In situ detection of antigenic glycoproteins in Taenia solium metacestodes

Taenia solium has a complex life cycle. Its cysticercus can lodge in the brain, causing neurocysticercosis (NCC), and the adult tapeworm's survival in the intestine results in taeniasis. In this study, the in situ detection of previously described glycoprotein antigens used for serological diagnosis of NCC and the detection of other glycoconjugates was explored in cysticerci and the surrounding porcine tissue to understand their potential role in pathogenesis. Immunohistochemistry with an antiserum specific for glycoprotein antigens rich in N-linked carbohydrates and in situ histochemistry with a battery of lectins that have affinity to a variety of glycoconjugates were performed. The glycoconjugates rich in N-linked carbohydrates were detected in the vesicular fluid and tegument of the vesicular membrane and scolex, where the parasite has direct contact with the host tissues during cysticercosis and taeniasis, respectively. Additionally, as the inflammatory response progressed, the parasite's antigenic glycoproteins were also detected in the cytoplasm of inflammatory cells in the surrounding granuloma. In contrast, the spiral canal tegument, which will be exposed to intestinal enzymes in taeniasis, had N-acetyl-galactosamine-rich mucins. Thus, the differential saccharidic composition in T. solium metacestode structures may be important for the survival of the parasite in different host sites.     

Characteristics of the effect of exometabolites of the cysticerci of the cat tapeworm Hydatigera taeniaeformis on fibroblasts in organ cultures

The influence of the cestode H. taeniaeformis cysticercus exometabolites on the fibroblasts of their capsule in organ culture was studied. Half of explants were cultured in the presence of cestodes (the ratio between the parasite body weight and the cultural medium volume being 1:10 g/ml). After 2-30 days of cultivation the explants were examined by histological, histoautoradiographic and electron microscopic methods. The influence of cysticercus exometabolites on the culture resembled that of the growth-stimulating factors. The young, actively proliferating fibroblasts were mainly observed in the explants of the capsules cultured in the presence of cysticerci. Among the mature cells, fibroblasts with the predominance of the fibroclastic function were noticed rather than with the function of collagen biosynthesis. It is suggested that the change in the differentiation ways of fibroblasts may be due to some biologically active substrates of the cysticercus to be directed on slowing down the maturation of the connective tissue capsule.     

Excretory secretory antigens of filarial parasite Setaria digitata

Excretory Secretory (ES) material isolated from the culture fluid of S. digitata was highly antigenic. Neither oesophagus nor excretory cells and excretory pore of the parasite showed reasonable fluorescence with ES antisera. However, the uterine tissue and the egg showed strong fluorescence. The egg showed fluorescence mainly in the space between embryo and egg membrane (amniotic fluid). The amniotic fluid was highly antigenic and appears to be the most important source of ES material released by the filarial parasites.     

Measurement of 150 kDa protein of Taenia solium metacestodes by antibody-sandwich ELISA in cerebrospinal fluid of neurocysticercosis patients.

An antigenic protein in cystic fluid of Taenia solium metacestodes (CF) of 150 kDa was measured by antibody-sandwich ELISA in serum and cerebrospinal fluid (CSF) of neurocysticercosis patients. Capture antibodies were rabbit antisera against CF (RACF) and a monoclonal antibody (MAb) against 150 kDa protein in CF. Lower limit of antibody-sandwich ELISA was 8 ng/ml of the protein. Except CF, no tested helminths extracts reacted. Levels of the protein in 351 sera from 255 patients (55 surgery confirmed and 202 antibody and CT/MRI confirmed) were below sensitivity of the assay. Of 276 CSF from 212 patients, 31 samples (11.2%) showed positive findings. This assay, therefore, was not sensitive enough to be a diagnostic. Instead, the 150 kDa protein appeared in CSF in such situations as in 2 days after praziquantel treatment, or as in a patient infected with a racemose cysticercus with degenerated cyst wall. Of cases whose follow-up CSF were assayed, 2 cases showed that the protein appeared intermittently. These results suggest strongly that appearance of free 150 kDa protein is associated with cyst wall rupture. In CSF which contained the 150 kDa protein over 61 ng/ml, the protein was recognized in SDS-PAGE before and after immunoprecipitation.     

