Echinococcus granulosus cyst fluid enhances epithelial-mesenchymal transition

Cystic echinococcosis is characterized by fluid-filled hydatid cysts in the liver and lungs. The cysts are surrounded by a host fibrous layer (the pericyst) which acts to isolate the parasite from surrounding tissues. Previous studies in liver cysts have indicated that the parasite may be a stimulating fibrosis. The aim of this study was to investigate whether hydatid cyst fluid (HCF) could influence the potential for fibrosis to occur in lung tissue by stimulating epithelial to mesenchymal transition (EMT) in a human lung epithelial cell line. An adenocarcinoma-derived alveolar basal epithelial cell line (A549) was used as a model for human alveolar epithelial cells (AEC II). These were cultured in vitro with HCF (UK sheep origin). Assays to investigate cell proliferation, cell migration and expression of cytoskeletal markers showed that HCF could stimulate changes indicative of EMT, including enhanced cell proliferation and migration; increased expression of mesenchymal cytoskeletal markers (fibronectin and vimentin) accompanied by a down-regulation of an epithelial marker (E-cadherin). Molecules within hydatid cyst fluid are capable of inducing phenotypic changes in A549 cells indicating that the parasite has the potential to modify lung epithelial cells which could contribute to fibrotic reactions.

Canine echinococcosis in Turkana (north–western Kenya): a coproantigen survey in the previous hydatid-control area and an analysis of risk factors

A study of Echinococcus granulosus infection in dogs, with risk-factor analysis, was carried out in the endemic area of northern Turkana district, Kenya, using necropsy on 42 strays and a coproantigen-ELISA survey of 161 owned animals. During the post-mortem examinations, 14 (33%) of the necropsied dogs were found infected with E. granulosus, with a mean burden of 540 worms (range=two to 4080 worms). The 26 necropsied dogs that came from the north-western Lokichoggio division--an area where, from 1983 to 1997, there had been a continuous programme of hydatid control--showed a similar prevalence of infection to the other dogs (34.6%) but a significantly lower mean burden, of 53 worms (range=two to 300). Forty-two (26%) of the animals tested for Echinococcus coproantigen were found positive. Although the dogs from the Lokichoggio division were more likely to be coproantigen-positive (29%) than those from the central Kakuma division (20%) or the north-eastern division (18%), the differences were not statistically significant. In questionnaire-based interviews, the owners of the dogs tested for coproantigens were asked about possible risk factors for canine infection with E. granulosus. Women were found to have twice the level of contact with dogs as men. The results of a univariate analysis of the dog-owners' responses revealed six factors that appeared to be significantly associated with a coproantigen-positive dog: non-restraint of the dog (P<0.001); dog fed on raw offal (P<0.001); the improper disposal of slaughter offal (P<0.001); the dog-owner's lack of knowledge about the transmission of echinococcosis (P=0.001); the dog not receiving anthelmintic treatment (P=0.003); and dog age < or =5 years (P=0.01). The results of a multivariate analysis confirmed that lack of dog restraint, access to raw offal, and young age of the dog (< or =5 years) each significantly increased the risk of coproantigen positivity (P, 0.005). Dogs that scavenged from cooking pots, were used to clean babies, had access to the inside of houses, and/or slept indoors appeared, however, to be at no increased risk of coproantigen positivity. The present results are discussed in relation both to older information on the epidemiology and role of human behaviour in the transmission of E. granulosus in Turkana, and the effects of the hydatid-control programme that ran continuously in the north-western division of Turkana between 1983 and 1997.

The occurrence of the trematode Plagiorchis muris in the wood mouse Apodemus sylvaticus in North Yorkshire, UK

Wood mice Apodemus sylvaticus were trapped each September over a 13-year period, from 1993 to 2005, in a wooded area adjacent to Malham Tarn, Yorkshire, UK. Plagiorchis muris was found to be the dominant intestinal trematode and occurred in every year of sampling, with an overall prevalence of 16.9%. This appears to be the first record of P. muris in A. sylvaticus within the UK. The mean worm burden was 2.03 and the distribution of the parasite within mice was typically overdispersed. No difference in prevalence relative to host sex was evident although there was a higher prevalence of 21.9% in larger older mice compared with 9.1% in juveniles, which probably relates to a greater foraging activity in older mice. Annual prevalence values of P. muris infections varied significantly over the study period with higher prevalences being associated with years with a high spring/summer rainfall. The second intermediate hosts for P. muris include a variety of aquatic insect larvae and it is likely that the higher rainfall may result in the occurrence of temporary water bodies suitable for the development of insect larvae.

Antibody responses in human cystic hydatid disease to the laminated layer of Echinococcus granulosus

The laminated layer of hydatid cysts of Echinococcus granulosus represents a considerable amount of parasite material. Its antigenic role, however, is unclear. Extracts of laminated layer taken from sheep cysts were analysed in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE) and were found to contain bands at 55 and 25-29 kDa, which reacted with an anti-sheep IgG antibody probe, indicating that these were likely to be host-contaminating components within the layer. However, the same bands were also recognised by a significant proportion of human hydatid patients, particularly by IgG4 antibodies, and not by negative control individuals. These individuals did not recognise immunoglobulin heavy and light chains in a sheep serum extract in the same manner. It seems likely that there are either host or parasite antigenic components at similar molecular weights or that certain parasite antigens may share epitopes with sheep immunoglobulins. The antigens at 25-29 kDa were found to be glycoproteins by lectin blot analysis and may be important markers of disease status.

