Characterization of Trichomonas vaginalis haemolysis

Hemoglobin uptake and utilization by human protozoan parasites: a review

The protozoan disease is a major global health concern. Amoebiasis, leishmaniasis, Chagas disease, and African sleeping sickness affect several million people worldwide, leading to millions of deaths annually and immense social and economic problems. Iron is an essential nutrient for nearly all microbes, including invading pathogens. The majority of iron in mammalian hosts is stored intracellularly in proteins, such as ferritin and hemoglobin (Hb). Hb, present in blood erythrocytes, is a very important source of iron and amino acids for pathogenic microorganisms ranging from bacteria to eukaryotic pathogens, such as worms, protozoa, yeast, and fungi. These organisms have developed adequate mechanisms to obtain Hb or its byproducts (heme and globin) from the host. One of the major virulence factors identified in parasites is parasite-derived proteases, essential for host tissue degradation, immune evasion, and nutrient acquisition. The production of Hb-degrading proteases is a Hb uptake mechanism that degrades globin in amino acids and facilitates heme release. This review aims to provide an overview of the Hb and heme-uptake mechanisms utilized by human pathogenic protozoa to survive inside the host.

The effect of iron on Trichomonas vaginalis TvCP2: a cysteine proteinase found in vaginal secretions of trichomoniasis patients

Trichomonas vaginalis (Tv) induces host cell damage through cysteine proteinases (CPs) modulated by iron. An immunoproteomic analysis showed that trichomoniasis patient sera recognize various CPs, also some of them are present in vaginal washes (VWs). Thus, the goal of this work was to determine whether TvCP2 is expressed during infection and to assess the effect of iron on TvCP2 expression, localization and contribution to in vitro cellular damage. Western-blotting (WB) assays using TvCP2r and vaginitis patient serum samples showed that 6/9 Tv (+) but none of the Tv (-) patient sera recognized TvCP2r. WB using an anti-TvCP2r antibody and VWs from the same patients showed that in all of the Tv (+) but none of the Tv (-) VWs, the anti-TvCP2r antibody detected a 27 kDa protein band that corresponded to the mature TvCP2, which was confirmed by mass spectrometry analysis. Iron decreased the amount of TvCP2 mRNA and the protein localized on the parasite surface and cytoplasmic vesicles concomitant with the cytotoxic effect of TvCP2 on HeLa cells. Parasites pretreated with the anti-TvCP2r antibody also showed reduced levels of cytotoxicity and apoptosis induction in HeLa cell monolayers. In conclusion, these results show that TvCP2 is expressed during trichomonal infection and plays an important role in the in vitro HeLa cell cytotoxic damage under iron-restricted conditions.

Efficacy of netropsin dihydrochloride against the viability, cytopathogenicity and hemolytic activity of Trichomonas vaginalis clinical isolates

Trichomonas vaginalis (T. vaginalis) is a common sexually transmitted infection, affecting the urogenital tract. Trichomoniasis is customarily treated with metronidazole (MTZ). MTZ is known to cause undesirable side effects and there is several reports on MTZ resistant T. vaginalis. Thus, the present study aimed to in-vitro evaluate the activity of DNA minor groove binder drug ''Netropsin dihydrochloride'' against metronidazole-sensitive T. vaginalis isolates (G and U isolates) and resistant T. vaginalis isolate (ATCC50138) (R isolate). Netropsin was tested at concentrations ranging from 3.5 to 200 μg/ml. It showed effectiveness against all isolates with MLC of 12.5 μg/ml for G and U isolates and of 25 μg/ml for R isolate. Cytotoxicity assay of isolates exposed to the respective MLC of netropsin for 42 h showed a highly significant reduction in the death percentage of MCDK cell line as compared to the effect elicited by drug free controls. The hemolytic activity was evaluated by hemolytic assay and by monitoring the interaction of T. vaginalis isolates with human erythrocytes by inverted microscopy and scanning electron microscopy. The hemolytic assay showed (0%) hemolysis of RBCs incubated with T. vaginalis isolates treated with the corresponding MLC of netropsin for 24 h. Scanning electron microscopy revealed cytoskeletal deformities of netropsin treated isolates. Taken together, these observations suggest that netropsin is a promising therapy for T. vaginalis infection affecting its viability, virulence, cytopathogenic and hemolytic activity with a mechanism of action that might overcome T. vaginalis resistance to metronidazole.

Characterization of a novel endogenous cysteine proteinase inhibitor, trichocystatin-3 (TC-3), localized on the surface of Trichomonas vaginalis

Trichomonas vaginalis is a flagellated protist responsible for human trichomoniasis. T. vaginalis has three genes encoding for endogenous cysteine proteinase (CP) inhibitors, known as trichocystatin-1 through trichocystatin-3 (TC-1, TC-2, and TC-3). These inhibitors belong to the cystatin family. In this study, we characterized trichocystatin-3 (TC-3), an endogenous cysteine proteinase (CP) inhibitor of T. vaginalis. TC-3 possesses a signal peptide in the N-terminus and two putative glycosylation sites (typical of family 2, cystatins) but lacks the PW motif and cysteine residues (typical of family 1, stefins). Native TC-3 was recognized as an ∼18 kDa protein band in a T. vaginalis protein extract. By confocal microscopy, endogenous TC-3 was found in the Golgi complex, cytoplasm, large vesicles, and the plasma membrane. These localizations are consistent with an in silico prediction. In addition, the purified recombinant protein (TC-3r) functions as an inhibitor of cathepsin L CPs, such as human liver cathepsin L and trichomonad CPs, present in a proteinase-resistant extract (PRE). Via a pull-down assay using TC-3r as bait and PRE, we identified several trichomonad CPs targeted by TC-3, primarily TvCP3. These CP-TC-3 interactions occur in vesicles, in the cytoplasm, and on the parasite surface. In addition, TC-3r showed a protective effect on HeLa cell monolayers by inhibiting trichomonad surface CPs involved in cellular damage. Our results show that the endogenous inhibitor TC-3 plays a key role in the regulation of endogenous CP proteolytic activity.

Trichomoniasis - are we giving the deserved attention to the most common non-viral sexually transmitted disease worldwide?

