Changes in Antigenicity of Trypanosoma lewisi During the Course of Infection in Rats*

SYNOPSIS. In rats infected with T. lewisi, 2 morphologically distinct forms of the trypanosome occur. By means of the immunodiffusion technic several antigenic differences between the 2 forms were observed. The time course in the antigenic and morphologic changes is somewhat different. The antigenic change from young to adult forms is gradual. It starts 12 days after infection and is complete in 14 days, 3 to 5 days after the morphologic appearance of the trypanosomes is that of adult forms. In addition, there appear to be 2 separate stages of young forms when they are analyzed for antigenic composition.     

Infection of white rat peritoneal macrophages with Toxoplasma gondii, (Coccidia: Sarcocystidae) after Trypanosoma lewisi (Kinetoplastida: Trypanosomatidae) infection

Peritoneal macrophages from Wistar rats, inoculated and non-inoculated with 10(6) T. lewisi trypomastigotes, were cultured and infected with 10(6) T. gondii tachyzoites. Multiplication rates of this parasite were studied after 1, 24 and 48 h of infection but there were not significant differences between the number of parasites found inside of macrophages coming, either from T. lewisi infected or non infected rats. On the other hand, in vivo studies of Toxoplasma multiplication inside peritoneal macrophages, showed that there is an increase of parasite number in cells from T. lewisi infected rats, as compared with those macrophages from non infected rats. This effect was statistically significant and was more evident after four days of infection. Therefore, it has been demonstrated that in vivo, but not in vitro T. lewisi infections, causes an important decrease of the natural resistance to T. gondii of the white rats, which is manifested by the major invasion and multiplication of the parasite inside of peritoneal macrophages.     

Effect of Holothurin on Trypanosoma lewisi Infections in Rats

SYNOPSIS. Crude holothurin from the Bahamian sea cucumber Actinopyga agassiz , inoculated intraperitoneally into rats with Trypanosoma lewisi infection, altered the host-parasite relationship. The effect was measured by a study of parasite population during infections. Rats treated with holothurin prior to and simultaneously with an infection of trypanosomes had lower parasitemias than controls. A higher level of parasitemia was observed in treated after infection with trypanosomes. Both dosage and timing appeared to have been important parameters of the observed effect. The reticuloendothelial system is suspected to play a role in these findings.     

The glycoproteins of the complex surface coat of Trypanosoma lewisi

Blood stream forms of Trypanosoma lewisi from rats previously infected were labelled in vitro by galactose-oxidase oxidation followed by NaB3H4 reduction and subjected to 7.5% SDS-polyacrylamide gel analysis, by this procedure 8 bands were detected on SDS polyacrylamide gel electrophoresis. We conclude that surface composition of Trypanosoma lewisi resulted more complex than that of Trypanosoma so far studied, suggesting a possible relation with induced immunity and reduced ability of the parasite to survive in its host.     

The relation of agglutinins to antigenic variation of Trypanosoma lewisi.

During the course of infection in the rat, Trypanosoma lewisi produces 2 antigenic variants: the 1st represents the initial, reproducing population of cells; and the 2nd the nonreproducing, ablastin-inhibited adult population. The specificities of the agglutinins elicited by the variants were studied by adsorption and agglutination methods and the newer immunoelectroadsorption technic. It was found that the reproducing variant has a surface antigen that reacts with the agglutinin specific for the adult variant, but this antigen does not become immunogenic until transformation to the adult variant occurs. It was also found, with fractions of immune sera obtained by gel filtration, that the agglutinin specific for the reproducing variant is IgG and that specific for the adult variant, IgM. The antigenic variants of pathogenic and nonpathogenic trypanosomes are compared, and the roles of trypanocidal and ablastic antibodies in the induction of antigenic variation are discussed.     