Human cystic echinococcosis in two Mongolian communities in Hobukesar (China) and Bulgan (Mongolia)

In order to investigate the prevalence of human cystic echinococcosis (CE) in traditional Mongolian communities in western Mongolia and Xinjiang (northwest China), studies were carried out between 1995 and 2000, on two ethnically identical populations in Hobukesar (China) and Bulgan (Mongolia). The prevalence of human hepatic CE in the two communities was significantly different. In Hobukesar, human CE prevalence by ultrasound was 2.7% (49/1844), while in Bulgan it was 0.2% (4/1609) (P<0.001). Dog surveys showed that coproantigen-positive rates or dog necropsy positives were similar in both communities (35.0% in Hobukesar and 35.7% in Bulgan). Comparing possible risk factors, there appeared to be some significant differences between the two communities, which might contribute to the observed difference in CE prevalence. These included: the proportion of herdsman or farmers recorded; the proportions of dog ownership and livestock ownership; and the proportion of families practising home slaughter. The presence of a Russian dog-dosing programme up to the mid-1980s may explain the lower prevalence of human CE in the Bulgan population; no similar programme operated in the China-administered Hobukesar community.

Detection of antibodies to Staphylococcus aureus Toxic Shock Syndrome Toxin-1 using a competitive agglutination inhibition assay

AIMS

To develop a competitive agglutination inhibition assay (CAIA) for the detection of anti-Toxic Shock Syndrome Toxin-1 (TSST-1) antibody in serum samples using a commercially available reverse passive agglutination assay (RPLA) kit.

METHODS AND RESULTS

TSST-1 toxin and sera were incubated together, so that anti-toxin IgG would complex with the toxin. Latex particles sensitized with rabbit IgG anti-TSST-1 were added to test for un-complexed toxin. The sensitivity and specificity of the CAIA assay was determined relative to positive and negative ELISA results. The sensitivity (proportion of positive ELISA sera which tested positive by CAIA) was 66% whilst the specificity (proportion of ELISA negative sera which tested negative by CAIA) was 75%. Seven sera (14%) were negative by ELISA but positive for CAIA and 12 (18.8%) were positive for ELISA but negative for CAIA, suggesting some interference with the assays. Statistical analysis showed no significant difference between the methods in terms of the numbers of individuals testing positive (chi2, P = 0.04).

CONCLUSIONS

The CAIA assay allowed detection of anti-TSST-1 within 18 h and was simple to read visually.

SIGNIFICANCE AND IMPACT OF THE STUDY

The method is a useful test for individual serum samples and a preliminary investigation for medical screening of suspected toxic shock syndrome and is applicable in situations where antibody assays are not routinely used for anti-TSST-1 and also where sophisticated equipment (e.g. microtitre plate reader) is not available.

Classification, follow-up and recurrence of hepatic cystic echinococcosis using ultrasound images

Ultrasound image and morphological structure of hepatic cystic echinococcosis (CE) were analysed in 277 human cases (385 hepatic hydatid cysts). These included 65 CE cases from community surveys carried out between 1995 and 2000 in 3 countries (China, Mongolia and Jordan) and 212 cases from a clinical hospital survey from Xinjiang, China. A new simplified WHO ultrasound classification for human CE was assessed, and considered useful. It is proposed that type, size and number in particular need to be included in the ultrasound classification of hepatic CE. For comparative purposes 6 categories of type were classified in the study as Type 0 to Type 5 (T0-T5): T0, univesicular without pathognomonic signs; T1, univesicular with pathognomonic signs; T2, cysts with sagging or floating laminated membrane; T3, cysts containing daughter cysts; T4, solid mass or mixed cysts; and T5, cysts with partial or full calcifications. This differs from the WHO classification wherein Type T3 cysts (daughter cysts present) are considered a pathological stage to occur in general prior to the sagging or floating membrane (T2) stage. Recurrent hydatid cysts in the liver were also studied based on morphological structures observed directly from surgical intervention. Case follow-up over 1-5 years since endocystectomy in the community surveys indicated 10% (2/10) recurrence of cysts in the residual surgical cavity. Recurrent CE included 2 (2/4) cases after percutaneous treatment.

Echinococcosis: disease, detection and transmission

Echinococcosis is one of the world's most geographically widespread parasitic zoonoses, with transmission occurring in tropical, temperate and arctic biomes. Most human infections are due to Echinococcus granulosus transmitted between domestic dogs and livestock, but this cosmopolitan species also cycles between wild carnivores (principally canids) and wild ungulates. The other species with significant zoonotic potential is E. multilocularis that occurs naturally in fox definitive hosts and small mammal intermediate hosts. These two species cause human cystic or alveolar echinococcosis respectively, which may be considered serious public health problems in several regions including developed countries. This review provides an introductory overview to the Supplement and summarises the biology and epidemiology of these two related cestodes with an emphasis on applied aspects relating to detection, diagnosis and surveillance in animal and human populations, and includes aspects of transmission ecology, and also considers aspects of community epidemiology and potential for control.

Rapid dot-ELISA for the detection of specific antigens in the cyst fluid from human cases of cystic echinococcosis

A rapid dot-ELISA was developed for the detection of specific antigens in samples of cyst fluid from human cases of Echinococcus granulosus infection, permitting the confirmation of cystic echinococcosis (CE). Peroxidase-conjugated antibodies against antigen B (derived from the fluid in the cysts of sheep infected with E. granulosus) were used to test cyst-fluid samples from 22, surgically confirmed cases of human CE and 21 domestic animals (horses, sheep, buffalo, a cow and a camel) with CE. All of these samples were found to be strongly positive in the dot-ELISA, by direct reading with the naked eye. In contrast, fluid samples from seven, non-parasitic liver cysts of human origin were all negative, and a sample taken from the residual cavity left in a patient after previous CE surgery showed a weakly positive reaction. The antigen-detection assay, which can be completed within 10 min, may be a useful 'bedside' test for the differential diagnosis of cysts during surgery or percutaneous treatment for suspected CE.

