Brugia malayi: Stage-specific expression of carbohydrates containing N-acetyl-d-glucosamine on the sheathed surfaces of microfilariae

Microfilariae, infective larvae, and adult worms of Brugia malayi were incubated with a panel of seven lectins in order to study the expression of surface carbohydrates. Infective larvae and adult worms did not bind any of the lectins utilized. Microfilariae, on the other hand, bound wheat germ agglutinin. The binding of this lectin was saturable and specific, and attributed to the presence of N-acetyl-D-glucosamine. In addition, microfilariae derived in vitro bound concanavalin A, indicating the presence of glucose and/or mannose on this stage of the parasite. The fact that similar concanavalin A binding was not seen on microfilariae recovered directly from the infected host implies that there is masking or loss of parasite surface antigens as microfilariae mature in vivo.

Delayed hypersensitivity granuloma formation around Schistosoma mansoni eggs in vitro. III. Granuloma formation and modulation in human Schistosomiasis mansoni

An in vitro model of granuloma formation was used to study the cellular immune responses of Schistosoma mansoni-infected patients. The purposes of this study were to determine the relationship of granulomatous hypersensitivity to S. mansoni eggs in recent, well-defined infections and long-term chronic infections, and to determine the role of T cell subsets (OKT3, 4, and 8) defined by monoclonal antibodies in granulomatous hypersensitivity. Peripheral blood mononuclear cells obtained from patients with recent S. mansoni infections demonstrated increased granulomatous hypersensitivity responses in vitro when compared to peripheral blood mononuclear cells obtained from patients infected for 5 yr or more. The selective removal of infected for 5 yr or more. The selective removal of OKT3+ or OKT4+ cells reduced the ability of peripheral blood mononuclear cells to form granulomas in vitro. Positive selection for OKT4+ T cells produced optimal granulomatous hypersensitivity when compared to that produced by the unfractionated peripheral blood mononuclear cell population. OKT8+ cells demonstrated no ability to form granulomas in vitro. Selective removal of OKT8+ T cells produced variable results in the ability of the remaining peripheral blood mononuclear cells to form granulomas in vitro. These studies demonstrate the feasibility of investigating granulomatous hypersensitivity and immunoregulatory mechanisms operative in S. mansoni-infected patients by using in vitro technology.

Delayed hypersensitivity granuloma formation around Schistosoma mansoni eggs in vitro. III. Granuloma formation and modulation in human Schistosomiasis mansoni

An in vitro model of granuloma formation was used to study the cellular immune responses of Schistosoma mansoni-infected patients. The purposes of this study were to determine the relationship of granulomatous hypersensitivity to S. mansoni eggs in recent, well-defined infections and long-term chronic infections, and to determine the role of T cell subsets (OKT3, 4, and 8) defined by monoclonal antibodies in granulomatous hypersensitivity. Peripheral blood mononuclear cells obtained from patients with recent S. mansoni infections demonstrated increased granulomatous hypersensitivity responses in vitro when compared to peripheral blood mononuclear cells obtained from patients infected for 5 yr or more. The selective removal of infected for 5 yr or more. The selective removal of OKT3+ or OKT4+ cells reduced the ability of peripheral blood mononuclear cells to form granulomas in vitro. Positive selection for OKT4+ T cells produced optimal granulomatous hypersensitivity when compared to that produced by the unfractionated peripheral blood mononuclear cell population. OKT8+ cells demonstrated no ability to form granulomas in vitro. Selective removal of OKT8+ T cells produced variable results in the ability of the remaining peripheral blood mononuclear cells to form granulomas in vitro. These studies demonstrate the feasibility of investigating granulomatous hypersensitivity and immunoregulatory mechanisms operative in S. mansoni-infected patients by using in vitro technology.

