A proteomic approach to identify proteins from Trichuris trichiura extract with immunomodulatory effects

Infections with Trichuris trichiura and other trichurid nematodes have been reported to display protective effects against atopy, allergic and autoimmune diseases. The aims of the present study were to investigate the immunomodulatory properties of T. trichiura adult worm extract (TtE) and its fractions (TtEFs) on the production of cytokines by peripheral blood mononuclear cells and to identify their proteinaceous components. Fourteen TtEFs were obtained by ion exchange chromatography and tested for effects on cytokine production by peripheral blood mononuclear cells. The molecular constituents of the six most active fractions were evaluated using nano-LC/mass spectrometry. The homology between T. trichiura and the related nematode Trichinella spiralis was used to identify 12 proteins in TtEFs. Among those identified, fructose biphosphate aldolase, a homologue of macrophage migration inhibitory factor and heat-shock protein 70 may contribute to the immunomodulatory effects of TtEFs. The identification of such proteins could lead to the development of novel drugs for the therapy of allergic and other inflammatory diseases.

Detection of parasite antigens in Leishmania infantum-infected spleen tissue by monoclonal antibody-, piezoelectric-based immunosensors

Diseases such as leishmaniases are important causes of morbidity and mortality in Brazil, and their diagnoses need to be improved. The use of monoclonal antibodies has ensured high specificity to immunodiagnosis. The development of an immunosensor, coupling a monoclonal antibody to a bioelectronic device capable of quickly detecting Leishmania sp. antigens both qualitatively and quantitatively, is a promising alternative for the diagnosis of leishmaniasis due to its high specificity, low cost, and portability, compared with conventional methods. The present work was aimed at developing an immunosensor-based assay for detecting Leishmania infantum antigens in tissues of infected hosts. Four hybridomas producing monoclonal antibodies against L. infantum had their specificity confirmed by enzyme-linked immunosorbent assay. These antibodies were immobilized on a gold surface, covered with a thin film of 2-aminoethanethiol (cysteamine) and glutaraldehyde, blocked with glycine, and placed into contact with extracts of L. infantum -infected and noninfected control hamster spleens. The assay was able to detect 1.8 × 10(4) amastigotes/g of infected tissue. These results demonstrated that this assay may be useful for quantifying L. infantum amastigotes in organs of experimental animals for studies on pathogenesis and immunity and that it is a promising tool for the development of a diagnostic method, based on antigen detection, of human and dog visceral leishmaniasis.

Inflammation and structural changes of splenic lymphoid tissue in visceral leishmaniasis: a study on naturally infected dogs

The aim of this study was to identify splenic immuno-inflammatory patterns associated with natural infection by Leishmania chagasi. Spleen samples were obtained from 72 stray dogs from an endemic area of visceral leishmaniasis. The animals were grouped into four categories as follows: (i) potentially resistant to visceral leishmaniasis, with a positive leishmanin skin test result, and negative splenic culture for Leishmania parasites (ii) potentially susceptible to visceral leishmaniasis, with a negative leishmanin skin test and positive splenic culture for Leishmania (iii) infected with undefined susceptibility status, with a positive leishmanin skin test and positive splenic culture for Leishmania, and (iv) noninfected, with a negative leishmanin skin test, negative splenic culture for Leishmania, and negative serology for anti-Leishmania antibodies. Histopathological analyses showed that there was a higher frequency of perisplenitis (18/25, P < 0.0001), granuloma (7/25, P = 0.0102), structural disorganization (14/25, P < 0.0001), and atrophy of the lymphoid follicles (20/25, P = 0.0036) and of the marginal zone (15/25, P = 0.0025) in the potentially susceptible group than in the other groups. The data presented here show changes in the white pulp of the spleen that are associated with naturally acquired visceral leishmaniasis.

Associations among immunological, parasitological and clinical parameters in canine visceral leishmaniasis: Emaciation, spleen parasitism, specific antibodies and leishmanin skin test reaction

Associations among parameters commonly used as markers of infection by Leishmania sp., or of susceptibility to visceral leishmaniasis, were investigated in 325 stray dogs from an area where this disease is endemic. Evidence of infection (presence of Leishmania in splenic cultures, positive leishmanin skin test (LST) or detection of anti-Leishmania antibody activity in the serum) was found in 57% of the animals. Both evidence of weight loss (chi(2)-test, P=0.0005) and presence of specific antibody activity in the serum (chi(2)-test, P<0.0001) were directly associated with positive splenic culture. The frequencies of animals with positive splenic culture were directly correlated with the intensities of antibody activity in the serum as measured by ELISA (relative risk of 3.4 for animals with moderate antibody levels and relative risk of 8.43 for animals with high-antibody levels). A negative association was observed between positive leishmanin skin test results and emaciation (chi(2), P=0.0089). Furthermore, animals with positive splenic cultures and negative leishmanin skin test results had higher levels of total serum IgG (Kruskal-Wallis test, P=0.001) and IgG2 (Kruskal-Wallis test, P=0.05) than animals with negative splenic cultures, and were more emaciated than animals with negative LST results and positive splenic cultures. The data presented herein suggest that associating these common parameters may improve their performance in predicting susceptibility to canine visceral leishmaniasis.