Prediction of viability of porcine neurocysticercosis with proton magnetic resonance spectroscopy: correlation with histopathology

Neurocysticercosis (NCC) is the most frequent parasitic disease of central nervous system. In our earlier study, we had observed creatine [(creatine + phosphocreatine); (tCr)] on ex vivo proton MR spectroscopy (1H MRS) in some of the cysticercus cyst fluid samples obtained from swine's brain parenchyma. In current study, swine brains of freshly slaughtered animals naturally infected with NCC were subjected to ex vivo magnetic resonance (MR) imaging on a 1.5Tesla MR system. Cysticercus cysts (n = 12) were removed from these brains and were labeled depending upon presence or absence of edema around cysts as observed on imaging. Cysticercus cyst fluid (100 microl) was subjected to different 1H MRS experiments and results were compared with histopathological examinations to look for any relationship between tCr and parameters like quantification of musculature, and cellular infiltration in wall of the parasite. Histopathology of cyst wall was categorized into two groups based on cellular characteristics and the amount of musculature. Grade I cysts (n = 5) with no or minimal inflammation and large amount of musculature showed tCr on 1H MRS. However, grade II cysts (n = 7) with profuse inflammation and less amount of musculature in the cyst wall lacked tCr. Higher amount of musculature in grade I cysts was associated with higher concentration of tCr in the cyst fluid (r2 = 0.93, P = 0.007). Creatine appears to be a marker of innocuous and viable NCC.     

Global profiling of miRNA and protein expression patterns in rabbit peritoneal macrophages treated with exosomes derived from Taenia pisiformis cysticercus

Infection of Taenia pisiformis cysticercus is very frequently found in lagomorphs and causes serious economic losses to rabbit breeding industry. T. pisiformis cysticercus has evolved numerous strategies to manipulate their hosts. The release of exosomes is of importance in the interaction between host and parasite. However, the mechanism by which T. pisiformis cysticercus evades the host immune system for long-term survival within the host remains unclear. Using small RNA sequencing and TMT labelling proteomic, we profiled the expression patterns of miRNAs and proteins in rabbit peritoneal macrophages treated with T. pisiformis cysticercus exosomes. Seven differentially expressed (DE)-miRNAs and six DE-proteins were randomly selected to validate the accuracy of the sequencing data by qRT-PCR or western blot. Functions of DE-miRNAs and proteins were analyzed using public data bases. And DE-miRNAs–DE-proteins correlation network were established. CCK-8 assay was used to evaluate the effect of exosomes on macrophages proliferation. Cell cycle of macrophages, isolated from T. pisiformis-infected rabbits, was determined using flow cytometry. A total of 21 miRNAs were significantly differentially expressed, including three worm-derived miRNAs. The expressions of miRNAs and proteins were consistent with the sequencing results. DE-miRNAs targets were related to cell proliferation and apoptosis. Exosomes treatment resulted in a decrease of macrophages proliferation. In vivo, T. pisiformis cysticercus significantly induced S phase cell arrest. Moreover, DE-proteins were related to production of interferon-gamma and interleukin-12, and immunoregulation. Correlation network analysis revealed a negative correlation relationship between DE-miRNAs and DE-proteins. Among them, novel334 and tpi-let-7-5p have potential regulatory effects on IL1β and NFκB2 respectively, which imply that novel334–IL1β/tpi-let-7-5p–NFκB2 axis may be an important way that T. pisiformis cysticercus modulates host immune response through exosomes. Further understanding of these potential regulatory mechanisms will contribute to clarify the mechanism of escape mediated by T. pisiformis exosomes.     

Sex steroids and parasitism: Taenia crassiceps cisticercus metabolizes exogenous androstenedione to testosterone in vitro

Sex hormones are known to modulate immune responses and may be implicated in sex associated susceptibilities to infections. Taenia crassiceps cysticerci grow to larger numbers in female mice than in males. Gonadectomy alters the course of this infection and hormone replacement with 17beta-estradiol increases the parasite numbers. However, in chronic Taenia crassiceps cysticercosis the sex-hormone profile of males becomes more like that of the females' and progressively loose their sexual behavior. To have further insight in these outstanding endocrinological effects induced by the parasite upon the host, we investigated the parasite's capacity to produce sex steroids. In vitro experiments showed that Taenia crassiceps cysticerci transform 3H-Androstenedione to 3(H)-Testosterone, but not 3H-Pregnenolone. The production of 3H-Testosterone increased when the parasite numbers doubled. A recrystallisation procedure demonstrated that the metabolite identified by TLC was in fact testosterone. Thus, the cysticercus has the ability to use 3H-Androstenedione to make Testosterone possibly by a 17beta-Hydroxysteroid deshidrogenase-like activity in the parasite. In vivo, the parasite could use steroid precursors from the host to produce sex hormones, either accidentally or as needed for its own development, and thus alters the host's normal environment with sexual and immunological repercussions.     

