Taenia taeniaeformis in mice: Protective immunization with oncospheres and their products

Taenia taeniaeformis oncospheres, injected parenterally with or without adjuvants, stimulated a high degree of protective immunity in mice against challenge infection with eggs. Furthermore, the supernatant from a centrifuged (twice for 30 min at 4500 g) preparation of oncospheres which had been frozen, thawed and sonicated, induced more than 90% protection when used as a vaccine with adjuvant. By contrast, centrifuged (1 h at 3500 g) supernatant medium collected during 72 h incubation of activated T. taeniaeformis oncospheres in vitro in serum-free culture medium was only marginally host-protective. The results indicate that materials from disrupted oncospheres should be a suitable starting preparation for identification and purification of ‘host-protective’ antigens.     

Immunization of mice against infection with Taenia taeniaeformis using various antigens prepared from eggs,oncospheres, developing larvae and strobilocerci

Rajasekariah G. R., Rickard M. D. and Mitchell G. F. 1980. Immunization of mice against infection with Taenia taeniaeformis using various antigens prepared from eggs, oncospheres, developing larvae and strobilocerci. International Journal for Parasitology10: 315–324. Antigens were collected during in vitro incubation of oncospheres, 3-week-old larvae and strobilocerci of T. taeniaeformis. Supernatants of these in vitro products centrifuged at 500 g contained antigens which stimulated a significant degree of protective immunity when injected into mice. However, centrifugation of the strobilocercus preparation at 4500 g yielded supernatants which failed to induce immunity. Suspensions of eggs and oncospheres disrupted by sonication stimulated a high level of immunity as also did 4500 g supernatants of the sonicated preparations. Centrifugation of sonicated oncospheres at 100,000 g yielded a supernatant which stimulated significantly less immunity than the 4500 g supernatant, although the protective capacity was not totally abolished. The pellet from 100,000 g centrifugation of sonicated oncospheres induced almost absolute immunity. These results are consistent with the suggestion that the ‘functional’ antigens in the preparations tested may initially be membrane-associated or particulate in nature and that sonication causes partial solubilization. Supernatants prepared from homogenised strobilocerci and centrifuged at 4500 g also stimulated protective immunity and presumably contain soluble antigens. No evidence is available to suggest whether or not the strobilocercus antigens which stimulated protective immunity are identical to those found in oncospheral preparations. Immunity was stimulated by subcutaneous, intraperitoneal and intramuscular injections of antigen and both Freund's complete adjuvant and Bordetella pertusiss vaccine were effective as adjuvants. Using sonicated oncospheres, a high level of immunity was stimulated without the use of adjuvant.     

Taenia taeniaeformis: immunoprecipitation analysis of the protein antigens of oncospheres and larvae

Biosynthetically or exogenously labeled proteins and immunoprecipitated protein antigens of established 28-day-old larvae of Taenia taeniaeformis were compared with proteins and antigens of infective oncospheres using single and two-dimensional gel electrophoresis. Immunoprecipitation was carried out using sera from infected mice and mouse antisera raised to larvae or oncospheres, and emphasis was placed on identifying antigens common to both oncospheres and larvae. Two major larval antigens of Mr 40,000 and 200,000, designated Tt40 and Tt200, are common to somatic larval preparations and oncospheres. Additionally, two major oncosphere antigens of Mr 55,000 and 60,000, designated Tt55 and Tt60, are also present in larval excretory and secretory (i.e., ES or exoantigen) products. Information obtained from these immunoprecipitation analyses will facilitate isolation and production of common as well as stage-specific protein antigens in the development of defined-antigen vaccines in this model system of cysticercosis.     

Antibody responses of experimentally infected lambs to antigens collected during in vitro maintenance of the adult, metacestode or oncosphere stages of Taenia hydatigena and Taenia ovis with further observations on anti-oncospheral antibodies

The antigenicity and specificity of crude antigens collected during the in vitro maintenance of Taenia hydatigena and T. ovis, excretory/secretory (ES) antigens, were assessed in a peroxidase microenzyme-linked immunosorbent assay (ELISA), using sera from lambs given experimental monospecific infections with T. hydatigena, T. ovis, Echinococcus granulosus or Fasciola hepatica. ES antigens of larval cysts of T. ovis and T. hydatigena were less reactive than those of adult or oncosphere stages. Strong interspecific cros-reactions occurred between all antigen preparations, and these antigens offered no better specificity than crude somatic extracts. IgG1 was the major immunoglobulin detected in sera from lambs experimentally infected with T. ovis or T. hydatigena using antigens prepared from sonicated oncospheres. Discrete peaks of anti-oncospheral antibodies were detected following initial and challenge infections with eggs (whether the homologous or heterologous species), when sera were assayed with a PBS sonicate or an ES antigen from oncospheres. However, when oncospheres solubilised with sodium deoxycholate were used, the antibody response was prolonged and resembled that reported previously when somatic extracts of adult and metacestode stages were used as antigen. The results showed that oncospheres share antigens in common with other life-cycle stages, but also support the notion that they may possess some unique stage-specific antigenic determinants.     

