Animal propagation and genomic survey of a genotype 1 isolate of Cryptosporidium parvum

Human cryptosporidiosis is attributed to two major Cryptosporidium parvum g enotypes of which type 1 appears to be the predominant. Most laboratory inv estigations however are performed using genotype 2 isolates, the only type which readily infects laboratory animals. So far type 1 has only been ident ified in humans and primates. A type 1 isolate, obtained from an individual with HIV and cryptosporidiosis, was successfully adapted to propagate in g notobiotic piglets. Genotypic characterization of oocyst DNA from this isol ate using multiple restriction fragment length polymorphisms, a genotype-sp ecific PCR marker, and direct sequence analysis of two polymorphic loci con firmed that this isolate, designated NEMC1, is indeed type 1. No changes in the genetic profile were identified during multiple passages in piglets. I n contrast, the time period between infection and onset of fecal oocyst she dding, an indicator of adaptation, decreased with increasing number of pass ages. Consistent with other type 1 isolates, NEMC1 failed to infect mice. A preliminary survey of the NEMC1 genome covering approximately 2% of the ge nome and encompassing 200 kb of unique sequence showed an average similarit y 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 characterizat ion of the unique features of this human pathogen. (C) 2000 Elsevier Scienc e B.V. All rights reserved.