Miller, H. W. | bioRxiv Science

bioRxiv2021

Entamoeba histolytica develops resistance to complement deposition and lysis after acquisition of human complement regulatory proteins through trogocytosis

Entamoeba histolytica is the cause of amoebiasis. The trophozoite (amoeba) form of this parasite is capable of invading the intestine, and can disseminate through the bloodstream to other organs. The mechanisms that allow amoebae to evade complement deposition during dissemination have not been well characterized. We previously discovered a novel complement-evasion mechanism employed by E. histolytica. E. histolytica ingests small bites of living human cells in a process termed trogocytosis. We demonstrated that amoebae were protected from lysis by human serum following trogocytosis of human cells, and that amoebae acquired and displayed human membrane proteins from the cells they ingested. Here, we aimed to define how amoebae are protected from complement lysis after performing trogocytosis. We found that amoebae were protected from complement lysis after ingestion of both human Jurkat T cells and red blood cells, and that the level of protection correlated with the amount of material ingested. Trogocytosis of human cells led to a reduction in deposition of C3b on the surface of amoebae. We asked whether display of human complement regulators is involved in amoebic protection, and found that CD59 was displayed by amoebae after trogocytosis. Deletion of a single complement regulatory protein, CD59 or CD46, from Jurkat cells was not sufficient to alter amoebic protection from lysis, suggesting that multiple, redundant complement regulators mediate amoebic protection. However, exogeneous expression of CD46 or CD55 in amoebae was sufficient to confer protection from lysis. These studies shed light on a novel strategy for immune evasion by a pathogen. IMPORTANCEEntamoeba histolytica is the cause of amoebiasis, a diarrheal disease of global importance. While infection is often asymptomatic, the trophozoite (amoeba) form of this parasite is capable of invading and ulcerating the intestine, and can disseminate through the bloodstream to other organs. Understanding how E. histolytica evades the complement system during dissemination is of great interest. Here we demonstrate for the first time that amoebae that have performed trogocytosis (nibbling of human cells) resist deposition of the complement protein C3b. Amoebae that have performed trogocytosis display the complement regulatory protein CD59. Overall, our studies suggest that acquisition and display of multiple, redundant complement regulators is involved in amoebic protection from complement lysis. These findings shed light on a novel strategy for immune evasion by a pathogen. Since other parasites use trogocytosis for cell killing, our findings may apply to the pathogenesis of other infections.

microbiology↗

bioRxiv2018

Trogocytosis by Entamoeba histolytica mediates acquisition and display of human cell membrane proteins and evasion of lysis by human serum

Entamoeba histolytica is the protozoan parasite responsible for amoebiasis. We previously showed that E. histolytica kills human cells through a mechanism that we termed trogocytosis (trogo-: nibble), due to its resemblance to trogocytosis in other organisms. In parasites, trogocytosis is used to kill host cells. In multicellular organisms, trogocytosis is used for cell-cell interactions in the immune system, in the central nervous system, and during development. Thus, nibbling is an emerging theme in cell-cell interactions both within and between species, and it is relevant to host-pathogen interactions in many different contexts. When trogocytosis occurs between mammalian immune cells, cell membrane proteins from the nibbled cell can be acquired and displayed by the recipient cell. In this study, we tested the hypothesis that through trogocytosis of human cells, amoebae acquire and display human cell membrane proteins. Here we demonstrate for the first time that through trogocytosis, E. histolytica acquires and displays human cell membrane proteins and that this leads to protection from lysis by human serum. Protection from human serum only occurs after amoebae have undergone trogocytosis of live cells, but not phagocytosis of dead cells. Likewise, mutant amoebae that exhibit a phagocytosis defect, but are unaltered in their capacity to perform trogocytosis, are nevertheless protected from human serum. Our studies are the first to demonstrate that amoebae can display human cell membrane proteins and suggest that acquisition and display of membrane proteins is a general feature of trogocytosis that is not restricted to trogocytosis between mammalian immune cells. These studies have major implications for interactions between E. histolytica and the immune system and also reveal a novel strategy for immune evasion by a pathogen. Since other microbial eukaryotes use trogocytosis for cell killing, our findings may apply to the pathogenesis of other infections.\n\nAuthor SummaryEntamoeba histolytica is an intestinal parasite that causes amoebiasis, a potentially fatal diarrheal disease. Abscesses in organs outside of the intestine, such as the liver, can occur when amoebae are able to breach the intestinal wall and travel through the blood stream to other areas of the body. We previously showed that E. histolytica kills human cells by taking \"bites\" of human cell material in a process that we named trogocytosis (trogo-: nibble). Mammalian immune cells use trogocytosis to acquire proteins from other cells which impacts cell-cell communication. Here we tested the hypothesis that trogocytosis allows E. histolytica to acquire and display proteins from human cells allowing amoebae to survive in the blood stream. We demonstrate for the first time that through trogocytosis, E. histolytica acquires and displays human cell membrane proteins. We also demonstrate that trogocytosis of human cells allows amoebae to survive in human serum. These studies reveal a novel strategy for immune evasion by a pathogen and may apply to the pathogenesis of other infections.

microbiology↗