Dissociation between vasodilation and Leishmania infection-enhancing effects of sand fly saliva and maxadilan

In this study, the ability of maxadilan and Lutzomyia longipalpis salivary gland lysate to enhance the infection of CBA mice by Leishmania major and of BALB/c mice by L. braziliensis was tested. No difference was observed between sizes of lesion in CBA mice infected with L. major and treated or not with salivary gland lysate or maxadilan, although they were injected in concentrations that induced cutaneous vasodilation. Although parasites were more frequently observed in foot pads and spleens of animals treated with maxadilan than in the animals treated with salivary gland lysate or saline, the differences were small and not statistically significant. The lesions in BALB/c mice infected with L. braziliensis and treated with maxadilan were slightly larger than in animals that received Leishmania alone. Such differences disappeared 14 weeks after infection, and were statistically significant only in one of two experiments.

Skin reactions to thimerosal and Leishmania in dogs from a leishmaniasis endemic area: it is better to keep them apart

Positive Montenegro's skin test is a delayed type hypersensitivity reaction widely used as indicative of previous infection with Leishmania in both humans and dogs. Montenegro's antigen consists of a crude Leishmania antigen solution, usually containing thimerosal as preserving agent. In this work it is shown that a large proportion of dogs (11 out of 56) examined in an endemic area of leishmaniasis presented induration at the site of injection of a diluent containing thimerosal alone. This clearly demonstrates that thimerosal leads to a high number of false positive skin reactions in dogs and that its use in Montenegro's skin test antigenic preparations should be avoided.

Cohort study on canine emigration and Leishmania infection in an endemic area for American visceral leishmaniasis. Implications for the disease control

American visceral leishmaniasis is a main public health matter in Brazil. Since dogs have been incriminated as the main urban reservoir of AVL agent Leishmania chagasi, a cohort study aimed at understanding the dynamics of the canine infection was carried out in Jequié--an endemic community in the Northeast of Brazil. The inhabited urban and periurban areas of Jequié were divided into 140 clusters of 0.25 km2. All 1681 dogs domiciled in 34 randomly selected clusters were screened for Leishmania antibodies in an enzyme-linked immunosorbent assay. After the seropositive dogs were painlessly eliminated, a cohort of 1286 seronegative dogs was followed up for 18 months, yielding a total of 1739.7 dog-years. The overall incidence of Leishmania infection, as assessed by the detection of Leishmania antibodies in blood samples collected every six months, was 6.55 cases/100 dog-years (95% confidence interval; CI 6.04-7.26). Two subsets of clusters, with 0.70 and 1.35 relative risks of infection, were identified. The annual emigration rate was 2.26 cases/100 dog-years (95% CI 1.86-2.66). The implications of these findings for the control of American visceral leishmaniasis are discussed.

Incomplete dominance of the low antibody response to Cryptosporidium parvum antigens in mice selected for high and low antibody responsiveness

The humoral antibody response to Cryptosporidium was investigated in mice genetically selected for high (H) and low (L) antibody responsiveness. Groups of 4-5 mice from two different selections, general primary (GP) and general secondary (GS), were studied. Following immunization with Cryptosporidium parvum antigens, the maximum levels of IgG in the HGP (X +/- SD = 1.13 +/- 0.35, N = 5) in the HGS (0.42 +/- 0.15, N = 4) lines, and of IgM in the HGP line (0.86 +/- 0.53, N = 5) were significantly higher than those in their L counterparts (0.04 +/- 0.02, N = 5; 0.05 +/- 0.02, N = 4 and 0.24 +/- 0.07, N = 5, respectively). These findings were similar to those reported for other immunogens. However, the IgG (0.22 +/- 0.05, N = 4) and the IgM (0.33 +/- 0.08, N = 4) responses to immunization of F1 (LGP x HGP) hybrids indicated an incomplete dominance of the low response, in contrast to the incomplete dominance of the high response described for many other antigens and representing an important exception. In addition, the H, L and F1 mice did not develop detectable infections when inoculated with live Cryptosporidium oocysts, supporting the view that a reduced or zero antibody production itself is not enough to permit the establishment of Cryptosporidium infection in adult mice.

A cross-sectional serodiagnostic survey of canine leishmaniasis due to Leishmania chagasi

Jequie, a community of about 144,500 inhabitants located in the State of Bahia, Brazil, is endemic for both visceral and cutaneous leishmaniases. In the present epidemiologic study, the urban and inhabited periurban areas of the town were divided into 140 clusters of 0.25 km2 each. The seroprevalence of canine Leishmania antibodies was investigated using an enzyme-linked immunosorbent assay as a screening test since its sensitivity was significantly higher than that of an indirect immunofluorescence assay. A total of 1,681 dogs was surveyed in 34 randomly sampled clusters. The overall prevalence of Leishmania antibodies in the dog population was 23.5%, with intracluster prevalences ranging from 0% to 67%. There was no correlation of these seroprevalences with the intracluster densities of canine populations, or with the distances from individual clusters to the town center. Moreover, the Leishmania transmission did not seem to follow any clear-cut spatial pattern, since large disparities in the seroprevalences of contiguous clusters were found. Curiously, human cases of visceral leishmaniasis have never been observed in some clusters with a relatively high prevalence of canine seroprevalences. Eight parasite isolates from seropositive dogs were found to belong to the same serodeme and zymodeme as Leishmania (L.) chagasi. The implications of these findings with respect to the epidemiology and control of American visceral leishmaniasis are discussed.

