P. H. De Rycke

Comparative cytotoxicity of secondary hydatid cysts, protoscoleces, and in vitro developed microcysts of Echinococcus granulosus.

Infection with the metacestode of Echinococcus granulosus is characterized by a concomitant immunity. Survival of established and developing hydatid cysts in the intermediate host implies a mechanism to modulate its immunological reactions. In order to investigate this mechanism, secondary hydatid cysts were isolated from intraperitoneally infected laboratory white mice (strain NMRI) 12 months p.i. A number of hydatid cysts were freed from the surrounding host adventitial tissue. Monolayer cultures of non-stimulated peritoneal macrophages of NMRI mice were prepared and incubated in the presence of the hydatid cysts. By means of a trypan blue exclusion test and by measuring the incorporation of tritium labelled uridine, it was found that the presence of hydatid cysts reduced the viability of the macrophages in vitro. Toxic substances are probably secreted since the medium of cultured hydatid cysts also displayed cytotoxic activity. Hydatid cysts with adventitia, as well as culture medium of those cysts, were less toxic. When toxins, partially purified from hydatid cyst fluid, were previously incubated on a collagen coated surface, a reduced level of toxicity was found, suggesting that collagen of the host adventitia may play a role in controlling the liberation of toxins by the hydatid cyst. Virtually no toxicity was exerted by protoscoleces or by the medium of cultured protoscoleces, in contrast to in vitro vesiculated protoscoleces (so called microcysts). The results reveal a novel feature of hydatid cysts that may play a role in the survival of the parasite in the immunized host.

Comparative Lipid Composition of Colony- and Laboratory-Stored Pollen

SummaryA comparative analysis of fatty acids and sterols in colony- and laboratory-stored pollen from the same source revealed some important differences. The sterol ester concentration was 56% higher in pollen stored in the colony; there was also a much lower concentration of the essential fatty acids linoleic (C18: 2) and linolenic (C18: 3), and more of the saturated C16 and C18 acids.

Serial passages of larval Echinococcus granulosus from equine origin in mice

SummaryStarting with protoscolices from Echinococcus granulosus cysts of equine origin it was possible to isolate and maintain several “strains” of the parasite in mice through successive transfers of protoscolices. The most advanced strain is now in its 7th generation. Several criteria to evaluate the results are presented and discussed. It is concluded that serial echinococcosis of E. granulosus through passages with protoscolices is a practical method to maintain different strains for fundamental and applied comparative studies.

IMMUNOMODULATION BY HYDATID CYST FLUID TOXIN (ECHINOCOCCUS GRANULOSUS)

Since the experimental infection by hydatid cysts (Echinococcus granulosus) in mice causes immunomodulation of the host, the effects of hydatid fluid (HF) and fractions of HF were compared in vitro and in vivo. Fractions of HF were obtained using ammonium sulphate precipitation, chloroform/methanol extraction and thin‐layer chromatography (TLC). HF proved to be toxic to murine peritoneal macrophages in vitro, and when macrophages were incubated with the different fractions of HF, most toxicity was found in a single TLC‐purified fraction with an adjuvant‐like effect on the production of specific antibodies against bovine albumin and human red blood cells in mice. Treatment of mice with the toxin caused a drop in the percentage of peripheral blood lymphocytes. Flow‐cytometric analysis showed that T‐cells from toxin‐treated mice had lower membrane‐CD3, CD4 and CD8 density, and had higher percentages of CD8+ splenocytes and CD4+ thymocytes expressing CD25. The toxin caused a down‐regulation of CD4 and CD8 expression on thymocytes in vitro, that was dependent on the presence of macrophages. The results may attribute to these toxins a role in the host‐parasite relationship of hydatidosis.

