Claudio Zuñiga

Action of Trypanosoma rangeli in infections with virulent Trypanosoma cruzi populations

In experimental murine infections with Trypanosoma rangeli it has been observed development immune response to Trypanosoma cruzi. The aim of the present work was to analyze the result of antigenic stimuli and the protective effect with T. rangeli in T. cruzi infections. Mice groups immunized with metacyclic trypomastigotes of T. rangeli (Choach -2V strain), derived from haemolymph and salivary gland and reinfected with T. cruzi virulent populations (Tulahuen strain, SA strain and Dm28c clone) from infected in vitro cells, showed decrease severity of disease outcomes, low parasitemia levels and 100% survival of all mice immunized, in comparison with groups infected only with T. cruzi populations, which demonstrated tissue affection, high parasitemia levels and the death of all animals. The above mentioned data contribute to understand the biological behaviour of T. cruzi and T. rangeli and their interaction with vertebrate host.

Protective effect of Trypanosoma rangeli against infections with a highly virulent strain of Trypanosoma cruzi

Summary We investigated the protective effect of Trypanosoma rangeli against infection with Trypanosoma cruzi in animal models of various ages and with different doses of inoculum. The age of the mice and the dose of parasites determined the course of the infection. When T. cruzi was inoculated into mice after challenge with T. rangeli, parasitaemia was more controlled, mortality decreased and histopathology showed lower inflammatory infiltration and pseudocysts. This study proposes a new murine model of the protective effect of recombinant proteins of T. rangeli for possible application in the vaccines field.

Characterization of a Trypanosoma rangeli strain of colombian origin

A Colombian strain of Trypanosoma rangeli was characterized by analyzing its behaviour in different axenic and cellular culture, its infection rate and the histopathological lesions produced in experimental animals. Although slight inflammatory infiltrations were shown in different histopathological sections, no pseudocysts could be observed. Graces insect medium is better than liver infusion tryptose or artificial triatomine urine supplemented with proline when studying T. rangeli metacyclogenesis, with a peak of 32% trypomastigotes. High infection rates were found in VERO and J774 cells. Because of its 100% infectivity rates and adequacy of parasitemia levels, C23 strain is a suitable model of T. rangeli biology study.

Does nocturnality drive binocular vision? Octodontine rodents as a case study.

Binocular vision is a visual property that allows fine discrimination of in-depth distance (stereopsis), as well as enhanced light and contrast sensitivity. In mammals enhanced binocular vision is structurally associated with a large degree of frontal binocular overlap, the presence of a corresponding retinal specialization containing a fovea or an area centralis, and well-developed ipsilateral retinal projections to the lateral thalamus (GLd). We compared these visual traits in two visually active species of the genus Octodon that exhibit contrasting visual habits: the diurnal Octodon degus, and the nocturnal Octodon lunatus. The O. lunatus visual field has a prominent 100° frontal binocular overlap, much larger than the 50° of overlap found in O. degus. Cells in the retinal ganglion cell layer were 40% fewer in O. lunatus (180,000) than in O. degus (300,000). O. lunatus has a poorly developed visual streak, but a well developed area centralis, located centrally near the optic disk (peak density of 4,352 cells/mm2). O. degus has a highly developed visual streak, and an area centralis located more temporally (peak density of 6,384 cells/mm2). The volumes of the contralateral GLd and superior colliculus (SC) are 15% larger in O. degus compared to O. lunatus. However, the ipsilateral projections to GLd and SC are 500% larger in O. lunatus than in O. degus. Other retinorecipient structures related to ocular movements and circadian activity showed no statistical differences between species. Our findings strongly suggest that nocturnal visual behavior leads to an enhancement of the structures associated with binocular vision, at least in the case of these rodents. Expansion of the binocular visual field in nocturnal species may have a beneficial effect in light and contrast sensitivity, but not necessarily in stereopsis. We discuss whether these conclusions can be extended to other mammalian and non-mammalian amniotes.

Experimental infection of Leishmania (L.) chagasi in a cell line derived from Lutzomyia longipalpis (Diptera:Psychodidae)

The present work describes the in vitro infection of a cell line Lulo, derived from Lutzomyia longipalpis embryonic tissue, by Leishmania chagasi promastigotes. This infection process is compared with a parallel one developed using the J774 cell line. The L. chagasi MH/CO/84/CI-044B strain was used for experimental infection in two cell lines. The cells were seeded on glass coverslips in 24-well plates to reach a final number of 2 x 10(5) cells/well. Parasites were added to the adhered Lulo and J774 cells in a 10:1 ratio and were incubated at 28 and 37 masculineC respectively. After 2, 4, 6, 8, and 10 days post-infection, the cells were extensively washed with PBS, fixed with methanol, and stained with Giemsa. The number of internalized parasites was determined by counting at least 400 cultured cells on each coverslip. The results showed continuous interaction between L. chagasi promastigotes with the cell lines. Some ultrastructural characteristics of the amastigote forms were observed using transmission electron microscopy. The highest percentage of infection in Lulo cells was registered on day 6 post-infection (29.6%) and on day 4 in the J774 cells (51%). This work shows similarities and differences in the L. chagasi experimental infection process in the two cell lines. However, Lulo cells emerge as a new model to study the life-cycle of this parasite.