ETIOLOGY

Trichomonas vaginalis is the etiologic agent of trichomoniasis, the most common non-viral sexually transmitted disease (STD) in the world. Transmission: Trichomoniasis is transmitted by sexual intercourse and transmission via fomites is rare. Epidemiology, incidence and prevalence: The WHO estimates an incidence of 276 million new cases each year and prevalence of 187 million of infected individuals. However, the infection is not notifiable. Pathology/Symptomatology: The T. vaginalis infection results in a variety of clinical manifestations - in most cases the patients are asymptomatic, but some may develop signs typically associated to the disease. Importantly, the main issue concerning trichomoniasis is its relationship with serious health consequences such as cancer, adverse pregnancy outcomes, infertility, and HIV acquisition. Molecular mechanisms of infection: To achieve success in parasitism trichomonads develop a complex process against the host cells that includes dependent- and independent-contact mechanisms. This multifactorial pathogenesis includes molecules such as soluble factors, secreted proteinases, adhesins, lipophosphoglycan that culminate in cytoadherence and cytotoxicity against the host cells. Treatment and curability: The treatment with metronidazole or tinidazole is recommended; however, cure failures remain problematic due to noncompliance, reinfection and/or lack of treatment of sexual partners, inaccurate diagnosis, or drug resistance. Therefore, new therapeutic alternatives are urgently needed. Protection: Strategies for protection including sexual behavior, condom usage, and therapy have not contributed to the decrease on disease prevalence, pointing to the need for innovative approaches. Vaccine development has been hampered by the lack of long-lasting humoral immunity associated to the absence of good animal models.

Mechanisms of Tritrichomonas foetus Pathogenicity in Cats with Insights from Venereal Trichomonosis

Almost 20 years has passed since trichomonosis was first recognized as a potential cause of diarrhea in domestic cats. Despite progress in confirming disease causation, developing means for diagnosis, and identifying approaches to treatment of the infection, we still know very little about how this parasite causes diarrhea. With increasing recognition of resistance of trichomonosis to treatment with 5‐nitroimidazole drugs, new treatment strategies based on an understanding of disease pathogenesis are needed. In this review, lessons learned from the pathogenesis of venereal trichomonosis in people and cattle are applied to clinical observations of trichomonosis in cats in effort to generate insight into areas where further research may be beneficial.

RNA-Binding Proteins in Trichomonas vaginalis: Atypical Multifunctional Proteins

Iron homeostasis is highly regulated in vertebrates through a regulatory system mediated by RNA-protein interactions between the iron regulatory proteins (IRPs) that interact with an iron responsive element (IRE) located in certain mRNAs, dubbed the IRE-IRP regulatory system. Trichomonas vaginalis, the causal agent of trichomoniasis, presents high iron dependency to regulate its growth, metabolism, and virulence properties. Although T. vaginalis lacks IRPs or proteins with aconitase activity, possesses gene expression mechanisms of iron regulation at the transcriptional and posttranscriptional levels. However, only one gene with iron regulation at the transcriptional level has been described. Recently, our research group described an iron posttranscriptional regulatory mechanism in the T. vaginalis tvcp4 and tvcp12 cysteine proteinase mRNAs. The tvcp4 and tvcp12 mRNAs have a stem-loop structure in the 5'-coding region or in the 3'-UTR, respectively that interacts with T. vaginalis multifunctional proteins HSP70, α-Actinin, and Actin under iron starvation condition, causing translation inhibition or mRNA stabilization similar to the previously characterized IRE-IRP system in eukaryotes. Herein, we summarize recent progress and shed some light on atypical RNA-binding proteins that may participate in the iron posttranscriptional regulation in T. vaginalis.

Trichomonas vaginalis Cysteine Proteinases: Iron Response in Gene Expression and Proteolytic Activity

We focus on the iron response of Trichomonas vaginalis to gene family products such as the cysteine proteinases (CPs) involved in virulence properties. In particular, we examined the effect of iron on the gene expression regulation and function of cathepsin L-like and asparaginyl endopeptidase-like CPs as virulence factors. We addressed some important aspects about CPs genomic organization and we offer possible explanations to the fact that only few members of this large gene family are expressed at the RNA and protein levels and the way to control their proteolytic activity. We also summarized all known iron regulations of CPs at transcriptional, posttranscriptional, and posttranslational levels along with new insights into the possible epigenetic and miRNA processes.

Biological roles of cysteine proteinases in the pathogenesis of Trichomonas vaginalis

Human trichomonosis, infection with Trichomonas vaginalis, is the most common non-viral sexually transmitted disease in the world. The host-parasite interaction and pathophysiological processes of trichomonosis remain incompletely understood. This review focuses on the advancements reached in the area of the pathogenesis of T. vaginalis, especially in the role of the cysteine proteinases. It highlights various approaches made in this field and lists a group of trichomonad cysteine proteinases involved in diverse processes such as invasion of the mucous layer, cytoadherence, cytotoxicity, cytoskeleton disruption of red blood cells, hemolysis, and evasion of the host immune response. A better understanding of the biological roles of cysteine proteinases in the pathogenesis of this parasite could be used in the identification of new chemotherapeutic targets. An additional advantage could be the development of a vaccine in order to reduce transmission of T. vaginalis.

Cysteine protease activity of feline Tritrichomonas foetus promotes adhesion-dependent cytotoxicity to intestinal epithelial cells

Trichomonads are obligate protozoan parasites most renowned as venereal pathogens of the reproductive tract of humans and cattle. Recently, a trichomonad highly similar to bovine venereal Tritrichomonas foetus but having a unique tropism for the intestinal tract was recognized as a significant cause of colitis in domestic cats. Despite a high prevalence, worldwide distribution, and lack of consistently effective drugs for treatment of the infection, the cellular mechanisms of T. foetus pathogenicity in the intestinal tract have not been examined. The aims of this study were to determine the pathogenic effect of feline T. foetus on porcine intestinal epithelial cells, the dependence of T. foetus pathogenicity on adhesion of T. foetus to the intestinal epithelium, and the identity of mediators responsible for these effects. Using an in vitro coculture approach to model feline T. foetus infection of the intestinal epithelium, these studies demonstrate that T. foetus promotes a direct contact-dependent activation of intestinal epithelial cell apoptosis signaling and progressive monolayer destruction. Moreover, these pathological effects were demonstrated to be largely dependent on T. foetus cell-associated cysteine protease activity. Finally, T. foetus cysteine proteases were identified as enabling cytopathic effects by promoting adhesion of T. foetus to the intestinal epithelium. The present studies are the first to examine the cellular mechanisms of pathogenicity of T. foetus toward the intestinal epithelium and support further investigation of the cysteine proteases as virulence factors in vivo and as potential therapeutic targets for ameliorating the pathological effects of intestinal trichomonosis.

