Quantitative analysis of Cryptosporidium growth in in vitro culture--the impact of parasite density on the success of infection

Carr J, Ryan U. Organoids and Bioengineered Intestinal Models: Potential Solutions to the Cryptosporidium Culturing Dilemma

Cryptosporidium is a major cause of severe diarrhea-related disease in children in developing countries, but currently no vaccine or effective treatment exists for those who are most at risk of serious illness. This is partly due to the lack of in vitro culturing methods that are able to support the entire Cryptosporidium life cycle, which has led to research in Cryptosporidium biology lagging behind other protozoan parasites. In vivo models such as gnotobiotic piglets are complex, and standard in vitro culturing methods in transformed cell lines, such as HCT-8 cells, have not been able to fully support fertilization occurring in vitro. Additionally, the Cryptosporidium life cycle has also been reported to occur in the absence of host cells. Recently developed bioengineered intestinal models, however, have shown more promising results and are able to reproduce a whole cycle of infectivity in one model system. This review evaluates the recent advances in Cryptosporidium culturing techniques and proposes future directions for research that may build upon these successes.

Long-Term Storage of Cryptosporidium parvum for In Vitro Culture

The long-term storage of Cryptosporidium life-cycle stages is a prerequisite for in vitro culture of the parasite. Cryptosporidium parvum oocysts, sporozoites, and intracellular forms inside infected host cells were stored for 6-12 mo in liquid nitrogen utilizing different cryoprotectants (dimethyl sulfoxide [DMSO], glycerol and fetal calf serum [FCS]), then cultured in vitro. Performance in vitro was quantified by estimating the total Cryptosporidium copy number with quantitative polymerase chain reaction (qPCR) in 3- and 7-day-old cultures. Although few parasites were recovered either from stored oocysts or from infected host cells, sporozoites stored in liquid nitrogen recovered from freezing successfully. More copies of parasite DNA were obtained from culturing those sporozoites than sporozoites excysted from oocysts kept at 4 C for the same period. The best performance was observed for sporozoites stored in Roswell Park Memorial Institute (RPMI) medium with 10% FCS and 5% DMSO, which generated 240% and 330% greater number of parasite DNA copies (on days 3 and 7 post-infection, respectively) compared to controls. Storage of sporozoites in liquid nitrogen is more effective than oocyst storage at 4 C and represents a more consistent approach for storage of viable infective Cryptosporidium aliquots for in vitro culture.

It's official - Cryptosporidium is a gregarine: What are the implications for the water industry?

Parasites of the genus Cryptosporidium are a major cause of diarrhoea and ill-health in humans and animals and are frequent causes of waterborne outbreaks. Until recently, it was thought that Cryptosporidium was an obligate intracellular parasite that only replicated within a suitable host, and that faecally shed oocysts could survive in the environment but could not multiply. In light of extensive biological and molecular data, including the ability of Cryptosporidium to complete its life cycle in the absence of a host and the production of novel extracellular stages, Cryptosporidium has been formally transferred from the Coccidia, to a new subclass, Cryptogregaria, with gregarine parasites. In this review, we discuss the close relationship between Cryptosporidium and gregarines and discuss the implications for the water industry.

An easy 'one tube' method to estimate viability of Cryptosporidium oocysts using real-time qPCR

Viability estimation of the highly resistant oocysts of Cryptosporidium remains a key issue for the monitoring and control of this pathogen. We present here a simple 'one tube' quantitative PCR (qPCR) protocol for viability estimation using a DNA extraction protocol which preferentially solubilizes excysted sporozoites rather than oocysts. Parasite DNA released from excysted sporozoites was quantified by real-time qPCR using a ribosomal DNA marker. The qPCR signal was directly proportional to the number of oocysts excysted, and a power-law relationship was noted between oocyst age and the proportion excysting. Unexcysted oocysts released negligible amounts of DNA making the method suitable for estimating viability of as few as 10 oocysts.