[Pathogenic protozoans in man: differential characterization of Entamoeba histolytica/Entamoeba dispar complex, Acanthamoeba spp., Microsporidia]

The review summarizes the results in the main parasitological topics of our Lab: amoebic infections due to Entamoeba histolytica/Entamoeba dispar complex and to Acanthamoeba spp. respectively, and human infections caused by microsporidia. Different rapid and advanced techniques have been included in the standardized diagnostic protocols for each topic, and a critical comparison among them was made, in order to define the gold standard diagnostic method: a) E. histolytica/E. dispar: in vitro culture, zymodeme typization, biomolecular identification (PCR), immunoenzymatic assay (ELISA) for direct detection in stools of specific surface antigenic lectins; b) Acanthamoeba spp.: in vitro culture, light and ultrastructural characterization, species identification by immunofluorescence method with monoclonal antibodies, in vitro pharmacological studies; c) Microsporidia: ultrastructural (TEM), biomolecular (PCR), biochemical and immunological (SDS-PAGE, Immunoblotting) studies for species identification, use of advanced ultrastructural techniques ("freeze-etching", "deep-etching") in order to deepen the spore wall structure, to study the cytoskeletal function of actin and to define the mode of infection, in vitro pharmacological assays on some inhibitors of chitin-synthases.

Endothelial targeting with C1-inhibitor reduces complement activation in vitro and during ex vivo reperfusion of pig liver

Tissue damage during cold storage and reperfusion remains a major obstacle to wider use of transplantation. Vascular endothelial cells and complement activation are thought to be involved in the inflammatory reactions following reperfusion, so endothelial targeting of complement inhibitors is of great interest. Using an in vitro model of human umbilical vein endothelial cells (HUVEC) cold storage and an animal model of ex vivo liver reperfusion after cold ischaemia, we assessed the effect of C1-INH on cell functions and liver damage. We found that in vitro C1-INH bound to HUVEC in a manner depending on the duration of cold storage. Cell-bound C1-INH was functionally active since retained the ability to inhibit exogenous C1s. To assess the ability of cell-bound C1-INH to prevent complement activation during organ reperfusion, we added C1-INH to the preservation solution in an animal model of extracorporeal liver reperfusion. Ex vivo liver reperfusion after 8 h of cold ischaemia resulted in plasma C3 activation and reduction of total serum haemolytic activity, and at tissue level deposition of C3 associated with variable level of inflammatory cell infiltration and tissue damage. These findings were reduced when livers were stored in preservation solution containing C1-INH. Immunohistochemical analysis of C1-INH-treated livers showed immunoreactivity localized on the sinusoidal pole of the liver trabeculae, linked to sinusoidal endothelium, so it is likely that the protective effect was due to C1-INH retained by the livers. These results suggest that adding C1-INH to the preservation solution may be useful to reduce complement activation and tissue injury during the reperfusion of an ischaemic liver.

Asymptomatic amoebic infection: Entamoeba histolytica or Entamoeba dispar? That is the question

Two cases of amoebic infection were diagnosed in a heterosexual couple. The cases, a Frenchman with previous trips to various African countries and his sexual partner, a Cameroonese woman immigrant living outside the community, were both asymptomatic; the infection had been diagnosed by chance in the man at the time of his employment in a hospital kitchen. Based on what is known of the epidemiology of amoebic infection, it may be acquired and then transmitted within a couple via the indirect faecal-oral route or, in greater likelihood, by sexual practices. Both amoebic isolates were characterised by isoenzyme electrophoresis as non-pathogenic Entamoeba dispar, zymodemel. Other diagnostic tools, such as ELISA direct stool antigen detection tests and serological assays were employed, confirming the diagnosis of E. dispar infection. Given there are a number of asymptomatic cyst passers of Entamoeba histolytica, besides human carriers of saprophyte E. dispar, we stress the importance of applying, when possible, advanced protocols of diagnosis to distinguish the microscopically identical pathogenic species from the non-pathogenic one.

Genotyping Encephalitozoon hellem isolates by analysis of the polar tube protein gene

To develop an alternative genotyping tool, the genetic diversity of Encephalitozoon hellem was examined at the polar tube protein (PTP) locus. Nucleotide sequence analysis of the PTP gene divided 24 E. hellem isolates into four genotypes, compared to two genotypes identified by analysis of the internal transcribed spacer of the rRNA gene. The four PTP genotypes differed from each other by the copy number of the 60-bp central repeat as well as by point mutations. A simple PCR test was developed to differentiate E. hellem genotypes based on the difference in the size of PTP PCR products, which should facilitate the genotyping of E. hellem in clinical samples.

