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PubMed1990

Eosinophil responses to Fasciola hepatica in rodents.

Qualitative and quantitative cellular changes in the peripheral blood and bone marrow of resistant (rat) and susceptible (mouse) hosts of Fasciola hepatica have been examined. Eosinophil numbers in the peripheral blood and bone marrow of both hosts increased almost immediately following infection. Rats responded more rapidly than mice. Bone marrow colony formation in both rats and mice was greatly enhanced following F. hepatica infection. Injection of excretory/secretory (E/S) antigens of the fluke into rats and mice caused peripheral eosinophilia. Eosinophil levels in mice dropped by day 7 post-injection, but those in rats remained high. Eosinophil precursors in the bone marrow of injected animals also rose. Bone marrow colony formation in antigen-injected mice peaked sharply at day 7 but then fell rapidly. Rats injected with E/S antigens had about twice the level of bone marrow colonies as controls, 12 days post-injection. For most parameters measured, the magnitude of the responses of rats was greater than mice, which may be significant in the context of the rat's ability to acquire resistance to reinfection.

Animals↗
PubMed1991

Seasonal dynamics of Fasciola hepatica burdens in grazing Timahdit sheep in Morocco.

Seasonal transmission of Fasciola hepatica was observed in sentinel sheep and the dynamics of the snail intermediate host, Lymnaea truncatula, was followed over a 3-year study period in the Middle-Atlas mountains in Morocco. High fluke burdens were recorded in both lambs and ewes in the fall and winter, suggesting that transmission occurred in late spring. Fluke burdens ranged from one to 302 in ewes and from one to 345 in lambs. Infections with 200 or more flukes were always fatal. A unique feature of this study was the annual cyclical fluctuation of the fluke burdens. Burdens reached maximum levels during the winter and then declined to low numbers by late spring and summer. This suggested self-regulation which may be dependent on breed resistance or may be related to forage factors, including lack of forage (nutritional stress). Snail populations were cyclical and correlated with fluke transmission as observed in the sentinel sheep. The weather was observed to affect the snail populations which in turn limited fluke transmission.

Animals↗
PubMed1991

Aberrant energy-linked reactions in mitochondria isolated from the livers of sheep infected with the liver fluke Fasciola hepatica.

Respiration by mitochondria isolated from the livers of sheep following infection up to 15 weeks with F. hepatica was measured with the respiratory substrates pyruvate (plus malate) and succinate in the absence and presence of ADP; the rates were compared with those obtained by mitochondria isolated from livers of uninfected sheep. It was found that respiration supported by both substrates in mitochondria isolated from the left lobe but not the middle lobe of 4-week infected sheep exhibited abnormalities such that the acceptor control ratios were only marginally above one. Some, but not total, recovery was seen in the later stages of infection. The aberrant respiratory behaviour is similar to that observed with infected rats.

Animals↗
PubMed1993

Analysis of the results obtained using a technic of experimental primary infestation with Fasciola hepatica in the rat.

In this work, we analyzed the results obtained using a technic of infestation with Fasciola hepatica in the rat. The infestations were carried out with 30 metacercariae in a gelatin capsule. The humoral immune response, measured by ELISA, and the liver necroses, spleen size, number and length of the flukes recovered at necropsy were followed during the course of four experimental primary infestations. The results showed that the magnitude of the parasitic burden did not correlate with the humoral immune response of the rat. The study of the liver necroses, spleen size, fluke length and antibody titres showed that the use of 30 metacercariae in a capsule as a technic of infestation in the rat ensured the homogeneity of the parasite development and the humoral immune response of the host.

Animals↗
PubMed1995

A study of hepatic mitochondrial respiration and microsomal cytochrome P450 content in mice infected with the liver fluke Fasciola hepatica.

Previous studies of the effects of infection of Wistar rats with the common liver fluke, Fasciola hepatica, on liver bioenergetic and drug metabolism have demonstrated a loss of respiratory control in isolated mitochondria and reduced microsomal cytochrome P450 content, respectively, from 2 weeks post-infection throughout the acute phase of the infection. In the present study male Balb/c mice infected with F. hepatica showed a loss of respiratory control in isolated liver mitochondria only at 4 weeks post-infection. A similar time course was demonstrated for a reduction in hepatic microsomal cytochrome P450 content. Preparations from infected CBA mice showed similar changes to Balb/c mice but mitochondrial respiration in preparations from infected Swiss outbred mice was normal. A host difference between strains of mice and between mice and rats is therefore evident in the timing and extent of liver mitochondrial dysfunction and in the timing of the decrease in the cytochrome P450 content of hepatic microsomes. This difference between hosts may be related to the reported differences in cellular inflammatory responses to the migrating juvenile flukes in the livers of rats and mice.

Adenosine Diphosphate↗
PubMed1995

Avermectins and milbemycins against Fasciola hepatica: in vivo drug efficacy and in vitro receptor binding.