Parasite antigen-specific human T cell lines and clones. Major histocompatibility complex restriction and B cell helper function

The development of T lymphocyte lines and clones of defined specificity has become an important method for investigating both T cell recognition of foreign antigens as well as T cell influence on B cells. In the present study, human antigen-specific T cell lines and clones have been derived from a patient with a naturally acquired filarial infection. These T cells are of the helper phenotype (Leu 1+, Leu 2-, Leu 3+) and are independent of exogenous interleukin-2. Furthermore, these T cells have been shown to require both antigen-presenting cells and antigen for optimal proliferation. Helper function mediated by these T cells as manifested by the in vitro induction of parasite-specific antibody was antigen-dose dependent, requiring much lower antigen concentrations than those necessary to induce blastogenesis. More importantly, there is an absolute requirement of the T cell line for HLA-DR histocompatible antigen-presenting cells; clones derived from this T cell line show a more specific DR-related restriction--to only one of the two parental DR haplotypes in antigen stimulated proliferative responses. Such parasite antigen specific human helper T cell lines and clones should prove useful in exploring the fine control of the host response to naturally acquired helminth infections. In addition, these long-term T cell lines and clones can provide a potent tool for examining not only the events involved in human T cell responses to parasite antigens, but also into the associated cellular and humoral factors necessary for the B cell responses which follow.

Excretory-secretory and somatic antigens in the diagnosis of human filariasis

In order to compare the immunodiagnostic value of excretory-secretory (E-S) antigens derived from adult Brugia malayi worms with somatic antigens derived from adults, microfilariae (Mf) and infective larvae (L3) of these parasites, well defined serum pools from patients with filarial (brugia, bancrofti, loa and perstans) and non-filarial (ascaris, stronglyoides, toxocara, echinococcus, cysticercus and schistosoma) helminth infections were tested against antigens derived from these different life cycle stages of B. malayi in a Staphylococcus aureus radioimmunoprecipitation assay (S. aureus RIA). The adult brugia antigens proved significantly more discriminatory than those of the other parasite stages, with the homologous brugia serum pool also showing greater reactivity to adult than to L3 and Mf antigens. Similar results were obtained when individual sera from patients (rather than serum pools) were tested in the same assay. The most surprising finding was the minimal reactivity seen between the adult filarial antigens and the non-filarial serum pools despite the presence in these pools of strong antibody reactivity with their homologous antigens. The reasons underlying the unexpected specificity of this S. aureus RIA for discriminating among sera from filarial and non-filarial infections were analysed qualitatively by immunoprecipitation techniques. It was found that use of the chloramine-T method for radioiodination resulted in preferential labelling of the low molecular weight (mol. wt) proteins (10-70,000 daltons) in the B. malayi adult somatic antigen and that these antigens were bound primarily by the filarial and not the non-filarial serum pools. These findings suggest that lower mol. wt helminth antigens may show greater species specificity than those with higher mol. wt, and those with higher mol. wt, greater cross-reactivity. If substantiated by further analysis, such results would have important implications for the subsequent isolation of diagnostically important filarial parasite antigens.

IgE responses in human schistosomiasis. I. Quantitation of specific IgE by radioimmunoassay and correlation of results with skin test and basophil histamine release

We have developed a non-competitive solid-phase radioimmunoassay (SPRIA) to quantitate human IgE antibodies to Schistosoma mansoni antigens that was capable of accurately measuring IgE antibodies in both high and low titer sera. Ninety sera from "early" or "chronic" schistosomiasis patients were studied. Both levels of parasite-specific IgE antibodies and the proportion of the total IgE response that was parasite-specific were significantly lower in "early infection" sera than in sera of patients with chronic infections. The SPRIA to adult worm antigen was compared with basophil histamine release and direct intradermal skin testing also performed with the adult antigen. Both tests showed significant correlations with the SPRIA in detecting specific anti-parasite antibody.

Cell-mediated and humoral immune responses in capuchin monkeys infected with Schistosoma japonicum or Schistosoma mansoni

Cell-mediated immune responses, assessed by lymphocyte clonal expansion in vitro, as well as humoral responses, assessed by an enzyme-linked immunosorbent assay (ELISA), were evaluated in capuchin monkeys during a 7-month infection with Schistosoma mansoni or with a Japanese or Philippine strain of Schistosoma japonicum. Although mounting a vigorous antibody response against parasite antigens, the S. mansoni-infected monkeys failed to show lymphocyte proliferation in response to stimulation with soluble adult worm antigen or soluble egg antigen derived from S. mansoni. Monkeys infected with S. japonicum responded to parasite antigens obtained from S. japonicum both by antibody production and lymphocyte blastogenesis. Monkeys infected with S. japonicum (Japanese strain) never developed detectable levels of circulating immune complexes (CIC). On the other hand high levels of CIC appeared at 7 months of infection in the monkeys infected with S. mansoni. The CIC levels exhibited negative correlations with intensity of infection. In studies of antigen species specificity, sera from S. mansoni-infected monkeys showed much higher IgG antibody titers to antigens derived from S. mansoni than to S. japonicum-derived antigens. On the other hand, monkeys infected with S. japonicum had comparable IgG antibody titers to antigens of both schistosome species.

