ABSTRACT
While conventional pathogenic protists have been extensively studied, there is an underappreciated constitutive protist microbiota that is an integral part of the vertebrate microbiome. The impact of these species on the host and their potential contributions to mucosal immune homeostasis remain poorly studied. Here, we show that the protozoan Tritrichomonas musculis activates the host epithelial inflammasome to induce IL-18 release. Epithelial-derived IL-18 promotes dendritic cell-driven Th1 and Th17 immunity and confers dramatic protection from mucosal bacterial infections. Along with its role as a "protistic" antibiotic, colonization with T. musculis exacerbates the development of T-cell-driven colitis and sporadic colorectal tumors. Our findings demonstrate a novel mutualistic host-protozoan interaction that increases mucosal host defenses at the cost of an increased risk of inflammatory disease.
Subject(s)
Colitis/immunology , Colitis/parasitology , Host-Parasite Interactions , Inflammasomes/immunology , Intestinal Mucosa/parasitology , Microbiota/immunology , Trichomonas Infections/immunology , Trichomonas/immunology , Animals , Colitis/microbiology , Dientamoeba/immunology , Immunity, Mucosal , Interleukin-18/immunology , Intestinal Mucosa/immunology , Intestinal Mucosa/microbiology , Mice , Mice, Inbred C57BL , Salmonella Infections/immunology , Salmonella typhimurium/immunology , Symbiosis , Th1 Cells/immunology , Th17 Cells/immunologyABSTRACT
We report the generation of monoclonal antibodies against a recombinant 170-kDa subunit of the Gal or GalNAc lectin of Entamoeba histolytica that specifically recognize E. histolytica but not Entamoeba dispar in preserved stool samples. These antibodies do not cross-react with other bowel protozoa, including Entamoeba coli, Giardia lamblia, and Dientamoeba fragilis.
Subject(s)
Antibodies, Monoclonal , Entamoeba histolytica/isolation & purification , Entamoebiasis/diagnosis , Animals , Antibody Specificity , Antigens, Protozoan/immunology , Cross Reactions , Dientamoeba/immunology , Entamoeba/immunology , Entamoeba histolytica/classification , Entamoeba histolytica/immunology , Feces/parasitology , Giardia lamblia/immunology , Recombinant Proteins/immunology , Sensitivity and SpecificityABSTRACT
Dientamoeba fragilis, a common intestinal protozoan parasite in Canada, has been associated with diarrhoea and abdominal pain in some patients. Seroprevalence of this organism has not been reported previously. In the present study sera from three symptomatic patients, 12 age- and sex-matched controls, and 189 randomly selected healthy individuals (age 6 months to 19 years) were tested for antibodies against Dientamoeba fragilis by an indirect immunofluorescence (IIF) assay. All three symptomatic patients infected with Dientamoeba fragilis had positive IIF titres of 80, and all 12 matched controls had positive titres ranging 20 to 160 (geometric mean titre 48). Of the 189 healthy children, 172 (91%) were positive at a serum dilution of 1:10 or higher. The specificity of the IIF assay was reinforced by immunoblotting 20 representative serum samples against Dientamoeba fragilis. In all 17 IIF-positive serum samples, a 39 kDa protein band of Dientamoeba fragilis was identified, the same band recognized by a mouse monoclonal antibody raised in our laboratory. Findings over a five-year period indicate that Dientamoeba fra-gilis was the most common protozoan, followed closely by Giardia lamblia and more distantly by Cryptosporidium parvum. The high seropositivity of 91% for Dientamoeba fragilis compares reasonably well with serologic data obtained by IIF and reported previously for Giardia lamblia (85.6%) and Cryptosporidium parvum (86%).
Subject(s)
Antibodies, Protozoan/analysis , Antigens, Protozoan/isolation & purification , Dientamoeba/immunology , Dientamoebiasis/epidemiology , Dientamoebiasis/immunology , Adolescent , Adult , Animals , Antibodies, Monoclonal/immunology , Canada/epidemiology , Child , Child, Preschool , Cryptosporidiosis/diagnosis , Cryptosporidiosis/epidemiology , Cryptosporidiosis/immunology , Cryptosporidium parvum/immunology , Dientamoebiasis/diagnosis , Electrophoresis, Polyacrylamide Gel , Female , Fluorescent Antibody Technique, Indirect , Giardia lamblia/immunology , Giardiasis/diagnosis , Giardiasis/epidemiology , Giardiasis/immunology , Humans , Immunoblotting , Infant , Male , Prevalence , Sensitivity and Specificity , Seroepidemiologic StudiesABSTRACT
An indirect fluorescent-antibody (IFA) assay was carried out to examine for the presence of Dientamoeba fragilis trophozoites in preserved fecal specimens. Antiserum to D. fragilis trophozoites was raised in a rabbit with a dixenic culture of D. fragilis (ATCC 30948) from the American Type Culture Collection. After absorption with Klebsiella pneumoniae and Bacteroides vulgatus, the immune rabbit serum was used for examination by the IFA assay. A total of 155 clinical samples were tested; 42 with no parasites, 9 with D. fragilis, and 104 with other parasites. The IFA assay identified seven D. fragilis organisms. Two specimens with doubtful IFA assay readings showed very scanty amounts of D. fragilis trophozoites on stained smears. There were no false-positive IFA assay readings. The IFA assay appeared to be a promising method because of its speed in screening. The specificity of the IFA assay indicates that other diagnostic tests such as an enzyme-linked immunosorbent assay could be developed to identify D. fragilis antigens in fecal specimens.