In-vitro susceptibility of hydatid cysts of Echinococcus granulosus to nitric oxide and the effect of the laminated layer on nitric oxide production

Murine hydatid cysts of Echinococcus granulosus were incubated in vitro in the presence of nitric oxide produced from S-nitroso-N-acetylpenicillamine (SNAP) or interferon-gamma activated peritoneal macrophages. In both situations, evidence of cyst damage and death was observed by microscopy in over 77% of cysts after 3 days, indicating that intact hydatid cysts could be susceptible to a Th1 driven macrophage attack. A crude extract of the laminated layer from cysts was found to be able to reduce the production of nitric oxide from activated macrophages in vitro and in vivo and this may have been due to phagocytosis of laminated layer fragments by the macrophages. The results indicate that, although cysts may be susceptible to the effects of nitric oxide, the laminated layer may be involved in downregulating nitric oxide production.

Cystic echinococcosis in semi-nomadic pastoral communities in north-west China

In order to determine the prevalence of human cystic echinococcosis (CE) in semi-nomadic traditional pastoralist groups in north-west China, 2 large community studies were undertaken in Altai and Tacheng Prefectures in 1990/91 and 1995/96, respectively. The Kekergash community (Altai) comprised mainly ethnic Kazakhs, whereas the Narenhebuke community (Tacheng) comprised mainly Mongolians. Populations were screened for CE by abdominal ultrasound scan (US) and serological tests. The total prevalence of confirmed human CE was higher in Narenhebuke (2.7%, 49/1844) than in Kekergash (0.9%, 17/1861; P < 0.01). Within each community there was no significant difference of CE prevalence between the Kazakh and Mongolian groups, although Han Chinese exhibited twice the rate of CE (4.9%) in Narenhebuke compared to the dominant Mongolian population. For each community, human CE prevalence increased with age and there was a greater risk associated with the practice of home slaughter of livestock. Dogs were screened for Echinococcus granulosus infection and re-infection levels using a highly specific coproantigen test. The proportion of dogs with positive coproantigen tests was significantly higher in Narenhebuke (36.0%, 50/139) compared to Kekergash (17.8%, 16/90). In Narenhebuke the re-infection levels of dogs, as determined by coproantigen positivity, were higher in the winter quarters (49.4%, 39/79) compared to the summer quarters (18.3%, 11/60; P < 0.01). Furthermore, coproantigen re-test positivity was 25% at 3 months and 29.2% at 7 months. Highest dog coproantigen positivity was obtained over the winter period.

Apoptosis in human Jurkat T cells after culture with live Taenia crassiceps cysticerci in vitro

This study examines the effects of Taenia crassiceps cysticerci on the viability of a human T lymphocyte cell line (Jurkat). Both budding and non-budding T. crassiceps metacestodes were cultured over 24 and 48 h in the presence of Jurkat cells. Cell viability decreased with increasing numbers of cysticerci, particularly budding cysticerci. Single cell gel electrophoresis (comet) analysis, which grades DNA damage, showed a significant increase in apoptosis at 24 and 48 h. The morphology of treated cells was determined using acridine orange with the classical morphology of apoptotic bodies seen to increase with increasing cysticerci numbers over time. These results indicate that parasite-induced apoptosis occurs during murine cysticercosis. Such a mechanism may be important in survival of other metacestode infections of medical or veterinary importance.

Helminth parasites of the wild rabbit Oryctolagus cuniculus near Malham Tarn, Yorkshire, UK

Between 1992 and 1996, 95 rabbits from the immediate locality of Malham Tarn, North Yorkshire, UK were examined for the presence of helminth parasites. All the examinations took place in late September or October. Three species of nematodes, Graphidium strigosum, Passalurus ambiguus and Trichostrongylus retortaeformis and two species of cestodes, Taenia pisiformis and Cittotaenia pectinata were identified. There were no associations between helminth species richness and year of sampling, host weight or sex. A logistic model was fitted to the prevalence data from these helminths as was an over-dispersed Poisson model to the worm burden data. Graphidium strigosum was the most frequently identified species with an average prevalence of 78%. The mean prevalence and intensity of Graphidium infection were significantly effected by sampling year. The lower than normal rainfall recorded at the Tarn during the years 1995 and 1996 may have be one reason for this pattern. The worm burden of G. strigosum was significantly positively associated with rabbit body weight. The intensity of infection with P. ambiguus was significantly higher in female rabbits. There was a significant non-linear relationship between P. ambiguus worm burden and rabbit weight (P = 0.002) with worm burdens being highest in the 1000 g to 1499 g weight cohort. Trichostrongylus retortaeformis was only identified in 1994 and male rabbits harboured significantly higher worm burdens than females (48 vs. 7, P = 0.022). Over the five years, the average Taenia pisiformis prevalence was 31% and there was a significant positive association between worm burden and rabbit weight (P = 0.001). Cittotaenia pectinata had a prevalence of 37% over the whole study period with no interactions between prevalence or intensity and body weight, year of sampling or rabbit sex. All five helminths showed an overdispersed distribution with k values less than 1.

