Affiliation:
1. Department of Protozoology and The Sanford F. Kuvin Center for the Study of Infectious and Tropical Diseases, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
Abstract
Leishmania
spp. growing in culture produce an immunologically active substance called excreted factor (EF), which precipitates antibodies raised against intact cells and has been implicated as the conditioning agent for parasite infection of host macrophages. An improved method for isolation of the material is described, based on Sephadex column chromatography of growth medium which had been boiled at pH 5.0. This procedure allows the detection of differences among the EF molecules of different species, and it overcomes previous shortcomings through the monitoring of immunological activity throughout. Analysis of the products of this procedure revealed that EFs from
Leishmania tropica
and
Leishmania donovani
share a common carrier protein, identified as rabbit serum albumin, and are chemically quite similar. Growth medium from
L. tropica
boiled at acidic pH contains primarily an EF-albumin complex of 75,000 molecular weight. Treated growth medium from
L. donovani
, on the other hand, contains both the albumin complex and a smaller molecule (less than 27,000 molecular weight) that is not associated with rabbit protein. This material accounts for nearly 20% of the EF of one
L. donovani
strain, but constitutes only a minute fraction of
L. tropica
EF. Treatment of the EF-albumin complex with trichloroacetic acid separates the molecule into two major subunits, one having a molecular weight of about 61,000 (without anti-
Leishmania
activity) and the other having a molecular weight of about 18,000 (with no anti-rabbit activity). The protein-free EF of
L. tropica
differs from that released by trichloroacetic acid extraction in that it is capable of precipitating antisera of nonhomologous serotypes, whereas the albumin complex and the trichloroacetic acid-treated EF fragment are not. EFs from both species display pH-dependent affinity for certain lectins.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
43 articles.
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