Genetic diversity in the microsporidian Encephalitozoon hellem demonstrated by pulsed-field gel electrophoresis

Encephalitozoon hellem is a microsporidian species responsible for opportunistic infections in AIDS patients. Use of a novel chitinase-based method allowed unsheared chromosomal DNA to be recovered from eleven E. hellem isolates derived from three geographic regions. All isolates were typed by 18S rDNA sequencing, which showed that they belonged to intemal transcribed spacer type 1. After ethidium bromide staining, pulsed-field gel electrophoresis (PFGE) analysis discriminated two new karyotypes comprising 7 and 8 chromosomal bands respectively, ranging in size from 205- to 272-kb pairs. Genomic size was estimated to be 2.39 Mb. Our data indicate PFGE is useful for typing E. hellem and confirms genetic diversity among E. hellem genotypes.

Reappearance of human diphyllobothriasis in a limited area of Lake Como, Italy

BACKGROUND

Very few sporadic cases of autochthonous diphyllobothriasis have been reported in Italy during the past 20 years, probably due to the drastic decrease or disappearance of some fish species, mainly Perca fluviatilis L., known as the intermediate host of the infective larval stage of this tapeworm. However, increasing consumption of raw or undercooked fish during the last years as influenced by Oriental cuisine, played an important role in a number of new single cases of the infection or microepidemics.

PATIENTS

We describe six cases which were diagnosed within a period of 4 months, which all originated from the area of Lake Como (Lombardy region). All subjects had previously eaten raw perch fillets. Four individuals complained of gastrointestinal signs and symptoms, whereas two were asymptomatic.

DISCUSSION

Parasitological diagnosis was achieved in four cases by recovery of typical operculated eggs in stool specimens; in two others by morphological features of proglottids recovered from feces. Treatment with niclosamide, as a single oral dose, cured the infection in all subjects. This is the first report of this infection in Italy in the last 10 years.

In vitro efficacy of nikkomycin Z against the human isolate of the microsporidian species Encephalitozoon hellem

Since 1985 microsporidia have been recognized as a cause of emerging infections in humans, mainly in immunocompromised human immunodeficiency virus-positive subjects. As chitin is a basic component of the microsporidian infective stage, the spore, we evaluated in vitro the susceptibility of a human-derived strain of Encephalitozoon hellem to nikkomycin Z, a peptide-nucleoside antibiotic known as a competitive inhibitor of chitin synthase enzymes. Transmission electron microscopy showed that this drug, at 25 microgram/ml, reduced the number of parasitic foci by about 35% +/- standard deviation after 7 days of culture (P < 0.0001) and induced cell damage of both mature and immature spores and also other sporogonic and merogonic stages. In particular, an irregular outline of the cell shape and an abnormally condensed cytoplasm in meronts and sporonts were documented. Also, the polar tubule and the polaroplast membranes appeared disarrayed in the sporoblast stage. The spore wall showed an enlarged endospore and delaminated exospore. Mature spores had a complete cytoplasmic disorganization and a swollen and delaminated cell wall. No ultrastructural cell damage was observed in uninfected control cultures treated with the drug.

Intestinal parasitic infections in an institution for the mentally retarded

Of 550 mentally retarded patients in an Italian institution, 125 (23%) were found to be infected with intestinal parasites. The infections were most frequent in young men, those with severe mental retardation, the chronically institutionalized and those living in older wards. Ninety-four (75.2%) of the parasitised subjects were infected only with protozoa, 25 (20%) only with helminths, and six (4.8%) with protozoa and helminths. Entamoeba histolytica and E. dispar infections were detected, but at low prevalences; in-vitro culture in Robinson's medium and isoenzyme electrophoresis of the cloned amoebic isolates indicated one infection with E. histolytica (zymodeme XII) and two infections with E. dispar (zymodemes I and III). All three Entamoeba-positive subjects were asymptomatic cyst-passers. Antibodies to E. histolytica were detected in seven (1%) of the sera from the 550 patients examined; only one of these was a carrier of an E. dispar strain at the time of investigation. The low prevalences of all the parasitic infections and of the amoebic infections in particular (compared with those observed previously in institutions for the mentally retarded) reflect relatively good facilities and sanitary conditions, an adequate number of well trained staff and good control of the more susceptible subjects.

Genetic identification of neurons controlling a sexually dimorphic behaviour

In the fruit fly Drosophila melanogaster, locomotor activity is sexually dimorphic: female flies constantly modulate their activity pattern whereas males show a steadier, stereotyped walking pace [1]. Here, we mapped the area of the brain controlling this behavioural dimorphism. Adult male Drosophila expressing a dominant feminising transgene in a small cluster of neurons in the pars intercerebralis exhibited a female-like pattern of locomotor activity. Genetic ablation of these neurons prevented the feminisation of the locomotor activity of transgenic males. The results suggest that this cluster of neurons modulates sex-specific activity, but is not involved in initiating fly locomotion. Nor does it control male courtship behaviour, because feminisation of courtship was not correlated with the feminisation of locomotor activity.

