Analysis of the reactivity of anti-bovine CD8 monoclonal antibodies with cloned T cell lines and mouse L-cells transfected with bovine CD8.

Mouse L-cells transfected with bovine CD8 and two Theileria parva-infected cloned T cell lines expressing bovine CD8 were used to screen the panel of ten monoclonal antibodies (mAbs) submitted to the workshop. Eight of the ten mAbs reacted with the transfectant and both the cloned T cell lines. However, two mAbs CC58 and BAT82A did not recognise the transfectant and only reacted with one of the T cell lines. Further biochemical studies indicated that the eight mAbs react with both homo- and heterodimeric forms of bovine CD8 whilst the two mAbs CC58 and BAT82A react with only heterodimeric forms. These data suggest that bovine DC8 is encoded by two genes as is the case in mouse and man.

Comparative studies on surface antigenicity of Trypanosoma cruzi trypomastigotes from infected mouse blood and infected L-cell cultures.

Differences in the antigenicities of surface components of blood-form trypomastigotes and trypomastigotes derived from L-cell cultures were studied by agglutination and indirect immunofluorescent tests on living parasites using various antisera from rabbits and mice. Antisera from rabbits immunized with L-cell-derived trypomastigotes and antisera obtained from rabbits infected with L-cell-derived trypomastigotes showed similar titers in both the agglutination and immunofluorescent test. Moreover, both antisera exhibited higher titers against trypomastigotes derived from L-cell cultures than against blood-form trypomastigotes. No detectable agglutination titer against either blood-form or L-cell-derived trypomastigotes was observed with sera from (a) mice infected with blood-form trypomastigotes after previous immunization with blood-form trypomastigotes, (b) mice infected with blood-form trypomastigotes and then treated with Lampit, or (c) mice infected with slightly less virulent trypomastigotes from L-cells. However, detectable and almost equal titers were observed with sera from (a), (b) and (c) in indirect immunofluorescent tests. Mouse sera also exhibited higher titers against trypomastigotes derived from L-cells than against the blood-form type. However, mouse sera showed more pronounced differences than rabbit sera. These results suggest that there may be two types of trypomastigotes in infected animals and that the surface components of blood-form trypomastigotes have lower antigenicity.

Pyrazolo[3,4-d]pyrimidine ribonucleosides as anticoccidials. 2. Synthesis and activity of some nucleosides of 4-(alkylamino)-1H-pyrazolo[3, 4-d]pyrimidines.

A series of 4-(alkylamino)-1-beta-D-ribofuranosyl-1H-pyrazolo[3, 4-d]pyrimidines was synthesized by enzymatic and chemical methods. On the basis of the previous finding that 4-(alkylthio)-1-beta-D-ribofuranosyl-1H-pyrazolo[3,4-d]pyrimidines were effective anticoccidial agents, this series was examined for efficacy against Eimera tenella in chicks. The most active anticoccidial agent in the present study was the 4-cyclopentylamino derivative (8), which cleared chicks of the parasite at 200 ppm in the diet. Some members of this series were toxic to embryonic chick liver cells, mouse cells, and human cells in vitro. The 4-diethylamino derivative (16), which was not toxic in vitro, appeared to be toxic in chicks.

Persistent infection of mouse fibroblasts (L cells) with Chlamydia psittaci: evidence for a cryptic chlamydial form.

When monolayers of mouse fibroblasts (L cells) were infected with enough Chlamydia psittaci (strain 6BC) to destroy most of the host cells, 1 in every 10(5) to 10(6) originally infected cells gave rise to a colony of L cells persistently infected with strain 6BC. In these populations, the density of L cells and 6BC fluctuated periodically and reciprocally as periods of host cell increase were followed by periods of parasite multiplication. Successive cycles of L-cell and 6BC reproduction were sustained indefinitely by periodic transfer to fresh medium. Isolation of L cells and 6BC from persistent infections provided no evidence that there had been any selection of variants better suited for coexistence. Persistently infected populations consisting mainly of inclusion-free L cells yielded only persistently infected clones, grew more slowly, and cloned less efficiently. They were also almost completely resistant to superinfection with high multiplicities of either 6BC or the lymphogranuloma venereum strain 440L of Chlamydia trachomatis. These properties of persistently infected L cells may be accounted for by assuming that all of the individuals in these populations are cryptically infected with 6BC and that cryptic infection slows the growth of the host cell and makes it immune to infection with exogenous chlamydiae. According to this hypothesis, the fluctuations in host and parasite density occur because some factor periodically sets off the conversion of cryptic chlamydial forms into reticulate bodies that multiply and differentiate into infectious elementary bodies in a conventional chlamydial developmental cycle.

African trypanosomes: cultivation of animal-infective Trypanosoma brucei in vitro.

Trypanosoma brucei grew in the presence of bovine fibroblast-like cells in Hepes-buffered RPMI 1640 medium with 20 percent fetal bovine serum for more than 220 days at 37 degrees C. The organisms grown in this system were infective to mammalian hosts, retained the morphological and biochemical characteristics of long slender bloodstream forms, and displayed variant-antigen on their surfaces.

Studies of in vitro infection by Trypanosoma cruzi. I. Ultrastructural studies on the invasion of macrophages and L-cells.

The interactions of Trypanosoma cruzi with L-cells, and with normal and activated macrophages in vitro were studied by ultrastructural techniques. T. cruzi actively invades cultured L-cells and uniformly destroys them. Normal macrophages could control a 1:1 (parasite to host cell) infection, but were destroyed by a 10:1 infection. BCG-activated macrophages, however, controlled a 10:1 infection but not one at a ratio of 100:1. It appears that parasites that survive within host cells do so outside cytoplasmic vacuoles, whereas when they are relegated to host cell phagosomes they are destroyed. Culture forms of T. cruzi have several means of access into host cells. Marcrophages are better able to survive infection than are non-phagocytic cells. Finally, it is suggested that control of an experimental infection in vitro is dependent upon numbers of parasites to macrophages as well as the state of the macrophages.