TvMP50 is an immunogenic metalloproteinase during male trichomoniasis

Trichomonas vaginalis, a human urogenital tract parasite, is capable of surviving in the male microenvironment, despite of the presence of Zn(2+). Concentrations > 1.6 mM of Zn(2+) have a trichomonacidal effect; however, in the presence of ≤1.6 mM Zn(2+), several trichomonad proteins are up- or down-regulated. Herein, we analyzed the proteome of a T. vaginalis male isolate (HGMN01) grown in the presence of Zn(2+) and found 32 protein spots that were immunorecognized by male trichomoniasis patient serum. Using mass spectrometry (MS), the proteins were identified and compared with 23 spots that were immunorecognized in the proteome of a female isolate using the same serum. Interestingly, we found a 50-kDa metallopeptidase (TvMP50). Unexpectedly, this proteinase was immunodetected by the serum of male trichomoniasis patients but not by the female patient serum or sera from healthy men and women. We analyzed the T. vaginalis genome and localized the mp50 gene in locus TVAG_403460. Using an RT-PCR assay, we amplified a 1320-bp mp50 mRNA transcript that was expressed in the presence of Zn(2+) in the HGMN01 and CNCD147 T. vaginalis isolates. According to a Western blot assay, native TvMP50 was differentially expressed in the presence of Zn(2+). The TvMP50 proteolytic activity increased in the presence of Zn(2+) in both isolates and was inhibited by EDTA but not by ptosyl-L-lysine chloromethyl ketone (TLCK), E64, leupeptin, or phenylmethane sulfonyl fluoride. Furthermore, the recombinant TvMP50 had proteolytic activity that was inhibited by EDTA. These data suggested that TvMP50 is immunogenic during male trichomoniasis, and Zn(2+) induces its expression.

The TvLEGU-1, a legumain-like cysteine proteinase, plays a key role in Trichomonas vaginalis cytoadherence

The goal of this paper was to characterize a Trichomonas vaginalis cysteine proteinase (CP) legumain-1 (TvLEGU-1) and determine its potential role as a virulence factor during T. vaginalis infection. A 30-kDa band, which migrates in three protein spots (pI~6.3, ~6.5, and ~6.7) with a different type and level of phosphorylation, was identified as TvLEGU-1 by one- and two-dimensional Western blot (WB) assays, using a protease-rich trichomonad extract and polyclonal antibodies produced against the recombinant TvLEGU-1 (anti-TvLEGU-1r). Its identification was confirmed by mass spectrometry. Immunofluorescence, cell binding, and WB assays showed that TvLEGU-1 is upregulated by iron at the protein level, localized on the trichomonad surface and in lysosomes and Golgi complex, bound to the surface of HeLa cells, and was found in vaginal secretions. Additionally, the IgG and Fab fractions of the anti-TvLEGU-1r antibody inhibited trichomonal cytoadherence up to 45%. Moreover, the Aza-Peptidyl Michael Acceptor that inhibited legumain proteolytic activity in live parasites also reduced levels of trichomonal cytoadherence up to 80%. In conclusion, our data show that the proteolytic activity of TvLEGU-1 is necessary for trichomonal adherence. Thus, TvLEGU-1 is a novel virulence factor upregulated by iron. This is the first report that a legumain-like CP plays a role in a pathogen cytoadherence.

Transcriptomic identification of iron-regulated and iron-independent gene copies within the heavily duplicated Trichomonas vaginalis genome

Gene duplication is an important evolutionary mechanism and no eukaryote has more duplicated gene families than the parasitic protist Trichomonas vaginalis. Iron is an essential nutrient for Trichomonas and plays a pivotal role in the establishment of infection, proliferation, and virulence. To gain insight into the role of iron in T. vaginalis gene expression and genome evolution, we screened iron-regulated genes using an oligonucleotide microarray for T. vaginalis and by comparative EST (expressed sequence tag) sequencing of cDNA libraries derived from trichomonads cultivated under iron-rich (+Fe) and iron-restricted (−Fe) conditions. Among 19,000 ESTs from both libraries, we identified 336 iron-regulated genes, of which 165 were upregulated under +Fe conditions and 171 under −Fe conditions. The microarray analysis revealed that 195 of 4,950 unique genes were differentially expressed. Of these, 117 genes were upregulated under +Fe conditions and 78 were upregulated under −Fe conditions. The results of both methods were congruent concerning the regulatory trends and the representation of gene categories. Under +Fe conditions, the expression of proteins involved in carbohydrate metabolism, particularly in the energy metabolism of hydrogenosomes, and in methionine catabolism was increased. The iron–sulfur cluster assembly machinery and certain cysteine proteases are of particular importance among the proteins upregulated under −Fe conditions. A unique feature of the T. vaginalis genome is the retention during evolution of multiple paralogous copies for a majority of all genes. Although the origins and reasons for this gene expansion remain unclear, the retention of multiple gene copies could provide an opportunity to evolve differential expression during growth in variable environmental conditions. For genes whose expression was affected by iron, we found that iron influenced the expression of only some of the paralogous copies, whereas the expression of the other paralogs was iron independent. This finding indicates a very stringent regulation of the differentially expressed paralogous genes in response to changes in the availability of exogenous nutrients and provides insight into the evolutionary rationale underlying massive paralog retention in the Trichomonas genome.

Comparative transcriptomic and proteomic analyses of Trichomonas vaginalis following adherence to fibronectin

The morphological transformation of Trichomonas vaginalis from an ellipsoid form in batch culture to an adherent amoeboid form results from the contact of parasites with vaginal epithelial cells and with immobilized fibronectin (FN), a basement membrane component. This suggests host signaling of the parasite. We applied integrated transcriptomic and proteomic approaches to investigate the molecular responses of T. vaginalis upon binding to FN. A transcriptome analysis was performed by using large-scale expressed-sequence-tag (EST) sequencing. A total of 20,704 ESTs generated from batch culture (trophozoite-EST) versus FN-amoeboid trichomonad (FN-EST) cDNA libraries were analyzed. The FN-EST library revealed decreased amounts of transcripts that were of lower abundance in the trophozoite-EST library. There was a shift by FN-bound organisms to the expression of transcripts encoding essential proteins, possibly indicating the expression of genes for adaptation to the morphological changes needed for the FN-adhesive processes. In addition, we identified 43 differentially expressed proteins in the proteomes of FN-bound and unbound trichomonads. Among these proteins, cysteine peptidase, glyceraldehyde-3-phosphate dehydrogenase (an FN-binding protein), and stress-related proteins were upregulated in the FN-adherent cells. Stress-related genes and proteins were highly expressed in both the transcriptome and proteome of FN-bound organisms, implying that these genes and proteins may play critical roles in the response to adherence. This is the first report of a comparative proteomic and transcriptomic analysis after the binding of T. vaginalis to FN. This approach may lead to the discovery of novel virulence genes and affirm the role of genes involved in disease pathogenesis. This knowledge will permit a greater understanding of the complex host-parasite interplay.

Identification and characterization of a surface-associated, subtilisin-like serine protease inTrichomonas vaginalis

Trichomonas vaginalisis a protozoan parasite causing trichomonosis, a sexually transmitted infection in humans. This parasite has numerous proteases, most of which are cysteine proteases that appear to be involved in adherence and cytotoxicity of host cells. In this report we identify and characterize a putative subtilisin-like serine protease (SUB1). Thesub1gene encodes a 101-kDa protein.In silicoanalyses predict signal and pro-peptides at the N-terminus, and a transmembrane helix at the carboxy-terminal region. Thesub1gene was found as single copy by Southern analysis, albeit additional serine protease related genes are annotated in theT. vaginalisgenome. The expression ofsub1could only be detected by RT-PCR and Ribonuclease Protection Assays, suggesting a low abundant mRNA. Thesub1gene transcription start site was correctly assigned by RPA. The transcript abundance was found to be modulated by the availability of iron in the growth medium. Antibodies raised to a specific SUB1 peptide recognized a single protein band (~82 kDa) in Western blots, possibly representing the mature form of the protein. Immunofluorescence showed SUB1 on the trichomonad surface, and in dispersed vesicles throughout the cytoplasm. A bioinformatic analysis of genes annotated as serine proteases in theT. vaginalisgenome is also presented. To our knowledge this is the first putative serine protease experimentally described forT. vaginalis.