Localisation of three host-protective oncospheral antigens of Taenia ovis

Immunohistochemistry, confocal immunofluorescence and immunogold labelling were used to determine the localisation of the host-protective antigens To16, To18 and To45W in Taenia ovis oncospheres. During maturation of the adult tapeworm the antigens were initially seen as diffuse staining in the developing oncospheres but in mature oncospheres four distinct cells stained positively for the antigens. Confocal fluorescence microscopy using different fluorophores revealed that each of the antigens co-localises within the same cells in the oncosphere. No surface localisation was seen in non-activated or recently activated parasites. Immunogold labelling of non-activated oncosphere sections viewed in transmission electron microscopy revealed labelling of bilateral cells, however the identities of these cells was unclear due to deficiencies in the current level of understanding of oncosphere ultrastructure. Localisation of all the antigens changed dramatically after oncospheres were activated in vitro with each of the antigens being dispersed more generally throughout the parasite parenchyma. During development of the parasites in in vitro culture, surface localisation of the proteins was seen in parasites after 3 or more days in culture. All three antigens were found to be completely absent in parasites by 15 days of culture. The location of the host-protective antigens suggests that initially the invading oncospheres are not susceptible to vaccine-induced antibody and complement mediated attack, but that as the parasites mature, the host-protective antigens come to be associated with the parasite’s surface, rendering them susceptible to immune attack.     

The fate of Taenia taeniaeformis oncospheres in normal and passively protected rats

Rats were passively protected against challenge infection with Taenia taeniaeformis by the administration of immune serum. Macroscopic liver lesions were rarely seen following challenge. The fate of oncospheres was determined by histological examination of rat livers at various intervals after infection, and also by in vitro experimentation.Oncospheres were killed soon after exposure to immune serum in vitro, but numbers reaching the liver were not significantly different in both passively protected and control rats. Oncospheral reorganisation did not take place in passively protected rats. In control rats, only 20 per cent of oncospheres reaching the liver were able to undergo reorganisation. Developing larvae also appeared to be susceptible to host rejection mechanisms, especially between days 5 and 9 after infection.     

Trypanosoma cruzi: Effect on B-cell-responsive and -responding clones

During the course of Trypanosoma cruzi infection in C57BL/6 mice, which are relatively resistant to the parasite, the hosts developed antibody activity against previously unencountered antigens. The anti-sheep erythrocyte and antitrinitrophenyl antibody levels increased rapidly from Day 7 of infection, reached a peak by the 21st day, and were maintained at this level through 120 days postinfection in these mice. In contrast, highly susceptible C3H(He) mice did not have demonstrable antibody responses to SRBC or TNP during the 24-day infection period. Autoantibody activity against the selfantigens presented on isologous erythrocytes or thymocytes, however, were reduced in infected C57BL/6 mice. No significant reduction in autoreactivity to the self-antigens on erythrocytes or thymocytes was observed in C3H(He) mice infected with T. cruzi although a trend of reduced autoresponsiveness toward erythrocytes appeared to be developing by the time of death. C57BL/6 mice immunized with sheep erythrocytes as neonates and infected with T. cruzi as adults, or adult mice primed with low doses of sheep erythrocytes prior to infection, had elevated antibody responses to sheep erythrocytes unless the mice were immunized with sheep erythrocytes during the course of infection, in which case suppression of the response against sheep erythrocytes resulted. The nonspecific synthesis of immunoglobulins in infected C57BL/6 mice was, in part, a result of the lymphocyteactivating properties of T. cruzi-associated antigens. The T. cruzi-associated antigens induced proliferative and differentiative responses in spleen cells in vitro. It is proposed that the T. cruzi-associated antigens differentially affect lymphocytes capable of responding to antigen and those lymphocytes previously stimulated by antigen.     