An extensive ultrasound and serologic study to investigate the prevalence of human cystic echinococcosis in northern Libya

A prevalence study of abdominal cystic echinococcosis (CE) was undertaken in the northwest, north-central, and northeast regions of Libya. A total of 36 villages along the coast were included, in which 20,220 people were screened by portable ultrasound. Three hundred thirty-nine (1.7%) were diagnosed with CE. There was no significant difference between CE prevalence rates in the three regions of Libya (mean = 1.6%); however, intervillage rates were variable, ranging from 0% to 4.5%. The prevalence of CE increased significantly with age (P < 0.0001) and females were significantly more affected (2%) than males (1.3%) (P < 0.0001). Cases of CE were distributed among 3.2% of housewives, 2.6% of farmers, 2.3% of male civil servants, 1.3% of female students, and 1.1% of male students. Housewives (P < 0.0001) and students (P < 0.0001) were significantly more at risk for CE. A statistically significant proportion (62% [210 of 339]) of CE cases kept dogs (P < 0.0001). Of the ultrasound-positive CE cases 69% (233 of 339) were antibody seropositive by ELISA using Echinococcus granulosus hydatid cyst fluid antigen B. Blood samples (n = 10,096) collected onto filter papers were taken randomly from ultrasound-negative people who entered the study, of which 11.2% were found to be seropositive. Seropositivity increased with age (P < 0.0001), with females exhibiting higher seroprevalence than males for all age groups (P < 0.0001). Seroprevalence was distributed occupationally among 17.3% of female students, 11.2% of male students, 8.3% of housewives, 7.3% of farmers, and 6.4% of male civil servants. Housewives and students were more likely to be seropositive (P < 0.0001). Forty-seven percent (526) of the seroreactors kept dogs. All liver hydatid cysts detected by ultrasound during community screening were classified according to morphology and size into six types. Type I (17.5% of all cases) were small univesicular cysts less than 50 mm in diameter with no laminations or daughter cysts. Type II (34%) were univesicular cysts with only laminations. Type IIIa (8.5%) were univesicular cysts with the appearance of laminations and daughter cysts. Type IIIb (13%) were univesicular with laminations and less prominent daughter cysts. Type IV (5.6%) presented as a solid mass. Type V were degenerated calcified or partially calcified cysts (13.2%). Type VI presented as multiple cysts (8% of all cases). The CE cases that exhibited Types II, IIIa, IIIb, IV or VI cysts showed the highest seropositivity (86%, 96%, 95%, 100%, and 96%, respectively), while Types I and V were the least seroreactive (38% and 22%, respectively). Cases of CE occurred in 311 families, with 93% having only one member as a CE case while 7% of the families had two or more cases. However, 25% of the ultrasound-negative persons belonging to families with an index CE case were seropositive for antibodies to Echinococcus. These results confirm the importance of human CE in Libya. They also confirm the usefulness of ultrasound combined with serology as a mass screening approach for CE in north African communities.

T-cell activity associated with secondary infections and implanted cysts of Echinococcus granulosus in BALB/c mice

Selected cytokine profiles of lymphocytes were assessed in BALB/c mice infected with protoscoleces of Echinococcus granulosus. Late stages of the infection (three months+) were characterized by more dominant Th2 activity with elevated IL-4 and IL-10 and reduced IFN-gamma output by Con-A and antigen stimulated splenocytes. Circumparasitic leucocytes produced mainly IL-10 by five months post infection. A peak in IFN-gamma production in the first month of infection may suggest Th1 or Th0 activity at this time and this may be correlated with initial protoscolex death. In addition, cytokine profiles from mice implanted with intact hydatid cysts were also assessed. At two weeks post implantation all cysts were still viable and cytokine production was characterized mainly by elevated IL-10 production. However, at four months post implantation, some of the cysts from two mice had been killed whilst all cysts in the remaining mouse remained viable. In the mice where dead cysts were present, elevated levels of IFN-gamma were detected from splenocytes and circumparasitic cells. Elevated IL-4 was also evident with the splenocytes. In the mouse with viable cysts IFN-gamma production was reduced Results indicate that IFN-gamma(Th1) activity may be correlated with killing of both protoscoleces and established cysts of E. granulosus.

Human cystic echinococcosis in a Uruguayan community: a sonographic, serologic, and epidemiologic study

A prevalence and transmission study of human cystic echinococcosis (CE), due to infection with the dog tapeworm Echinococcus granulosus, was undertaken in the village of La Paloma in central Uruguay. The human population was registered and screened for CE by abdominal ultrasound scan as well as a number of serologic tests. Dogs were screened for E. granulosus infection by arecoline purgation as well as specific coproantigen testing. The total prevalence of human CE (new cases and those with a previous history) was 5.6% (64 of 1,149); 3.6% (40) of the cases were new ultrasound detected asymptomatic cases (mean age = 45 years). Age prevalence increased from 1.1% in the 4-6-year-old group to > 11% in the > 60-year-old group; the 20-29-year-old group had a significantly higher CE rate of 7.4%, compared with younger and older age groups, and there was no difference between sexes. A CE rate of 3.9% (20 of 514) was also recorded by ultrasound for new cases in the population residing outside the village. Most of the hydatid cysts were located in the liver presenting as either univesicular cysts or a solid mass, and of those 71% and 63%, respectively, with such cyst presentations were seropositive against E. granulosus cyst fluid antigens. Two of eight individuals who were filter paper blood spot seropositive, but ultrasound scan negative, were subsequently diagnosed respectively with pulmonary hydatidosis after radiography, and hepatic hydatidosis after computed tomography scan. Of 36 households with a CE patient, 32 were single cases while four households each harbored two CE cases. This did not represent a clustered distribution within families (23 of 117). Almost 20% of the dogs from La Paloma were found infected with E. granulosus after purge examination, with a mean worm number of 67 (range = 1-1,020). An additional eight dogs that were purge negative were Echinococcus coproantigen positive. The study showed that human CE is highly endemic in Uruguay, with one of the highest local prevalence rates in the world. Transmission appears to occur readily within well-developed towns, as well as on rural sheep ranches. Mass screening by ultrasound scanning with confirmatory serologic testing is an effective approach to case detection at the community level.

