Cz加SEGN24A相同的佐剂。接种疫苗的小鼠在免疫后显着产生Nt-Cz特异性IgG效价，并产生比IgG1效价更高的IgG2a。特定细胞介导的免疫力通过体内获得了DTH和显着的反应。为了评估保护作用，将小鼠的乳腺乳突象攻击克鲁斯。两种方案都降低了整个急性期的寄生虫负荷，但是只有用NCz-SEGN24A免疫的小鼠表现出明显的对照差异。而且，这些小鼠维持100％存活。这些结果鼓励测试与特定抗原融合的突变超抗原，作为针对病原体的免疫调节剂。