Immunoproteomics of the active degradome to identify biomarkers for Trichomonas vaginalis

Trichomonas vaginalis, a sexually transmitted parasite, has many cysteine proteinases (CPs); some are involved in trichomonal pathogenesis, express during infection, and antibodies against CPs have been detected in patient sera. The goal of this study was to identify the antigenic proteinases of T. vaginalis as potential biomarkers for trichomonosis. The proteases detected when T. vaginalis protein extracts are incubated without protease inhibitors, the trichomonad-active degradome, and the immunoproteome were obtained by using 2-DE, 2-D-zymograms, 2-D-Western blot (WB) assays with trichomonosis patient sera, and MS analysis. Forty-nine silver-stained spots were detected in the region of 200-21 kDa of parasite protease-resistant extracts. A similar proteolytic pattern was observed in the 2-D zymograms. Nine CPs were identified in the 30 kDa region (TvCP1, TvCP2, TvCP3, TvCP4, TvCP4-like, TvCP12, TvCPT, TvLEGU-1, and another legumain-like CP). The major reactive spots to T. vaginalis-positive patient sera by 2-D-WB corresponded to four papain-like (TvCP2, TvCP4, TvCP4-like, TvCPT), and one legumain-like (TvLEGU-1) CPs. The genes of TvCP4, TvCPT, and TvLEGU-1 were cloned, sequenced, and expressed in Escherichia coli. Purified recombinant CPs were recognized by culture-positive patient sera in 1-D-WB assays. These data show that some CPs could be potential biomarkers for serodiagnosis of trichomonosis.

Trichomonas vaginaliskills and eats – evidence for phagocytic activity as a cytopathic effect

This study reports that the cytopathic effect ofTrichomonas vaginalis, an important human parasite of the urogenital tract, occurs due to mechanical stress and subsequent phagocytosis of the necrotic cells. The investigation was done using a primary culture of bovine oviduct epithelial cells (BOECs), grown either in monolayers or as floating cells. Trophozoites displaying different virulence levels were co-incubated with BOECs for times varying between 1 min and 48 h. Analyses were performed using videomicroscopy, scanning and transmission electron microscopy, colourimetric assays and cytochemistry. Injury was observed as early as 1 h after incubation, while after 12 h the host cells were severely damaged when a fresh trichomonad isolate was used. Trichomonads attack the host cells by clustering around them. Mechanical stress on the microvilli of the host cells was observed and appeared to induce plasma membrane damage and cell death. After membrane injury and lysis, fragments of the necrotic cells were ingested by trichomonads. Phagocytosis occurred by trichomonads avidly eating large portions of epithelial cells containing the nucleus and other organelles, but living or intact cells were not ingested. Necrotic fragments were rapidly digested in lysosomes, as shown by acid phosphatase and ruthenium red assays where only the BOECs were labelled. The lytic capacity of the trichomonads was more pronounced in host cell suspensions.

Anti-Trichomonas activity of Sapindus saponins, a candidate for development as microbicidal contraceptive

OBJECTIVES

Trichomoniasis is the most common non-viral sexually transmitted disease and is caused by the protozoan Trichomonas vaginalis. In view of increased resistance of the parasite to classical drugs of the metronidazole family, the need for new unrelated agents is increasing. This study evaluates anti-Trichomonas activity of Sapindus saponins, a component of a herbal local contraceptive Consap recently marketed in India.

METHODS

The parasites were treated with saponins for MIC determination. Anti-Trichomonas activity of the saponins was evaluated using a cytoadherence assay, the substrate gel electrophoresis method and RT-PCR analysis. The effect of saponins on the mitochondrial potential of the host was determined by florescence-activated cell sorter. Actin cytoskeletal staining was used to determine the effect on parasite cytoskeleton.

RESULTS

Using in vitro susceptibility assay, the MIC of Sapindus saponins for T. vaginalis (0.005%) was found to be 10-fold lower than its effective spermicidal concentration (0.05%). Saponins concentration dependently inhibited the ability of parasites to adhere to HeLa cells and decreased proteolytic activity of the parasite's cysteine proteinases. This was associated with decreased expression of adhesin AP65 and membrane-expressed cysteine proteinase TvCP2 genes. Saponins produced no adverse effect on host cells in mitochondrial reduction potential measurement assay. Saponins also reversed the inhibitory mechanisms exerted by Trichomonas for evading host immunity. Early response of saponins to disrupt actin cytoskeleton in comparison with their effect on the nucleus suggests a membrane-mediated mode of action rather than via induction of apoptosis.

CONCLUSIONS

Findings demonstrate the potential of Sapindus saponins for development as a microbicidal contraceptive for human use. Further studies are required to evaluate its microbicidal activity against other sexually transmitted infections.

Negative iron regulation of the CP65 cysteine proteinase cytotoxicity in Trichomonas vaginalis

Several cysteine proteinases (CPs) participate in the virulence of Trichomonas vaginalis. One of them is a 65kDa CP, CP65, involved in cytotoxicity. The aim of this work was to investigate the effect of iron on the trichomonal CP65-dependent cytotoxicity using parasites grown under distinct iron concentrations. Cytotoxicity and cell-binding assays, and zymograms were performed. At the highest iron concentration (250 microM), parasites exhibited the lowest levels of cytotoxicity and less CP65 proteolytic activity. Other cations in the culture medium did not affect the trichomonal CP65-dependent cytotoxicity as iron did. Another four trichomonad fresh isolates presented similar iron negative effect over cytotoxicity. Western blot and RT-PCR experiments also showed reduction in the amount of protein and transcript of CP65 in trichomonads grown under iron-rich conditions, as compared with parasites grown in normal and iron-depleted media. Indirect immunofluorescence using the anti-CP65 antibody showed that parasites grown in iron-rich medium expressed less CP65 than those grown in normal and iron-depleted media. Cytotoxicity inhibition experiments with the anti-CP65 antibody confirmed the iron negative effect over the CP65-dependent cytotoxicity. In conclusion, our data show that iron specifically down-regulates proteolytic activity, expression, and transcription of CP65, negatively affecting trichomonal cytotoxicity in vitro.

