Kelsall B L, Ravdin J I
Division of Infectious Diseases, University of Virginia Medical Center, Charlottesville.
J Infect Dis. 1993 Nov;168(5):1319-22. doi: 10.1093/infdis/168.5.1319.
To determine whether the virulent enteric pathogen Entamoeba histolytica degrades human IgA molecules, serum and secretory IgA was exposed to viable axenic trophozoites (strain HM1:IMSS), a parasite sonicate, and medium conditioned by incubation with live trophozoites. IgA was completely degraded under all conditions, proteinase activity was maximal at a neutral pH, and there was a four- to eightfold enrichment of amebic IgA proteolytic activity in a soluble fraction of amebic sonicate. Degradation of serum IgA by amebic sonicate was completely inhibited by the cysteine proteinase inhibitors trans-epoxysuccinyl-L-leucyl-amino(4-guanidino)butane (E-64, 100 microM) and benzyloxycarbonyl-phenyl-alanyl-alanyl-fluoromethyl (Z-Phe-Ala-CH2F, 12.5 microM). Secretion of degradative activity, the optimal pH, and the inhibition by E-64 and Z-Phe-Ala-CH2F indicates that cysteine proteinase activity is predominantly responsible for the degradation of human IgA by E. histolytica.
为了确定致病性肠道病原体溶组织内阿米巴是否会降解人IgA分子，将血清IgA和分泌型IgA分别暴露于无菌培养的活滋养体（HM1:IMSS株）、寄生虫超声破碎物以及与活滋养体共同孵育的培养基条件下。在所有条件下，IgA均被完全降解，蛋白酶活性在中性pH值时达到最高，并且在阿米巴超声破碎物的可溶部分中，阿米巴IgA蛋白水解活性富集了4至8倍。半胱氨酸蛋白酶抑制剂反式环氧琥珀酰-L-亮氨酰-氨基(4-胍基)丁烷（E-64，100微摩尔）和苄氧羰基-苯丙氨酰-丙氨酰-氟甲基酮（Z-Phe-Ala-CH2F，12.5微摩尔）可完全抑制阿米巴超声破碎物对血清IgA的降解。降解活性的分泌、最适pH值以及E-64和Z-Phe-Ala-CH2F的抑制作用表明，半胱氨酸蛋白酶活性是溶组织内阿米巴降解人IgA的主要原因。