Trypanosoma rangeli : increase in virulence with inocula of different origins in the experimental infection in mice

Abstract We compared two murine models of Trypanosoma rangeli infection. The same inoculum dose and age-matched hosts were used in both cases. One group was infected with trypomastigotes obtained from passages in mice and the other, with trypomastigotes obtained from cell culture after a passage in mice. We observed that trypomastigotes obtained from the in vitro cellular infection showed increased virulence in␣experimental animals, with a 70% rate of death being noted in experimental mice instead of the lack of mortality seen when in vivo-derived parasites were used. The greatest levels of parasitemia and tissual lesions in the presence of the parasite also occurred when in vitro-derived parasites were used.

Sexo del hospedero y dosis infectante de parásitos como factores en el desarrollo de la infección con Trypanosoma cruzi en un modelo murino

CONSTANZA URZUA* , MARIA ANGELICA MORALES*, ULISES VERGARA*MARIA TERESA PALAU* y CLAUDIO ZUNIGA** Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile.Casilla 2 ,Correo 15, La Granja, Santiago, Chile. E-mail: clzuniga@uchile.clFinanciado por SIDA / SAREC.

Evolución de la infección con Trypanosoma cruzi en cepas susceptibles y resistentes de ratones

Ratones de las cepas ACA y A. Sn fueron altamente susceptibles, con un 100% de mortalidad alrededor de las 3 semanas postinfeccion (p. I), con un inoculo por via intraperitoneal de 2000 tripomastigotes sanguineos de la cepa Tulahuen de Trypanosoma cruzi, mientras que las cepas A. Sw y HTI se comportaron como resistentes con un 100% de sobrevida, pasados los 6 meses p.i. Sin embargo, los animales de las cepas resistentes mostraron niveles maximos de parasitemia significativamente mas altos que las cepas susceptibles. Se realizo un estudio histopatologico de musculo cardiaco y esqueletico de los ratones infectados. En los primeros 10 dias p.i. No se observaron diferencias claras entre cepas resistentes y susceptibles, en cuanto al dano tisular y presencia de parasitos intracelulares (pseudoquistes). Pero alrededor de la tercera semana p.i. Ya se vieron diferencias evidentes, mientras los animales de las cepas A. Sw y HTI mostraron bajos niveles de inflamacion y signos de recuperacion de las lesiones, los ratones ACA y A. Sn evidenciaron un progresivo aumento del dano tisular, aunque no se observaron, en este momento, formas sanguineas ni intracelulares del parasito. Muestras de suero de los ratones infectados fueron probados por un ensayo inmunoradiometrico (IRMA), para analizar la reactividad contra los antigenos recombinantes 1, 2, 13, 26, 30, 36 y SAPA de T cruzi. Todos los sueros solo mostraron reconocimiento de las proteinas 13 y SAPA, sugiriendo que esta reactividad no pareciera estar relacionada directamente con el fenomeno de resistencia o susceptibilidad a la infeccion con la cepa Tulahuen de T cruzi, en el modelo murino.

INFECCION EXPERIMENTAL CON Trypanosoma cruzi EN MACHOS Y HEMBRAS DE TRES CEPAS DE RATONES

Se inocularon 3 cepas de ratones, machos y hembras, con 2.000 trypomastigotes sanguineos del clon Dm 28c de Trypanosoma cruzi. Los ratones HTI de ambos sexos se comportaron como resistentes, en cambio, murio el 100% de los animales de las cepas A/Sn y AKR entre los 30 y 50 dias post-infeccion, respectivamente. En las tres situaciones se observaron diferencias significativas en los niveles maximos de parasitemia entre machos y hembras, teniendo los primeros niveles mas altos. Los sueros de los ratones infectados obtenidos a distintos tiempos post-infeccion, se probaron con una bateria de antigenos recombinantes de T. cruzi. Los sueros de los ratones A/Sn y AKR mostraron reactividad preferencial. Con los antigenos recombinantes SAPA y 13. Los sueros de los ratones HTI reconocieron ademas de SAPA y 13, al antigeno recombinante 36 y tardiamente al antigeno 1. En cuanto al sexo, la unica diferencia parece ser los niveles de parasitemias, pero este hecho no se refleja en diferencias a nivel de susceptibilidad o resistencia, como tampoco en el reconocimiento de los antigenos recombinantes

ESTUDIO HISTOPATOLOGICO EN RATONES INFECTADOS EXPERIMENTALMENTE CON Trypanosoma cruzi

Se infectaron cuatro cepas de ratones, machos y hembras, con 2000 trypomastigotes sanguineos de la cepa Tulahuen de Trypanosoma cruzi. Los animales de las cepas A.Sw y HTI se comportaron como resistentes y los de las cepas A/Sn y HTG como susceptibles, independiente del sexo de los animales infectados. En los casos de las cepas A.Sw, HTG y HTI se observo niveles significativamente mas altos de parasitemia en los machos. A nivel histopatologico el dano tisular no presenta inicialmente diferencias significativas entre cepas resistentes y susceptibles, sin embargo, con el tiempo se puede ver que en los animales resistentes se inducen fenomenos de reparacion del dano, en cambio en los ratones susceptibles las lesiones parecen aumentar a pesar de no observarse parasitos intracelulares o circulantes