Progress 10/01/06 to 09/30/07
Outputs
Using a cell-suspension sporozoite adhesion/invasion assay we have purified a lipid fraction that inhibits sporozoite-host cell invasion. Characterization of this lipid revealed it is a long-chain polyunsaturated fatty acid (L-PUFA). Substrate specificity experiments indicated a strict specificity exists for which L-PUFAs are able to inhibit sporozooite invasion. Only L-PUFAs which are between 18-20 carbons long, have at least one double bond which is in the cis configuration, and have an unsubstituted carboxyl group are able to block sporozoite invasion. Preliminary data suggest these L-PUFAs inhibit invasion by blocking both sporozoite microneme secretion and gliding motility. Suppressive subtractive hybridization experiments aimed at identifying specific sporozoite genes expressed in response to host cell attachment or exposure to the inhibitory lipid indicate these processes occur without the necessity for attachment-or lipid-induced differential gene expression.
Impacts
Cryptosporidium parvum causes a debilitating diarrhea of livestock either alone or in concert with other enteropathogens. This agricultural problem is compounded by the public health concern of contamination of municipal water supplies by domestic and wild animal feces such as occurred in Milwaukee. In addition, cryptosporidiosis is part of the AIDS related disease complex. Despite decades of research in a variety of animal models and utilizing varied technologies, effective prophylaxis or therapeutics for C. parvum infection or disease are not available. Our approach to the control of enteric diseases of livestock has been non-traditional in the sense that it is not aimed towards vaccine production or immune regulation. Instead, we reason that if we develop assay systems that are biologically relevant and can precisely reproduce, in vitro, the interactions between the infectious agent and the host cell, then we can use these assays to identify natural products (e.g.
the inhibitory L-PUFAs described above) or synthetic derivatives that interfere with parasite-host cell interactions required for infection. Such molecules, particularly natural products, could be utilized as nutriceutical feed additives to inactivate parasites and thus prevent or reduce parasite load and limit the severity of disease. Furthermore, the identification of L-PUFAs which block sporozoite invasion will also serve as valuable research reagents which can be used to probe the specific parasite molecullar targets that control parasite invasion. These new reagents will be useful in identifying potentially new drug targets for the control and treament of cryptosporidiosis in both animals and people.
Publications
- Johnson, J.K., Schmidt, J., Gelberg, H.B. and Kuhlenschmidt, M.S. 2004. Microbial adhesion of Cryptosporidium parvum sporozoites: Purification of an inhibitory lipid from Bovine Mucosa. J. Parasitology 90:980-990.
- Wetzel, D.M., Schmidt, J., Kuhlenschmidt, M.S., Dubey, J.P. and Sibley, L.D. 2005. Gliding motility leads to active cellular invasion by Cryptosporidium parvum sporozoites. Infection and Immunity 73:5379-5387.
- Salzer, J.S., Rwego, I.B., Goldberg, T.L., Kuhlenschmidt, M.S. and Gillespie, T.R. 2007. Giardia sp. and Cryptosporidium sp. infections in primates in distrubed and undisturbed forest in western Uganda. J. Parasitology 93 (2):439-40.
- Schmidt, J.A. and Kuhlenschmidt, M.S. 2008. Characterization of a colostrum-derived lipid that blocks Cryptosptoridium parvum sporozoite adhesion (Submitted).
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