Nutritional and immunological factors in the control of infections with Trypanosoma lewisi

This paper is an attempt to view the infection with T. lewisi as a balance of host nutritional factors to which the parasite is attuned and the host defensive system, which recognizes and attempts to subdue him. The host nutritional factors seem to bring parasite numbers to a high level operating through many log units of growth. The host defense system has far narrower limits and can be overwhelmed by much smaller modifications. An essential feature of the host defense is an exceedingly active lymphomyeloid interaction, so far visualized in the spleen. Here the very proximity of plasma cells and reticular cells affords great opportunities for direct transfer of immunoglobulins without evidence of these molecules as agglutinating antibodies in the blood. This mechanism of active trypanosome venting foci with selectivity for younger forms seems more satisfactory than proposing a unique and unusual antibody system.     

Pathological developments mediated by cyclophosphamide in rats infected with Trypanosoma lewisi

Trypanosoma lewisi is an obligatory, flagellated parasite of the rat. Despite the fact that naturally the rats overcome the disease, a lethal infection can be induced by the administration of an immunosuppressive agent, i.e. cyclophosphamide (Cy). In the Cy treated infected rats (CyI) the severity of the trypanosome infection was demonstrated in the internal organs, in the following order: lungs > liver > heart > spleen > kidney. The parasites were not detected in the brain. The accumulation of the parasites in the lungs led to the development of hemorrhagic inflammatory foci. The rupture of blood vessels was accompanied by lymphocyte infiltrations into the damaged tissues and multiple foci of edema around the blood vessels. In most cases the lungs were dark brown in color due to intra-alveolar hemorrhages. The spleen of the CyI rats showed general deformation of the tissue's architecture, migration of macrophages and cell depletion due to the Cy action. The liver showed inflammatory hemorrhagic foci associated with massive destruction of the parenchyma. In spite of the heavy parasitemia (> 50%) developed in the CyI rats the brain remained free of parasites, which might explain the non-virulent character of this parasite compared to the African trypanosomes.     

Anemia, splenomegaly, and glomerulonephritis associated with autoantibody in Trypanosoma lewisi infections.

Anemia with splenomegaly and signs of glomerulonephritis were found associated with the acute and post-acute phase of Trypanosoma lewisi infections of laboratory rats. The onset of the anemia was associated with the peak of parasitemia and the development of cold-active hemagglutinin (HA) for trypsinized rat erythrocytes. It persisted with gradual recovery for as long as the trypanosomes and HA were detected in the blood. Signs of glomerulonephritis consisted of hypercellularity of the glomerular tuft, swelling of vascular endothelium and tubular epithelium, thickening of Bowman's membrane and tubular basement membrane, and abnormal numbers of hyaline casts in the distal convoluted tubules. Residual damage to the kidneys was not evaluated.     

The role of the macrophage in immunity to Trypanosoma lewisi infections in the rat.

The data show that in the presence of specific antibody, glass-adherent peritoneal exudate cells from the rat are able to kill Trypanosoma lewisi. These cells have the typical appearance of macrophages. Using light and electron microscopy it has been found that this large parasite is killed following ingestion by these cells.     

Bent helical structure in Trypanosoma lewisi minicircles

By gel retardation assay and computational analysis we demonstrated a bent region in Trypanosoma lewisi, localized in two different classes of minicircles. We showed that in each minicircle this bent region is unique, adjacent to one of two highly conserved regions and characterized by adenine stretches. The same properties are conserved in the majority of minicircles from Trypanosomes tested so far. Therefore, we suggest that the genetic information could be located in a definite structure of minicircle DNA molecules rather than in the nucleotide sequence.     

Trypanosoma lewisi: pyruvate and transketolase activity in normal and thiamine deficient rats

Transketolase and pyruvate changes were studied in rats infected with Trypanosoma lewisi and fed complete, thiamine-deficient and pair-fed control diets. Regardless of the dietary group, marked increases in pyruvate levels were observed in the infected animals. There were no significant differences in erythrocyte transketolase activity of rats given a full complement diet. Significant decreases, however, were observed in the transketolase activity of pair-fed and thiamine deficient rats. The greater decreases occurred in the infected animals.     

PCR identification of Trypanosoma lewisi,a common parasite of laboratory rats

Trypanosoma (Herpetosoma) lewisi is a trypanosome of the sub-genus Herpetosoma (Stercoraria section), parasite of rats (Rattus rattus and Rattus norvegicus) transmitted by fleas. T. lewisi has a stringent species specificity and cannot grow in other rodents such as mice. Rats are infected principally by oral route, through contamination by flea faeces or ingestion of fleas. Trypanosoma lewisi infections in rat colonies can interfere with research protocols and fleas of wild rats are often the source of such infections. Currently, diagnosis of T. lewisi in rats is performed by microscopic observation of stained blood smears. In the course of a research project at CIRDES, a T. lewisi infection was detected in the rat colony. In this study we evaluated PCR primer sets for their ability to diagnose multiple species of trypanosomes with a single amplification. We show that the use of ITS1 sequence of ribosomal DNA provides an efficient and sensitive assay for detection and identification of T. lewisi infection in rats and recommend the use of this assay for monitoring of T. lewisi infections in rat colonies.     

Histones from Trypanosoma lewisi nuclei]

A preparation of total histones has been isolated for the first time from the purified fractions of T. lewisi cell nuclei and characterized in terms of its chemical composition and RNA-polymerase activity. A special attention during the isolation procedure was given to the repression of proteolytic degradation of the histones. The amount of protein in the chromatin is equivalent to that of DNA. The amino acid composition and heterogeneity of the protein during polyacrylamide gel electrophoresis in an acid system and in the presence of sodium dodecyl sulfate are typical for histones. Using two-dimensional electrophoresis, differential staining of electrophoregrams and ion-exchange chromatography on CM-cellulose the total preparation has been found to be made up of five fractions: two -- arginine-rich (one of them identical to histone H4, the other being similar to histone H3 from calf thymus); two -- moderately lysine-rich fractions, slightly differing in their properties from histones H2A and H2B from calf thymus, and one specific fraction with mol. weight of 16 000 and an extremely high positive charge. The above methods in combination with specific extraction have been used to demonstrate the absence of a typical lysine histone in the preparation, which is correlated with the absence of typical methaphase chromosomes during mitosis in T. lewisi.