Immunization of mice with Trypanosoma rhodesiense exposed to ultraviolet irradiation.

Exposure time of Trypanosoma rhodesiense as short as 1 minute to ultraviolet (U.V.) light prevents the organisms from causing infection. Live trypanosome challenge of mice immunized with U.V.-irradiated trypanosomes results in sterile immunity. This allows a method for the induction of protective immunity to experimental trypanosomiasis which can be performed in most laboratories using U.V. germicidal lamps found in sterile hoods.

Studies on antigenic variation of cyclically transmitted Trypanosoma congolense.

Antigenic variants of T. congolense transmitted by G. m. morsitans through normal and X-irradiated mice were investigated by means of the neutralization test and IFAT. Clones of a cyclically passaged derivative strain were isolated from irradiated and normal mice. The IFAT revealed cross immunofluorescent reactions between most of the stabilates, whereas only the two clones obtained from irradiated mice were totally neutralized by their homologous antisera. These two antisera showed no cross neutralizing activity. The results indicate a possible antigenic heterogeneity of the extruded metacyclic forms.

Immunosuppression in deer mice with experimentally induced trypanosomiasis.

Light and electron microscopic examinations of deer mice (Peromyscus maniculatus) chronically infected with Trypanosoma equiperdum revealed hyperplasia of germinal center lymphocytes (germanocytes) in the lymph follicles of spleen and lymph nodes and infiltration of the splenic red pulp cords and nodal medullary cords with plasma cells. Proliferation and infiltration of plasma cells caused disruption of the B- and T-lymphocyte areas in these organs. Stimulation of splenic lymphocytes in vitro by phytohemagglutinin and concanavalin A revealed marked depression in T-lymphocyte response; stimulation with lipopolysaccharide and pokeweed mitogens showed depression of B-cell response. Deer mice infected with virulent trypanosomes had decreased immunologic response to injection of sheep red blood cells, whereas deer mice given radioattenuated trypanosomes had normal to enhanced immunologic response to injection of sheep red blood cells.

Chemical and biological mechanisms of pathogen reduction technologies.

Within the last decade new technologies have been developed and implemented which employ light, often in the presence of a photosensitizer, to inactivate pathogens that reside in human blood products for the purpose of transfusion. These pathogen reduction technologies attempt to find the proper balance between pathogen kill and cell quality. Each system utilizes various chemistries that not only impact which pathogens they can inactivate and how, but also how the treatments affect the plasma and cellular proteins and to what degree. This paper aims to present the various chemical mechanisms for pathogen reduction in transfusion medicine that are currently practiced or in development.

Effects of gamma irradiation on the development of Trypanosoma rangeli in the vector Rhodnius prolixus.

Studies on the effects of gamma radiation on the infectivity of Trypanosoma rangeli (strain H14) for the vector Rhodnius prolixus revealed that (i) the LD(50) (lethal dose for 50% of bugs) for uninfected insects was 4147 rads; (ii) irradiated insects with a dose of 1200 rads subsequently infected with the flagellates exhibited a mortality of 45%, while uninfected irradiated insects showed a mortality of 5%, and infected nonirradiated insects exhibited 10% mortality; (iii) flagellates were present in the hemolymph of irradiated insects 7 days postinfection (p.i.), while in nonirradiated insects the parasites appeared in the hemocoel 18 days p.i.; (iv) T. rangeli infection decreased the number of hemocytes significantly and induced the formation of nodules in the hemolymph of both irradiated and nonirradiated insects; and (v) gamma irradiation affected the ultrastructural organization of the epithelial cells of the small intestine, principally the perimicrovillar membranes and microvilli. In this paper, we discuss the significance of the intestinal microenvironment of R. prolixus with regard to its interaction with T. rangeli.

Effect of methylene blue and illumination on the process of differentiation of the protozoan Herpetomonas samuelpessoai.

Herpetomonas samuelpessoai is a non-pathogenic protozoan that shares important antigens with Trypanosoma cruzi (the agent of Chagas' disease) and which shows three developmental stages: promastigote, paramastigote and the highly differentiated form opisthomastigote. Due to the difficulties in obtaining the last form, its physiology and biochemistry are not well understood, and procedures which can induce the process of differentiation promastigote-opisthomastigote are desirable. In this work we show that illumination of H. samuelpessoai with white light in the presence of methylene blue and oxygen (photodynamic effect) triggers the process of differentiation in a very efficient manner (the cultures show up to 70 per cent of the cells in the opisthomastigote form). We also observed that illumination alone and incubation with methylene blue in the dark can trigger the process but in levels markedly lower than illumination in the presence of the dye.

Control of trypanodestructive antibody responses and parasitemia in mice infected with Trypanosoma (Duttonella) vivax.

After infection with a cloned population of Trypanosoma vivax, C57BL/6 mice controlled parasitemia during the exponential growth phase and survived, with intermittent parasitemia, for several weeks. In contrast, most mice of the C3H/He strain did not control the first wave of parasitemia and died within 9 to 13 days after infection. Control of parasitemia in C57BL/6 mice was mediated by the production of a variant surface glycoprotein-specific trypanodestructive antibody response which was accompanied by production of antibodies against antigens shared between procyclic and bloodstream T. vivax as well as antibodies against trinitrophenyl (TNP) and sheep erythrocytes. The infected C3H/He mice did not produce trypanodestructive antibodies or antibodies against procyclic antigens or TNP but did produce antibodies against sheep erythrocytes. Although infected C57BL/6 mice produced levels of serum immunoglobulin M four times higher than infected C3H/He mice, their parasite-induced B-cell DNA synthetic responses were similar, and both sets of mice developed similar numbers of spleen cells with cytoplasmic immunoglobulin M, a proportion of which could react with TNP. In vitro biosynthetic labeling studies accompanied by immunoglobulin precipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that the immunoglobulin-containing cells of infected C3H/He mice synthesized and secreted less immunoglobulin than similar cells from infected C57BL/6 mice. We concluded that some parasite-induced antibody-forming cells in C3H/He mice, perhaps including parasite-specific and certainly including TNP-specific cells, had an impaired capacity to make and release immunoglobulin. Within 24 h after Berenil-mediated elimination of T. vivax from infected C3H/He mice, a population of cyclophosphamide-sensitive spleen cells produced large amounts of parasite-specific and TNP-specific antibody. We concluded that the defect in terminal B-cell function leading to suppressed parasite-specific and TNP-specific antibody responses was induced either by living trypanosomes or short-lived factors from degenerating trypanosomes or by short-lived parasite-induced host responses.