Fear conditioning induces associative long-term potentiation in the amygdala

Long-term potentiation (LTP) is an experience-dependent form of neural plasticity believed to involve mechanisms that underlie memory formation. LTP has been studied most extensively in the hippocampus, but the relation between hippocampal LTP and memory has been difficult to establish. Here we explore the relation between LTP and memory in fear conditioning, an amygdala-dependent form of learning in which an innocuous conditioned stimulus (CS) elicits fear responses after being associatively paired with an aversive unconditioned stimulus (US). We have previously shown that LTP induction in pathways that transmit auditory CS information to the lateral nucleus of the amygdala (LA) increases auditory-evoked field potentials in this nucleus. Now we show that fear conditioning alters auditory CS-evoked responses in LA in the same way as LTP induction. The changes parallel the acquisition of CS-elicited fear behaviour, are enduring, and do not occur if the CS and US remain unpaired. LTP-like associative processes thus occur during fear conditioning, and these may underlie the long-term associative plasticity that constitutes memory of the conditioning experience.

Expression and immunological characterisation of Echinococcus granulosus recombinant antigen B for IgG4 subclass detection in human cystic echinococcosis

A 165bp DNA fragment derived from the 12 kDa subunit of Echinococcus granulosus antigen B (AgB), a major hydatid cyst fluid antigen was cloned in the pMa1-c2 expression vector. A 52 kDa maltose binding-AgB fusion protein (rAgB.MBP) was produced and inclusion bodies containing the fusion protein were solubilised in urea and affinity purified on an amylose-Sepharose 6B column. The immunogenicity of the purified recombinant antigen for IgG4 antibody detection was tested with human serum using immunoblotting, ELISA and dot-ELISA assays and compared to native AgB. Both recombinant and native AgB preparations were highly reactive for human IgG4 antibodies in serum of cystic echinococcus (CE) patients. Recombinant AgB.MBP (rAgB.MBP) showed approximately 65% sensitivity in detection of IgG4 serum antibodies by ELISA from confirmed CE patients. Cross-reactivity (33%) occurred with alveolar echinococcosis (E. multilocularis) sera but recombinant AgB showed no seroreactivity with sera from other helminth infections tested (schistosomsis, onchocercsis, cysticercosis) or from uninfected individuals residing in CE endemic or non-endemic regions. The serologic sensitivity (63%) for IgG4 antibodies of a native AgB fraction enriched from human hydatid cyst fluid was similar to that for recombinant AgB (65%) though specificity was slightly lower (81%). A dot-ELISA for detection of total IgG, incorporating the rAgB.MBP resulted in 74% sensitivity and 88% specificity for human CE and 93% sensitivity and 65% specificity for native AgB. Recombinant AgB is a potential replacement for native antigens currently being used and could provide a better standardised E. granulosus specific test for clinical confirmation for CE especially for IgG4 antibody detection which appears to be predominantly associated with advanced disease.

AMPA receptor facilitation accelerates fear learning without altering the level of conditioned fear acquired

Rats treated with the AMPA receptor-facilitating drug 1-(quinoxolin-6-ylcarbonyl)piperidine (BDP-12) during training acquired fear conditioning to a tone faster than vehicle-treated controls. The effect on acquisition was dependent on the dose given. BDP-12-treated rats and vehicle-treated controls reached the same level of conditioned fear and extinguished at the same rate. The dissociation of learning rate from these other normally covariant measures suggests that the drug had a specific and isolated effect on acquisition. Controls for drug effects on stimulus sensitivity, locomotor activity, generalized fearfulness, and other performance factors support this interpretation. The known action of BDP-12 on receptor dynamics suggests that its effect on acquisition may be attributed to specific modulation of an AMPA and NMDA receptor-dependent plasticity mechanism. The finding that the drug accelerates acquisition but does not affect the level of conditioned fear acquired parallels the effect of the drug on long-term potentiation (LTP) (increasing the rate but not the ceiling of potentiation) and suggests that common mechanisms may underlie fear conditioning and LTP.

IgG1 and IgG4 serum antibody responses in asymptomatic and clinically expressed cystic echinococcosis patients

IgG1 and IgG4 subclass antibody responses were investigated in two clinically different groups of hepatic cystic echinococcosis (CE) patients. One group consisted of surgically proven CE cases (clinically expressed hospitalized cases) and a second group comprised asymptomatic CE patients (first time community detected cases) diagnosed by portable ultrasound and serology in four different endemic communities. Fifty eight sera from surgically proven CE patients and 133 sera from asymptomatic ultrasound diagnosed CE cases were screened by ELISA using purified human hydatid cyst fluid antigen B for total specific IgG, IgG1 and IgG4 antibodies. Fifty sera from healthy individuals from within endemic regions were used as control negatives. Compared to control negatives total IgG antibody levels were elevated in both surgically proven (85%) and asymptomatic CE cases (77%) but there was no significant difference between the two groups. IgG1 subclass antibody levels were also elevated in both surgically proven (55%) and asymptomatic cases (58%) compared to endemic controls and similarly the difference in this response was not significant between these two groups. In contrast the prevalence of IgG4 antibodies in surgically confirmed chronic CE patients was greater (71%) than the respective IgG1 antibody levels (55%). The greatest difference in specific antibody response, between advanced surgically confirmed CE patients and ultrasound detected asymptomatic CE cases, was observed for IgG4 antibody levels which were detected in 71% of symptomatic compared to only 23% of asymptomatic patients (P < 0.0001). These observations confirm that IgG4 is an important diagnostic parameter for clinically expressed cystic echinococcosis in humans and suggest that a switch from a predominant IgG1 response to IgG4 might occur in CE patients as the disease progresses.