Identification of Surface Antigens of Sarcocystis muris (Coccidia)

Zoites of Sarcocystis muris were recovered from the skeletal muscles of infected mice by trypsin digestion. Extracts of zoites prepared by freeze-thaw, Triton X-100 (0.1%), or a combination of the two treatments contained antigenic components. Testing of these antigens by agar gel diffusion and immunoelectrophoresis against sera from infected mice showed one major precipitin band. SDS-polyacrylamide-gel electrophoresis (SDS-PAGE) of the extracts revealed at least eight detectable polypeptides ranging in molecular weight from 10,000 to 220,000. The antigenic components of the extract were identified by labeling the parasite surface with [¹²⁵I] and precipitation of the [¹²⁵I]-labeled antigens with immune sera. Analysis of the immunoprecipitates by SDS-PAGE and autoradiography revealed three antigens with molecular weights of 27,500, 43,000 and 90,000. The smallest of these was the predominant antigen as suggested by labeling intensity.     

Trypanosoma cruzi: immunosuppressed response to different antigens in the infected mouse.

Trypanosoma cruzi: Immunosuppressed response to different antigens in the infected mouse. Experimental Parasitology45, 190–199. Trypanosoma cruzi infection in mice results in functional changes in the normal immunological responses to heterologous antigens. An immunosuppression of the 19 and 7S antibody response is observed in infected animals against both a particulate antigen and against soluble antigens. Furthermore, the immune response to the soluble T-independent antigens, DNP-Ficoll and LPS, was also similarly impaired when antigen was administered to trypanosome-infected animals. The suppression of the immune response to these antigens does not seem to involve an alteration in the macrophage, as evidenced by a normal uptake and handling of soluble ¹³¹I-labeled HSA and by a normal immune response when antigen-exposed peritoneal macrophages from trypanosome-infected mice were transferred to normal mice. These data support the concept that T. cruzi induces an immunosuppression to both T-dependent and T-independent antigens and that the depression observed is not due to an alteration in macrophage function.     

Immunological response of the rat to infection with Taenia taeniaeformis: protective antibody response to implanted parasites.

Intraperitoneally implanted metacestodes of either T. taeniaeformis or T. crassiceps in rats provoked a high degree of resistance to oral challenge with eggs of T. taeniaeformis. This resistance was passively transferred to normal recipients with serum. Immunoglobulin fractions of immune serum containing IgG₁ or IgM were most effective in passive transfer and little activity was associated with IgG₂ antibodies. No skin-sensitizing antibodies were detectable in immune sera. These findings are in sharp contrast to previous observations involving protective immunoglobulins and reaginic antibodies in serum from rats with hepatic cysticerci of T. taeniaeformis. Possible reasons for this are discussed. Cysticerci implanted into normal rats survived for at least 21 days with no sign of host rejection, whereas those implanted into rats with hepatic infections with T. taeniaeformis were killed and encapsulated. Similar results were obtained by implanting cysticerci in normal rats given inoculations of complete Freund's adjuvant. Repeated inoculations of immune serum had no effect on the survival of implanted cysticerci, and it was concluded that exposure to infection by oncospheres provokes cellular defense mechanisms which can be effective against cysticerci in abnormal sites. Why these mechanisms are inoperative against hepatic cysticerci remains unclear.     

Stimulation of resistance to Taenia taeniaeformis in the rat by infection with Fasciola hepatica

Homologous resistance to F. hepatica and T. taeniaeformis and cross resistance between these two parasites was investigated in the rat. Rats given a primary infection with F. hepatica were challenged with either F. hepatica or T. taeniaeformis. Conversely rats given a primary infection with T. taeniaeformis were challenged with either F. hepatica or T. taeniaeformis.Infection with F. hepatica generated significant resistance against challenge with F. hepatica given 9 weeks later. Similarly, infection with T. taeniaeformis protected against challenge with T. taeniaeformis given 6 weeks later. Infection with F. hepatica also generated significant resistance against challenge with T. taeniaeformis given 4, 8 or 9 weeks later. Primary infection with T. taeniaeformis did not protect against challenge with F. hepatica.     

Hymenolepis nana: Protective immunity against mouse-derived cysticercoids induced by initial inoculation with eggs

Mice were almost completely resistant to a mouse-derived cysticercoid (cyst) challenge after 6 to 10 months following an initial immunizing inoculation with eggs of Hymenolepis nana. Previously uninfected control mice of the same age became infected with the cyst-derived tapeworms. There was no age resistance to H. nana in mice. Immunity against the cyst challenge was acquired by initial egg inoculation and blocked by injecting cortisone acetate just prior to the challenge. However, the number of worms recovered from mice given cortisone was significantly less than that from nonimmunized controls. Unexpected evidence was obtained that a few of the egg-derived tapeworms can survive for 6 or more months in some of the immunized mice, which are resistant to both egg and cyst challenges. The relative immunogenicity of oncospheres and cysts is discussed. It is strongly suggested that the cysts are different from the oncospheres in their immunogenicity, and, because of this, H. nana can complete its life cycle in the same immunized host. It is also suggested that the host possesses at least two separate immune responses: One is an early response directed exclusively against the oncosphere and/or the early postoncospheral stage (s) acquired within 2 days of egg inoculation, and the other is a late response against the cyst acquired after a time lag of unknown duration.     

