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Research has been conducted on the infectivity of Cryptosporidium parvum. The relationship between cell culture-based and animal-based infectivity of C. parvum has been investigated in determining whether different methods vary in their sensitivity to dose-response curves and infection and the results are reported.

Background: Cryptosporidiosis affects all human populations, but can be much more severe or life-threatening in children and individuals with weak or weakened immune systems. However, current options to treat cryptosporidiosis are limited.Methods: An in vitro phenotypic screening assay was employed to screen 1200 existing drugs for their anticryptosporidial activity and to determine the inhibitory kinetics of top hits. Selected top hits were further evaluated in mice. The action of the lead compound vorinostat on the parasite histone deacetylase (HDAC) was biochemically validated.Results: Fifteen compounds exhibited anticryptosporidial activity at nanomolar level in vitro. Among them, the histone deacetylase (HDAC) inhibitor vorinostat retained outstanding efficacy in vitro (half maximal effective concentration, EC50 = 203 nM) and in an interleukin 12 knockout mouse model (50% inhibition dose = 7.5 mg/kg). Vorinostat was effective on various parasite developmental stages and could irreversibly kill the parasite. Vorinostat was highly effective against the parasite native HDAC enzymes (half maximal inhibitory concentration, IC50 = 90.0 nM) and a recombinant Cryptosporidium parvum HDAC (the inhibitor constant, Ki = 123.0 nM).Conclusions: These findings suggest the potential for repurposing of vorinostat to treat cryptosporidiosis, and imply that the parasite HDAC can be explored for developing more selective anticryptosporidial therapeutics. [ABSTRACT FROM AUTHOR]

Auranofin is an FDA-approved gold-containing compound used for the treatment of rheumatoid arthritis. Recent reports of antimicrobial activity against protozoa and bacteria indicates auranofin targets the reductive enzyme thioredoxin reductase (TrxR). We evaluated auranofin as well as 5 auranofin analogs containing N-heterocyclic carbenes (instead of the triethylphosphane present in auranofin) and 5 gold-carbene controls for their ability to inhibit or kill Helicobacter pylori in vitro. Auranofin completely inhibited bacterial growth at 1.2 µM. Purified H. pylori TrxR was inhibited by auranofin in a cell-free assay (IC50 ~88 nM). The most active gold(I)-N-heterocyclic carbene compounds exhibited MICs comparable to auranofin against H. pylori (2 µM) while also exhibiting lower toxicities for human embryonic kidney cells (HEK-293T cells). Median toxic concentrations (TC50) were 13-20 fold higher compared to auranofin indicating they were less cytotoxic. The N-heterocyclic carbene analogs maybe well tolerated, but further evaluation is needed in vivo. Finally, auranofin was synergistic with the antibiotic amoxicillin suggesting that targeting both the reductive enzyme TrxR and cell wall synthesis may be effective against H. pylori infections. [ABSTRACT FROM AUTHOR]

IL-18 is known to play a key role limiting Cryptosporidium parvum infection. In this study, we show that IL-18 depletion in SCID mice significantly exacerbates C. parvum infection, whereas, treatment with recombinant IL-18 (r IL-18), significantly decreases the parasite load, as compared to controls. Increases in serum IFN-γ levels as well as the up-regulation of the antimicrobial peptides, cathelicidin antimicrobial peptide and beta defensin 3 ( Defb3) were observed in the intestinal mucosa of mice treated with r IL-18. In addition, C. parvum infection significantly increased m RNA expression levels (> 50 fold) of the alpha defensins, Defa3 and 5, respectively. Interestingly, we also found a decrease in m RNA expression of IL-33 (a recently identified cytokine in the same family as IL-18) in the small intestinal tissue from mice treated with r IL-18. In comparison, the respective genes were induced by IL-18 depletion. Our findings suggest that IL-18 can mediate its protective effects via different routes such as IFN-γ induction or by directly stimulating intestinal epithelial cells to increase antimicrobial activity. [ABSTRACT FROM AUTHOR]