Willy F. Piessens

Pathogenesis of Lymphatic Disease in Bancroftian Filariasis:: A Clinical Perspective

The pathogenesis of lymphatic filariasis has been a matter of debate for many decades. Here, Gerusa Dreyer and colleagues propose a dynamic model of bancroftian filariasis, integrating clinical, parasitological, surgical, therapeutic, ultrasonographic and histopathological data. This model has profound implications for filariasis control programs and the management of the individual patient.

Lymphocyte Surface Immunoglobulins: Distribution and Frequency in Lymphoproliferative Diseases

Abstract The frequency and distribution of surface immunoglobulins, a B-cell marker, were studied on peripheral blood lymphocytes from normal controls and patients with infectious mononucleosis, chronic lymphatic leukemia, and lymphosarcoma. IgG, IgA, IgM, IgD, and IgE determinants were demonstrated on lymphocytes from normal donors. In infectious mononucleosis there was a transient increase of surface IgM early in the disease. When these patients were retested several months later, the percentage of lymphocytes with surface IgM had reverted to the normal range. Chronic lymphatic leukemia and lymphosarcoma could be divided into two groups: one with no detectable surface Ig on their lymphocytes; and another with increased numbers of lymphocytes with surface Ig. There was no correlation between surface and serum immunoglobulins. The absence of surface Ig in lymphosarcoma correlated with nonprogressive disease restricted to lymph nodes. These findings suggest that some forms of chronic lymphatic leukemia and...

Antigen-specific suppressor cells and suppressor factors in human filariasis with Brugia malayi.

We investigated the mechanisms of specific immune unresponsiveness to microfilarial antigens. The blood of patients with obvious Brugia malayi infections contains an adherent cell type that specifically suppresses reactions to microfilarial antigens but not to other antigens. In the absence of continued stimulation by parasite antigens, this suppressor cell loses its functional activity after overnight culture in vitro. Furthermore, serums from patients with and without microfilaremia contain factors that also suppress reactions to filarial antigens in vitro. These results suggest that immune unresponsiveness in human beings with patent filarial infections is due to active suppression of immune responses directed against the parasite and not to an intrinsic inability of infected patients to react to parasite antigens.

Antigen-Specific Suppressor T Lymphocytes in Human Lymphatic Filariasis

Immune responses to parasite antigens are much lower in patients with microfilaremia than in persons with other manifestations of brugian filariasis. To determine whether hyporeactivity is associated with changes in populations of lymphocytes that regulate immune responses, we quantitated helper and suppressor T cells in the blood of patients infected with Brugia malayi. Increased numbers of suppressor T cells were present in 15 of 17 patients with microfilaremia and in six of 11 patients with elephantiasis. This increase correlated with hyporeactivity to filarial antigens but not to nonparasite antigens. Removal of suppressor T cells activated in vivo or in vitro improved reactivity to filarial antigens. These results suggest that immunosuppression induced by filarial parasites is a possible mechanism of survival of these organisms in an immunocompetent host.

Chitin synthesis and sheath morphogenesis in Brugia malayi microfilariae.

Brugia malayi microfilariae and gravid adult females were examined to determine whether chitin (poly beta(1----4)-linked N-acetylglucosamine) is a structural component of the microfilarial sheath. Two lectins which are specific for beta(1----4)-linked oligomers of N-acetylglucosamine bind to the sheaths of living microfilariae. Diflubenzuron, a potent inhibitor of chitin synthesis in insects and crustaceans, causes gravid female worms to shed progeny microfilariae with truncated sheaths. A chitin-like fraction (hot alkali-insoluble and chitinase-sensitive) can be isolated from gravid female (but not male) worms. This fraction can be metabolically labelled with radioactive glucosamine, but such labelling is inhibited by diflubenzuron. These data suggest that chitin synthesis is critical to microfilarial sheath morphogenesis in this parasitic nematode.