Vaccination against Taenia solium cysticercosis in pigs using native and recombinant oncosphere antigens.

Pigs were immunised with antigens derived from Taenia solium oncospheres or with a pool of three recombinant antigens from Taenia ovis, and subsequently challenged with T. solium eggs. The native oncosphere antigens induced 83% protection against viable, and 89% protection against the total number of cysticerci established following the challenge infection. Immunisation with the recombinant T. ovis antigens induced 93% protection against the establishment of viable cysticerci, and 74% protection against the total number of cysticerci. These results, and those achieved elsewhere with Taenia saginata and T. ovis, support the possibility of developing a practical vaccine to assist in the control of transmission of T. solium through pigs.     

Schistosoma mansoni: reactivity with infected human sera and monoclonal antibody characterization of a glycoprotein in different developmental stages

Cercarial glycoproteins of Schistosoma mansoni were purified by concanavalin A affinity chromatography. The purified fraction consisted of at least 15 polypeptides when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sera of infected humans specifically immunoprecipitated all of these polypeptides. These purified glycoproteins were used as antigen for preparing monoclonal antibodies. One of these monoclonal antibodies immunoprecipitated cercarial polypeptides that were identical to polypeptides immunoprecipitated with sera of infected humans as analyzed by two-dimensional gel electrophoresis. Direct binding assays with ¹²⁵I-labeled monoclonal antibody showed that proteins sharing antigenic determinants recognized by this monoclonal antibody were present not only in cercariae (the source of the immunogen) but also in adult male and female worms and in eggs. The protein molecules expressing these antigenic determinants were glycosylated in each of the developmental stages of the larvae, but differed with respect to molecular weight. These findings indicate a role for this monoclonal antibody in serodiagnosis and immunoprophylaxis.     

Antigenic Similarity Between the Coccidian Parasites Toxoplasma gondii and Hammondia hammondi1

The antigens that are present in the coccidian parasites Toxoplasma gondii and Hammondia hammondi were demonstrated and defined by using SDS-PAGE and immunoenzymatic techniques with ¹²⁵I-labeled and unlabeled antigens of T. gondii and sera of mice infected orally or intraperitoneally with H. hammondi. All cell surface antigens of T. gondii that were labeled with ¹²⁵I were recognized by antibodies in the sera of the mice infected with H. hammondi except the antigen of approximate molecular weight of 21.5 Kd. This suggests that this antigen is specific for T. gondii. Various antigens in the T. gondii-lysed antigen preparations were recognized by antibodies to H. hammondi. The number of recognized antigens increased as the infection of the mice with H. hammondi progressed. Oral infection with H. hammondi appeared to induce the formation of antibodies that recognized more T. gondii antigens than infection by intraperitoneal inoculation.     

Echinococcus granulosus: use of an intermediate host mouse model to evaluate sources of protective antigens and a role for antibody in the immune response.

A Balb/cJ mouse model was used to determine which stage of the E. granulosus life cycle possessed the most potent protective antigens. Mice were immunized with crude extracts of protoscoleces, brood capsules, cyst fluid, adult worm tissue, eggs or oncospheres and then challenged intraperitoneally with 600 activated oncospheres. Sonically disrupted oncospheres induced the highest levels of protection (greater than 90%) at doses greater than or equal to 10(3) oncosphere equivalents per mouse. High levels of protection were maintained when these preparations were solubilized in SDS. Immunization with Taenia ovis or T. hydatigena oncosphere preparations induced a maximum of 62 and 40% cross-protection, respectively. In passive transfer experiments, serum from triple-infected immune donors that were completely resistant to subsequent challenge induced 69% protection in naive recipients (P less than 0.01). Serum from mice that had been immunized with oncosphere sonicates that were shown to be highly immune, failed to induce statistically significant protection in recipients. A sheep trial confirmed the protective ability of prior infections. Immunization of sheep with a SDS solubilized oncosphere preparation produced 91% protection (P less than 0.01).     

