Strong expression of TGF-beta in human host tissues around subcutaneous Dirofilaria repens.

Dirofilaria repens and other Dirofilaria species are widely distributed parasitic nematodes of carnivores, which occasionally are transmitted to men, causing subcutaneous nodules. In humans, it usually occurs only as single male or female filariae without production of microfilariae. The non-productive living or dead Dirofilaria worms in subcutaneous biopsies from 15 human patients permitted us to study the role of the pleiotropic and immunoregulatory cytokine transforming growth factor beta (TGF-beta) independent from the influence of microfilariae. Antiserum against latent TGF-beta 1 was used for an immunohistological examination. In the infiltrates around female and male filariae, there occurred strongly TGF-beta-positive macrophages, mast cells, endothelial cells, fibrocytes, and giant cells adjacent to dead worms. In one nodule, secondary lymph follicles were observed with clearly TGF-beta-positive B cells in the mantle zone and weakly positive macrophages and B cells in the germinal centre. A network of CD35-positive follicular dendritic cells was observed in the germinal centre. All Dirofilaria contained Wolbachia endobacteria, which probably had attracted the numerous TGF-beta-negative neutrophils near to the worm. Wolbachia were phagocytosed by neutrophils adjacent to dead filariae. Macrophages and lymphocytes expressed the MHC class II molecule HLA-DR in small accumulations of immune cells in the outer zone of the infiltrate and the mantle zone and germinal centre of secondary lymph follicles. It is concluded that single non-productive Dirofilaria worms elicit a strong expression of TGF-beta. This result is in accordance with observations on Onchocerca volvulus from patients with the hyporeactive (generalised) form.

Immunohistology of ectopic secondary lymph follicles in subcutaneous nodules from patients with hyperreactive onchocerciasis (sowda).

Ectopic secondary lymph follicles emerge in patients with autoimmune or infectious diseases, e.g. in the synovium in rheumatoid arthritis or the skin in Borrelia burgdorferi infection, but ectopic localisations in the skin are rarely described for helminth infections. We investigated the cellular composition of secondary lymph follicles in subcutaneous nodules from eight patients with hyperreactive onchocerciasis (synonymous "localised" form or sowda) using immunohistology. CD3- and CD45RO-positive T cells and CD20-positive B cells were present in the mantle zone. The germinal centre was characterised by many B cells and CD35-positive follicular dendritic cells, which formed a network of attached IgE- and CD23-positive cells with the low-affinity IgE (epsilon) receptor. Few of the B cells were labelled for IgG1, IgG2 and IgG4, whereas in other zones of the nodule IgG1 was expressed by plasma cells and IgG1-coated dead microfilariae. B cells and few macrophages expressed the MHC class II molecule HLA-DR. Mature CD68-positive tingible body macrophages with phagocytosed leukocytes and CD57-positive lymphocytes occurred in the germinal centre. Macrophages in the germinal centre only weakly expressed alpha1-antichymotrypsin in contrast to macrophages in other zones of the onchocercoma. Furthermore, the multifunctional cytokine TGF-beta was only weakly expressed by macrophages and lymphocytes in the secondary follicles. Only few tryptase-positive mast cells, calprotectin-positive young macrophages, eosinophils and neutrophils occurred in the secondary follicles, although these cells were abundant in the onchocercomas. In conclusion, the ectopic secondary lymph follicles in onchocercomas and lymph nodes from hyperreactive onchocerciasis patients are equally composed.

Immunohistological studies on Onchocerca volvulus paramyosin.

Paramyosin is a muscular protein exclusively found in invertebrate species, which has been proposed as a vaccine candidate against infections with Schistosoma mansoni and Brugia malayi. Here, we report the studies on the distribution of Onchocerca volvulus paramyosin, designated OvPmy, in different O. volvulus stages by immunohistochemistry using rabbit antibodies raised against the recombinant OvPmy protein as well as the induction of the human humoral immune response to OvPmy. To conduct the studies, OvPmy was expressed in Escherichia coli as a fusion protein to raise the rabbit antibodies. The recombinant OvPmy was tested in immunoblots using sera from individuals living in an area hyperendemic for onchocerciasis in Liberia, West Africa. The antibodies used here localised paramyosin exclusively in the muscle tissue of O. volvulus as well as Onchocerca ochengi. No extracellular compartments, such as the cuticle or the lumina of the pseudocoeloma cavity, were labelled; however, labelling was seen in microfilarial fragments taken up by host immune cells, such as giant cells. It was recognised by anti-paramyosin antibodies of a group of onchocerciasis patients.