Cloning and characterization of an Onchocerca volvulus specific DNA sequence

A cloned sequence, pOvs134, was isolated from a genomic library prepared from Onchocerca volvulus of savanna origin in the plasmid pUC9. pOvs134 hybridizes to all the geographic isolates of O. volvulus tested from both the New and the Old World, but not to the species Onchocerca gibsoni, Onchocerca gutturosa, Onchocerca ochengi, Onchocerca cervicalis, the filarial parasites Brugia malayi, or Dirofilaria immitis, nor to human or simuliid DNA. As little as 250 pg of DNA can be detected on a dot blot hybridization, suggesting that pOvs134 is sensitive enough to detect a single third stage larva. DNA sequence analysis of the inserted DNA of pOvs134 revealed that it consisted of twelve examples of a 149-bp repeat. The sequence of this repeat is strikingly similar to that of two O. volvulus genomic clones previously described, one of which has been reported to be specific for forest form O. volvulus, and one of which hybridizes to genomic DNA of several species of Onchocerca. These results suggest that the 149-bp repeat sequence is highly repeated in the genome of O. volvulus, and that variants of this repeat with different specificities exist.

Stimulation of Nonimmunized Lymphocytes by Platelet-Antibody Complexes in Idiopathic Thrombocytopenic Purpura

Abstract Platelets preincubated in serum from patients with immunologic thrombocytopenia stimulate autologous lymphocytes in culture. Stimulation of new deoxyribonucleic acid synthesis by cultured lymphocytes was measured by the uptake of tritiated thymidine. The lymphocyte-stimulating activity in serum was heat stable, could be adsorbed by autologous and homologous platelets, was inhibited by anti-human immunoglobulin G, and chromatographed as immunoglobulin G on diethylaminoethyl cellulose. The degree of stimulation was proportional to the number of platelets in each culture and was maximal on the sixth day of culture. With this technic, presumptive antibody was detected in 25 of 26 patients with idiopathic thrombocytopenic purpura and eight of nine with other types of immune thrombocytopenia. The lymphocyte-stimulating activity in idiopathic thrombocytopenic purpura persisted after clinical remission induced by steroids, splenectomy or cyclophosphamide therapy. Normal lymphocytes thus appear to be nons...

Studies on a filarial antigen with collagenase activity

We examined the ability of two filarial species, Onchocerca volvulus and Brugia malayi, to solubilize collagen molecules from native collagen fibrils. Collagenolytic activity was detected in extracts of adult worms, in living microfilariae of O. volvulus and in live infective larvae and adult female worms of B. malayi. Excretion-secretion factors produced in vitro by infective larvae of B. malayi also contained large amounts of collagenase. Studies with enzyme inhibitors suggest that the latter may be a metallo-protease. Antibodies to filarial collagenase were present in sera from patients with onchocerciasis and brugian filariasis and from mice immunized with B. malayi. These antibodies and a monoclonal antibody raised against O. volvulus antigens immunoprecipitate filarial collagenase but appear not to be directed against the active site of the enzyme.

Genus- and species-specific DNA probes to identify mycobacteria using the polymerase chain reaction

Differential diagnosis of Mycobacterium tuberculosis, M. avium, and other mycobacteria remains a lengthy process. Recently, the use of DNA probes has been proposed as a new approach for a more specific and rapid diagnosis. Here, we report the cloning and sequencing of a genus-specific probe for Mycobacterium and a species-specific M. avium probe. The genus-specific probe hybridizes with DNA from nine ATCC type strains and 13 isolates of mycobacteria but not to non-mycobacterial DNA. In addition, the cloned fragment could also be amplified by polymerase chain reaction (PCR) in DNa of ten different mycobacterial type strains. The M. avium specific probe hybridizes strongly to sequences amplified in M. avium but not other mycobacterial or non-mycobacterial DNA. Amplification of the target sequence by PCR allowed the detection of 1 fg of all mycobacterial DNA tested for the genus-specific probe and 1 fg of M. avium DNA for the species-specific probe.

Reduction of Suppressor T Lymphocytes in the Tropical Splenomegaly Syndrome

To study the pathogenesis of tropical splenomegaly syndrome, we compared immunologic findings in patients from Flores, Indonesia, with those obtained in local residents without splenomegaly and in controls. Villagers with tropical splenomegaly syndrome had markedly elevated levels of total IgM, higher titers of IgM antibodies to Plasmodium vivax, and reduced levels of circulating T lymphocytes. The latter were caused by a decrease in the total number of T cells with the suppressor/cytotoxic phenotype (T8+). Levels of B lymphocytes were similar in all groups. All immunologic abnormalities reverted toward normal in patients treated weekly for 9 to 26 months with chloroquine phosphate. These findings suggest that overproduction of immunoglobulins in patients with tropical splenomegaly syndrome is caused by an imbalance in the normal ratio of helper: suppressor T cells that regulate B-lymphocyte function, and that this imbalance is due to a decrease in suppressor T lymphocytes.