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The relationship between Kaposi's sarcoma and intestinal parasites among homosexual males in the United States.

An interesting temporal relationship exists between the emergence of the epidemic of intestinal parasites in the homosexual male population and the subsequent appearance of Kaposi's sarcoma. Existent models suggest possible links between chronic parasitosis, viral infection, and the emergence of malignant disease. Patients with AIDS-related conditions have been demonstrated to have a high rate of asymptomatic amebiasis. Possible links between intestinal parasites and the development of Kaposi's sarcoma in human immunodeficiency virus-infected patients are explored.

Acquired Immunodeficiency Syndrome↗

Advances in ulcerative colitis.

Ulcerative colitis is one of the two common chronic inflammatory bowel diseases which affect the colon of children. The disease can occur at any time during infancy and childhood and is far commoner than Crohn's disease of the colon in children less than 6 years old. The Jewish population outside of Israel is at far greater risk of developing the condition than any other ethnic group. The reason for this is unknown. The chances of a family member developing the condition is 2-3 times as great as in the general population. The etiology of the condition remains unknown; however, recent advances in the understanding of the immune mechanisms in the bowel and circulation indicate there are major immunological differences between ulcerative colitis and Crohn's disease. Intestinal B cells secrete enormously increased amounts of IgG1 and a lesser increase in IgG3 in ulcerative colitis whereas in Crohn's disease, all IgG subclasses are increased, but especially IgG2. Failure of the gut immune system to control antigen crossing the colonic mucosa may be the basis for the condition. The disease is classified as moderate to severe two thirds of children as opposed to less than one third of adults. Diagnostic testing must include 3 stool cultures negative for bacterial and viral pathogens, 3 stools negative for amebiasis, trichuriasis and other intestinal parasites and absence of clostridium difficile and its toxin in the stool. Flexible proctosigmoidoscopy and/or colonoscopy should be done in every case with biopsies. Barium enema is contraindicated in the severely ill patient. Major improvements in medical treatment being tested involve the development of nonabsorbable corticosteroid enemas and sulfapyridene-free forms of salicylazosulfapyridene for use in enema and oral form. Surgery for ulcerative colitis has made major advances with the development of the Koch pouch (internal ileostomy) and ileoproctostomy. Both procedures although associated with relatively high complication rates, are esthetically and psychologically better than standard ileostomy because in neither procedure must the patient wear an ileostomy appliance. However these advanced surgical procedures are typically not done until adolescence is reached.

Adolescent↗

Hepatic amebiasis.

Amebiasis can be considered the most aggressive disease of the human intestine, responsible in its invasive form for clinical syndromes, ranging from the classic dysentery of acute colitis to extra-intestinal disease, with emphasis on hepatic amebiasis, unsuitably named amebic liver abscess. Found worldwide, with a high incidence in India, tropical regions of Africa, Mexico and other areas of Central America, it has been frequently reported in Amazonia. The trophozoite reaches the liver through the portal system, provoking enzymatic focal necrosis of hepatocytes and multiple micro-abscesses that coalesce to develop a single lesion whose central cavity contains a homogeneous thick liquid, with typically reddish brown and yellow color similar to "anchovy paste". Right upper quadrant pain, fever and hepatomegaly are the predominant symptoms of hepatic amebiasis. Jaundice is reported in cases with multiple lesions or a very large abscess, and it affects the prognosis adversely. Besides chest radiography, ultrasonography and computerized tomography have brought remarkable contributions to the diagnosis of hepatic abscesses. The conclusive diagnosis is made however by the finding of Entamoeba histolytica trophozoites in the pus and by the detection of serum antibodies to the amoeba. During the evolution of hepatic amebiasis, in spite of the availability of highly effective drugs, some important complications may occur with regularity and are a result of local perforation with extension into the pleural and pericardium cavities, causing pulmonary abscesses and purulent pericarditis, respectively The ruptures into the abdominal cavity may lead to subphrenic abscesses and peritonitis. The treatment of hepatic amebiasis is made by medical therapy, with metronidazole as the initial drug, followed by a luminal amebicide. In patients with large abscesses, showing signs of imminent rupture, and especially those who do not respond to medical treatment, a percutaneous drainage must be performed with either ultrasound or computerized tomography guidance. Surgical drainage by laparotomy is reserved to patients with secondary infections.

Animals↗

Protection of gerbils from amebic liver abscess by immunization with a recombinant Entamoeba histolytica antigen.

Amebiasis, infection by the intestinal protozoan parasite Entamoeba histolytica, is a leading parasitic cause of death. As a step in the development of a recombinant antigen vaccine to prevent E. histolytica infection, we looked at the ability of a recombinant version of the serine-rich E. histolytica protein (SREHP) to elicit a protective immune response against invasive amebic disease. Gerbils, a standard model for amebic liver abscess, were immunized with either a recombinant SREHP/maltose-binding protein (MBP) fusion, recombinant MBP alone, or phosphate-buffered saline (PBS), all combined with complete Freund's adjuvant. In the first trial (group 1), gerbils received a primary and two booster immunizations intraperitoneally; in the second trial (group 2), gerbils were immunized by a single intradermal injection. SREHP/MBP-immunized gerbils in both groups produced antibody to native SHEHP and developed delayed-type hypersensitivity responses to recombinant SREHP. All gerbils were challenged by an intrahepatic injection with 5 x 10(4) virulent E. histolytica HM1-IMSS trophozoites. Complete protection from amebic liver abscess was seen in 64% of the SHEHP/MBP-immunized gerbils in group 1 and in 100% of the SREHP/MBP-immunized gerbils in group 2. There was no protection observed in MBP- or PBS-immunized gerbils in either group. Our results indicate that the SREHP molecule has potential as a vaccine to prevent amebic infection and demonstrate that successful vaccination of animals with recombinant E. histolytica antigen vaccines is possible.

Animals↗