The Journal of Immunology, Vol 155, Issue 1 266-274, Copyright © 1995 by American Association of Immunologists

ARTICLES

The extracellular neutral cysteine proteinase of Entamoeba histolytica degrades anaphylatoxins C3a and C5a

SL Reed, JA Ember, DS Herdman, RG DiScipio, TE Hugli and I Gigli
Department of Medicine, University of California, San Diego Medical Center 92103, USA.

We have shown previously that the extracellular cysteine proteinase of Entamoeba histolytica trophozoites activates the alternative pathway of complement by specifically cleaving C3. This unique mechanism of complement activation leads to passive lysis of nonpathogenic, but not of pathogenic strains. In an attempt to investigate the relationship between the cleavage of complement components C3 and C5 and the pathogenesis of amebiasis, we investigated the production of the anaphylatoxins C3a and C5a, which have diverse effects on the host immune response. The concentration of proteinase required to cleave purified C5 was at least 5 to 10 times that needed for C3 cleavage, but these levels are easily obtainable as demonstrated by cleavage of 125I- labeled C5 during incubation with purified trophozoites. When the C3a- like cleavage fragments were purified by gel filtration, they were found to be extensively degraded during a 1-h incubation of C3 with the proteinase. Subsequent evaluations of the C3a- and C5a-like cleavage products generated earlier in the reaction using immunoblots and cellulose acetate electrophoresis revealed rapid degradation, even during incubation periods as short as 5 min. Because C-terminal fragments as small as 20 amino acid residues can mimic the biologic functions of C3a or C5a, we tested cleavage products for activity. In sensitive bioassays, including guinea pig platelet aggregation for C3a activity and chemotaxis for C5a activity, we demonstrated that proteolysis renders these molecules inactive. These studies suggest that the extracellular cysteine proteinase of E. histolytica, which is capable of activating the complement system, may also provide a mechanism to circumvent normal host immunity by inactivating the proinflammatory factors C3a and C5a.

This article has been cited by other articles:

				H. Nitta, T. Imamura, Y. Wada, A. Irie, H. Kobayashi, K. Okamoto, and H. Baba Production of C5a by ASP, a Serine Protease Released from Aeromonas sobria J. Immunol., September 1, 2008; 181(5): 3602 - 3608. [Abstract] [Full Text] [PDF]

				G. C. McGugan Jr., M. B. Joshi, and D. M. Dwyer Identification and Biochemical Characterization of Unique Secretory Nucleases of the Human Enteric Pathogen, Entamoeba histolytica J. Biol. Chem., October 26, 2007; 282(43): 31789 - 31802. [Abstract] [Full Text] [PDF]

				S. G. Melendez-Lopez, S. Herdman, K. Hirata, M.-H. Choi, Y. Choe, C. Craik, C. R. Caffrey, E. Hansell, B. Chavez-Munguia, Y. T. Chen, et al. Use of Recombinant Entamoeba histolytica Cysteine Proteinase 1 To Identify a Potent Inhibitor of Amebic Invasion in a Human Colonic Model Eukaryot. Cell, July 1, 2007; 6(7): 1130 - 1136. [Abstract] [Full Text] [PDF]

				R. Haque, C. D. Huston, M. Hughes, E. Houpt, and W. A. Petri Jr. Amebiasis N. Engl. J. Med., April 17, 2003; 348(16): 1565 - 1573. [Full Text] [PDF]

				X. Que, S.-H. Kim, M. Sajid, L. Eckmann, C. A. Dinarello, J. H. McKerrow, and S. L. Reed A Surface Amebic Cysteine Proteinase Inactivates Interleukin-18 Infect. Immun., March 1, 2003; 71(3): 1274 - 1280. [Abstract] [Full Text] [PDF]

				S. L. Stanley Jr. and S. L. Reed Microbes and Microbial Toxins: Paradigms for Microbial-Mucosal Interactions: VI. Entamoeba histolytica: parasite-host interactions Am J Physiol Gastrointest Liver Physiol, June 1, 2001; 280(6): G1049 - G1054. [Abstract] [Full Text] [PDF]

				X. Que and S. L. Reed Cysteine Proteinases and the Pathogenesis of Amebiasis Clin. Microbiol. Rev., April 1, 2000; 13(2): 196 - 206. [Abstract] [Full Text] [PDF]

				M. Espinosa-Cantellano and A. Martinez-Palomo Pathogenesis of Intestinal Amebiasis: From Molecules to Disease Clin. Microbiol. Rev., April 1, 2000; 13(2): 318 - 331. [Abstract] [Full Text] [PDF]

				P. Gasque, S. K. Singhrao, J. W. Neal, P. Wang, S. Sayah, M. Fontaine, and B. P. Morgan The Receptor for Complement Anaphylatoxin C3a Is Expressed by Myeloid Cells and Nonmyeloid Cells in Inflamed Human Central Nervous System: Analysis in Multiple Sclerosis and Bacterial Meningitis J. Immunol., April 1, 1998; 160(7): 3543 - 3554. [Abstract] [Full Text] [PDF]