ABSTRACT
A novel fecal antigen detection assay for fresh and frozen human samples that detects but does not differentiate Giardia spp, Cryptosporidium spp, and Entamoeba histolytica, the Tri-Combo parasite screen, was compared to three established enzyme-linked immunosorbent assays (ELISAs) at three international sites. It exhibited 97.9% sensitivity and 97.0% specificity, with positive and negative predictive values of 93.4% and 99.1%, respectively. The Tri-Combo test proved a reliable means to limit the use of individual parasite ELISAs to positive samples.
Subject(s)
Antigens, Protozoan/analysis , Clinical Laboratory Techniques/methods , Cryptosporidium/isolation & purification , Entamoeba histolytica/isolation & purification , Feces/parasitology , Giardia/isolation & purification , Parasitology/methods , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Enzyme-Linked Immunosorbent Assay/methods , Female , Humans , Infant , Male , Middle Aged , Sensitivity and Specificity , Young AdultABSTRACT
The single-celled parasite, Entamoeba histolytica, is an enteric pathogen that ingests bacteria and host cells. Inhibition of phagocytosis renders the parasite avirulent. The ligand/receptor interactions that allow E. histolytica to phagocytose are not well understood. We hypothesised that E. histolytica trophozoites might accomplish ingestion through the utilisation of a scavenger receptor for cholesterol. Here we show that acetylated low density lipoprotein cholesterol was phagocytosed by amoebae via receptor mediated mechanisms. Acetylated low density lipoprotein cholesterol competitively inhibited by 31 ± 1.3% (P < 0.005) the ingestion of Escherichia coli, but not erythrocytes and Jurkat T lymphocytes, suggesting a partially redundant phagocytic pathway for E. coli and cholesterol. Inducible expression ofa signalling-dead dominant-negative version of E. histolytica transmembrane kinase 39 inhibited ingestion of E. coli by 55 ± 3% (P < 0.005) but not LDL particles. We concluded that ingestion of E. coli was regulated by TMK39 and partially shared the acetylated low density lipoprotein cholesterol uptake pathway.
Subject(s)
Cholesterol, LDL/metabolism , Entamoeba histolytica/enzymology , Entamoeba histolytica/physiology , Escherichia coli/isolation & purification , Phagocytosis , Phosphotransferases/metabolism , Protein Transport , Entamoeba histolytica/metabolism , Entamoeba histolytica/microbiology , Erythrocytes/metabolism , Erythrocytes/microbiology , Humans , Jurkat Cells/metabolism , Jurkat Cells/microbiologyABSTRACT
The unicellular parasite Entamoeba histolytica, the causative agent of the human disease amebiasis, has traditionally been distinguished from its nonpathogenic cousin Entamoeba dispar by its propensity for the ingestion of erythrocytes. This classic feature, along with the parasite's ability to cause extensive host cell death, are critical mechanisms of pathogenesis during human infection. Recent advances have led to a greater understanding of the molecular components that allow E. histolytica to kill and phagocytose extracellular targets during human infection and include detailed studies of the role of the parasite's cysteine proteinases and other effectors of cytotoxicity, as well as the mechanisms of ligand recognition, signaling and intracellular trafficking during phagocytosis.