Criteria for the differentiation between young and old Onchocerca volvulus filariae.

Drugs exist that show long-lasting inhibition of embryogenesis and microfilaria production or macrofilaricidal activity against Onchocerca volvulus. Therefore, the patients have to be followed-up for several years. Clinical drug trials have to be performed in areas with ongoing transmission to assess the efficacy on younger worms. In addition, future vaccine trials may also require demonstrating efficacy against establishment of new worms. For the evaluation of the efficacy, it is necessary to differentiate between older worms, which were exposed to the drug, and younger worms newly acquired after drug treatment or vaccination. Here, we describe criteria for the differentiation between young and old filariae based on histological studies of worms with a known age from travellers, or from children, or patients living in areas with interrupted transmission in Burkina Faso, Ghana or Uganda. Older worms were larger and presented degenerated tissues. Gomori's iron stain showed that the worms accumulated more iron with increasing age, first in the gut and later in other organs. Using an antibody against O. volvulus lysosomal aspartic protease, the gut of young worms was stained only weakly; whereas, it was stronger labelled in older worms, accompanied by additional staining of hypodermis and epithelia. Using morphological and immunohistological criteria, it was possible to differentiate young (1-3 years old) from older females and to identify young males.

The nematode parasite Onchocerca volvulus generates the transforming growth factor-beta (TGF-beta).

Transforming growth factor-beta (TGF-beta) is a highly conserved cytokine that has a well-known regulatory role in immunity, but also in organ development of most animal species including helminths. Homologous tgf-b genes and mRNA have been detected in the filaria Brugia malayi. The in situ protein expression is unknown for filariae. Therefore, we examined several filariae for the expression and localization of latent (stable) TGF-beta in adult and larval stages. A specific goat anti-human latency associated protein (LAP, TGF-beta 1) antibody, purified by affinity chromatography, was used for light and electron microscopic immunohistochemistry. Adult Onchocerca volvulus, Onchocerca gibsoni, Onchocerca ochengi, Onchocerca armillata, Onchocerca fasciata, Onchocerca flexuosa, Wuchereria bancrofti, Dirofilaria sp., B. malayi, and infective larvae of W. bancrofti reacted with the antibody. Labeling of worm tissues varied between negative and all degrees of positive reactions. Latent TGF-beta was strongly expressed adjacent to the cell membranes of the hypodermis, epithelia, and muscles and adjacent to many nuclei in all organs. TGF-beta was well expressed in worms without Wolbachia endobacteria eliminated by doxycycline treatment. Pleomorphic neoplasms in O. volvulus were also labeled. We conclude that latent TGF-beta protein is expressed by filariae independently of Wolbachia, possibly regulating worm tissue homeostasis.

Newly acquired Onchocerca volvulus filariae after doxycycline treatment.

Despite successful mass drug administration and vector control programs, the nematode Onchocerca volvulus is far from being eradicated. Therefore, new long-term sterilizing or macrofilaricidal drugs are needed. The depletion of Wolbachia endobacteria using doxycycline leads to long-term sterilizing effects and macrofilaricidal activity against female filariae of more than 60%. The worms die or degenerate 18-27 months after doxycycline. However, during this time patients may be exposed to new infections. We evaluated these newly acquired worms in onchocercomas of doxycycline-treated patients in relation to transmission using morphology, histochemistry, and immunohistology. On an average, 10% of the female filariae had been newly acquired per year in the treated groups. Our observations showed: (a) Sixty-three of 68 newly acquired worms harbored many intact Wolbachia, whereas none of the other surviving worms contained many bacteria. (b) Higher percentages of dead filariae than originally reported were calculated, when the new worms were excluded, indicating a stronger macrofilaricidal activity than previously reported. The difference was significant for female filariae after doxycycline treatment for 6 weeks. (c) Only newly acquired worms presented normal embryogenesis and microfilariae production after sufficient treatment. We conclude that newly acquired filariae have to be considered when evaluating drug efficacy in onchocerciasis.

Natural death of adult Onchocerca volvulus and filaricidal effects of doxycycline induce local FOXP3+/CD4+ regulatory T cells and granzyme expression.

