Hassan M, Hegab M, Abaza B E, Nasr M E, Mowafy N M
Department of Parasitology, Faculty of Medicine, Zagazig University, Egypt.
J Egypt Soc Parasitol. 1999;29(1):119-29.
The possibility of rat re-infection with different Toxoplasma gondii stages was studied in this work. Two groups of rats were infected with either intra-peritoneal injection of 1000 trophozoites of virulent Toxoplasma strain or 1000 oocysts through oral routes. IgA, IgM and IgG were detected 15, 30, 60 and 120 days post infections. IgA and IgM appeared as early as 15 days post infection but declined afterwards. IgA antibody response was more prominent with oocyst infection and IgM was more prominent with tachyzoite infection with insignificant statistical difference. On the other hand, IgG started to increase 60 days post infection, then increased gradually till the end of the experiment (120 days). The primary orally infected rats were either re-infected orally with oocysts or intra-peritoneal trophozoites and re-examined after 15 and 120 days for the same immunological parameters. Those rats which primary infected with intra-peritoneal trophozoites were re-examined after oral infection with oocysts or injection of trophozoites intra-peritoneal. The level of IgA and IgM in one rat of group A and 2 rats of group B were significantly increased and this occurred in presence of anti-Toxoplasma IgG from the primary infection. In this study, the rats were lab-bred so, the factors affect the immune system could be under control, also strain variability was excluded as the infection was only by one strain, and as the IgG level was high, these rats were presumed to be immune from the primary infection. So, the rats which became positive after challenge most probably re-infected.
本研究探讨了大鼠再次感染不同阶段刚地弓形虫的可能性。将两组大鼠分别通过腹腔注射1000个强毒株刚地弓形虫滋养体或经口途径感染1000个卵囊。在感染后15、30、60和120天检测IgA、IgM和IgG。IgA和IgM在感染后15天最早出现，但随后下降。卵囊感染时IgA抗体反应更显著，速殖子感染时IgM更显著，差异无统计学意义。另一方面，IgG在感染后60天开始升高，然后逐渐升高直至实验结束（120天）。初次经口感染的大鼠，再分别经口感染卵囊或腹腔注射滋养体，并在15天和120天后重新检测相同的免疫参数。初次腹腔注射滋养体感染的大鼠，在经口感染卵囊或腹腔注射滋养体后重新检测。A组1只大鼠和B组2只大鼠的IgA和IgM水平显著升高，且这种情况发生在初次感染产生的抗弓形虫IgG存在的情况下。在本研究中，大鼠为实验室饲养，因此影响免疫系统的因素可控，且由于仅用一个毒株感染，排除了毒株变异性，并且由于IgG水平较高，推测这些大鼠对初次感染具有免疫力。所以，攻击后呈阳性的大鼠很可能是再次感染。