Circulating trans-sialidase activity and trans-sialidase-inhibiting antibodies in Trypanosoma cruzi-infected mice

Parasite-derived trans-sialidase (TS) activity was demonstrated in the serum and blood of Trypanosoma cruzi-infected mice. Serum TS activity levels correlated well with parasitemia in BALB/c and Swiss mice during the initial stages of the infection. However, in later stages the TS activity levels decreased despite increasing parasitemia. This coincided with the appearance of circulating TS antibodies. On the other hand, there was always a good correlation between TS activity and parasitemia in athymic nude mice. Sera from mice with high parasitemia and low TS activity inhibited TS activity in vitro. The inhibition was also observed with purified serum IgG, and it was absorbed by staphylococcal protein A, indicating that it was caused by anti-TS IgG antibodies. These antibodies inhibited the enzymatic activity of insolubilized TS, indicating that they act by interfering with the catalytic site rather than by aggregating the enzyme. The presence of inhibitory antibodies, however, did not prevent the progression of parasitemia in BALB/c mice.

Combined occurrence of trypanosomal sialidase/trans-sialidase activities and leishmanial metalloproteinase gene homologues in Endotrypanum sp

Endotrypanum (order Kinetoplastida: family Trypanosomatidae) is a parasite of forest dwelling tree sloths (Edentata: genera Choleopus and Bradypus). Unique among the haemoflagellates, this protozoan has an intraerythrocytic phase in the mammalian host. Nevertheless, many striking similarities exist between Endotrypanum and the human pathogen Leishmania that make it a useful model for epidemiological and evolutionary aspects of the biology of trypanosomatids. Importantly, Endotrypanum species share both the insect vector and host reservoir with certain species of Leishmania (subgenus Viannia). Because mixed infections with Endotrypanum and Leishmania are common in sloths and, therefore, likely to occur in the sandfly vector, there is a need for adequate biochemical markers to distinguish Endotrypanum from Leishmania infections. In this paper we show that Endotrypanum promastigotes possess sialidase and trans-sialidase activities, which are absent from Leishmania, and which are not closely related to the previously described trypanosomal sialidase/trans-sialidase enzyme. We also document the occurrence in Endotrypanum of homologues of the leishmanial surface metalloproteinase gp63 genes. The combined occurrence of sialidase/trans-sialidase activities and gp63 gene homologues in a unique organism has important ramifications for both field and laboratory studies on the biology of trypanosomatids, especially those related to host infection and evolution.

Trypanosoma rangeli sialidase lacks trans-sialidase activity

Extracts and tissue culture supernatants of axenic forms of T. rangeli were assayed for the presence of sialidase and trans-sialidase activities. Using sialyl(alpha 2-3)lactose, sialyl(alpha 2-6)lactose, poly(alpha 2-8)N-acetylneuraminic acid, fetuin and 4-methylumbelliferyl-N-acetylneuraminic acid as sialic acid donors, and lactose as a sialic acid acceptor, no trans-sialidase activity was detected. Nevertheless, T. rangeli lysates and culture supernatants contain a sialidase that hydrolyzes sialyl(alpha 2-3)lactose, and much less efficiently sialyl(alpha 2-6)lactose, but not poly(alpha 2-8)N-acetylneuraminic acid. T. cruzi trans-sialidase hydrolyzed only sialyl(alpha 2-3)lactose under the same conditions. The T. rangeli and the T. cruzi enzymes differ antigenically and in their pH optimum for hydrolase activity.

A protein A-binding, polyethylene glycol precipitation-based immunoradiometric assay. Application to the detection of immune complexes and C3 in human sera and of private antigens in cross-reacting parasite extracts

An immunoradiometric assay, based on the precipitation of antigen-antibody complexes by polyethylene glycol (PEG) and on the subsequent binding of PEG-soluble radiolabelled staphylococcal protein A to the PEG-insoluble complexes, is described. The assay can be applied to the detection of naturally occurring, circulating immune complexes, and of complexes artificially created by mixing antigen and antibody solutions, which makes it of potential use for the detection of either antigen or antibody in several situations. Pre-treatment of the antibody-containing sera with 3% PEG greatly reduced the background values and increased the sensitivity of the assay. The assay was also applied to the detection and isolation of Leishmania donovani antigens that did not cross-react with antigens of the related parasite Trypanosoma cruzi (private antigens) and private antigens of insect-derived metacyclic trypomastigotes of T. cruzi in relation to culture-derived metacyclic trypomastigotes of T. cruzi. A simple and extremely effective procedure for washing precipitates with just one centrifugation is also described.