Immunosuppression in human filarial disease involves regulatory T cells. We hypothesized that natural or worm antigen-induced FOXP3 regulatory T cells could be involved locally, suppressing effector cells via granzymes. Natural and treatment-induced death of worms implies enhanced exposure to worm antigens. Therefore, we examined FOXP3+T cells and granzyme expression in onchocercomas harbouring adult Onchocerca volvulus worms, with respect to worm viability, productivity, the patient's immune status and filaricidal treatment. The immunohistological analysis revealed that dead adult worms were strongly associated with FOXP3+T cells in generalized hyporeactive onchocerciasis. FOXP3+ cells hardly expressed granzymes, but cell contacts with granzyme A+ or B+ cells were frequent. While suramin directly kills most adult worms within 6 months, the Wolbachia depleting antibiotic doxycycline indirectly causes adult worm degeneration within 18 months. Contrary to suramin, depletion of Th1-driving endobacteria most strongly promoted FOXP3+T cells and granzyme-expressing cells. In hyperreactive patients, FOXP3+ cells were less frequent. This is the first demonstration of local FOXP3+Treg cells in human filariasis and their induction by natural worm death and anti-parasitic treatment. We newly report granzyme responses to helminths and their association with immunosuppression. FOXP3+Treg and granzyme+ cells might locally suppress defence against newly acquired worms.

Cloning, characterization and DNA immunization of an Onchocerca volvulus glyceraldehyde-3-phosphate dehydrogenase (Ov-GAPDH).

In the search for Onchocerca volvulus antigens possibly involved in protection against human onchocerciasis, partial amino acid sequence analysis of one of the O. volvulus antigens of the serologically identified proteins showed a close relationship to the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein family. Subsequent adult worm cDNA library screening and cloning produced a clone of 1650 bp. An open reading frame spans over 1020 bp encoding for a protein of 340 amino acids with an apparent molecular weight of 38000. Comparison of the complete amino acid sequence identified this protein as a member of the GAPDH protein family. The recombinantly expressed protein shows GAPDH enzymatic activity as well as plasminogen-binding capacity. DNA sequence analysis of the corresponding gene revealed the presence of two introns. Using immunohistology Ov-GAPDH was observed in microfilariae, infective larvae, and adult male and female worms. Most striking was the labelling of the musculature of the body wall. Labelling was also observed in the pseudocoeloma cavity and in a subset of cell nuclei, suggesting additional, non-glycolytic functions of the Ov-GAPDH. Gene gun immunization with the DNA-construct in cattle led to specific humoral immune responses. Thus, the protective potential of the DNA-construct of Ov-GAPDH can be evaluated in vaccination trials using animal models such as the cattle/Onchocerca ochengi model.

The filarial parasite Onchocerca volvulus generates the lipid mediator prostaglandin E(2).

Prostaglandins exhibit regulatory effects on the vascular and immune system. Prostaglandin E(2) (PGE(2)) modulates T helper (Th) cell and effector cell functional reactivity, thereby promoting Th2 responses. We found significant expression of PGE(2) in male and female Onchocerca volvulus. Using immunohistology, PGE(2) was predominantly detected in the hypodermis of adult O. volvulus, the metabolically most active tissue of the filaria. In contrast, the muscles were PGE(2)-negative and the epithelia of intestine and uterus and male genital tract showed only weak staining. Oocytes were well labeled whereas embryos and sperms did not react. Less pronounced PGE(2) staining was observed in some dermal microfilariae. The expression of PGE(2) was found independent of antifilarial (ivermectin) as well as anti-endobacterial (doxycycline) treatment of O. volvulus-infected patients. PGE(2) was also demonstrated in extracts of adult worms by high-performance liquid chromatography-mass spectrometry. Release of PGE(2) from live or moribund filariae can affect the host s metabolism and immune response in favor of the filarial parasite.

Subcutaneous Taenia crassiceps infection in a patient with non-Hodgkin's lymphoma.

Infections with larvae of Taenia crassiceps are rare in humans and have mostly affected patients with acquired immunodeficiency syndrome. We report the first case of a patient with malignancy (non-Hodgkin's lymphoma) and infection of the subcutis and muscles of the hand and forearm. Surgery and antiparasitic chemotherapy led to a complete cure.

Molecular cloning of an alpha-enolase from the human filarial parasite Onchocerca volvulus that binds human plasminogen.