A pilot, serological survey for cystic echinococcosis in north-western Mongolia

The seroprevalence of cystic echinococcosis in north-western Mongolia was determined in a cross-sectional study of 334 semi-nomadic pastoralists in their summer grazing areas. Overall, 5.2% of the subjects were found to be strongly seropositive for antibodies to Echinococcus granulosus antigen B by ELISA. Only 10% of the adult subjects (aged > or = 15 years) had heard of the disease and only 5% recognized hydatid cysts in their livestock (in contrast to the neighbouring province in China, where 76% had seen and recognized cysts in the organs of slaughtered animals). The close association between Mongolian pastoralists, their dogs and livestock is likely to encourage ready transmission of the parasite in a region where home slaughter is practised and offal for various scavengers, including domestic dogs. Further information is needed to determine the prevalence of infection in other intermediate hosts and in dogs and the clinical importance of the disease in this remote region.

Echinococcus granulosus antigen B and seroreactivity in natural ovine hydatidosis

Hydatid cyst fluid from sheep and camels infected with Echinococcus granulosus, together with partially purified preparations of hydatid fluid antigen B and a recombinant antigen B product, were tested in an ELISA for their ability to detect IgG antibodies against E granulosus in the serum of naturally infected sheep. The antibody activity in sera from sheep naturally infected with Taenia hydatigena cysticercosis or Fasciola hepatica was also tested. All the antigen preparations from native hydatid cyst fluid were able to detect antibodies in the sera from a significant proportion of sheep with natural hydatid cyst infection, as identified by inspection at slaughter, although the seroreactivity was variable. The native antigen B preparation from camel hydatid cyst fluid gave the highest sensitivity in the ELISA (total 90 per cent), with 99 per cent specificity. In all cases, the recombinant antigen B was the least sensitive antigen (25 per cent) although it was highly specific (99 per cent).

Immunoblot evaluation of IgG and IgG-subclass antibody responses for immunodiagnosis of human alveolar echinococcosis

Antigen binding of total-IgG and IgG-subclass antibodies from patients with alveolar or cystic echinococcosis (AE and CE) was assessed by immunoblotting. Antigen extracts were prepared from Echinococcus multilocularis protoscoleces (EmP) or from homogenized E. multilocularis metacestode tissue (EmCH). Antigens of approximately 44, 35, 21, 17.5 and 16.5 were recognized by total-IgG and IgG1- and IgG4-subclass antibodies in some of 50 human AE sera from China, Japan or France. The 44- and 35-kDa polypeptides, present in both EmP and EmCH extracts, were recognized by total-IgG antibodies in sera from 82% and 66% of the AE patients, respectively. However, over 30% cross-reactivity occurred between these two antigens and sera from CE and Taenia solium cysticercosis patients. The immunoblot specificities of the 27-, 21- and 17.5-kDa antigens in EmP for E. multilocularis infection were 73%, 88% and 93%, respectively. Recognition of the 17.5-kDa antigen in the EmP immunoblot was much higher for the Japanese AE cases (11/13; 85%) than for the French (9/19; 47%) or Chinese (9/18; 50%) AE cases. None of the CE cases from Uruguay or Libya, where human AE has not been reported, was seropositive for the 17.5-kDa antigen. Antibodies from three (7.3%) of the 41 Chinese CE cases recognized the 17.5-kDa antigen. Within the 13 Japanese AE sera, the combined detection by IgG1, IgG4 and total-IgG antibodies of the 27-, 21- and 17.5-kDa antigens in either EmP or EmCH immunoblots was greater than that by each class/subclass alone, increasing the overall sensitivity for AE patients. A combined ELISA/immunoblot approach, including IgG-subclass detection using E. multilocularis protocolex or cyst extracts, could be useful for the differential diagnosis of human alveolar echinococcosis. An algorithm for such an approach is given.

LTP is accompanied by commensurate enhancement of auditory-evoked responses in a fear conditioning circuit

Transmission of auditory information from the medial geniculate body to the lateral nucleus of the amygdala is believed to be involved in the conditioning of fear responses to acoustic stimuli. This pathway exhibits LTP of electrically evoked field potentials after high frequency stimulation of the medial geniculate body. High frequency stimulation of the medial geniculate body also results in a long-lasting potentiation of a field potential in the lateral amygdala elicited by a naturally transduced acoustic stimulus. This demonstrates that natural information processing can make use of the physiological mechanisms set in motion by LTP induction.

Immunocytochemical localization of serotonin (5-HT) in the nervous system of the hydatid organism, Echinococcus granulosus (Cestoda, Cyclophyllidea)

The localization and distribution of the serotoninergic components of the nervous system in the hydatid organism, Echinococcus granulosus, were determined by immunocytochemical techniques in conjunction with confocal scanning laser microscopy (CSLM). The distribution of serotonin immunoreactivity (IR) paralleled that previously described for cholinesterase activity, although it was more widespread. Nerve cell bodies and nerve fibres immunoreactive for 5-HT were present throughout the central nervous system (CNS), occurring in the paired lateral, posterior lateral and rostellar ganglia, their connecting commissures and nerve rings in the scolex and in the ten longitudinal nerve cords that run posteriorly throughout the body of the worm. A large population of nerve cell bodies was associated with the lateral nerve cords. In the peripheral nervous system (PNS), immunoreactive nerve fibres occurred in well-developed nerve plexuses innervating the somatic musculature and the musculature of the rostellum and suckers. The genital atrium and associated reproductive ducts were richly innervated with serotoninergic nerve cell bodies and nerve fibres.

