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 37ºC 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.

Males and females from A.Sn, HTG, HTI and A.Sw strains of mouse were intraperitoneally infected with 2000 trypomastigotes from Tulahuen strain of Trypanosma cruzi. All mice from A.Sn and HTG strains were equally susceptible (100% mortality) to the parasite infection, while males and females from A.Sw and HTI mouse strains were resistent (100% survival). However males from A.Sw, HTG and HTI strains showed significantly higher level of parasitemia than the corresponding females. The possible effect of parasitemia on tissue pathology and mice mortality was evaluated by comparing the histopathology of miocardial and skeleton muscle in the susceptible and resistant strains of mice. In the first ten days post infection no significant differences in tissue damage were observed between susceptible and resistent strain of mice. However in the third week of infection while A.Sw and HTI mice showed recovery of tissue lessions, the susceptible A.Sn and HTG showed increased tissue damage although no blood forms and no intracellular parasites were detected

Se infectaron cuatro cepas de ratones, machos y hembras, con 2000 trypomastigotes sanguíneos 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 observó niveles significativamente más altos de parasitemia en los machos. A nivel histopatológico el daño 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 fenómenos de reparación del daño, en cambio en los ratones susceptibles las lesiones parecen aumentar a pesar de no observarse parásitos intracelulares o circulantes

Males and females fron three different strains of mice have been experimentally infected with 2000 bloodstream trypomastigotes from clon DM 28c of Trypanosoma cruzi, in order to evaluate the role of sex difference in the evolution of parasitic infection. Males and females from HTI (H-2) strain were resistant (100% survival), while males and females from Asn (H2ª) and AKR (H-2k) starins were highly susceptible with 100%mortality between days 34 and 54 post experimental infection. In all these strains of mice males showed significally higher levels of parasitemia than the corresponding females. Serum samples from all infected mice were then tested by dot immunoradiometric assay, for reactivity against recombinant antigens 1, 2, 13, 26, 30, 36, 54 and SAPA of T. cruzi. Males and females from Asn and AKR susceptibles strains only showed reactivity against clones SAPA and 13. Mice from HTI resistant strain not only reacted with clon SAPA and 13, but also with clones 1 and 36. In conclusion, in this present study we showed no sex difference in susceptibility or resistance to T. cruzi infection in mice. Although males showed higher levels of parasitemia than females, this phenomenon has no effect in mortality of the infected mice. We also found that there were no dyfferences in the reactivity against the recombinant DNA clones from T. cruzi

Se inocularon 3 cepas de ratones, machos y hembras, con 2.000 trypomastigotes sanguíneos del clon Dm 28c de Trypanosoma cruzi. Los ratones HTI de ambos sexos se comportaron como resistentes, en cambio, murió el 100% de los animales de las cepas A/Sn y AKR entre los 30 y 50 días post-infección, respectivamente. En las tres situaciones se observaron diferencias significativas en los niveles máximos de parasitemia entre machos y hembras, teniendo los primeros niveles más altos. Los sueros de los ratones infectados obtenidos a distintos tiempos post-infección, se probaron con una batería de antígenos recombinantes de T. cruzi. Los sueros de los ratones A/Sn y AKR mostraron reactividad preferencial. Con los antígenos recombinantes SAPA y 13. Los sueros de los ratones HTI reconocieron además de SAPA y 13, al antígeno recombinante 36 y tardíamente al antígeno 1. En cuanto al sexo, la única 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 antígenos recombinantes