Enolase represents a multifunctional protein involved in basic energy metabolism and plasminogen binding and activation at the surface of prokaryotic pathogens. A complete cDNA of 1615 bp of an alpha-enolase from Onchocerca volvulus (Ov-ENO) was isolated using a PCR-based approach. The open reading frame encoded for 435 amino acids and the high degree of conservation included the crucial amino acid residues that participate in the formation of the catalytic site, Mg(2+) binding site, and a hydrophobic motif reported to relate to surface expression. A 1089-bp fragment was expressed in a N-terminal 6 x His-tag expression vector in Escherichia coli. By immunohistological analysis using anti-Ov-ENO rabbit antibodies, native enolase could be detected in most tissues of adult O. volvulus, microfilariae, and infective larvae. Intense staining was observed in the muscles, where the energy consumption is high. The purified recombinant protein fragment revealed plasminogen binding activity in a blot-overlay assay employing anti-plasminogen antibodies. In sera from individuals infected with O. volvulus, IgG antibodies reactive with recombinant Ov-ENO were demonstrated by immunoblot and enzyme-linked immunosorbent analyses. The plasminogen-binding property of O. volvulus alpha-enolase may support plasmin-mediated proteolysis including degradation of host's extracellular matrix thereby promoting the migration of larval stages through tissues. The recognition by antibodies in sera of O. volvulus-infected persons indicate an involvement of the protein in the interaction between the parasite and the human host.

Wolbachia endosymbionts of Onchocerca volvulus express a putative periplasmic HtrA-type serine protease.

Wolbachia are intracellular bacteria of many filarial nematodes. A mutualistic interaction between the endobacteria and the filarial host is likely, because the clearance of Wolbachia by tetracycline leads to the obstruction of embryogenesis and larval development. Databases were searched for exported molecules to identify candidates involved in this mutualism. Fragments of a Wolbachia serine protease from the human filarial parasite Onchocerca volvulus were obtained (Wol-Ov-HtrA) by the use of a PCR technique and primers based on the Rickettsia prowazekii genome. The deduced amino acid sequence exhibited 87% and 81% identity to the homologous Wolbachia proteases identified from Brugia malayi and Drosophila melanogaster, respectively. The full-length cDNA encodes 494 amino acids with a calculated mass of 54 kDa. Three characteristic features, (i) a catalytic triad of serine proteases, (ii) two PDZ domains and (iii) a putative signal peptide, classify the endobacterial protein as a member of the periplasmic HtrA family of proteases known to express chaperone and regulator activity of apoptosis. Using a rabbit antiserum raised against a recombinantly expressed 33-kDa fragment of Wol-Ov-HtrA, strong labelling of the antigen was found associated with endobacteria in hypodermis, oocytes, zygotes, all embryonic stages and microfilariae of O. volvulus. Staining of hypodermal cytoplasm surrounding the endobacteria indicated a possible release of the protein from the Wolbachia. The demonstration of Wol-Ov-HtrA-reactive IgG1 antibodies in sera of O. volvulus-infected persons indicated the exposure to the protein and its recognition by the human immune system. Wol-Ov-HtrA is a candidate for an exported Wolbachia protein that may interact with the filarial host metabolism.

Doxycycline in the treatment of human onchocerciasis: Kinetics of Wolbachia endobacteria reduction and of inhibition of embryogenesis in female Onchocerca worms.

Recently, experts have warned that mass treatment with ivermectin alone may not interrupt the transmission of Onchocerca. Hence, additional drugs are needed, such as antibiotics acting on symbiotic endobacteria of the filariae, the causative agents of onchocerciasis. Based on animal experiments, human onchocerciasis was treated with doxycycline, and preliminary observations published in 2001 in The Lancet showed sterility in female worms by depletion and marked reduction in symbiotic Wolbachia endobacteria from the filariae. Here, a detailed kinetic analysis of the features of the worms, following administration or not of doxycycline to the patients is reported. Sixty-three onchocerciasis patients in Ghana were treated with 100 mg doxycycline daily for 6 weeks and 2 or 6 months later with ivermectin. Onchocercomas were extirpated 2, 6, 11 and 18 months after the onset of treatment and the filariae were examined by immunohistology and PCR. The analysis showed: (i) progressive depletion of Wolbachia from adult worms and microfilariae by doxycycline over a period of 6 months; (ii) inhibition of embryogenesis by doxycycline after 6 months with respect to all embryo stages followed by decline in microfilariae after 11 months; (iii) reduction in spermatozoa in the female genital tract by doxycycline, whereas spermiogenesis was only partly reduced after 11 and 18 months; (iv) no relevant macro- or microfilaricidal activity; (v) depletion/marked reduction in endobacteria and inhibition of embryogenesis were sustained until 18 months after doxycycline and 12 months after co-administration of ivermectin; (vi) no severe adverse side effects were seen. Due to its long-lasting inhibition of embryogenesis, doxycycline presents an additional strategy for the treatment of onchocerciasis and control of Onchocerca microfilariae transmission. Extension of the existing registration will not require much time or high cost. Treatment of individual patients can be considered immediately.

