ACTIVITY 6 - HUMORAL/CELLULAR RESPONSE IN MICE - FHEPATICA VACCINE CANDIDATE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 最近克隆并鉴定了一种新的肝片吸虫抗原。它是肝片吸虫皂苷样蛋白家族的成员，在感染的早期阶段由寄生虫表达，当注射到兔体内时，可以诱导对攻击感染的强烈抵抗力。以前在小鼠身上的免疫研究表明，FhSAP-2诱导了混合的Th1/Th2反应，当作为DNA疫苗接种时，这种反应与Th1略有极化。已有研究表明，在慢性肝片吸虫病中，感染与Th2应答有关。然而，在对感染产生天然抵抗力的动物中，观察到了具有Th1型反应特征的高水平的IgG2和IFNG。因此，Th1反应似乎是诱导对感染的抵抗力所必需的。本课题组先前的研究结果表明，FhSAP-2是一种肝片吸虫/血吸虫交叉反应抗原。由于这两个物种之间的异源免疫已被证明，FhSAP-2有可能形成针对这两种疾病的多组分疫苗的一部分。因此，FhSAP-2已成为一种新的有希望的候选疫苗，也可能构成双片吸虫/血吸虫疫苗的基础。在启动大规模疫苗接种试验之前，需要汇编更多的初步结果。我们以前证明了FhSAP-2对挑战感染有显著的保护作用。然而，在那项研究中，我们未能确定这种保护是偏向Th1还是偏向Th2。在小鼠研究中，我们评估了FhSAP-2免疫后的免疫反应，表明Th1偏向反应可能占主导地位，但未能确定该免疫方案是否具有任何保护作用。我们还证明了FhSAP-2是一种片吸虫/血吸虫交叉反应抗原。然而，简单的交叉反应不应成为开发血吸虫病疫苗的唯一标准。目前的提议意在实现两个具体目标。在Aim1中，我们将描述小鼠对FhSAP-2产生的免疫反应，并确定这种保护是偏向Th1还是偏向Th2。在AIM-2中，我们将确定辐照尾虫(血吸虫病的黄金标准疫苗)免疫的小鼠血清是否识别FhSAP-2，以及曼氏血吸虫中是否存在同源FhSAP-2。目前试点项目将取得的成果将有助于在短时间内提交RO1项目。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A novel F. hepatica Ag was recently cloned and characterized. It is a member of the F. hepatica saposin-like protein family which is expressed by parasite at early stages of infection and when it is injected in rabbits induce a strong resistance to a challenge infection. Previous immunization studies in mice have revealed that FhSAP-2 induce a mixed Th1/Th2 response, which is slightly polarized to Th1 when is delivered as DNA vaccine. It has been demonstrated that in chronic fascioliasis the infection is associated to Th2 response. However, in animals than develop a natural resistance to infection high levels of IgG2 and IFNg characteristic of a Th1 type response have been observed. Thus, the Th1 response appears to be necessary for inducing resistance to infection. A previous result obtained from our group suggests that FhSAP-2 is a Fasciola/Schistosoma cross-reactive antigen. Because of the heterologous immunity between both species has been demonstrated it is possible that FhSAP-2 could form part of a multi-component vaccine against both diseases. Thus, FhSAP-2 has become in a novel promising vaccine candidate that could also constitute the base for a dual-Fasciola/Schistosoma vaccine. Additional preliminary results need to be compiled before to initiate large vaccination trials. We previously demonstrated that FhSAP-2 induces significant protection against a challenged infection. However, in that study we failed to determine whether this protection is Th1-biased or Th2-biased. In the mouse study we evaluated the immune response after immunization with FhSAP-2 and showed that Th1-biased response may be predominant, but failed to determine whether this immunization protocol conferred any protection. We also demonstrated that FhSAP-2 is a Fasciola/Schistosoma cross-reactive Ag. However, the simple cross-reactivity should not be the only criterion for developing a vaccine against schistosomiasis. The current proposal intends to accomplish two specific aims. In the Aim1 we will characterize the immune responses to FhSAP-2 produced in mice and we will determine if this protection is Th1-biased or Th2-biased. In the Aim-2 we will determine whether sera from mouse immunized with irradiated cercariae (the gold standard vaccine for schistosomiasis) recognize FhSAP-2 and whether a homolog FhSAP-2 exits in S. mansoni. The results to be obtained in the present pilot project will serve to submit an RO1 project in short period of time.