IgE responses in human filariasis. II. Qualitative characterization of filaria-specific IgE

Crossed radioimmunoelectrophoresis (CRIE) was used to characterize human IgE antibody responses to filarial parasites by using antigens derived from Brugia malayi (Bm) adult worms. A reference pool of patient sera was initially used to determine the sensitivity and specificity of CRIE. Because IgG-blocking antibodies interfered with IgE binding in certain sera, all sera were preabsorbed with protein A-Sepharose. As little as 50 ng of specific IgE antibody (determined by quantitative radioallergosorbent test [RAST]) in the reference pool bound to 20 of the 35 antigen precipitates in crossed immunoelectrophoresis. Increasing IgE antibody concentration did not increase the number of IgE-binding precipitates. Six patients from each of the three major clinical groups in lymphatic filariasis (i.e., tropical pulmonary eosinophilia [TE], chronic lymphatic pathology [CP], or circulating microfilaremia [MF]) were studied by CRIE with the use of a constant amount of IgE antibody (50 ng IgE anti-BmA). Distinct patterns of allergen recognition were observed among the groups. Individuals with TE recognized both anodic and cathodic antigens as allergens, whereas the other two groups recognized predominantly anodic antigens. The greatest number of allergens was recognized by patients with TE; this number ranged from nine to 18, whereas patients with CP or circulating MF recognized from six to 11 allergens. Although potentiated IgE responses at a quantitative level in parasitic helminth infections is a well-established phenomenon, our studies showing the diversity of antigens recognized as allergens indicate for the first time potentiated IgE responses at a qualitative level as well.

Cellular responses in human strongyloidiasis

Peripheral lymphocytes from 16 patients with chronic uncomplicated strongyloidiasis and 15 non-infected controls were stimulated in vitro with Strongyloides stercoralis larval antigens, other non-parasite antigens and the T cell mitogen phytohemagglutinin (PHA). In the presence of autologous plasma the patients' responses to Strongyloides antigens were similar to those of controls. When lymphocytes from nine patients were cultured in the presence of normal human serum, responses to parasite antigens were enhanced, while responses to other antigens and to PHA were unaffected. Lymphoproliferative responses to PHA were significantly lower in the patients' group than in the controls. These findings suggest that in chronic strongyloidiasis, in addition to a depression of T cell activity, factors are present in the patients' serum that inhibit parasite-specific cellular responses in vitro.

IgE responses in human filariasis. II. Qualitative characterization of filaria-specific IgE

Crossed radioimmunoelectrophoresis (CRIE) was used to characterize human IgE antibody responses to filarial parasites by using antigens derived from Brugia malayi (Bm) adult worms. A reference pool of patient sera was initially used to determine the sensitivity and specificity of CRIE. Because IgG-blocking antibodies interfered with IgE binding in certain sera, all sera were preabsorbed with protein A-Sepharose. As little as 50 ng of specific IgE antibody (determined by quantitative radioallergosorbent test [RAST]) in the reference pool bound to 20 of the 35 antigen precipitates in crossed immunoelectrophoresis. Increasing IgE antibody concentration did not increase the number of IgE-binding precipitates. Six patients from each of the three major clinical groups in lymphatic filariasis (i.e., tropical pulmonary eosinophilia [TE], chronic lymphatic pathology [CP], or circulating microfilaremia [MF]) were studied by CRIE with the use of a constant amount of IgE antibody (50 ng IgE anti-BmA). Distinct patterns of allergen recognition were observed among the groups. Individuals with TE recognized both anodic and cathodic antigens as allergens, whereas the other two groups recognized predominantly anodic antigens. The greatest number of allergens was recognized by patients with TE; this number ranged from nine to 18, whereas patients with CP or circulating MF recognized from six to 11 allergens. Although potentiated IgE responses at a quantitative level in parasitic helminth infections is a well-established phenomenon, our studies showing the diversity of antigens recognized as allergens indicate for the first time potentiated IgE responses at a qualitative level as well.