Cysteine proteinase 30 in clinical isolates of T. vaginalis from symptomatic and asymptomatic infected women

A cysteine proteinase of 30 kDa (CP30) of Trichomonas vaginalis, is known to play a role in cytoadherence of the parasite to host cells. However, the CP30 activity in clinical isolates from symptomatic and asymptomatic patients has not been analyzed. In the present study, CP30 was detected in 20 fresh and long-term culture maintained T. vaginalis isolates each from symptomatic and asymptomatic women by substrate gel electrophoresis and immunoblotting. Though CP30 was detected in all the fresh isolates from 20 symptomatic and 20 asymptomatic women, the intensity of CP30 band was significantly higher in isolates from symptomatic as compared to asymptomatic women indicating higher expression in former. CP30 was found in all the 20 long-term cultured isolates from symptomatic whereas only in 70% of asymptomatic women indicating that CP30 expression is a more stable characteristic of symptomatic isolates. The isolates from symptomatic women, demonstrated significantly higher cytoadherence to VECs as compared to asymptomatic women. In both the types of isolates, this cytoadherence was inhibited significantly by CP30 specific hyperimmune serum. These results confirm that CP30 is an important virulence factor of T. vaginalis and has an important role in cytoadherence to VECs and thus has a role in pathogenesis of trichomoniasis.

Location of the cell-binding domain of CP65, a 65kDa cysteine proteinase involved in Trichomonas vaginalis cytotoxicity

The cysteine proteinase (CP) of 65kDa, CP65, binds to the surface of HeLa cells and is involved in Trichomonas vaginalis cellular damage. To identify and locate the CP65 cellular-binding domain, we enriched the CP65 protein band by ammonium sulfate fractionation and ion-exchange chromatography and the N-terminal sequence was obtained. A 618bp gene fragment was obtained by PCR using genomic DNA as template and primers derived from the N-terminal sequence of CP65 and the Asn papain-catalytic conserved region. This gene fragment encodes for 206 amino acid (aa) residues corresponding to the N-terminal region of a mature CP with 67-76% identity to the reported trichomonad cathepsin-L-like CPs. This gene fragment was expressed in a bacterial system for antibody production and functional analysis. Antibodies against the native trichomonad CP65 recognized the recombinant protein, referred to as rCP65, confirming its relationship with the CP65 gene. The rCP65 protein was bound to the surface of HeLa cells and competed with the native CP65 for binding. Antibodies to the rCP65 (alpha-rCP65) reacted with the trichomonad CP65 located on the parasite surface, and inhibited trichomonal cytotoxicity in a concentration-dependent manner. These data strongly suggest that this gene fragment encodes for the putative cell-binding domain (CBD) of CP65 located at its N-terminal region.

Trichomonas vaginalis: Identification of a triacylglycerol acylhydrolase

This work describes the identification of a triacylglycerol lipase named TVLip directly onto blood-LB-agar plates by hemolytic screening of a Trichomonas vaginalis cDNA expression library. Sharing significant similarity in the primary sequence with other lipases, the theoretical 3D structure of the TVLip was resolved. The structure reveals the predictive conserved characteristics of other lipases from EC3.1.1.3 group, although presenting one amino acid change in the catalytic triad Ser-His-Asp. Finally, analysis of Northern blot indicates that the expression of the TVLip gene is up-regulated by iron.

Trichomonas vaginalis: characterization of a 39-kDa cysteine proteinase found in patient vaginal secretions

Trichomonosis, a chronic sexually transmitted disease, remains a public health problem affecting yearly over 170 million people worldwide. This disease is caused by Trichomonas vaginalis, a protozoan flagellate rich in cysteine proteinases (CPs). Although CPs are involved in trichomonal cytopathogenicity, only few of them have been defined as virulence factors. In this study, we characterize a T. vaginalis 39-kDa proteinase (CP39) found in vaginal secretions from patients with trichomonosis. The CP39 proteinase bound to HeLa epithelial cells, vaginal epithelial cells (VECs), and human prostatic cancer cells (DU-145). CP39 did not bind to a human colon cancer (CaCo) cell line, suggesting tissue-specific binding. CP39 was found in six fresh trichomonad isolates tested. In two-dimensional gels, CP39 appeared as a single spot with a pI 4.5. CP39 is inhibited by E-64, stable at 50 degrees C, and active in a wide pH range (3.6-9.0), with an optimum pH at 7.0. In addition, CP39 degraded collagens I, III, IV, and V, human fibronectin, human hemoglobin, and human immunoglobulins A and G. Indirect immunofluorescence detected CP39 on the parasite surface with specific polyclonal antibody to purified CP39. Finally, CP39 was found to be immunogenic, as evidenced by detection on immunoblots with serum of patients with trichomonosis, but not control individuals. These data suggest that CP39 may play a role during trichomonal infection.

tvcp12: a novel Trichomonas vaginalis cathepsin L-like cysteine proteinase-encoding gene

Trichomonas vaginalis is the causative agent of trichomoniasis, one of the most common sexually transmitted diseases in humans. This protozoan has multiple proteinases that are mainly of the cysteine proteinase (CP) type, some of which are known to be involved in the parasite's virulence. Here, a novel T. vaginalis CP-encoding gene, tvcp12, was identified and characterized. tvcp12 is 948 bp long and encodes a predicted 34.4 kDa protein that has the characteristics of the papain-like CP family. TvCP12 does not appear to have a signal peptide, suggesting that this is a cytoplasmic CP. By Southern blot assays, the tvcp12 gene was found as a single copy in the T. vaginalis genome. Remarkably, Northern blot experiments showed a single transcript band of approximately 1.3 kb in the mRNA obtained from parasites grown in low iron conditions and no transcript was observed in the mRNA from parasites grown in high iron conditions. By RT-PCR assays, a 270 bp band was amplified from the cDNA of parasites grown in low iron medium, which was very faint when cDNA from parasites grown in high iron conditions was used. Transcripts of the 3' region obtained in both iron conditions presented differences in their poly(A) tail length. These data suggest that tvcp12 is another gene that is negatively regulated by iron and that the length of the poly(A) tail may be one of the factors involved in the iron-modulated protein expression.

