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

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 一个新的F. Hepatica Ag最近被克隆和表征。它是F.由寄生虫在感染的早期阶段表达的肝鞘脂激活蛋白样蛋白家族，当将其注射到兔中时，诱导对攻击感染的强抗性。先前在小鼠中的免疫研究揭示了FhSAP-2诱导混合的Th 1/Th 2应答，当作为DNA疫苗递送时，该混合的Th 1/Th 2应答略微极化为Th 1。已经证明，在慢性片形吸虫病中，感染与Th 2应答相关。然而，在对感染产生天然抗性的动物中，已经观察到Th 1型应答特征性的高水平IgG 2和IFNg。因此，Th 1应答似乎是诱导抗感染所必需的。本课题组先前的研究结果提示FhSAP-2是一种片形吸虫/血吸虫交叉反应抗原。由于两种物种之间的异源免疫已经被证明，FhSAP-2可能形成针对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疫苗候选物，也可以构成双重片形吸虫/血吸虫疫苗的基础。在开始大规模疫苗接种试验之前，需要汇编更多的初步结果。我们先前证明FhSAP-2诱导针对挑战感染的显著保护。然而，在该研究中，我们未能确定这种保护是Th 1偏向还是Th 2偏向。在小鼠研究中，我们评估了用FhSAP-2免疫后的免疫应答，并显示Th 1偏向性应答可能占主导地位，但未能确定该免疫方案是否赋予任何保护。我们还证明了FhSAP-2是片形吸虫/血吸虫交叉反应性Ag。然而，简单的交叉反应性不应成为研制血吸虫病疫苗的唯一标准。目前的建议旨在实现两个具体目标。在Aim 1中，我们将表征小鼠中产生的对FhSAP-2的免疫应答，并确定这种保护是Th 1偏向还是Th 2偏向。在目的-2中，我们将确定用辐照尾蚴（血吸虫病的金标准疫苗）免疫的小鼠血清是否识别FhSAP-2以及在S. mansoni本试验项目取得的结果将有助于在短时间内提交一个RO 1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.