Antigenic extracts of Leishmania braziliensis and Leishmania amazonensis associated with saponin partially protects BALB/c mice against Leishmania chagasi infection by suppressing IL-10 and IL-4 production

This study evaluated two vaccine candidates for their effectiveness in protecting BALB/c mice against Leishmania chagasi infection. These immunogenic preparations were composed of Leishmania amazonensis or Leishmania braziliensis antigenic extracts in association with saponin adjuvant. Mice were given three subcutaneous doses of one of these vaccine candidates weekly for three weeks and four weeks later challenged with promastigotes of L. chagasi by intravenous injection. We observed that both vaccine candidates induced a significant reduction in the parasite load of the liver, while the L. amazonensis antigenic extract also stimulated a reduction in spleen parasite load. This protection was associated with a suppression of both interleukin (IL)-10 and IL-4 cytokines by spleen cells in response to L. chagasi antigen. No change was detected in the production of IFN-γ. Our data show that these immunogenic preparations reduce the type 2 immune response leading to the control of parasite replication.     

The effect of host heterogeneity and parasite intragenomic interactions on parasite population structure

Understanding the processes that shape the genetic structure of parasite populations and the functional consequences of different parasite genotypes is critical for our ability to predict how an infection can spread through a host population and for the design of effective vaccines to combat infection and disease. Here, we examine how the genetic structure of parasite populations responds to host genetic heterogeneity. We consider the well-characterized molecular specificity of major histocompatibility complex binding of antigenic peptides to derive deterministic and stochastic models. We use these models to ask, firstly, what conditions favour the evolution of generalist parasite genotypes versus specialist parasite genotypes? Secondly, can parasite genotypes coexist in a population? We find that intragenomic interactions between parasite loci encoding antigenic peptides are pivotal in determining the outcome of evolution. Where parasite loci interact synergistically (i.e. the recognition of additional antigenic peptides has a disproportionately large effect on parasite fitness), generalist parasite genotypes are favoured. Where parasite loci act multiplicatively (have independent effects on fitness) or antagonistically (have diminishing effects on parasite fitness), specialist parasite genotypes are favoured. A key finding is that polymorphism is not stable and that, with respect to functionally important antigenic peptides, parasite populations are dominated by a single genotype.     

An integrated model of Plasmodium falciparum dynamics

The within-host and between-host dynamics of malaria are linked in myriad ways, but most obviously by gametocytes, the parasite blood forms transmissible from human to mosquito. Gametocyte dynamics depend on those of non-transmissible blood forms, which stimulate immune responses, impeding transmission as well as within-host parasite densities. These dynamics can, in turn, influence antigenic diversity and recombination between genetically distinct parasites. Here, we embed a differential-equation model of parasite-immune system interactions within each of the individual humans represented in a discrete-event model of Plasmodium falciparum transmission, and examine the effects of human population turnover, parasite antigenic diversity, recombination, and gametocyte production on the dynamics of malaria. Our results indicate that the local persistence of P. falciparum increases with turnover in the human population and antigenic diversity in the parasite, particularly in combination, and that antigenic diversity arising from meiotic recombination in the parasite has complex differential effects on the persistence of founder and progeny genotypes. We also find that reductions in the duration of individual human infectivity to mosquitoes, even if universal, produce population-level effects only if near-absolute, and that, in competition, the persistence and prevalence of parasite genotypes with gametocyte production concordant with data exceed those of genotypes with higher gametocyte production. This new, integrated approach provides a framework for investigating relationships between pathogen dynamics within an individual host and pathogen dynamics within interacting host and vector populations.     

Oncospheres of Taenia solium and T. saginata asiatica develop into metacestodes in normal and immunosuppressed mice.

Normal and immunosuppressed mice were infected with oncospheres of Taenia saginata asiatica and T. solium. Although normal ICR mice were not susceptible to these two parasites, cysticerci were recovered from the immunosuppressed ones following venous injection. For T. s. asiatica, immunosuppressed ICR mice had an infection rate of 12.5% and six cysticerci of this parasite were recovered from three males. After injection of T. solium oncospheres, a high infection rate of 57% was obtained and 23 cysticerci were collected from 13 male immunosuppressed ICR mice. The immunosuppressed C57 mice had the highest infection rate (100%) and cysticercus recovery rate (2.4%) for T. solium. The infection rate and cysticercus recovery rate in six normal C57 mice were 40% and 3% respectively. The immunosuppressed ICR, Balb/c and C3H mice were also susceptible to T. s. asiatica.     