Two novel asparaginyl endopeptidase-like cysteine proteinases from the protist Trichomonas vaginalis: their evolutionary relationship within the clan CD cysteine proteinases

Cysteine proteinases (CPs) are important virulence factors of the protozoan parasite Trichomonas vaginalis. A total of six genes coding for cathepsin L-like CPs belonging to clan CA have been identified in T. vaginalis. At least 23 distinct spots with proteolytic activity have been detected by two-dimensional (2-D) substrate gel electrophoresis from in vitro grown parasites; however, only few of them have been characterized. In this work, we detected six spots with proteolytic activity and molecular weights between 25 and 35 kDa. The six proteinases correspond to two distinct CP families: the papain-like family, represented by four spots with pIs between 4.5 and 5.5; and the legumain-like family represented by two spots with pI 6.3 and 6.5. Next, we obtained two cDNAs encoding for legumain-like CPs from T. vaginalis, which were named Tvlegu-1 and Tvlegu-2. The size of these cDNA clones were 1225 and 1364 bp, which encoded for 388 and 415 amino acids, respectively. Their putative translation products have molecular masses of 42.8 and 47.2 kDa, corresponding to inactive legumain-like CP precursors. The two sequences share approximately 40% identity at the amino acid level. These protein products can be classified within a branch of the legumain-like family in clan CD cysteine proteinases due to their sensitivity to specific proteinases inhibitors, their DNA sequences, and phylogenetic reconstruction. However, they do not correspond either to the typical asparaginyl endopeptidase or the glycosylphosphatidylinositol (GPI): protein transamidase subfamilies. These results suggest that the TVLEGU-1 and TVLEGU-2 peptidases are likely to be part of a new subfamily within the legumain-like family of clan CD cysteine proteinases. Furthermore, they could be one of the missing links between prokaryotic and eukaryotic CPs in clan CD enzymes.

Purification and analysis of a phospholipase A2-like lytic factor of Trichomonas vaginalis

Trichomonas vaginalis produces soluble factors that have been reported to have the ability to damage target cells in vitro, and it has been hypothesized that these factors may play a role in the pathogenesis of human trichomoniasis. A lytic factor (LF) was purified from T. vaginalis, and the molecular characteristics of LF were determined. T. vaginalis extract was subjected to hydrophobic chromatography with a 10 to 60% N-propanol gradient in 0.1 M ammonium acetate, resulting in the elution of LF from the column at 30% N-propanol. Cytotoxicity assays revealed that LF was cytotoxic to WEHI 164 cells and bovine red blood cells, and inactivation of LF by treatment with trypsin suggested that the active component of LF was a protein. Size exclusion chromatography of LF produced two fractions at 144 and 168 kDa, and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of LF under reducing conditions revealed two subunits of 57 and 60 kDa. Results of a fluorescence assay of LF on carboxyfluorescein-labeled liposomes composed of phosphatidylcholine-cholesterol showed that liposomes were hydrolyzed, suggesting that LF had phospholipase activity. Thin-layer chromatography analysis of BODIPY (4,4-difluoro-3a,4adiaza-s-indacene)-labeled phosphatidylcholine treated with LF demonstrated products that migrated identically to the products produced by treatment with phospholipase A(2) (PLA(2)). These results suggest that LF is a PLA(2) and may be an important virulence factor of T. vaginalis mediating the destruction of host cells and contributing to tissue damage and inflammation in trichomoniasis.

Trichomonas vaginalis: identification of a phospholipase A-dependent hemolytic activity in a vesicular subcellular fraction

Trichomonad total extracts (TTE), or vesicular (P30) and soluble (530) subcellular fractions from 3 pathogenic Trichomonas vaginalis strains (GT-3. GT-13. and GT-15), lysed both human and Sprague-Dawley rat erythrocytes in a time- and dose-dependent manner. The entire hemolytic activity of TTE was located in P30, showing 2 peaks of maximum activity, one at pH 6.0 and another at pH 8.0. in the presence of 1 mM Ca2+. Hemolytic activity on rat erythrocytes was greater at pH 6.0 16.71 +/- 0.33 hemolytic units IHU]/mg/hr to 11.60 +/- 0.24 HU/mg/hr) than at pH 8.0 (3.81 +/- 0.30 HU/mg/hr to 5.75 +/- 0.65 HU/mg/hr). and it was greater than that on human red blood cells at pH 6.0 (2.67 +/- 0.19 HU/mg/hr to 4.08 +/- 0.15 HU/mg/hr) or pH 8.0 (2.24 +/- 0.0 9 HU/mg/hr to 2.81 +/- 0.06 HU/mg/hr). The alkaline and acidic hemolytic activity diminished (60-93% at pH 6.0 and 78-93% at pH 8.0) by the effect of 80 microM Rosenthal's inhibitor, which also inhibited 27-45% and 29-54% trichomonad alkaline and acidic phospholipase A activities, respectively. Vesicles, vacuoles, and hydrogenosomes were rich in P30. Trichomonas vaginalis has a hemolytic PLA, which could be involved in its cytopathogenic mechanism.

The chitinase system from Trichomonas vaginalis as a potential target for antimicrobial therapy of urogenital trichomoniasis

Chitinolytic activities in Trichomonas vaginalis membrane extracts were assessed by assays of three enzyme systems: N-acetyl-beta-D-hexosaminidase (NAHase), chitobiosidase and chitotriosidase. N-acetyl-beta-D-hexosaminidase was the enzyme that showed the highest specific activity. After successive subcutaneous inoculations into mice and parasite recovery in culture, the enzyme activities increased significantly with the number of inoculations for up to eight passages. In addition, enzyme activities were maximum at the logarithmic phase of growth. Glycol chitin, a chitinase substrate, enhanced all chitinolytic activities by about 30% and a clear-cut correlation is shown between the capacity for erythrocyte lysis by parasites and NAHase expression. Chitobiosidase and chitotriosidase activities were both inhibited at 58% and 100%, respectively, by allosamidine, a chitinase inhibitor used at 3 microM, whereas NAHase activity was not affected. Seven putative NAHase inhibitors (compounds n, 1-7), ureido and thioureido derivatives of 2-amino-2-deoxy-D-glucose were evaluated and five of them had K(i) values in the range 30-70 microM. The most active compound (compound 6) was functionally competitive with respect to the substrate with a K(i) value of 30 microM. The IC(50) values of the most active compounds on T. vaginalis were in the range 62-85 microM. These results indicate that chitinases of T. vaginalis are involved in pathogenicity and they could be an interesting target for drugs since chitinase inhibitors also inhibit parasite growth.

Trichomonas gallinae: a possible contact-dependent mechanism in the hemolytic activity

The in vitro hemolytic activity of Trichomonas gallinae was investigated. The parasite was tested against human erythrocytes of groups A, B, AB, and O, and against erythrocytes of six adult animals of different species (rabbit, rat, chicken, horse, bovine, and sheep). Results showed that T. gallinae lysed all human erythrocytes groups, as well as rabbit, rat, chicken, horse, bovine and sheep erythrocytes. No hemolysin released by the parasites could be identified. Hemolysis did not occur with trichomonad culture supernatants, with sonicated extracts of T. gallinae, or with killed organisms. The scanning electron microscopy (SEM) showed that the erythrocytes adhered to the parasite surface and were phagocytosed. These observations suggest that the contact between T. gallinae and erythrocytes may be an important mechanism in the injury caused to the erythrocytes. The hemolytic activity of T. gallinae may be an efficient means of obtaining nutrients for the parasite and allow the investigation of the mechanism used by T. gallinae to damage cellular membranes.