Fatty Acid and Sterol Composition During Larval Development in the Honeybee

SummaryThe most important changes in lipid composition during larval development in the honeybee, Apis mellifera, were noted in the total weight of the fatty acid classes. Palmitic acid and a C18:1 acid, presumably oleic, were the most abundant fatty acids in the different lipid classes during larval development, together accounting for more than 70% of the total. The proportions of the fatty acids changed very little during development. Of the sterols, 24-methylene cholesterol was most abundant in both the free and esterified forms except on the first and second days when cholesterol ester was more abundant. Cholesterol-ester concentration decreased in such a way that on the fifth larval day the percentage composition of the sterol esters was almost identical to that of the free sterols. The composition of the free sterols remained practically constant during development.

Changes in T-cell subpopulations in mice during prolonged experimental secondary infection with Echinococcus granulosus

Balb/c mice were infected intraperitoneally with protoscoleces ofEchinococcus granulosus. After 15 months of infection, and by means of flow cytometry, the expression of T-cell markers CD3, CD4, and CDS on T cells from peripheral blood, spleen, and thymus was analyzed and compared with that of age-matched controls. Infected mice had higher percentages of CD3+, and CD4+ cells in peripheral blood, and higher percentages of CD8+ cells in the spleen, when compared with control mice. CD4+ and CD8+ cells in peripheral blood and CD8+ cells in thymus also showed higher percentages of expression of interleukin-2 receptor. The results infer a role for interleukin-2 in experimental secondary echinococcosis.

Hymenolepis muris-sylvaticae in laboratory rodents

The establishment, growth, survival and distribution ol Hymenolepis muris-sylvaticae m different laboratory animals (Wistar rats, golden hamsters, CFLP and NMRI mice) after oral infection and surgical transplantation were determined. Worms that establish in CFLP and NMRI mice grow exponentially but are rejected at different times p.i. depending on the strain of mice and mode of infection. Only in golden hamsters will H. muris-sylvaticae develop to a mature worm; in rats there is no growth at all. Worms of all sizes are found in the posterior half of the small intestine in rats and both strains of mice; in hamsters the worms are recovered more anteriorly.

Immunological aspects in the rejection process of Hymenolepis muris-sylvaticae from CFLP and NMRI mice.

When mice were treated with 1.25 mg cortisone acetate thrice weekly, recovery of Hymenolepis muris-sylvaticae was significantly higher than in untreated controls, both in oral infections with six cysticercoids and surgical transplantations of one 7-day or 8-day-old worm. Cortisone treatment also resulted in the worms being located more anteriorly in the small intestine. Evidence of an immunological response against the tapeworm in the intestine is given by: an accelerated rejection of a secondary oral cysticercoid infection and a significant difference of the dry weights of the worms recovered on day 10 in CFLP mice; an accelerated rejection of a secondary surgical infection on days 4 and 6 in CFLP mice and on days 3 and 4 in NMRI mice; an accelerated rejection of a secondary surgical infection given 3 and 6 months after the primary immunizing infection in SWISS-albino mice.

Hymenolepis muris-sylvaticae and H. microstoma: immunological cross-reaction in mice.

A primary infection with Hymenolepis microstoma strongly protects against cross-infection with H. muris-sylvaticae and also against secondary infection with H. microstoma in NMRI mice, resulting in an accelerated loss of worms and a weight reduction of the remaining worms. A primary infection with H. muris-sylvaticae causes an accelerated rejection of secondary infection with H. muris-sylvaticae but it has no effect on cross-infection with H. microstoma, neither with regard to worm recovery nor with regard to worm biomass. Determinations by enzyme-linked immunosorbent assay of antibody concentrations in the mouse sera revealed that: (1) the antibody response evoked by H. microstoma infection is much greater than by H. muris-sylvaticae infection; (2) a cross-infection with H. muris-sylvaticae boosts the antibody response evoked by H. microstoma infection; (3) H. microstoma antigen can be used to measure antibody concentration against both H. microstoma and H. muris-sylvaticae; and (4) although H. muris-sylvaticae is rejected faster in a cross-infection (i.e., after a primary H. microstoma infection) than in a secondary infection (i.e., after a primary H. muris-sylvaticae infection), antibodies evoked by the primary H. microstoma infection show little cross-reaction with H. muris-sylvaticae antigen. This suggests that it is doubtful whether serum antibodies are the direct effectors in worm rejection.