Schistosoma mansoni: immediate hypersensitivity to adult antigens in the rat

Antigen fractions from adult S. mansoni, obtained from infected mice, were isolated by a variety of methods. A readily soluble fraction was obtained in good yield by freezing and thawing the schistosomes, while the less soluble residue was fractionated by the use of a number of the methods currently used for the extraction of tissue and cell surface antigens. The dialyzed, centrifuged products were characterized by acrylamide gel disc electrophoresis methods, agar gel precipitin reactions with antisera from rabbits immunized with whole schistosome homogenate, and by Prausnitz-Kustner (P-K) assay with sera from schistosome infected rats. The pattern of P-K reactivity suggested that there were a number of different antigen specificities involved in the reaginic antibody response to schistosome infection in rats. With repeated infection and increased duration of infection, more different antigens seemed to be involved in the reagin response. The schistosome antigen fraction obtained by freezing and thawing was especially reactive with both early infection rat sera and sera from multiply infected rats. Both the soluble fraction isolated by freezing and thawing and residue solubilized materials were found to be able to induce the formation of reagin antibodies on immunization with alum and B. pertussis vaccine.     

Variable dependency on BAFF in IgG antibody production during Leishmania infection

B-cell activating factor (BAFF) is known as a cytokine responsible for survival and activation of B cells. However, involvement of the molecule in IgG antibody production during infection remains elusive. In this study, dependency of antibody production in Leishmania infection on BAFF was examined by using BAFF-knockout (BAFF-KO) mice. When BAFF-KO mice were infected with L. major, there was no significant difference in lesion development or parasite burden from those in infected wildtype mice. In contrast, levels of IgG antibodies to Leishmania crude antigen were lower in BAFF-KO mice, suggesting that antibody production during L. major infection is BAFF-dependent. ELISA using defined leishmanial antigens demonstrated that the influence of BAFF on antibody production during L. major varies depending on antigens; IgG production to tandem repeat proteins were more affected by BAFF than non-repeat antigens. On the contrary, all of the defined antigens tested were strongly affected by BAFF for IgG antibody production during L. donovani infection. These results suggest degree of BAFF contribution to antibody production during infection is variable depending on the type of infection and even on the type of antigen in a given infection. These results may explain contradictory roles of BAFF in antibody production in previous works.     

Ultrastructural reconstruction of Taenia ovis oncospheres from serial sections

The cellular organisation of Taenia ovis oncospheres is interpreted from ultrathin serial sections and transmission electron microscopy following high pressure freezing and freeze-substitution. The surface of a hatched, non-activated T. ovis oncosphere is covered by an oncospheral membrane below which is the tegument bearing microvilli. The basal lamina of the tegument is underlain by broad bands of peripheral somatic musculature. Three pairs of hooks and associated muscles are present in the somatophoric third of the oncosphere. Approximately 19 cells of seven different types were identified which include: (i) a quadri-nucleated syncytium of penetration gland type 1 containing two lateral pairs of cell bodies interconnected by narrow cytoplasmic bridges (PG1); (ii) a quadri-nucleated syncytium of penetration gland type 2 (PG2); (iii) a single-nucleated median mesophoric gland cell; (iv) 10 somatic cells; (v) two germinative cells; (vi) two nerve cells; and (vii) a pair of median somatophoric cells. This study provides a clear understanding of the morphology of T. ovis oncospheres and forms the basis for further investigations into the biology of taeniid oncospheres.     

Fasciola hepatica: Comparative studies on fascioliasis in rats and mice

Chapman C. B. and Mitchell G. F. 1982. Fasciola hepatica: comparative studies on fascioliasis in rats and mice. International Journal for Parasitology12: 81–91. Certain characteristics of infection differ between rats and mice exposed to metacercariae of the trematode parasite, Fasciola hepatica. Rats develop a degree of age-related resistance (and infected older females contain fewer parasites than older males), resistance to reinfection in infected rats is demonstrated readily though is partial, and a comparable degree of resistance can be obtained in recipients of infected rat serum provided the serum is given at about the time of challenge. None of these features of F. hepatica infection is seen in mice. Rats also differ from mice in that they can be vaccinated against infection (although again, resistance is incomplete) using larval antigen mixtures in adjuvants. Mice do respond to infection by production of antilarval antibodies and a slight IgG₁ hypergammaglobulinaemia and larvae will sensitize mice for delayed hypersensitivity. The results of this study indicate that sera from infected rats versus infected mice will be useful in pinpointing antigens of F. hepatica larvae which are involved in expression of partial host protection.