Two distinct hemolysins in Trichomonas tenax ATCC 30207

An oral protist Trichomonas tenax ATCC 30207 was investigated for the ability to lyse erythrocytes of sheep, rabbits, horses and humans. Five fractions, including intact cells, culture supernatant, culture filtrate, cell debris and lipid-enriched fractions, were prepared from the protozoan cells, and their hemolytic activities were assayed under various conditions. All the samples except culture supernatant had hemolytic activities, which were due to two different kinds of hemolysins. One hemolysin was protein-like and mainly found in cell-free fractions: culture supernatant and culture filtrate. It was heat-labile and inhibited by various cysteine-proteinase inhibitors. The other hemolysin was lipid-like and found in cell-associated fractions: intact cells, cell-debris and lipid-enriched fractions. It was heat-stable, organic solvent-tolerant and unaffected by various proteinase inhibitors and stimulators. These results suggested that T. tenax ATCC 30207 possessed two distinct hemolysins, protein and lipid.

The interaction of trichomonas vaginalis with epithelial cells, polymorphonuclear leucocytes and erythrocytes on vaginal smears: light microscopic observation

In this study, vaginal smears taken from 400 patients were examined cytologically using the Papanicolaou technique. Twenty of the 400 patients were detected as harbouring Trichomonas vaginalis. The interactions of T. vaginalis with epithelial cells, polymorphonuclear leucocytes (PMNLs) and erythrocytes were determined at light microscopic level. It was observed that T. vaginalis were juxtaposed to the epithelial cells and changed shape according to the contours of the epithelial cell revealing the cytopathic effect of trichomonads on epithelial cells. Trichomonads attached to PMNLs produced pseudopodia to phagocytose the cells. Occasionally an amoeboid shaped T. vaginalis organism was seen trailed by a row of PMNLs. This light microscopic study supports the production by trichomonads of a chemotactic factor for PMNLs. Phagocytosed erythrocytes were also seen in the cytoplasm of T. vaginalis, suggesting the need for the patient to be tested for anaemia.

CP30, a cysteine proteinase involved in Trichomonas vaginalis cytoadherence

We describe here the participation of a Trichomonas vaginalis 30-kDa proteinase (CP30) with affinity to the HeLa cell surface in attachment of this parasite to host epithelial cells. The CP30 band is a cysteine proteinase because its activity was inhibited by E-64, a thiol proteinase inhibitor. In two-dimensional substrate gel electrophoresis of total extracts of the trichomonad isolate CNCD 147, three spots with proteolytic activity were detected in the 30-kDa region, in the pI range from 4.5 to 5.5. Two of the spots (pI 4.5 and 5.0) bound to the surfaces of fixed HeLa cells corresponding to the CP30 band. The immunoglobulin G fraction of the rabbit anti-CP30 antiserum that recognized a 30-kDa band by Western blotting and immunoprecipitated CP30 specifically inhibited trichomonal cytoadherence to HeLa cell monolayers in a concentration-dependent manner and reacted with CP30 at the parasite surface. CP30 degraded proteins found on the female urogenital tract, including fibronectin, collagen IV, and hemoglobin. Interestingly, CP30 digested fibronectin and collagen IV only at pH levels between 4.5 and 5.0. Moreover, trichomonosis patients whose diagnosis was confirmed by in vitro culture possessed antibody to CP30 in both sera and vaginal washes, and CP30 activity was found in vaginal washes. Our results suggest that surface CP30 is a cysteine proteinase necessary for trichomonal adherence to human epithelial cells.

Strategies by which some pathogenic trichomonads integrate diverse signals in the decision-making process

The interaction between each one of Trichomonas vaginalis and Tritrichomonas foetus with their hosts is a complex process in which components associated to the cell surfaces of both parasites and host epithelial cells, and also to soluble components found in vaginal/urethral secretions, are involved. Either cytoadhesion or the cytotoxicity exerted by parasites to host cells can be dictated by virulence factors such as adhesins, cysteine proteinases, laminin-binding proteins, integrins, integrin-like molecules, a cell detachment factor, a pore-forming protein, and glycosidases among others. How trichomonads manipulate informations from the extracellular medium, transduce such informations, and respond to them by stimulating the activities of some surface molecules and/or releasing enzymes are the aspects concerning trichomonal virulence which are here briefly reviewed and discussed.

A novel cysteine proteinase (CP65) of Trichomonas vaginalis involved in cytotoxicity

The goal of this study was to demonstrate the participation in cellular damage of a Trichomonas vaginalis proteinase with a molecular mass of 65 kDa (CP65). By two dimensional gelatin-gel electrophoresis of trichomonad proteins we detected four spots with proteolytic activity on the 65 kDa region, but only one, pI 7.2, binds to the HeLa cell surface. By indirect immunofluorescence, rabbit antibodies against this proteinase localized the CP65 on the plasma membrane and in the cytoplasm of T. vaginalis. Pretreatment of parasites with the specific anti-CP65 antibody reduced trichomonal cytotoxicity to HeLa cell monolayers. The specific cysteine proteinase inhibitor, L-3-carboxy-2, 3-trans-epoxypropionyl-leucylamido (4-guanidino) butane (E64) abrogated the proteinase activity and reduced cytotoxicity levels of T. vaginalis in cell culture monolayers, indicating that the trichomonad CP65 is a cysteine proteinase. Activity of the CP65 proteinase was optimal at pH 5.5 and 37 degrees C, conditions similar to those of patients with trichomonosis. Also, this proteinase degraded some of the proteins found in the vagina, i.e. collagen IV and fibronectin, but not laminin-1 or haemoglobin. Finally, immunoprecipitation assays showed that sera and vaginal washes from trichomonosis patient possess anti-CP65 antibodies. In conclusion, results presented in this work demonstrate that the CP65 is a surface cysteine proteinase involved in T. vaginalis cytotoxicity to HeLa cell monolayers, as a virulence factor. It is immunogenic during human infection and degrades some extracellular matrix proteins, i.e. collagen IV and fibronectin.

Biology of trichomonosis

Trichomonas vaginalis is emerging as a major pathogen of men and women and is associated with serious health consequences. Advances in diagnosis and treatment are presented. The complexity of trichomonad pathogenesis is illustrated in the interaction of this parasite with human cells, tissues and the immune system. It is now becoming evident that the interaction of trichomonads with the host is frequently modulated by environmental signals. The molecular biology of trichomonads is still in its infancy, but analysis of genes, genomic structure and transcriptional mechanisms suggest that trichomonads combine both prokaryotic and eukaryotic features. Evidence for the ancient divergence of trichomonads from other eukaryotic lineages is discussed.

The flagellated parasite Trichomonas vaginalis: new insights into cytopathogenicity mechanisms

Our knowledge concerning cytopathogenicity of Trichomonas vaginalis has been enriched in the past by numerous findings. In this paper, we review the latest advances in the field and discuss the different mechanisms and molecules responsible for the parasite's virulence.

