@article {782,
	title = {Experimental evidence for genetic recombination in the opportunistic pathogen Cryptosporidium parvum.},
	journal = {Mol Biochem Parasitol},
	volume = {119},
	year = {2002},
	month = {2002 Jan},
	pages = {55-62},
	abstract = {Cryptosporidium parvum is an intracellular protozoan parasite causing intestinal malabsorption and diarrhea in humans. The infection is usually self-limiting, although persistent cryptosporidosis is observed in immunocompromised and malnourished individuals. As with other Apicomplexa, the life cycle of Cryptosporidium is thought to comprise a sexual phase, during which a motile microgamont fuses with a sessile macrogamont. The four sporozoites found within each oocyst (the infectious form excreted in the feces) are thought to be the product of a meiotic division taking place immediately following fertilization, but the existence of a meiotic cycle in this genus has not been tested experimentally. To substantiate the occurrence of meiotic recombination in this species, we performed a genetic cross between two distinct isolates of C. parvum co-infected in INF-gamma knockout mice. We found that mixed infections produced recombinant progeny characterized by multilocus genotypes comprising alleles inherited from each parental line. This observation represents the first demonstration of sexual recombination in this pathogen. Together with the occurrence of genetically heterogeneous infections, this finding suggests that outcrossing between genotypes may occur in nature. Experimental crosses among Cryptosporidium populations will facilitate mapping of clinically relevant genes, the delineation of Cryptosporidium species, and defining the taxonomical status of C. parvum subtypes and host-specific genotypes.},
	keywords = {Animals, Conserved Sequence, Crosses, Genetic, Cryptosporidiosis, Cryptosporidium parvum, Deer, Female, Genotype, Humans, Male, Mice, Mice, Knockout, Microsatellite Repeats, Opportunistic Infections, Polymerase Chain Reaction, Recombination, Genetic, Survival Rate},
	issn = {0166-6851},
	author = {Feng, Xiaochuan and Rich, Stephen M and Tzipori, Saul and Widmer, Giovanni}
}
@article {779,
	title = {Infectivity of a Cryptosporidium parvum isolate of cervine origin for healthy adults and interferon-gamma knockout mice.},
	journal = {J Infect Dis},
	volume = {185},
	year = {2002},
	month = {2002 May 1},
	pages = {1320-5},
	abstract = {The infectivity of a Cryptosporidium parvum isolate of cervine origin (type 2, Moredun) propagated in calves was investigated simultaneously in healthy adult human volunteers and in interferon-gamma knockout (GKO) mice. After exposure to 100-3000 oocysts, 16 volunteers recorded, for a duration of 6 weeks, the number and form of stools that they passed and any symptoms that they experienced. Oocyst excretion was assessed by enzyme-linked immunosorbent assay and direct immunofluorescence assay. Eleven subjects (69\%) became ill, and 8 subjects (50\%) shed oocysts in stool. The median duration of illness was 169 h, and the median number of unformed stools passed was 24. The duration and intensity of symptoms were more severe than were those associated with previously studied isolates. The median infectious dose was estimated to be 300 oocysts for humans and 1 oocyst for the GKO mouse model. The Moredun isolate was more pathogenic than the reference GCH-1 isolate. The GKO mouse model of cryptosporidiosis is useful for discerning isolate-specific differences in pathogenicity.},
	keywords = {Adult, Animals, Body Weight, Cryptosporidiosis, Cryptosporidium parvum, Deer, Diarrhea, Disease Susceptibility, Female, Humans, Interferon-gamma, Mice, Mice, Knockout},
	issn = {0022-1899},
	doi = {10.1086/340132},
	author = {Okhuysen, Pablo C and Rich, Stephen M and Chappell, Cynthia L and Grimes, Kevin A and Widmer, Giovanni and Feng, Xiaochuan and Tzipori, Saul}
}
@article {789,
	title = {Animal propagation and genomic survey of a genotype 1 isolate of Cryptosporidium parvum.},