Few studies have examined activity against trematodes for the avermectin/milbemycin class of anthelmintics. To gain insight into this, 12 different members of the avermectin/milbemycin mode of action class were tested against juvenile Fasciola hepatica in a mouse model. The compounds chosen were Avermectin A1, Avermectin A2, Avermectin B1, Avermectin B2, Ivermectin, Ivermectin monosaccharide, Ivermectin aglycone, 13-deoxy ivermectin aglycone, Moxidectin, 13-O-methoxyethoxymethyl ivermectin aglycone, 4"-deoxy-4"-epi-methylamino avermectin B1, and 4"-deoxy-4"-epi-acetylamino avermectin B1 5-oxime. Each of these compounds was administered orally to 4 mice at 2.0 mg kg-1. These mice had been administered 3 metacercariae of F. hepatica 14 days prior to treatment and all mice were necropsied 4 days after treatment. At necropsy, none of the individual avermectin or milbemycin-treated groups showed any significant activity (P > 0.05) against juvenile F. hepatica relative to a vehicle-treated control. In a receptor binding study, adult F. hepatica that had been obtained from sheep were homogenized, their membranes incubated in the presence of 3H-ivermectin, and then measured for high affinity binding sites. The same was done with the free-living nematode, Caenorhabditis elegans. While the C. elegans membranes displayed high affinity 3H-ivermectin binding sites over the range of ivermectin concentrations tested (5-100 nM), no significant 3H-ivermectin binding sites were detected in the F. hepatica membranes. Based on these data, it seems unlikely that any avermectin or milbemycin will show activity against F. hepatica, and certainly makes one pessimistic about possible activity of this mode of action class against trematodes in general.

Animals↗
PubMed1995

Humoral and cellular immune responses to Fasciola hepatica experimental primary and secondary infection in sheep.

Blood leukocyte changes, serum hepatic enzyme levels, lymphocyte proliferation in response to Concanavalin A (ConA) and to parasitic excretory-secretory products (FhESP), and antibody (IgG and IgM) responses (ELISA and Western blot) were studied in sheep, the natural susceptible host of F. hepatica, during the first 3 months of an experimental primary or secondary infection. The proportion of flukes established was similar in once- and twice-infected groups, but the flukes originating from the secondary infection migrated more rapidly to the bile ducts. Primary infection induced a marked peripheral eosinophilia from 3 to 13 weeks post-primary infection (PPIW). FhESP-specific IgM were produced from PPIW 2 with peaks in PPIW 3 and 9-10; FhESP-specific IgG increased from PPIW 2 to 6 and became stable afterwards. Western blotting revealed 12 major antigenic fractions in FhESP from 12, 15, 20, 24, 27, 28.5, 30, 41, 51, 56, 69 and 156 kDa; some non-specific ones have been characterized. A sequential recognition of higher then lower molecular weight antigens was observed. FhESP-specific lymphocyte proliferation was marked from PPIW 2 to 5. In contrast, ConA stimulation of lymphocytes was decreased. After secondary infection in PPIW 6, immune responses were modified. The ConA-induced lymphocyte proliferation was transitorily increased. In contrast, the humoral response, in particular against the early recognized antigens, and the level and the duration of the FhESP-specific lymphocyte proliferative response, were reduced.

Animals↗
PubMed1995

Importance of T-cell-dependent inflammatory reactions in the decline of microsomal cytochrome P450 concentration in the livers of rats infected with Fasciola hepatica.

The concentration of cytochrome P450, measured spectrophotometrically in microsomal preparations from the livers of rats infected with 30 metacercariae of Fasciola hepatica, declined by approximately 50% at 3 weeks post-infection. Treatment of infected rats with the anti-inflammatory agent dexamethasone (2 mg/kg at 48 h intervals for 8 days prior to assay) abolished the decline in P450 content. Assay of P450 in infected congenitally athymic (nude) rats showed normal levels. These results demonstrate that the T-cell-dependent inflammatory response in the liver of the host is a necessary factor in the development of the decline in hepatic P450, which is known to compromise the metabolism of certain drugs in infected hosts.

Animals↗
PubMed1996

Polarization and chemokinesis of ovine and human neutrophils in response to Fasciola hepatica excretory-secretory products.

The effect of Fasciola hepatica excretory-secretory products (ES products) on the polarization and chemokinesis of sheep and human neutrophils was investigated. Flukes were cultured overnight in RPMI-1640 medium, and the resulting ES products concentrated by dialysis (cut-off 1.2 kDa) before use. At the concentrations used toxicity tests showed no effect on neutrophil viability, but ES products were capable of causing morphological changes and chemokinesis in both sheep and human neutrophils. The polarizing effect of the ES products was found to be greater in the case of sheep neutrophils with 81% of cells polarizing at 80 micrograms total ES protein/ml as opposed to 36% of human neutrophils. Chemokinesis in response to 80 micrograms total ES protein/ml was significant (P < 0.01) in both species with sheep producing the stronger response. Delipidation of the ES products with Lipidex caused no loss of polarizing activity, nor did the purified lipid fraction show any polarizing effect. ES products lost polarizing activity after heat treatment or trypsin digestion. Preliminary fractionation on an S-300 Sephacryl column suggested the presence of at least four fractions capable of causing polarization in sheep neutrophils.

Analysis of Variance↗