Novel diamidines with activity against Babesia divergens in vitro and Babesia microti in vivo.

Dicationic diamidines, such as diminazene and pentamidine, are well-studied chemotherapeutic agents with significant activity against parasitic diseases. The in vitro activities of novel diamidine compounds against the Babesia divergens strains 1903B and 4201 were investigated. The most potent compound, a diphenyl furan, had a 50% inhibitory concentration (IC(50)) of 1.5 ng/ml. In a murine model, several test compounds were effective enough to cure mice infected with Babesia microti at a dose of 12.5 and/or 25 mg/kg of body weight given by the subcutaneous route for 4 days. The best antibabesial properties were exhibited by terphenyls, benzimidazoles, diphenyl furans, pentamidine, and pentamidine analogues.

Peroxide bond-dependent antiplasmodial specificity of artemisinin and OZ277 (RBx11160).

Using nonperoxidic analogs of artemisinin and OZ277 (RBx11160), the strong in vitro antiplasmodial activities of the latter two compounds were shown to be peroxide bond dependent. In contrast, the weak activities of artemisinin and OZ277 against six other protozoan parasites were peroxide bond independent. These data support the iron-dependent artemisinin alkylation hypothesis.

Presence of MLH1 protein aggravates the potential of the HSP90 inhibitor radicicol to sensitize tumor cells to cisplatin.

MLH1 is one of five proteins crucial to DNA mismatch repair (MMR) function the loss of which is associated with a cisplatin resistance phenotype in tumor cells. An experimental approach was designed to determine whether the presence or absence of MLH1 affects the potential of radicicol to increase the sensitivity of tumor cells to cisplatin and oxaliplatin, and whether perhaps radicicol increases sensitivity to cisplatin specifically in cisplatin-resistant, MLH1-deficient cells. Radicicol is a novel specific inhibitor for heat shock protein 90 (HSP90) and structurally unrelated to geldanamycin. Clonogenic data demonstrated that sublethal concentrations of radicicol increased the sensitivity to cisplatin and to oxaliplatin in both MLH1-proficient cells and MLH1-deficient cells. Notably, the radicicol-imposed increase in sensitivity to cisplatin was up to 1.6-fold higher in MLH1-proficient cells than in MLH1-deficient cells, whereas no difference in the extent of the increase in sensitivity between the two sublines was observed for oxaliplatin. This indicates that the presence of MLH1 protein aggravates the radicicol-imposed increase in sensitivity of cells to cisplatin but not to oxaliplatin. However, the increases in platinum drug sensitivity imposed by radicicol observed in the clonogenic assay were not accompanied by reproducible alterations in the susceptibility to apoptosis and to changes in cell cycling. Although not conclusive at this point, the results seem to argue against radicicol as a means to selectively re-sensitize cisplatin-resistant, MLH1-deficient tumor cells to this drug. But they may point to a possible functional relationship between HSP90 and MLH1, where HSP90 might affect the function of MLH1 in a way that this leads to the counter-regulation of cytotoxic pathways initiated by MMR as a consequence of the presence of DNA damage introduced by cisplatin.

Mixed infections in vitro with different Chlamydiaceae strains and a cell culture adapted porcine epidemic diarrhea virus.

Assuming a synergistic or additive effect of Chlamydiaceae in coexistence with other enteropathogenic agents, the viral/bacterial interaction between a cell culture adapted porcine epidemic diarrhea virus (ca-PEDV) and different Chlamydiaceae strains was studied in vitro. Vero cells were dually infected with ca-PEDV and one of the three chlamydial strains Chlamydia trachomatis S45, Chlamydophila abortus S26/3 or Chlamydophila pecorum 1710S. Three experimental protocols were designed varying the inoculation sequence. Cell layers were first inoculated with Chlamydiaceae and 20 h later with ca-PEDV in protocol one. In protocol two, both agents were administered concurrently, whereas in protocol three, ca-PEDV was applied 20 h in advance of the Chlamydiaceae. Immunofluorescence techniques, immunohistochemical (IH) staining and electron microscopy were subsequently employed to investigate the cell layers. Using indirect immunofluorescence (IF) labeling, all mixed infections revealed dually infected cells, however, only incidentally and in low numbers. Characteristically, ca-PEDV syncytia with one or more chlamydial inclusions were detected but dually infected single cells were absent. Some syncytial cells contained enlarged C. abortus or C. pecorum inclusions with abnormally large developmental forms. In comparison with simultaneously conducted monoinfections, larger chlamydial inclusions were observed in dually infected cell layers. Experiments with C. trachomatis showed significantly increased numbers of chlamydial inclusions in dually infected cell layers compared to monoinfected ones. These findings indicate an influence of ca-PEDV on the chlamydial developmental cycle and in the case of C. trachomatis, a positive effect on chlamydial colonization in mixed infections.