Fig. 3 | Nature Communications

Fig. 3

From: Cryopreservation of infectious Cryptosporidium parvum oocysts

Fig. 3

Cryopreserved C. parvum oocysts are infectious to IFN-γ knockout mice. Dehydrated oocysts were vitrified using either the 0 min or 20 min DMSO incubation protocol. IFN-γ knockout mice (n = 2–3) were inoculated orally with 5000 PI- thawed or unfrozen control oocysts. Intensity of fecal shedding was quantified daily by microscopic enumeration of oocysts in 30 fields of acid-fast stained fecal smears under 1000× magnification. Positive (unfrozen) and negative controls (heat-inactivated) were included as matched controls. To determine whether oocyst age has effect on the success of the cryopreservation protocol, a 1- b 6- and c 12-week-old oocysts were studied. Values indicate means of log transformed oocyst counts and error bars indicate standard deviation. Viability of oocysts was determined by PI exclusion prior to inoculation and was as follows: (a) 43.1% and 76.7% (b) 45.2% and 80.6% (c) 53.1% and 72.4%, for 20 min and 0 min incubations, respectively. d Micrographs of hematoxylin and eosin–stained jejunal sections from IFN-γ mice infected with fresh, cryopreserved or heat-inactivated 12-week-old oocysts are shown. Arrows indicate intracellular stages of the parasite located in the apical region of intestinal epithelial cells. Scale indicates 20 µm. Data regarding infectivity of each individual mouse can be found in Supplementary Fig. 6

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