Degradations of human immunoglobulins and hemoglobin by a 60 kDa cysteine proteinase of Trichomonas vaginalis

The present study was undertaken to investigate the role of cysteine proteinase of Trichomonas vaginalis in escaping from host defense mechanism. A cysteine proteinase of T. vaginalis was purified by affinity chromatography and gel filtration. Optimum pH for the purified proteinase activity was 6.0. The proteinase was inhibited by cysteine and serine proteinase inhibitors such as E-64, NEM, IAA, leupeptin, TPCK and TLCK, and also by Hg2+, but not affected by serine-, metallo-, and aspartic proteinase inhibitors such as PMSF, EDTA and pepstatin A. However, it was activated by the cysteine proteinase activator, DTT. The molecular weight of a purified proteinase was 62 kDa on gel filtration and 60 kDa on SDS-PAGE. Interestingly, the purified proteinase was able to degrade serum IgA, secretory IgA, and serum IgG in time- and dose-dependent manners. In addition, the enzyme also degraded hemoglobin in a dose-dependent manner. These results suggest that the acidic cysteine proteinase of T. vaginalis may play a dual role for parasite survival in conferring escape from host humoral defense by degradation of immunoglobulins, and in supplying nutrients to parasites by degradation of hemoglobin.

Clinical and microbiological aspects of Trichomonas vaginalis

Trichomonas vaginalis, a parasitic protozoan, is the etiologic agent of trichomoniasis, a sexually transmitted disease (STD) of worldwide importance. Trichomoniasis is the most common nonviral STD, and it is associated with many perinatal complications, male and female genitourinary tract infections, and an increased incidence of HIV transmission. Diagnosis is difficult, since the symptoms of trichomoniasis mimic those of other STDs and detection methods lack precision. Although current treatment protocols involving nitroimidazoles are curative, metronidazole resistance is on the rise, outlining the need for research into alternative antibiotics. Vaccine development has been limited by a lack of understanding of the role of the host immune response to T. vaginalis infection. The lack of a good animal model has made it difficult to conduct standardized studies in drug and vaccine development and pathogenesis. Current work on pathogenesis has focused on the host-parasite relationship, in particular the initial events required to establish infection. These studies have illustrated that the pathogenesis of T. vaginalis is indeed very complex and involves adhesion, hemolysis, and soluble factors such as cysteine proteinases and cell-detaching factor. T. vaginalis interaction with the members of the resident vaginal flora, an advanced immune evasion strategy, and certain stress responses enable the organism to survive in its changing environment. Clearly, further research and collaboration will help elucidate these pathogenic mechanisms, and with better knowledge will come improved disease control.

The vagina has reducing environment sufficient for activation of Trichomonas vaginalis cysteine proteinases

BACKGROUND

Trichomonas vaginalis, a worldwide distributed sexually transmitted protozoan, is remarkable for synthesis of numerous, distinct cysteine proteinases, the significance of which is evidenced by the presence in vivo of soluble proteinases in secretions and antiproteinase antibody in serum of patients with trichomonosis. These proteinases purportedly play a role in host parasitism and immune evasion.

OBJECTIVE

It is known that for cysteine proteinases to be functional, they must be activated by disulphide reducing reagents. Whether or not the host vaginal environment has the reducing environment essential for activation of the trichomonad cysteine proteinases is unknown. Our goal, therefore, was to determine whether or not vaginal secretions had sufficient reducing power to activate the trichomonad proteinases.

METHODS

48 vaginal washes (VWs) from patients were assayed for reducing equivalents and a score in dithiothreitol (DTT) reducing equivalents was assigned to each VW. Activation of trichomonad cysteine proteinases was then tested under the range of reducing equivalents detected from VWs. The possible protective effect of hydrogen peroxide, an oxidising agent produced by some Lactobacillus species, on proteinase activity was also determined.

RESULTS

Nine of 48 VWs (18.7%) possessed < or = 10 microM DTT reducing equivalents, four VWs (8.3%) had from 20 microM DTT to 40 microM DTT reducing equivalents, and most (50%) were between 10 microM to 15 microM. Overall, the range in VWs was from approximately 10 microM to 40 microM reducing equivalents. Importantly, data suggest differential proteinase activation over this in vivo range of reducing level. Only two T vaginalis cysteine proteinase activities were stimulated at 2.5 microM DTT in contrast with all proteinase activities present at 40 microM DTT, albeit quantitatively diminished compared with the activity at 1 mM DTT, the concentration routinely used in vitro. Finally, hydrogen peroxide reversibly neutralised all trichomonad proteinases.

CONCLUSIONS

These results show that the vagina of women has a reducing environment adequate for activation of trichomonad proteinases. The data underscore that the host environment plays a role in the host-parasite interrelation. Finally, hypotheses can now be formulated to help explain resistance and susceptibility to infection commonly reported among women and between men and women with trichomonosis.

Degradation of human immunoglobulins and cytotoxicity on HeLa cells by live Trichomonas vaginalis

The present study was undertaken to determine whether live T. vaginalis degrades human secretory IgA, serum IgA and IgG molecules. Human immunoglobulins were exposed to live trophozoites, parasite lysate, and excretory-secretory product (ESP) of T. vaginalis. To determine the fragmentation of immunoglobulins, the reaction sample was subjected to SDS-PAGE and EITB, and peroxidase conjugated antihuman IgA and IgG were used as probes. Live trophozoites degraded secretory IgA. Serum IgA and IgG, and degradation were pressed forward by the prolongation of the incubation time and by increasing the number of trichomonads respectively. Also the lysates and ESP of trichomonads degraded IgA and IgG. The cysteine and serine proteinase inhibitors such as E-64, antipain, iodoacetic acid, iodoacetamide, TLCK reduced the ability of cleaving immunoglobulins. The proteinase activity and cytotoxicity of T. vaginalis to HeLa cells were decreased when live T. vaginalis was treated with metallo-proteinase inhibitor as well as cysteine and serine proteinase inhibitors. These results suggest that proteinase secreted from live T. vaginalis may play a part role in host pathogenesis by T. vaginalis, and the cleaving ability of host immunoglobulins by the proteinase may contribute as a one of immune evasion mechanism for parasite survival in the host.

Hemolytic activity of Trichomonas vaginalis and Tritrichomonas foetus

The hemolytic activity of live isolates and clones of Trichomonas vaginalis and Tritrichomonas foetus was investigated. The isolates were tested against human erythrocytes. No hemolytic activity was detected by the isolates of T. foetus. Whereas the isolates of T. vaginalis lysed erythrocytes from all human blood groups. No hemolysin released by the parasites could be detected. Our preliminary results suggest that hemolysis depend on the susceptibility of red cell membranes to destabilization and the intervention of cell surface receptors as a mechanism of the hemolytic activity. The mechanism could be subject to strain-species-genera specific variation of trichomonads. The hemolytic activity of T. vaginalis is not due to a hemolysin or to a product of its metabolism. Pretreatment of trichomonads with concanavalin A reduced levels of hemolysis by 40%.