Large deletions result from breakage and healing of P. falciparum chromosomes

The human malaria parasite P. falciparum exhibits extensive strain-dependent chromosomal polymorphisms that have been implicated in the generation of antigenic variability in this organism. These polymorphisms can result in large deletions in chromosomes as determined by pulsed-field gradient gel electrophoresis. We have investigated the molecular basis for extensive deletions in chromosomes 2 and 8 in multiple geographic isolates of this parasite that result in the loss of expression of well-characterized parasite antigens. The structure of these polymorphic chromosomes reveal that a mechanism of chromosome breakage and healing by the addition of telomeric repeats most plausibly accounts for these karyotypes. Furthermore, the orientation of these gene fragments on their truncated chromosomes reveal that the healed chromosome originally associated with centromeric elements is mitotically stable and maintained. A model for the possible role of this mechanism in the complex parasite life-cycle is discussed.     

Taeniosis-cysticercosis complex in individuals of a peasants' settlement (Teodoro Sampaio, Pontal of Paranapanema, SP, Brazil)

In order to evaluate the taeniosis-cysticercosis complex in a population of a peasants' settlement, located at Teodoro Sampaio, state of S?o Paulo, Brazil (longitude 52 degrees 36'12 ", latitude 22 degrees 17'12 ") a series of laboratory markers were determined. After signing an informed consent, participants answered a standardized questionnaire. To determine anti-Taenia solium cysticercus antibodies, the samples were tested by enzyme linked immunoabsorbent assay using 18-and 14-kDa antigen proteins from vesicular fluid of Taenia crassiceps (VF-Tcra). The reactive and inconclusive ELISA samples were tested by immunoblotting. Total IgE levels were determined by chemmiluminescence's assay and hemogram by flow cytometer flux counter. A total of 84 individuals, 5.9% presented anti-T. solium cysticercus antibodies in ELISA and 3.6% were strongly reactive in the 18/14 kDa immunoblotting confirmatory test. All of the individuals with positive antibodies showed elevated Total IgE levels. We conclude that the frequency of anti-T. solium cysticercus antibodies in this population is higher than other regions considered endemic in S?o Paulo. Thus, it is important to carry out surveys in Peasants' settlement areas with the objective of establishing public health measures for prevention and control of infectious diseases such as taeniosis-cysticercosis.     

Preferential growth of Taenia crassiceps cysticerci in female mice holds across several laboratory mice strains and parasite lines

A retrospective study of our 14-yr records on experimental Taenia crassiceps (ORF(fast) line) cysticercosis (n = 1,198) shows that in 16 of 17 different mice strains, female mice are more frequently infected and carry larger individual parasite loads than males. However, sexual differences in parasite loads significantly varies between strains in relation to their different genetic backgrounds (BALB > C57Bl = OTHERS > C3H). The coefficient of variation in all female mice is significantly smaller than that of all males, an indication of males' more potent, but erratically effective, restraint of cysticercus growth. Similar positive growth bias for female mice is shown by other lines of cysticerci, i.e., HYG(slow) and WFU(slow). These results contravene the usual expectation of female hosts being more resistant than males to parasite infections, and they point to the multiple factors that combined determine sex related differences of mice to experimental cysticercosis infection.     

Molecular cross-talk in host-parasite relationships: the intriguing immunomodulatory role of Echinococcus antigen B in cystic echinococcosis

Cystic echinococcosis (CE), a zoonosis caused by the development of Echinococcus granulosus tapeworm larvae in the internal organs of ungulates and humans, continues to pose a major public health burden in underdeveloped and industrialised areas worldwide. Research designed to improve parasitic disease control and find out more about parasite biology has already identified a number of E. granulosus antigenic molecules. The major E. granulosus immunomodulant antigen isolated from hydatid fluid is antigen B, a 120kDa polymeric lipoprotein consisting of various 8kDa subunits. By inhibiting elastase activity and neutrophil chemotaxis and eliciting a non-protective Th2 cell response, antigen B helps the parasite evade the human response. In this review, we briefly discuss current information on the molecular characteristics and immunomodulatory properties of E. granulosus antigen B. Besides focusing on findings that provide intriguing insights into the complex interplay between host and parasite, we suggest how this information could extend the current therapeutic options in inflammatory diseases.     

