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Identification and initial characterization of five Cryptosporidium parvum sporozoite antigen genes
1Parasitology Laboratory, San Francisco General Hospital, California.
Abstract:
Cryptosporidium parvum, an Apicomplexan parasite of gastrointestinal epithelial cells, causes severe disease in persons with AIDS and is a common cause of self-limited diarrhea in children, animal handlers, and residents of developing countries. No approved therapy exists; in research studies, however, hyperimmune bovine colostrum raised to Cryptosporidium oocysts and sporozoites has eradicated disease or decreased parasite burden in some AIDS patients. Although the protective antigens recognized by bovine hyperimmune colostrum have not been defined, protective antigens of other Apicomplexan parasites frequently have been associated with two unique structures of invasive forms, the trilaminar pellicle and the apical complex. In order to identify immunogenic Cryptosporidium proteins that may be protective antigens for use as recombinant immunogens in passive and/or active immunotherapy, we screened two genomic DNA expression libraries with polyspecific anti-Cryptosporidium antibodies. We used an approach to cloning apical complex and pellicle protein antigens that succeeded despite the lack of large numbers of organisms that would be necessitated for conventional biochemical approaches requiring organelle or membrane purification. We report here the molecular cloning of five C. parvum genes and the characterization of the cognate sporozoite proteins having molecular masses of greater than 500, 68/95, 45, 23, and 15/35 kDa. The light microscopic immunofluorescence pattern of antibodies recognizing these protein antigens suggest that they are located in the pellicle or apical complex of Cryptosporidium sporozoites.
Insights
Researchers identified five Cryptosporidium parvum genes encoding sporozoite proteins. These proteins, located in the parasite
Area of Science:
- Parasitology
- Immunology
- Molecular Biology
Background:
- Cryptosporidium parvum causes significant gastrointestinal illness, particularly in immunocompromised individuals and children.
- No definitive therapy exists for cryptosporidiosis, highlighting the need for novel treatment strategies.
- Hyperimmune bovine colostrum shows promise in managing cryptosporidiosis, suggesting the presence of protective antigens.
Purpose of the Study:
- To identify immunogenic Cryptosporidium parvum proteins potentially serving as protective antigens.
- To facilitate the development of recombinant immunogens for passive or active immunotherapy against cryptosporidiosis.
- To clone and characterize C. parvum genes encoding proteins located in the pellicle and apical complex.
Main Methods:
- Screening of two genomic DNA expression libraries using anti-Cryptosporidium antibodies.
- Molecular cloning of C. parvum genes encoding potential protective antigens.
- Characterization of cloned genes and their corresponding sporozoite proteins using immunofluorescence microscopy.
Main Results:
- Five C. parvum genes were molecularly cloned.
- The study characterized cognate sporozoite proteins with molecular masses >500, 68/95, 45, 23, and 15/35 kDa.
- Immunofluorescence indicated these proteins are localized to the pellicle or apical complex of C. parvum sporozoites.
Conclusions:
- The identified genes encode proteins likely located in critical structures of the parasite.
- These proteins represent potential targets for developing new therapies against Cryptosporidium parvum infections.
- The findings support the development of recombinant vaccines or immunotherapies for cryptosporidiosis.