Serotoninergic and peptidergic nerve elements in the protoscolex of Echinococcus granulosus (Cestoda, Cyclophyllidea)

The localisation and distribution of 5-hydroxytryptamine (5-HT, or serotonin) and neuropeptides in the nervous system of the protoscolex of the hydatid organism Echinococcus granulosus were determined by an indirect immunofluorescence technique. Nerve-cell bodies immunoreactive for 5-HT occurred in the lateral ganglia and in association with the lateral longitudinal nerve cords. 5-HT immunostaining was also evident in the central nerve ring, in the rostellar nerves and in the nerve plexus innervating the suckers. Of the antisera used to screen the protoscolex for neuropeptide immunoreactivity (IR), immunostaining was obtained with those raised against pancreatic polypeptide (PP), peptide YY (PYY), substance P (SP), peptide histidine isoleucine (PHI) and vasoactive intestinal peptide (VIP). The most extensive pattern of IR occurred with antisera to PP and PYY. Immunoreactive nerve elements were evident in the lateral ganglia, central nerve ring, rostellar nerves, rostellar ganglia, sucker plexus and longitudinal nerve cords. The distribution of SP-, PHI- and VIP-IRs was more restricted: SP-IR occurred in the lateral ganglia and sucker nerves, whilst PHI- and VIP-immunoreactive nerve elements were associated with the lateral longitudinal nerve cords. Protoscoleces cultured in vitro for 29 days were also examined and neuroanatomical changes noted. A greater development of the longitudinal nerve cords and their cross-connectives in the body of the worm was evident, and a group of nerve cells were seen to develop at the posterior end of the main lateral nerve cords.

The potential of vervet monkeys (Cercopithecus aethiops) and baboons (Papio anubis) as models for the study of the immunology of Echinococcus granulosus infections

Nine vervet monkeys and nine baboons were infected with eggs of Echinococcus granulosus per os. Six of the vervets and one of the baboons possessed hydatid cysts at autopsy, 15-28 months post-infection. The sequential IgG response to hydatid fluid and protoscolex antigens showed considerable inter-animal variation. Infected vervets and baboons became seropositive after an average of 8 months post-infection. Considerable fluctuation in the IgG response was observed, particularly to the hydatid fluid antigen which, in humans, may contribute to the existence of a significant proportion of seronegative individuals. Vervets, in particular, may be useful to study immunological events associated with exposure, development and resolution of hydatid disease in outbred human populations.

Evaluation of a rapid dot-ELISA as a field test for the diagnosis of cystic hydatid disease

A rapid dot enzyme-linked immunosorbent assay (dot-ELISA) was developed as a field test for the diagnosis of cystic hydatid disease caused by Echinococcus granulosus. The 30 min test was based on the detection of antibodies to antigen B of hydatid fluid and was carried out using 50 microliters of whole blood in a field assessment in the Turkana region of north-west Kenya. Initial laboratory studies showed antigen B to be preferable to crude cyst fluid, with 94% sensitivity and 90.3% specificity for Echinococcus infections. The field test was rapid, inexpensive and simple to perform and is considered to be a useful back-up to ultrasound scanning.

Necator americanus secretory acetylcholinesterase and its purification from excretory-secretory products by affinity chromatography

Acetylcholinesterase (AChE) secretion by adult N. americanus was enhanced in vitro by incorporating insoluble collagen rafts into culture dishes. Enzyme produced in this way had preferential substrate specificity for acetylthiocholine iodide (ATC), and its activity was inhibited by eserine (1.1 x 10(-8) M). Ancylostoma ceylanicum, another hookworm species, failed to produce comparable amounts of AChE in culture. AChE was efficiently purified from culture medium by affinity chromatography on edrophonium sepharose; 81% of the AChE activity was retained by the affinity matrix, although this fraction contained only 4.3% of the protein loaded. Antisera raised against purified AChE in rabbits immunohistochemically stained the oesophageal glands of the parasite, and reacted with molecules of 32, 60, 80, 140 and 220 kDa in reduced adult ES products on Western blotting, although differential activity was observed against worm homogenates and earlier developmental stages. On IEF, purified AChE resolved predominantly with a pl of 3.55; proteins with a similar pl were recognized by rabbit anti-AChE. IgG preparations of this antiserum inhibited AChE activity in ES products, and inhibited AChE secretion by adult worms in culture. The availability of this immunological probe will allow definitive experiments to be conducted on the role of this enigmatic enzyme in the host-parasite relationship.

The identification of a species-specific antigen from Necator americanus

A 17 kD protein of Necator americanus was isolated by SDS-PAGE and used to raise monospecific antisera in rabbits. ELISA and Western blotting against a range of parasite extracts demonstrated the species specificity of this protein. It is expressed at all stages of the life-cycle, appears to be accumulated through the larval stages to adulthood, and can be localized in the oesophageal glands and cuticle of the adult parasite. The possible nature and diagnostic potential of this protein is discussed.

Echinococcus granulosus: the potential use of specific radiolabelled antibodies in diagnosis by immunoscintigraphy

Diagnosis of hydatid disease in man is frequently dependent on the imaging of cysts in situ by techniques such as ultrasonography and CAT scans. Such methods are useful but are not specific and can lead to errors in diagnosis. The present work reports preliminary experiments on the development of a specific imaging technique for hydatid cysts using radiolabelled antibodies. A purified preparation of antigen B of hydatid fluid was used to raise polyclonal antisera in rabbits and the resulting affinity-purified IgG labelled with 131I. Gerbils with an established Echinococcus granulosus infection were injected intraperitoneally with the labelled antibody and imaged 48 h later with a gamma camera. Hydatid cysts could be identified within the peritoneal cavity and post-mortem assessment of activity showed the cysts to contain approximately four times as much activity as the surrounding organs thereby indicating successful targeting of the antibody to the cysts.