Isolation and characterization of the regulatory subunit of cAMP-dependent protein kinase from the filarial parasite Onchocerca volvulus.

Protein kinases exert major regulatory effects in eukaryotic signaling events. As these proteins play central regulatory and sensory functions they are interesting targets for antiparasitic drug development and serve as vaccine candidates. A cDNA with an open reading frame of 1122 bp coding for the regulatory subunit of the cAMP-dependent protein kinase (Ov-pka-r) of the pathogenic human nematode Onchocerca volvulus has been isolated. The predicted protein displays 84% homology to the corresponding protein of Caenorhabditis elegans and 71% to the human homologue. The O. volvulus protein has unique features, it includes six cysteine residues, as compared to four residues in mammals. Ov-PKA-r was recombinantly expressed as His-tagged protein and under reducing conditions showed a molecular mass of 52 kDa. In sera from O. volvulus patients IgG antibodies were found that strongly reacted with the recombinant Ov-PKA-r. Using rabbit antisera raised against the recombinant protein for immunohistology allowed the localization of the native Ov-PKA-r within the nervous system and sensory organs of adult O. volvulus worms and of microfilariae. The predominant expression in the nervous system and sensory organs as well as the unique structural features identify this signaling molecule of O. volvulus as a new and interesting target for drug or vaccine development.

Antibiotics for the treatment of onchocerciasis and other filarial infections.

More effective drugs are needed for the treatment of human filarial diseases and the elimination of these infections as a public health problem. The drugs must either kill or sterilize adult worms. The relevant filariae, Onchocerca volvulus, Wuchereria bancofti and Brugia species, harbor rickettsial endoboacteria of the genus Wolbachia as symbionts. Animal experiments have shown that the elimination of these endobacteria causes inhibition of embryogenesis, and with Onchocerca ochengi a macrofilaricidal effect. Trials with human onchocerciasis patients using doxycydine demonstrated a long-term sterilizing activity, opening up a new strategy for the control of filarial infections. Indications of antiwolbachial therapy against onchocerciasis are discussed.

Adverse reactions to ivermectin treatment in Simulium neavei-transmitted onchocerciasis.

To assess adverse effects of ivermectin treatment in a Simulium neavei-transmitted focus of onchocerciasis, a study was conducted with 1,246 patients infected with Onchocerca volvulus in eight villages in western Uganda. Study participants were treated the first time with a single dose of 150 microg/kg of ivermectin. Adverse reactions to ivermectin were determined through questioning and clinical examination during house-to-house visits to the participants within 48 hours after ivermectin treatment. Overall adverse reactions were observed in 737 (59.1%) patients. Severe reactions were rare (10 patients, 1.4%). Our data show that adverse reactions to ivermectin in an S. neavei-transmitted onchocerciasis focus in western Uganda occur frequently. In spite of the fact that many patients showed adverse reactions to ivermectin, the drug was well accepted and appreciated by the population.

Obligatory symbiotic Wolbachia endobacteria are absent from Loa loa.

BACKGROUND: Many filarial nematodes harbour Wolbachia endobacteria. These endobacteria are transmitted vertically from one generation to the next. In several filarial species that have been studied to date they are obligatory symbionts of their hosts. Elimination of the endobacteria by antibiotics interrupts the embryogenesis and hence the production of microfilariae. The medical implication of this being that the use of doxycycline for the treatment of human onchocerciasis and bancroftian filariasis leads to elimination of the Wolbachia and hence sterilisation of the female worms. Wolbachia play a role in the immunopathology of patients and may contribute to side effects seen after antifilarial chemotherapy. In several studies Wolbachia were not observed in Loa loa. Since these results have been doubted, and because of the medical significance, several independent methods were applied to search for Wolbachia in L. loa. METHODS: Loa loa and Onchocerca volvulus were studied by electron microscopy, histology with silver staining, and immunohistology using antibodies against WSP, Wolbachia aspartate aminotransferase, and heat shock protein 60. The results achieved with L. loa and O. volvulus were compared. Searching for Wolbachia, genes were amplified by PCR coding for the bacterial 16S rDNA, the FTSZ cell division protein, and WSP. RESULTS: No Wolbachia endobacteria were discovered by immunohistology in 13 male and 14 female L. loa worms and in numerous L. loa microfilariae. In contrast, endobacteria were found in large numbers in O. volvulus and 14 other filaria species. No intracellular bacteria were seen in electron micrographs of oocytes and young morulae of L. loa in contrast to O. volvulus. In agreement with these results, Wolbachia DNA was not detected by PCR in three male and six female L. loa worms and in two microfilariae samples of L. loa. CONCLUSIONS: Loa loa do not harbour obligatory symbiotic Wolbachia endobacteria in essential numbers to enable their efficient vertical transmission or to play a role in production of microfilariae. Exclusively, the filariae cause the immunopathology of loiasis is patients and the adverse side effects after antifilarial chemotherapy. Doxycycline cannot be used to cure loiais but it probably does not represent a risk for L. loa patients when administered to patients with co-infections of onchocerciasis.