	journal = {Mol Biochem Parasitol},
	volume = {108},
	year = {2000},
	month = {2000 May},
	pages = {187-97},
	abstract = {Human cryptosporidiosis is attributed to two major Cryptosporidium parvum genotypes of which type 1 appears to be the predominant. Most laboratory investigations however are performed using genotype 2 isolates, the only type which readily infects laboratory animals. So far type 1 has only been identified in humans and primates. A type 1 isolate, obtained from an individual with HIV and cryptosporidiosis, was successfully adapted to propagate in gnotobiotic piglets. Genotypic characterization of oocyst DNA from this isolate using multiple restriction fragment length polymorphisms, a genotype-specific PCR marker, and direct sequence analysis of two polymorphic loci confirmed that this isolate, designated NEMC1, is indeed type 1. No changes in the genetic profile were identified during multiple passages in piglets. In contrast, the time period between infection and onset of fecal oocyst shedding, an indicator of adaptation, decreased with increasing number of passages. Consistent with other type 1 isolates, NEMC1 failed to infect mice. A preliminary survey of the NEMC1 genome covering approximately 2\% of the genome and encompassing 200 kb of unique sequence showed an average similarity of approximately 95\% between type 1 and 2 sequences. Twenty-four percent of the NEMC1 sequences were homologous to previously determined genotype 2 C. parvum sequences. To our knowledge, this is the first successful serial propagation of genotype 1 in animals, which should facilitate characterization of the unique features of this human pathogen.},
	keywords = {Animals, Cryptosporidiosis, Cryptosporidium parvum, Genome, Protozoan, Genotype, Germ-Free Life, Humans, Mice, Mice, Knockout, Molecular Sequence Data, Polymerase Chain Reaction, Polymorphism, Restriction Fragment Length, Sequence Analysis, DNA, Swine},
	issn = {0166-6851},
	author = {Widmer, G and Akiyoshi, D and Buckholt, M A and Feng, X and Rich, S M and Deary, K M and Bowman, C A and Xu, P and Wang, Y and Wang, X and Buck, G A and Tzipori, S}
}
@article {787,
	title = {Extensive polymorphism in Cryptosporidium parvum identified by multilocus microsatellite analysis.},
	journal = {Appl Environ Microbiol},
	volume = {66},
	year = {2000},
	month = {2000 Aug},
	pages = {3344-9},
	abstract = {Restriction fragment length polymorphism and DNA sequence analysis discern two main types of Cryptosporidium parvum. We present a survey of length polymorphism at several microsatellite loci for type 1 and type 2 isolates. A total of 14 microsatellite loci were identified from C. parvum DNA sequences deposited in public databases. All repeats were mono-, di-, and trinucleotide repeats of A, AT, and AAT, reflecting the high AT content of the C. parvum genome. Several of these loci showed significant length polymorphism, with as many as seven alleles identified for a single locus. Differences between alleles ranged from 1 to 27 bp. Karyotype analysis using probes flanking three microsatellites localized each marker to an individual chromosomal band, suggesting that these markers are single copy. In a sample of 19 isolates for which at least three microsatellites were typed, a majority of isolates displayed a unique multilocus fingerprint. Microsatellite analysis of isolates passaged between different host species identified genotypic changes consistent with changes in parasite populations.},
	keywords = {Animals, Base Sequence, Cattle, Cryptosporidiosis, Cryptosporidium parvum, DNA, Protozoan, Humans, Karyotyping, Mice, Mice, Knockout, Microsatellite Repeats, Molecular Sequence Data, Polymerase Chain Reaction, Polymorphism, Genetic, Sequence Analysis, DNA},
	issn = {0099-2240},
	author = {Feng, X and Rich, S M and Akiyoshi, D and Tumwine, J K and Kekitiinwa, A and Nabukeera, N and Tzipori, S and Widmer, G}
}