Prenatal allergic sensitization to helminth antigens in offspring of parasite-infected mothers

Total and filaria-specific immunoglobulin E (IgE) levels were studied in cord blood from infants born in Madras, India, where filariasis and intestinal helminth infections are highly endemic. Increased total IgE levels were observed in 82% of 57 cord sera tested (geometric mean 12.6 ng/ml; range 1-1,900 ng/ml). 33 of these sera also contained IgE antibodies specific for filarial antigens as determined by solid-phase radioimmunoassay. Comparison of ratios of filaria-specific IgE to total IgE in paired maternal and cord sera suggested that cord blood IgE was derived from the fetus in most cases and not from transplacental antibody transfer. Our results suggest that prenatal allergic sensitization to helminth parasites occurs in the tropics. Such sensitization may contribute to the heterogeneity in host immune response and disease expression noted in filariasis and other helminth infections.

Specific allergic sensitization to Strongyloides antigens in human strongyloidiasis

Reaginic antibodies to antigens from the human parasite Strongyloides stercoralis were studied by histamine release from basophils in 15 patients with chronic uncomplicated strongyloidiasis and in 12 controls (six North Americans with no evidence of parasitic diseases, two patients with Schistosoma mansoni, two with hookworm, one with Ascaris lumbricoides, and one with Onchocerca volvulus). All of the patients had antibodies to the somatic larval antigens, and 14 of 15 patients also had antibodies to the excretory/secretory products of S. stercoralis larvae. None of the controls had a positive response to any of the antigens tested. These findings indicate that patients with chronic strongyloidiasis have parasite-specific IgE antibodies and that S. stercoralis larval allergens may have a potential role in the immunodiagnosis of strongyloidiasis.

Modulation of the host response in human schistosomiasis. IV. Parasite antigen induces release of histamine that inhibits lymphocyte responsiveness in vitro

Several mechanisms underlying the suppression of in vitro lymphocyte transformation responses to parasite antigens in human schistosomiasis have been previously described, but the role that immediate hypersensitivity reactions may have in regulating these lymphocyte transformation responses has been little explored. Using Hypaque-Ficoll-separated peripheral blood mononuclear cells (PBMC) from patients with schistosome infections, we found that histamine release could be demonstrated routinely in lymphocyte cultures challenged with adult worm, egg, or cercarial antigens. Release occurred within 1 hr of stimulation, and histamine persisted in the cultures for 6 days at levels of 10(-6) to 10(-7) M. That such concentrations were capable of suppressing LT responses in vitro was shown by the addition of exogenous histamine to modified PBMC culture systems from 10 normal individuals and eight patients with Schistosoma mansoni or Schistosoma mekongi infections. Responses to phytohemagglutinin, streptokinase-streptodornase, and tetanus were equivalently suppressed in both groups (50.8 +/- 6% in normals and 55.9 +/- 6.2% in patients), and the doses required for maximal suppression were similar. Passage of PBMC from infected patients over nylon wool, in addition to removing adherent suppressor cells, also markedly reduced the number of histamine-containing basophils (74 +/- 4.5% removed). The enhanced responsiveness to parasite antigen by PBMC depleted by nylon wool passage was abrogated by the addition of exogenous histamine to the cultures. These results indicate that in routine PBMC cultures 'nonspecific' lymphocyte suppression by histamine liberated from basophils in an antigen-specific fashion may help to account for the specific suppression of lymphocyte responses to parasite antigens so characteristic of patients with schistosome and other helminth infections.