Transforming growth factor-beta expression by host cells is elicited locally by the filarial nematode Onchocerca volvulus in hyporeactive patients independently from Wolbachia.

Transforming growth factor-beta (TGF-beta) is a key cytokine in immune regulation, cell differentiation, development, wound healing, and tissue remodelling. It mediates immunosuppression in filarial infections facilitating parasite persistence, while attenuating immunopathology, which is induced by migrating microfilariae. Immunosuppression rises with parasite burden, but it remains unknown whether filariae elicit local release of immunosuppressive cytokines. Therefore, using immunohistology, we investigated the expression of stable, released latent TGF-beta1 in subcutaneous nodules from highly infected, hyporeactive onchocerciasis patients, harbouring adult Onchocerca volvulus. Since many cell types produce TGF-beta, we elucidated the cellular source, distribution and dependency on the worms' sex, productivity and vitality. We found TGF-beta1 to be abundantly expressed by T cells, plasma/B cells, macrophages, mast cells, fibrocytes, and vascular endothelial cells, particularly in onchocercomas with productive or previously productive females, damaged, dead and resorbed adult worms or microfilariae. We conclude TGF-beta to be antigen induced by the filariae since expression was scarce around subcutaneous arthropods or cholesterol crystals in onchocercomas. Enhanced expression after ivermectin or endobacteria-depleting doxycycline treatment indicates induction to depend on filariae and not on Wolbachia endobacteria. TGF-beta(+) cells were reduced in HIV co-infection. This finding of local and sustained TGF-beta induction by vital and dead filariae, untreated and after treatment, adds new aspects to immunomodulation by helminths.

Characterization of the allergen filarial tropomyosin with an invertebrate specific monoclonal antibody.

Tropomyosins of invertebrates are pan-allergens responsible for wide spread allergic reactions against seafood and arthropods. As invertebrate tropomyosins are highly conserved, helminth tropomyosins are likely to show properties similar to these medically important allergens. Studies with a monoclonal antibody, NR1, raised against tropomyosin of the rodent filarial nematode Acanthocheilonema viteae revealed a B cell epitope common to helminths and marine mollusks, which does not occur in vertebrate tropomyosin. This antibody detected tropomyosin of A. viteae, other filariids, nematodes, trematodes and a cestode, and recognized as well tropomyosin of oyster, squid and octopus, but not of arthropods and vertebrates. Immunohistological analyses of A. viteae, Onchocerca volvulus and other nematodes using NR1 showed that tropomyosin is located in the fibrillar part of the body wall muscles and the uterus, and is also conspicuous in muscles of the pharynx, the vagina and other organs of the nematodes. The abundance of a pan-allergen like tropomyosin in parasitic worms and the counterintuitive, but well documented protection against allergic reactivity by some chronic helminth infections is discussed.

Diagnosis of human visceral pentastomiasis.

Visceral pentastomiasis in humans is caused by the larval stages (nymphs) of the arthropod-related tongue worms Linguatula serrata, Armillifer armillatus, A. moniliformis, A. grandis, and Porocephalus crotali. The majority of cases has been reported from Africa, Malaysia, and the Middle East, where visceral pentastomiasis may be an incidental finding in autopsies, and less often from China and Latin America. In Europe and North America, the disease is only rarely encountered in immigrants and long-term travelers, and the parasitic lesions may be confused with malignancies, leading to a delay in the correct diagnosis. Since clinical symptoms are variable and serological tests are not readily available, the diagnosis often relies on histopathological examinations. This laboratory symposium focuses on the diagnosis of this unusual parasitic disease and presents its risk factors and epidemiology.