Calcipotriol treatment of confluent and reticulated papillomatosis (Gougerot-Carteaud syndrome)

Gougerot-Carteaud syndrome or confluent and reticulated papillomatosis (CRP), was first described by Gougerot and Carteaud as dermatosis. It is generally considered a rare condition. The eruption consists confluent, flat, brown papules localized primarily to the intermammary and interscapular regions with subsequent spread to the breast and abdomen; at the periphery, the papules spread out forming a pigmented reticulated pattern. At present, the aetiology of CRP remains unknown. The two prominent theories are an abnormal host response to fungi and a keratinization defect. Other hypothesis include photosensitivity, genetic factor, amyloidosis cutis and endocrinopathy.

Symptomatic and asymptomatic amoebiasis in two heterosexual couples

Four cases of amoebiasis are described: two symptomatic with intestinal and hepatic involvement and two asymptomatic, diagnosed in two, heterosexual, Italian couples. Infection was probably acquired first by the men, via an indirect faccal-oral route, and then transmitted to their partners in the same way. The two amoebic strains isolated, from the woman of one couple and the man of the other, were characterized by electrophoresis as zymodemes II alpha- and XIX of Entamoeba histolytica. These four cases emphasise once more the role of cyst-passers in the spread of infection and the importance of biochemical identification of the amoebic isolates, enabling more specific treatment.

Experimental respiratory cryptosporidiosis in immunosuppressed rats: a light and electron microscopy study

Cryptosporidium parvum is a coccidian protozoon that causes diarrhoeal enteritis in immunocompetent and immunocompromised humans and other mammals. Sometimes, chiefly in HIV-infected subjects, anatomical sites other than gastro-intestinal tract, such as the biliary and respiratory tree, are involved. We performed an experimental respiratory infection in immunosuppressed albino rats with a C. parvum human-derived isolate, to confirm the possibility of a primary infection at this site and to evaluate the protozoan damages by light and also by transmission electron microscopy (TEM). The animals were infected intratracheally with 1 x 10(6) C. parvum oocysts/ml and, from the 7th day post-infection, biological specimens of trachea, bronchi, lung and ileum were zoopsied. A sole cryptosporidial colonization of the respiratory tract, from the trachea to the median bronchi, without lung parenchyma infection, was observed. Moreover 13/33 (39.4%) rats also developed intestinal infection. TEM study of the respiratory tree specimens demonstrated that cryptosporidia infect either ciliated or goblet cells, and confirmed the role of microvilli in the parasite cell adhesion. The most relevant alterations involved the ciliated cells, with loss of cilia and nuclear and cytoplasmic damages.

Biotechnologies and acute hepatic failure

Orthotopic liver transplantation survival for patients with acute liver failure is poor (50%). Mortality on the waiting list is high due to the lack of donors. For these reasons, the possibility of sustaining hepatic function by extra-corporeal liver perfusion must be considered. In this experimental research, two groups of pigs have been submitted to total de-vascularisation of the liver causing acute hepatic failure. In the first group (4 pigs) no extra-corporeal assistance has been used after total de-vascularisation. All pigs died between 16 and 33 hours after the acute hepatic failure was induced. In the second group (8 pigs) after complete hepatic de-vascularisation an extra-corporeal hepatic support by continuous allo-perfusion of isolated liver was performed using the Abouna-Costa extra-corporeal circuit. All pigs were observed during the acute hepatic failure which lasted from 6.30 to 7.30 hours. The data that were more positively influenced by the extra-corporeal assistance were ammonia and lactates that improved after the application of hepatic assistance.

Evidence of actin in the cytoskeleton of microsporidia

Using transmission electron microscopy, immuno-electron microscopy, and biochemical techniques such as 2-D electrophoresis and immunoblotting, actin was found in all biological stages of the microsporidia Encephalitozoon hellem and Encephalitozoon cuniculi.

Fever: links with an ancient receptor

Recent advances have provided evidence that prostaglandin E2 mediates the generation of fever in response to interleukin-1 or lipopolysaccharide and have reinforced the similarities of signaling downstream of these two pyrogens.

Neuroprotective effects of Gly-Pro-Glu, the N-terminal tripeptide of IGF-1, in the hippocampus in vitro

Insulin-like growth factor 1 (IGF-1) plays a critical role in CNS development. IGF-1 can block neuronal apoptosis in vitro and in vivo. IGF-1 is thought to be cleaved into des-N-(1-3)-IGF-1 and an amino terminal glycine-proline-glutamate (GPE tripeptide). Here we report a neuroprotective role for GPE tripeptide, with enhanced survival of the CA1-2 hippocampal neurons following an excitotoxic insult in vitro. Binding and displacement studies suggest uniquely distributed sites of action within the rat including the hippocampal CA1-2, pyriform cortex, amygdala, choroid plexus, blood vessels and to a lesser extent in the cortical regions. A similar pattern of binding was seen in the human. This finding could lead to new strategies to reduce neuronal death after injury and in disease.