Modulation of the host response in human schistosomiasis. IV. Parasite antigen induces release of histamine that inhibits lymphocyte responsiveness in vitro

Several mechanisms underlying the suppression of in vitro lymphocyte transformation responses to parasite antigens in human schistosomiasis have been previously described, but the role that immediate hypersensitivity reactions may have in regulating these lymphocyte transformation responses has been little explored. Using Hypaque-Ficoll-separated peripheral blood mononuclear cells (PBMC) from patients with schistosome infections, we found that histamine release could be demonstrated routinely in lymphocyte cultures challenged with adult worm, egg, or cercarial antigens. Release occurred within 1 hr of stimulation, and histamine persisted in the cultures for 6 days at levels of 10(-6) to 10(-7) M. That such concentrations were capable of suppressing LT responses in vitro was shown by the addition of exogenous histamine to modified PBMC culture systems from 10 normal individuals and eight patients with Schistosoma mansoni or Schistosoma mekongi infections. Responses to phytohemagglutinin, streptokinase-streptodornase, and tetanus were equivalently suppressed in both groups (50.8 +/- 6% in normals and 55.9 +/- 6.2% in patients), and the doses required for maximal suppression were similar. Passage of PBMC from infected patients over nylon wool, in addition to removing adherent suppressor cells, also markedly reduced the number of histamine-containing basophils (74 +/- 4.5% removed). The enhanced responsiveness to parasite antigen by PBMC depleted by nylon wool passage was abrogated by the addition of exogenous histamine to the cultures. These results indicate that in routine PBMC cultures 'nonspecific' lymphocyte suppression by histamine liberated from basophils in an antigen-specific fashion may help to account for the specific suppression of lymphocyte responses to parasite antigens so characteristic of patients with schistosome and other helminth infections.

Immunologic responses to experimental strongyloidiasis in rats

Humoral and cellular immune responses were evaluated in Lewis rats infected with high (3000) inocula of Strongyloides ratti larvae (L3). The responses of peripheral and mesenteric node lymphocytes to crude larval antigen (by lymphocyte proliferation assay) sharply rose between days 12 and 16 of the primary infection and days 8 and 12 of the challenge, and decreased promptly to almost preinfection levels. Spleen lymphocytes failed to show any response to the primary infection, but did exhibit a modest response after challenge. The responses of peripheral lymphocytes to the mitogen phytohemagglutinin fell considerably on infection day 8 and then rose sharply to very high levels. Reinfection caused a small decrease in responsiveness, followed by another increase after 10 days. Inoculation of 3000 heat-killed larvae stimulated a response in peripheral lymphocytes similar to that elicited by the inoculation of live larvae. Spleen lymphocytes appeared to be stimulated more by the killed larvae inoculation, whereas only a limited response was found in mesenteric node lymphocytes in animals inoculated with dead larvae. IgG antibody titers against S. ratti antigen were measured by the enzyme-linked immunoabsorbent assay (ELISA). A significant elevation was noted between days 12 and 20 with a return to pre-infection levels between days 80 and 150. Challenge with 3,000 L3 induced a rapid and significant elevation. These data indicate that in rats experimentally inoculated with large numbers of S. ratti larvae a direct relationship exists between the development of cellular and humoral immune responses to larval antigens, the expulsion of the intestinal worms, and the acquisition of resistance to subsequent challenge.

Specificity of antibody and cellular immune responses in human schistosomiasis

Thirty patients infected with Schistosoma mekongi, S. mansoni or S. japonicum had cell-mediated immune responses assessed by lymphocyte transformation in vitro (LT), immediate hypersensitivity responses determined by basophil histamine release in vitro (HR) and IgG antibody responses evaluated in an enzyme-linked immunosorbent assay (ELISA). Species specificity was evaluated with antigens obtained from adult worms or eggs of the three schistosome species. Though cross-reactivity was present in all tests, homologous antigens elicited responses significantly greater than those to heterologous antigens in all comparisons of parasite specific IgG and IgE antibody in these groups of patients. A similar generalization could be made for the lymphocyte responses to the same antigen preparations, but statistically significant differences were achieved only in certain comparisons.

Schistosome infections in humans: perspectives and recent findings. NIH conference

Approximately 200 million persons are infected with schistosomes. Of those infected, a small proportion develop serious chronic disease, usually after years of intensive exposure and infection. Schistosoma mansoni and Schistosoma japonicum reside in the mesenteric veins and produce liver fibrosis, which results in portal hypertension and bleeding esophageal varices but little hepatocellular dysfunction. Schistosoma haematobium resides primarily in the pelvic veins and produces mass lesions in the bladder and ureters, which lead to hydroureter and hydronephrosis. The intensity of infection is a major factor determining development of disease, but differences in worm strain and host response may also be important. In acute schistosomiasis there is an intense response to the parasite, which is suppressed as the infection becomes chronic. The marked inflammatory response seen in early and acute schistosomiasis becomes less intense and fibrotic lesions predominate. The recent advent of safe, effective, and easily administered chemotherapeutic reagents will aid in the control of schistosomiasis.

