Immunity of rats and mice following injection with⁶⁰Co irradiatedBabesia rodhainiinfected red cells

Abstract

Babesia rodhaini infected mouse and rat red cells were non-infective after receiving 40 or 60 krad irradiation from a 60Co source.Rats inoculated with irradiated infected red cells were subsequently found to show strong resistance to homologous challenge.Mice, which are more susceptible to B. rodhaini, showed less resistance to challenge, following immunization with irradiated B. rodhaini infected red cells.Splenectomized rats were immunized with irradiated infected blood. There was a delay compared with the controls in the onset of acute fatal parasitaemias in these rats. A population of parasites was isolated by taking and mixing blood from each of the splenectomized rats during the patent parasitaemia following challenge. This population appeared to be an antigenic variant of the original immunizing population.I thank Mrs J. Page for excellent technical assistance and Dr K. N. Brown for criticizing the manuscript.

X-irradiation of Eimeria tenella oocysts provides direct evidence that sporozoite invasion and early schizont development induce a protective immune response(s)

“…This point remains controversial, as other studies, using similar anticoccidial agents (8), have found that merogonic development is not required and sporozoites themselves are capable of eliciting a protective response. Consistent with the latter hypothesis is the demonstration that resistance to challenge appears to be directed against sporozoites (12,23) or sporozoite-infected host cells (17,23 Attempts to identify the targeted developmental stage for several other protozoa, including Plasmodium (5,18,29,30), Trypanosoma (27), and Babesia (19) species, by using X-radiation have implicated initial invasive forms of the parasite. Our recent work using X-irradiated oocysts of a related coccidium, E. acervulina, suggest that sporozoite invasion of intestinal host cells and subsequent metabolism therein are sufficient to establish resistance (9).…”

Evaluation of the Presence of a Thapsigargin-Sensitive Calcium Store in Trypanosomatids Using Trypanosoma evansi as a Model

“…Exposing C. parvum oocysts to gamma irradiation may prevent schizont development and thus overt cryptosporidiosis. Gamma irradiation of various protozoa has been used to prevent associated diseases such as malaria (Clyde et al, 1975;Scheller and Azad, 1995;Chatterjee et al, 1999), avian coccidiosis (Jenkins, Augustine et al, 1991;Jenkins, Danforth et al, 1991;Jenkins et al, 1993), babesiosis (Phillips, 1971;Purnell et al, 1979), and toxoplasmosis (Dubey et al, 1996). The present study was designed to identify a dose of gamma irradiation that inhibits oocyst development and determine whether gamma-irradiated C. parvum oocysts could be used to vaccinate calves against cryptosporidiosis.…”