Deveropmental biotechnological analysis of host defense mechanisms against protozoan infection

(L)基因敲除小鼠的研究利用巨噬细胞清道夫受体(SR)基因敲除小鼠对原虫感染的宿主防御机制进行了实验。由于SR已知可以结合非常广泛的配体，包括细菌病原体和介导巨噬细胞黏附，因此了解SR基因敲除小鼠对原虫感染的反应将是很有兴趣的。结果表明，SR-/-小鼠和SR-/-小鼠的寄生虫血症进程无明显差异，但SR-/-小鼠感染后16-30天的红细胞压积下降幅度小于SR/-小鼠。小球虫感染后，SR-/-小鼠的脾重量增加也比SR/小鼠小。流式细胞仪研究表明，与SR/…小鼠相比，SR-/-小鼠脾中Thy1.2和CD4T细胞的百分比保持相对较高的水平感染后的小鼠更多。这些结果表明，SR基因敲除小鼠可能成为分析原虫感染的有用模型，特别是在恢复过程中，尽管它似乎不直接参与对微小球虫感染的防御机制。还进行了使用其他类型的敲除小鼠的研究，如干扰素-γ和诱导型一氧化氮合酶。(2)制备携带弓形虫主要表面蛋白原虫基因SAG-I(P30)的转基因小鼠，被认为是宿主细胞入侵过程中的重要配体。如果这种蛋白质由宿主细胞产生并干扰寄生虫的蛋白质，那么宿主就会对寄生虫的入侵产生抵抗力，或者，由于缺乏对P30抗原的免疫反应，它可能会变得更容易受到感染。为了获得携带P30基因的转基因小鼠，将一段3.3kb的DNA片段显微注射到C57BL/6J、BALB/c或F1(C57BL/6J x C3H/He)小鼠的单细胞胚胎的原核中，该片段含有P30与CAG启动子融合的DNA片段。将胚胎移植到假孕ICR小鼠的输卵管中，在第一系列近交系实验中，从159只注射的卵子中获得了两只P30阳性的小鼠(雄性C57BL/6J和雌性BALB/c)。此外，我们还利用F1(C57BL/6J x C3H/He)胚胎获得了几只表达该基因产物并将其传递给下一代的P30小鼠。据我们所知，这是第一只携带弓形虫原生动物基因的转基因小鼠。较少

(l)Studies on gene knock-out miceExperiments on the host defense mechanisms against protozoan infection were performed using a macrophage scavenger receptor (SR) knock-out mice. As the SR is known to bind an extraordinary wide range of ligands including bacterial pathogens and mediate macrophage adhesion, it would be of interest to know the response of SR knock-out mice against protozoan infection. After intraperitoneal inoculation with Babesia microti, parasitemia was monitored daily by counting parasitized erythrocytes.It was found that the course of parasitemia was not different between SR-/- and SR+/+ mice but the decrease in packed cell volume at 16-30 days after infection was less obvious in SR-/- than in SR+/+ mice. Increase in spleen weight after B.microti infection was also smaller in SR-/- than in SR+/+ mice. Flow cytometric studies revealed that the percentages of Thy 1.2+ as well as CD4+ T cells in spleen remained relatively higher in SR-/- mice as compared to those in SR+/ … More + mice after infection. These results suggest that the SR knock-out mouse may become a useful model for the analysis of protozoan infection, especially with regard to the recovery processes, although it seems not to be directly involved in the defense mechanisms against B.microti infection.Studies using other types of knock-out mice, such as IFN gamma and iNOS, were also conducted.(2) Production of transgenic mice carrying protozoan geneSAG-i (p30), the major surface protein of Toxoplasma gondii, is considered as an important ligand in the process of host cell invasion. If this protein is produced by host cells and interfere with that of parasites, then the host will become resistant to parasite invasion, Or, it may become more susceptible to infection due to the lack of immune response against p30 antigen. To generate transgenic mice carrying p30 gene, a 3.3kb DNA fragments, containing p30 cDNA fused with CAG promoter, that has been shown to direct a ubiquitous expression of a reporter gene in transgenic mice, were microinjected into one of the pronuclei of one-cell embryos of C57BL/6J, BALB/c or F1 (C57BL/6J x C3H/He) mice. The embryos were transferred to the oviducts of pseudopregnant ICR mice, In the first series of experiment using inbred strains, two p30-positive founders (male C57BL/6J and female BALB/c) were obtained among 159 mice that developed from the injected eggs. Furthermore, we have obtained several P30-founder mice expressing the gene product and transmitting the gene to the next generation, by using F1 (C57BL/6J x C3H/He) embryos. As far as we are aware, this is the first transgenic mice bearing a protozoan gene derived from T.gondii. Less