Endemic filariasis on a Pacific Island. II. Immunologic aspects: immunoglobulin, complement, and specific antifilarial IgG, IgM, and IgE antibodies

Sixty-eight individuals from a Pacific island hyperendemic for subperiodic bancroftian filariasis were selected from a larger study population to include the entire clinical spectrum of filarial infection in that region and also an "endemic control" group without clinical or parasitologic evidence of filarial infection. Analysis of their blood leukocyte and humoral immune responses yielded the following major findings: 1) levels of specific antifilarial antibodies of three different immunoglobulin class (IgG and IgM measured by ELISA and IgE determined by radioimmunoassay) were significantly greater in the "endemic control" population than in the patients with filariasis, an observation true for both children and adults; 2) the endemic controls also had significantly higher levels of serum IgM and C3 than did the filariasis patients 3) while individuals with "filarial fevers" and "chronic (lymphatic) pathology" did have significantly lower IgG antibody responses to filarial antigen than the controls, the lowest antibody levels were found in the patients with microfilaremia; 4) symptomatic patients (i.e., those with filarial fevers or lymphatic obstruction) regularly showed higher specific antibody responses to filarial antigens than asymptomatic, infected individuals, although the difference did not reach statistical significance. These findings are in concert with our previously reported, intriguing observation that lymphocyte proliferative responsiveness to filarial antigens was much greater in individuals of the "non-infected" endemic control population than in patients with filariasis; furthermore, they indicate the important issues that must be approached and resolved to define the immunologic determinants leading both to the various filarial clinical syndromes and to protective immunity.

Endemic filariasis on a Pacific island. I. Clinical, epidemiologic, and parasitologic aspects

The clinical and parasitologic aspects of filariasis were investigated in 459 inhabitants of a South Pacific island endemic for subperiodic Wuchereria bancrofti filariasis. Episodes of filarial fevers, usually with concomitant lymphangitis and/or lymphadenitis, were experienced by 26%. Lymphobstructive lesions, manifest in the later decades of life, were present in 12 with elephantiasis and 24 with hydroceles. Microfilaremia was detectable by membrane filtration of 1 ml of blood in 33% of persons, with a quarter of these having less than 50 microfilariae/ml. Microfilaremia and filarial fevers were more frequent in males than females and in residents of the most inland villages. Neither presence nor magnitude of lymphadenopathy correlated with other manifestations of filariasis except that markedly enlarged inguinal-femoral nodes were more common in those with elephantiasis or hydroceles. A history of filarial fevers did not correlate with presence of microfilaremia. Over 70% of adults had microfilaremia and/or historical or physical manifestations of filariasis. The absence of detectable microfilaremia in many residents with clinical evidence of filariasis and the presence of asymptomatic microfilaremia emphasize the limitations in relying only on microfilaremia rates or clinical findings in the study of the prevalence or manifestations of filarial infection.

Treatment of Schistosoma mekongi with praziquantel: a double-blind study

Praziquantel is a newly developed drug effective in the treatment of schistosomiasis. In order to assess the efficacy and toxicity of praziquantel in the treatment of Schistosoma mekongi, 11 infected Laotian refugees, all belonging to a single extended family, were treated in a double-blind crossover trial with praziquantel and placebo. Initially, one group of five received praziquantel 60 mg/kg body weight in three divided doses orally while the remainder received an identically appearing placebo. Patients were evaluated clinically before, during and following therapy for 2 days. After 2.5 months the patients were re-evaluated and subjected to the opposite treatment, and final follow-up took place 5-7 months later. Three other patients were treated using an open protocol. All but one person was cured (91%). This patient failed to show a decrease in egg excretion 2.5 weeks after praziquantel therapy and was lost to follow-up thereafter. Side effects were common and consisted primarily of abdominal pain, malaise, and fever. These were generally mild and transient. No abnormal laboratory findings were associated with praziquantel therapy. At the final evaluation 6/6 patients with initial hepatomegaly showed a decrease in liver size.