Further Studies on Antigenic Changes in Trypanosoma lewisi*

SYNOPSIS. An investigation of day-to-day changes in adult form antigens of T. lewisi in the rat shows that adult antigens, 2 of which are present in trace amounts in young forms, suddenly appear in large amounts in 9-day-old trypanosomes. An additional antigen is formed on the 13th day. In addition, 2-day-old trypanosomes contain some antigens not present in 6-day-old forms. The combined results of the present paper and a previous one indicate that there are antigenically 3 distinct stages of T. lewisi in the rat: 1- to 3-day-old, 4- to 8-day-old, and 9- to 14-day-old forms. From 9- to 11-day-old trypanosomes, there is a form containing both young and adult antigens.     

Development of Trypanosoma lewisi in Experimental Chimaeras*

SYNOPSIS. Development of Trypanosoma lewisi in chimaeric mice with and without rat serum supplements was studied in 5 protocols. Chimaeric mice were male and female C₃H/An Cum and 1C₃F₁, [(101/CUM × C₃H/An Cum) F₁] exposed to 950-1000 R of whole-body X-irradiation. Their hemopoietic systems were replaced with Sprague-Dawley rat bone marrow. Trypanosomes did not develop in any mice not supplemented with rat serum. Ih those chimaeric and normal mice given rat serum the trypanosomes grew and developed large populations, more so in chimaeric than in normal animals. The development of this trypanosome cell in heterologous mice is viewed as mediated principally thru nutritional factors supplied by rat serum with alteration of host-immune status being of lesser importance.     

The Relation of Agglutinins to Antigenic Variation of Trypanosoma lewisi*

SYNOPSIS. During the course of infection in the rat, Trypanosoma lewisi produces 2 antigenic variants: the 1st represents the initial, reproducing population of cells; and the 2nd the nonreproducing, ablastin-inhibited adult population. The specificities of the agglutinins elicited by the variants were studied by adsorption and agglutination methods and the newer immunoelectroadsorption technic. It was found that the reproducing variant has a surface antigen that reacts with the agglutinin specific for the adult variant, but this antigen does not become immunogenic until transformation to the adult variant occurs. It was also found, with fractions of immune sera obtained by gel filtration, that the agglutinin specific for the reproducing variant is IgG and that specific for the adult variant, IgM. The antigenic variants of pathogenic and nonpathogenic trypanosomes are compared, and the roles of trypanocidal and ablastic antibodies in the induction of antigenic variation are discussed.     

The kinetoplast DNA of the Australian trypanosome,Trypanosoma copemani,shares features with Trypanosoma cruzi and Trypanosoma lewisi

Kinetoplast DNA (kDNA) is the mitochondrial genome of trypanosomatids. It consists of a few dozen maxicircles and several thousand minicircles, all catenated topologically to form a two-dimensional DNA network. Minicircles are heterogeneous in size and sequence among species. They present one or several conserved regions that contain three highly conserved sequence blocks. CSB-1 (10?bp sequence) and CSB-2 (8?bp sequence) present lower interspecies homology, while CSB-3 (12?bp sequence) or the Universal Minicircle Sequence is conserved within most trypanosomatids. The Universal Minicircle Sequence is located at the replication origin of the minicircles, and is the binding site for the UMS binding protein, a protein involved in trypanosomatid survival and virulence. Here, we describe the structure and organisation of the kDNA of Trypanosoma copemani, a parasite that has been shown to infect mammalian cells and has been associated with the drastic decline of the endangered Australian marsupial, the woylie (Bettongia penicillata). Deep genomic sequencing showed that T. copemani presents two classes of minicircles that share sequence identity and organisation in the conserved sequence blocks with those of Trypanosoma cruzi and Trypanosoma lewisi. A 19,257?bp partial region of the maxicircle of T. copemani that contained the entire coding region was obtained. Comparative analysis of the T. copemani entire maxicircle coding region with the coding regions of T. cruzi and T. lewisi showed they share 71.05% and 71.28% identity, respectively. The shared features in the maxicircle/minicircle organisation and sequence between T. copemani and T. cruzi/T. lewisi suggest similarities in their process of kDNA replication, and are of significance in understanding the evolution of Australian trypanosomes.