Parasitology: CRISPR for Cryptosporidium.

Abstract

Study of the diarrhoea-causing pathogen Cryptosporidium has been hindered by a lack of genetic-modification and culture tools. A description of genome editing and propagation methods for the parasite changes this picture. See Letter p.477 The protozoan parasite Cryptosporidium is a major cause of diarrhoeal disease in young children but until now it has been difficult to study and there is currently no vaccine and only a single drug (nitazoxanide) available to counter the infection. Here Boris Striepen and colleagues describe a robust genetic system for cryptosporidiosis. They genetically modify Cryptosporidium parvum by optimizing transfection of sporozoites using a CRISPR/Cas9 system, to generate stable transgenic lines suitable for in vitro and in vivo drug screening. Using this system they knockout the gene encoding thymidine kinase which increases susceptibility to trimethoprim, an antimalarial drug to which wild-type Cryptosporidium is resistant.