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PubMed1989

Theileria parva: bovine helper T cell clones specific for both infected lymphocytes and schizont membrane antigens.

Two Theileria parva-specific bovine helper T cell clones were used to identify T. parva-derived antigens expressed on the surface of schizont infected lymphoblastoid cells. Although the clones proliferated in response to both the immunizing (Muguga) and heterologous stocks of T. parva, the patterns of the responses differed, showing that the two clones recognized different antigenic epitopes. Both clones were stimulated by autologous infected cells, without an additional source of antigen-presenting cells, as well as by purified schizonts and by a subcellular membrane fraction prepared from infected lymphoblastoid cells, when antigen-presenting cells were present. The membrane fraction was shown to be enriched for schizont membranes as indicated by the presence of a schizont surface antigen detected by immunoblotting using a schizont-specific monoclonal antibody. Elimination of schizonts with the anti-theilerial drug, parvaquone, resulted in reduced antigenicity of the membrane fraction as detected by both the T cell clones and the schizont-specific monoclonal antibody. We conclude that the T. parva-infected cell surface antigens recognized by the T cell clones are of schizont membrane origin. Although the antigens have not yet been characterized biochemically, the monoclonal antibody-specific epitope appears to be distinguishable from the T cell epitopes.

Animals↗
PubMed1989

Theileria parva: reappearance of schizonts in infected lymphoblastoid cells treated with parvaquone is dependent on interleukin 2-like growth factors.

Schizont-infected cell lines derived by in vitro infection of bovine T cell clones with the Muguga isolate of Theileria parva were treated for 72 hr with the theileriacidal drug, parvaquone, at a concentration of 10 micrograms/ml. This treatment completely eliminated schizonts from the recovered cells, which failed to undergo further proliferation and died. However, treated cells cultured with either bovine T cell growth factor or human recombinant interleukin 2 remained viable, underwent proliferation, and in many instances, schizonts reappeared. When cultured in the presence of supernatant obtained from an actively growing T. parva-infected cell line, treated cells did not proliferate, but schizonts reappeared. The cells became transformed by the parasite and grew continuously in the absence of exogenous growth factor. The appearance of schizonts was preceded by the development of densely staining intracytoplasmic inclusions, visualized by light and electron microscopy. Electron-dense inclusions were shown to contain DNA. Hybridization of a T. parva-specific DNA probe to Southern blots of restriction enzyme-digested DNA prepared from parvaquone-treated cells which developed inclusions but not schizonts produced a pattern similar to that seen with DNA prepared from schizont-infected cells. We conclude that reorganization of schizonts can occur in T. parva-infected T lymphocytes cured of infection with parvaquone in the presence of interleukin 2 or growth factors produced by T. parva-infected cells. The implications of these results for the establishment of a carrier state following parvaquone therapy are discussed.

Animals↗
PubMed1984

The genome of Theileria parva: some structural properties.

The DNA of the protozoan Theileria parva, the causal agent of the bovine East Coast Fever, has been prepared at least 99% pure from the intra-erythrocytic form of the parasite. Its buoyant density was found to be 1.696 g/cm3 and its calculated G + C content was 36.7%. Fragmentation of T. parva by the restriction enzyme EcoRI provides some evidence of the presence of repetitive DNA sequences.

Animals↗
PubMed1985

Electron microscopy of the intestine and rectum in acquired immunodeficiency syndrome.

To provide a better understanding of the morphologic changes that take place in the intestine and colon in acquired immunodeficiency syndrome (AIDS), electron microscopy was performed on intestinal or colonic biopsy specimens obtained from 6 patients with AIDS and from 2 patients with AIDS-related lymphadenopathy syndrome. Cryptosporidia were attached to the plasma membrane of epithelial cells in 2 patients and were noninvasive. An invasive protozoan organism identified as Microsporidia was found in 1 patient. Evidence for epithelial cell injury was limited. Unusually prominent secretory granules in colonic epithelial cells (a morphologic counterpart of secretion) was found in 2 patients. Tubuloreticular structures were observed in 7 patients. The structures were found in endothelial cells, lymphocytes, monocytes, intraepithelial lymphocytes, and free in the capillary lumen. Tube- and ring-shaped forms were observed in 2 patients, prominent intraepithelial mast cells in 4 patients, rectal spirochetosis in 1 patient, and pseudomembranous colitis in 1 patient with intestinal and systemic shigellosis. Vesicular rosettes, retroviruses, other viruses, and Mycobacterium avium-intracellulare were not observed. These observations expand our knowledge of morphologic changes in the colonic and intestinal mucosa in patients with AIDS. Tubuloreticular structures are so prominent, in contrast to our previous electron-microscopic observations in other disease and normal states of the intestine and colon, that their finding (though clearly nonspecific) may be a clue to the diagnosis of AIDS in an otherwise equivocal situation.

Acquired Immunodeficiency Syndrome↗