Development of the tegument of Echinococcus granulosus (Cestoda) protoscoleces during cystic differentiation in vivo

During the first 4 days following infection, early tegumentary changes are confined to the protoscolex soma of Echinococcus granulosus, the thick glycocalyx being lost and the blunt elevations, flattened. The Golgi complexes within the tegumentary cytons produce T2 vesicles that increase in number in the tegument from days 4 to 12, whereas T1 vesicles decline. Spineless, truncated microtriches develop at the somal surface, and the laminated layer starts to form around the developing cyst from days 20-40 onwards. T2 vesicles do not appear to be involved in its formation and decline in number. Two additional vesicle types participate in the production of the laminated layer: T4 vesicles contribute to the carbohydrate matrix, and 'G' vesicles form granular accumulations. Cystic differentiation is completed after 2-3 months, when the spined microtriches and rostellar hooks of the scolex are shed into the laminated layer and replaced by truncated microtriches. These ultrastructural changes are discussed with respect to parasite survival.

Cuticle preparations from Necator americanus and their immunogenicity in the infected host

Cuticle samples have been prepared from the human parasitic nematode Necator americanus using detergent solubilisation with sodium dodecyl sulphate and subsequent reduction of disulphide bonds using 2-beta-mercaptoethanol. It would appear that N. americanus, like many other nematodes, relies on relatively small collagenous proteins, linked by disulphide bonds, to maintain the integrity of its cuticle. These molecules are normally hidden from the immune system during the course of infection but are potentially immunogenic. It is suggested that waves of antibodies, firstly with specificity against superficial cuticular epitopes followed by antibodies against deeper lying, structural elements, should be induced during vaccination to effectively destroy the nematode at the cuticular level.

Echinococcus granulosus: changes in the surface ultrastructure during protoscolex formation

Changes in the tegumentary projections of protoscoleces of Echinococcus granulosus, developing within brood capsules, were examined at the ultrastructural level. The original scant covering of spineless, truncated microtriches was supplemented by a population of microvilli covering the entire surface of protoscoleces in the early stages of formation. As differentiation continued, rostellar hooks were formed by enlargement of single large (T1) microtriches, and normal spined microtriches were produced on the sucker region. These were formed in two ways: by addition of spine material to the truncated microtriches, and de novo followed by up-lifting from the tegumentary surface. A second type of large microthrix (T2) was present in a band immediately below the developing hooks. These microtriches appeared to be formed from a fusion of existing microtriches, but were subsequently lost prior to scolex invagination. The microvilli were also shed from both the sucker and soma regions, to be replaced by microtriches and small blunt elevations respectively.

Echinococcus granulosus: in vitro effect of monensin on the tegument of the protoscolex

Protoscoleces of Echinococcus granulosus were incubated in a 10 microM solution of monensin and their viability and the ultrastructure of their tegument were monitored over a 36 h period. The earliest effects of the ionophore, apparent within 15 min, involved a degree of cisternal swelling of the tegumentary Golgi complexes. Swelling became more pronounced with time and cytons eventually contained numerous large electron-lucent vesicles. Residual bodies indicative of autophagy were observed in the cytons and distal cytoplasm from 1 h onwards. All movement of protoscoleces ceased after 1 h and the surface of the soma subsequently became folded, possibly suggesting spastic paralysis. Later, vacuoles and large cytoplasmic blebs were observed in the distal cytoplasm and viability dropped rapidly after 12 h. All protoscoleces were dead at 36 h. The potential of monensin as an in vivo protoscolicidal agent is discussed.

In vitro development of hydatid cysts from posterior bladders and ruptured brood capsules of equine Echinococcus granulosus

A variety of morphological forms developed during monophasic culture of ruptured brood capsules of equine Echinococcus granulosus. Attached to some protoscoleces were small posterior bladders, with a surface ultrastructure of truncated microtriches, and these never developed a laminated layer. In contrast, small free vesicles of similar size and ultrastructure, but devoid of an attached protoscolex, produced a layer by 20-30 days. The surface ultrastructure of both these forms is similar to that of the protoscolex attachment stalk and the brood capsule lining, and posterior bladders and small free vesicles are considered to be derived from portions of the stalk +/- part of the brood capsule lining retained at protoscolex release. Also present were large vesicles interpreted from their size and surface anatomy as ruptured, everted brood capsules. When devoid of attached protosoleces these formed cysts each with a laminated layer, whereas similar vesicles with several attached protoscoleces did not develop a layer, or only very occasionally after 70 or more days. In contrast, a few large vesicles with a single attached protoscolex produced a laminated layer. The possibility that protoscolex attachment to stalk remnants or brood capsules inhibits the cystic development of these structures is discussed.

Fasciola hepatica: tegumental alterations as a consequence of lectin binding

Adult flukes, Fasciola hepatica, incubated in Hedon - Fleig saline containing concanavalin A (Con A) for 10 and 45 min, respectively, exhibited severe alterations to tegumental morphology involving increased secretory activity, blebbing of the apical plasma membrane, increased total surface area, and swelling of the basal infolds . The effects of Con A were prevented by the addition of alpha-methyl-D-mannoside to the incubating medium. Similar, but less pronounced, effects were caused by wheat germ agglutinin (WGA) binding. Con A and WGA binding indicate the presence of mannose, glucosamine, or glucose moieties and of N-acetylglucosamine. The effects of lectin binding were similar to the early effects of antibody attachment, and it was considered that accelerated membrane turnover was occurring in both cases. Swelling of the basal infolds was thought to be a result of increased apical surface membrane and/or increased permeability due to lectin binding.