Budding of Taenia crassiceps cysticerci in vitro is promoted by crowding in addition to hormonal, stress, and energy-related signals

In vitro system for the growth and asexual multiplication of Taenia crassiceps cysticerci

Taenia solium is the aetiological agent of cysticercosis, a zoonosis that causes severe health and economic losses across Latin America, Africa and Asia. The most serious manifestation of the disease is neurocysticercosis, which occurs when the larval stage (cysticercus) establishes in the central nervous system. Using Taenia crassiceps as an experimental model organism for the study of cysticercosis, we aimed to identify the in vitro conditions necessary to allow parasite development at the short- and long terms. First, cysticerci were incubated for 15 days in different media and parasite densities. The number of buddings and cysticerci diameter were measured to evaluate asexual multiplication and parasite growth, respectively. Vitality was determined by trypan blue staining and morphology analysis. As a result, high cysticerci density and medium containing FBS and the excretion/secretion (E/S) products of feeder cells induced parasite survival, growth and multiplication. Then, the long-term (5 weeks) incubation of the parasites in co-culture with feeder cells was evaluated. Consequently, the mammalian cell lines induced a significant increase in total parasite volume while axenic cultures did not show any statistically significant change over time. In this study, the proper conditions to maintain T. crassiceps in vitro are described for the first time in a simpler and more controlled setting other than experimental infections. In addition, it was shown that cysticerci growth, survival and asexual multiplication depend on a complex network of secreted factors from both parasite and host.

[Subcutaneous Taenia crassiceps-cysticercosis in a dog with Cushing's syndrome]

A male, 12-year-old Cairn terrier suffering from Cushing's syndrome with two therapy-resistant inflammatory subcutaneous lesions was examined pathomorphologically and parasitologically. Within the subcutaneous tissue, there was a suppurative to necrotizing and histiocytic inflammation present with the formation of caverns. Intralesional whitish-grey cysts with a diameter of 1-4 mm were detected. Molecular investigations of the cysts confirmed the preliminary morphological identification as Cysticercus longicollis. The adenohypophysis showed an infiltrative growing carcinoma. Cysticercus longicollis is the metacestode of Taenia (T.) crassiceps, a tapeworm of foxes and coyotes. Small rodents are typical intermediate hosts, in which the metacestode develops within the body cavities as well as in the subcutis. Subcutaneous cysticercosis after infection with eggs of T. crassiceps is also described in different domestic animal species and in humans, who represent aberrant intermediate hosts. Immunosuppression due to Cushing's syndrome, probably caused by the tumor of the adenohypophysis, may have played a role in the pathogenesis of the present case.

Crosstalk among Taenia crassiceps (ORF Strain) cysts regulates their rates of budding by ways of soluble and contact signals exchanged between them

Herein we report that in vitro experiments with different initial parasite densities (1, 5, and 10 cysts per mL of culture medium) show that cysts at densities of 10 and 5 grow faster than those at 1, and that they release into the culture medium factors which increase the budding rates of the slower lower-density ones. Close contact among the incubated cysts also favors budding, thus suggesting the participation of surface sensors of parasite crowding. Thus, contact signals, together with the release of soluble growth factors, could endow cysts with the capacity to sense and regulate their numbers inside their habitat in relation to their population density.