Modulation of the host response in human schistosomiasis. III. Blocking antibodies specifically inhibit immediate hypersensitivity responses to parasite antigens

Mechanisms for modulating the host's immune response in human Schistosomiasis mansoni have been described for delayed hypersensitivity responsiveness and antibody production. Since clinical symptoms of immediate hypersensitivity (i.e. allergic reactivity) are rare in schistosomiasis despite the presence of parasite-specific immunoglobulin E, circulating parasite antigen, and normal numbers of basophils and mast cells in infected patients, it seemed likely that there was host modulation of immediate hypersensitivity responsiveness as well. Using an in vitro basophil histamine release assay we have shown that basophils from fifteen patients with S. mansoni infections are sensitized with schistosome-specific immunoglobulin E and will release histamine in an antigen-dose-dependent manner when challenged with a soluble adult worm antigen. This histamine release was suppressed by autologus, but not normal serum. Fractionation of the serum over staphylococcal protein A and antigen affinity columns identified an immunoglobulin G parasite-specific `blocking antibody', analogous to blocking antibodies elicited during immunotherapy of atopic patients, as being responsible for the modulation of this immediate hypersensitivity responsiveness in vitro. Blocking antibody specificity varied from patient to patient, an observation suggesting that different allergens were being recognized by different individuals.

These studies demonstrate that in addition to the immunoregulatory mechanisms previously described in patients with schistosome infections, there is host modulation of immediate hypersensitivity responsiveness that appears to involve specific immunoglobulin G blocking antibodies.

Identification and characterization of excretory-secretory products of Brugia malayi, adult filarial parasites

Although E-S antigens may be particularly important for both the pathogenesis and immunodiagnosis of helminth infections, little is known about the immunochemistry or functional roles in human filarial infections. In the present paper, we have done some initial identification and characterization of E-S products of adult Brugia malayi by employing a combination of sensitive biochemical and immunochemical techniques. E-S products, collected by incubating B. malayi adults in vitro in a defined protein-free medium, were radiolabeled with 125I. SDS-polyacrylamide gel electrophoresis (PAGE) and autoradiography of labeled E-S products revealed 11 protein bands in the m.w. range of 10,000 to 70,000. Comparison of radiolabeled E-S products and adult somatic antigen (B.m.A) in SDS-PAGE indicated many common bands, and crossed immunoelectrophoresis and competitive Staph-A RIA confirmed the presence of most E-S antigens in B.m.A. Of the 11 E-S bands, two appeared to be derived from the surface of the adult worms and microfilariae as shown by SDS-PAGE and autoradiography of lodogen surface-labeled parasites; the presence of two host proteins in E-S was detected by crossed-line immunoelectrophoresis. The E-S antigens were highly immunogenic when tested both with rabbit antiserum raised against B.m.A and with a serum pool of patients with natural filarial infection.

Identification and characterization of excretory-secretory products of Brugia malayi, adult filarial parasites

Although E-S antigens may be particularly important for both the pathogenesis and immunodiagnosis of helminth infections, little is known about the immunochemistry or functional roles in human filarial infections. In the present paper, we have done some initial identification and characterization of E-S products of adult Brugia malayi by employing a combination of sensitive biochemical and immunochemical techniques. E-S products, collected by incubating B. malayi adults in vitro in a defined protein-free medium, were radiolabeled with 125I. SDS-polyacrylamide gel electrophoresis (PAGE) and autoradiography of labeled E-S products revealed 11 protein bands in the m.w. range of 10,000 to 70,000. Comparison of radiolabeled E-S products and adult somatic antigen (B.m.A) in SDS-PAGE indicated many common bands, and crossed immunoelectrophoresis and competitive Staph-A RIA confirmed the presence of most E-S antigens in B.m.A. Of the 11 E-S bands, two appeared to be derived from the surface of the adult worms and microfilariae as shown by SDS-PAGE and autoradiography of lodogen surface-labeled parasites; the presence of two host proteins in E-S was detected by crossed-line immunoelectrophoresis. The E-S antigens were highly immunogenic when tested both with rabbit antiserum raised against B.m.A and with a serum pool of patients with natural filarial infection.