Trypanosoma cruzi proteins which are antigenic during human infections are located in defined regions of the parasite

Polyclonal antibodies obtained against antigenic proteins encoded by six recombinant DNA clones of Trypanosoma cruzi were used for the ultrastructural localization of the respective antigens in thin sections of parasites (epimastigote, amastigote and trypomastigote forms of T. cruzi) embedded at low temperature in Lowicryl K4M resin. Antigens of high molecular weight containing tandemly repeated amino acid sequence motifs and recognized by sera from patients with Chagas' disease, were located only in the flagellum, where it contacts the parasite cell body. Other antigens were located on the surface of the parasite while still others were found within the flagellar pocket, as is the case with an antigen released during the acute phase of Chagas' disease. Thus, we conclude that some of the T. cruzi proteins which are antigenic in human infections are located in defined regions of the parasite. Some of the antigens were not expressed to the same extent in the three different developmental stages of the parasite.     

Dirofilaria immitis: biochemical and immunological characterization of the surface antigens from adult parasites

The molecules associated with the surface of adult Dirofilaria immitis were identified and characterized employing IODO-GEN-mediated surface labeling methods. D. immitis female and male parasites were found to have a limited number of surface-associated proteins (17.5, 16, and 14.5 kDa) and glycoproteins (49 and 20 kDa) which were readily extracted from parasite homogenates in the absence of detergent. The major surface labeled proteins and glycoproteins were antigenic in rabbits, but appeared to elicit only a weak humoral response in dogs with patent dirofilariasis. In addition, a 10- to 6-kDa surface-associated glycolipid was identified which may form a coat on the outside of the parasite and play a role in immune evasion. In immunoprecipitation experiments, the glycolipid was not recognized by the antibodies from rabbits exposed to the glycolipid or by antibodies in the sera of patently infected animals. The glycolipid and the 14.5-kDa surface protein were selectively released by the adult parasite during in vitro culture.     

Localization and identification of Schistosoma mansoni/KLH-crossreactive components in infected mice.

KLH (Keyhole limpet hemocyanin) is highly immunogenic, and crossreactive epitopes occur widely in nature. In schistosomiasis, infected hosts generate antibodies reactive with KLH. This is of diagnostic importance but we lack detailed information on the immunogen-carrying molecules and their distribution in the worm. We used anti-KLH antibodies to localize cross-reacting epitopes in the various developmental stages of the parasite in experimental Schistosoma mansoni infection. The staining results show KLH crossreactivity in the life stages of the parasite. By immunoblotting we show that KLH-crossreactive antigenic epitopes in the parasite eggs are carbohydrates, also recognized by antibodies against soluble schistosome egg antigens. The localizations in the larval stages and in adult worms suggest that crossreacting antigenic epitopes are secretory products.     

Cuticle specific antigens from filarial parasite Setaria digitata

A fairly clean antigenic cuticle was isolated from the S. digitata by dissection. Crossed immunoelectrophoresis of cuticular antigens against rabbit antiserum to cuticular antigens gave 30 anodic and 5 cathodic precipitin arcs. The cuticle antiserum cross reacted with muscle, uterus and pseudocoelomic fluid. When the antiserum was absorbed individually with these cross reacting somatic preparations, analysis against cuticle antigens gave only a limited number of precipitin arcs. But the results are clear enough to indicate the presence of cuticle specific antigens. As the cuticle of the parasite is in contact with the host system, an antigenic preparation from it may prove a useful tool for the detection of filariasis.     

Vaccine-driven evolution of parasite virulence and immune evasion in age-structured population: the case of pertussis

Despite enormous success of mass immunization programs in reducing incidence of infectious diseases, vaccine-escape strains have emerged perhaps as a consequence of strong selection pressures exerted on parasites by vaccines. Pertussis presents a well-documented example. As a childhood infection, it exhibits age-specific transmission biased to children. Assuming different transmission rates between children and adults, I study, by means of an age-structured epidemic model, evolutionary dynamics of parasite virulence in a vaccinated population. I find that the age-structure does not affect the evolutionary dynamics of parasite virulence. Also, based on empirical data reporting antigenic divergence with vaccine strains and mutations in virulence-associated genes in pertussis populations, I allow for parallel occurrence of mutations in parasite virulence and associated immune evasion. I conclude that this simultaneous adaptation of both traits may substantially alter the evolutionary course of the parasite. In particular, higher values of virulence are favoured once the parasite is able to evade the transmission-blocking vaccine-induced immunity. On the other hand, lower values of virulence are selected for once the parasite evolves the ability to evade the virulence-blocking vaccine-induced immunity. I emphasize the importance of multi-trait evolution to assess the direction of parasite adaptation more accurately.