Program 
Abstract
Systems Vaccinology for Cryptosporidium
 
Gregory A. Buck, Ph.D
Director, Center for the Study of Biological Complexity, Virginia Commonwealth University
 
Cryptosporidium species are apicomplexan parasites that contaminate water supplies world-wide and cause serious disease in humans and animals in both developing and developed areas of the world. The parasite is extremely resistant to water treatment and causes disease after very low-dose exposures. As a result, cryptosporidiosis is responsible for approximately 30% of the chronic diarrhea endemic in children in developing parts of the world, and remains one of the most important water borne diseases in the U.S. and other developing countries. Because water supplies are vulnerable to deliberate contamination, Cryptosporidium spp. are considered candidates for biological terrorism. Despite its world-wide importance, Cryptosporidiosis was only recognized as a serious pathogen associated with the advent of AIDS. Thus, the greatest impact of cryptosporidiosis is among the immunocompromised. However, children are the primary targets in developing countries, and adults are seriously affected in the background of low ‘herd’ immunity. Thus, approximately 400,000 individuals were sickened by exposure to contaminated water supplies in Milwaukee, Wisconsin, in 1993. Currently, there are no prophylactic strategies to combat the disease, and treatment is only available early after exposure with toxic drugs. Despite their prevalence and world-wide importance, Cryptosporidium have proven to be extremely difficult to study by conventional parasitological approaches. There is no system available for in vitro culture of the parasite and obtaining sufficient biomass for analysis is a challenge. Moreover, simple animal models of the disease are nonexistent. There has been some success with immunocompromised murine models, but most work is done in large animals (e.g., biomass is generated by infection of neonatal calves or pigs). As a result of these challenges, we have applied non-traditional approaches to the study of Cryptosporidium spp. and cryptosporidiosis. Thus, we sequenced the genomes of the two most important species, C. hominis and C. parvum. These analyses permitted us to predict the metabolic capabilities of Cryptosporidium and led to hypotheses that might explain the fastidiousness of the organism and its recalcitrance to be cultured. In addition, we have dissected the life cycle of C. parvum using gene expression and proteomics analysis strategies. These studies provided a picture of the biochemical capabilities of the sporozoite stage of the parasite, which is the most important infectious stage of the organism. In parallel, we analyzed the genome of these organisms, searching for those genes encoding predicted membrane bound, surface associated, or secreted proteins, or other proteins with pathogenic relevance.  Combining these wet-lab approaches with in silico analyses, we prioritized a panel of ~80 gene products that we predicted could be effective targets as recombinant vaccinogens.n conclusion, starting with genomic sequence and applying transcriptomic, proteomic and bioinformatics strategies, we identified a panel of Cryptosporidium genes as potential vaccinogens. Several of these potential vaccinogens have shown promise in subsequent immunological tests. Thus, using this systems biology approach has demonstrated potential to streamline vaccine development for this important but very difficult to study parasite.
Biosketch
Gregory A. Buck Ph.D.
Dr. Gregory A. Buck obtained a B.S. in Genetics from the University of Wisconsin-Madison. He did his graduate work and obtained a M.S. and Ph.D. from the Department of Microbiology and Immunology at the University of Washington Seattle in the laboratory of Dr. Neal Groman, where he studied the molecular biology of toxin-encoding diphtheria phages and identified the gene encoding diphtheria toxin. Dr. Buck did a postdoctoral stint at the Institut Pasteur in Paris studying the molecular basis of antigenic variation in the African Trypanosomes with Dr. Harvey Eisen. After his postdoctoral training, Dr. Buck accepted a position as Assistant Professor of Microbiology and Immunology at Virginia Commonwealth University, where he is now Professor. Since joining VCU, Dr. Buck has pursued his interest in studying the molecular biology and genomics of single celled eukaryotic parasites, including Trypanosoma cruzi and related kinetoplastid parasites, and Cryptosporidium species. In 2000, Dr. Buck was invited to organize and direct the new Center for the Study of Biological Complexity at VCU. The CSBC houses VCU’s undergraduate and graduate programs in Bioinformatics, and maintains VCU’s high throughput ‘omics’ infrastructure, including core resources in genomics, transcriptomics, proteomics and bioinformatics. In 2004, the CSBC launched VCU’s Center for High Performance Computing. Since launching the CSBC, Dr. Buck continues to apply high throughput technologies to study the biology and pathogenesis of T. cruzi, C. parvum, and related parasites.