Silencing the ap65 gene reduces adherence to vaginal epithelial cells by Trichomonas vaginalis

Trichomonas vaginalis adhesion protein 65 (TvAP65) modulates parasite pathogenicity by interacting with host cell proteins

Trichomonas vaginalis (T. vaginalis) is a widespread and important sexually transmitted pathogen. Adherence to the surface of the host cell is the precondition forthis parasite's parasitism and pathogenicity. Adhesion protein 65 (TvAP65) plays a key role in the process of adhesion. However, how TvAP65 mediates the adhesion and pathogenicity of T. vaginalis to host cellsis unclear. In this study, we knocked down the expression of TvAP65 in trophozoites by small RNA interference. The number of T. vaginalis trophozoites adhering to VK2/E6E7 cells was decreased significantly, and the inhibition of VK2/E6E7 cells proliferation and VK2/E6E7 cells apoptosis and death induced by T. vaginalis were reduced, after the expression of TvAP65 was knocked down. Animal challenge experiments showed that the pathogenicity of trophozoites was decreased by passive immunization with anti-rTvAP65 PcAbs or blocking the TvAP65 protein. Immunofluorescence analysis showed that TvAP65 could bind to VK2/E6E7 cells. In order to screen the molecules interacting with TvAP65 on the host cells, we successfully constructed the cDNA library of VK2/E6E7 cells, and thirteen protein molecules interacting with TvAP65 were screened by yeast two-hybrid system. The interaction between TvAP65 and BNIP3 was further confirmed by coimmunoprecipitation and colocalization. When both TvAP65 and BNIP3 were knocked down by small RNA interference, the number of T. vaginalis adhering to VK2/E6E7 cells and the inhibition of VK2/E6E7 cells proliferation were significantly lower than those of the group with knockdown of TvAP65 or BNIP3 alone. Therefore, the interaction of TvAP65 and BNIP3 in the pathogenesis of T. vaginalis infecting host cells is not unique and involves other molecules. Our study elucidated that the interaction between TvAP65 and BNIP3 mediated the adhesion and pathogenicity of T. vaginalis to host cells, provided a basis for searching for the drug targets of anti-T. vaginalis, and afforded new ideas for the prevention and treatment of trichomoniasis.

Endomembrane Protein Trafficking Regulated by a TvCyP2 Cyclophilin in the Protozoan Parasite, Trichomonas vaginalis

In Trichomonas vaginalis, the TvCyP1-catalyzed conformational switches of two glycinyl-prolyl imide bonds in Myb3 were previously shown to regulate the trafficking of Myb3 from cytoplasmic membrane compartments towards the nucleus. In this study, TvCyP2 was identified as a second cyclophilin that binds to Myb3 at the same dipeptide motifs. The enzymatic proficiency of TvCyP2, but not its binding to Myb3, was aborted by a mutation of Arg⁷⁵ in the catalytic domain. TvCyP2 was localized to the endoplasmic reticulum with a weak signal that extensively extends into the cytoplasm as well as to the plasma membrane according to an immunofluorescence assay. Moreover, TvCyP2 was co-enriched with TvCyP1 and Myb3 in various membrane fractions purified by differential and gradient centrifugation. TvCyP2 was found to proficiently enzymatically regulate the distribution of TvCyP1 and Myb3 among purified membrane fractions, and to localize TvCyP1 in hydrogenosomes and on plasma membranes. Protein complexes immunoprecipitated from lysates of cells overexpressing TvCyP1 and TvCyP2 were found to share some common components, like TvCyP1, TvCyP2, TvBip, Myb3, TvHSP72, and the hydrogenosomal heat shock protein 70 (HSP70). Direct interaction between TvCyP1 and TvCyP2 was confirmed by a GST pull-down assay. Fusion of vesicles with hydrogenosomes was observed by transmission electron microscopy, whereas TvCyP1, TvCyP2, and Myb3 were each detected at the fusion junction by immunoelectron microscopy. These observations suggest that T. vaginalis may have evolved a novel protein trafficking pathway to deliver proteins among the endomembrane compartments, hydrogenosomes and plasma membranes.

Host-Pathogen Interactions during Female Genital Tract Infections

Dysbiosis in the female genital tract (FGT) is characterized by the overgrowth of pathogenic bacterial, fungal, or protozoan members of the microbiota, leading to symptomatic or asymptomatic infections. In this review, we discuss recent advances in studies dealing with molecular mechanisms of pathogenicity factors of Gardnerella vaginalis, Mycoplasma genitalium, Mycoplasma hominis, Neisseria gonorrhoeae, Streptococcus agalactiae, Chlamydia trachomatis, Trichomonas vaginalis, and Candida spp., as well as their interactions with the host and microbiota in the various niches of the FGT. Taking a holistic approach to identifying fundamental commonalities and differences during these infections could help us to better understand reproductive tract health and improve current prevention and treatment strategies.

Antiparasitic activity of synthetic curcumin monocarbonyl analogues against Trichomonas vaginalis

Trichomoniasis is a parasitic infection caused by Trichomonas vaginalis and it is considered to be the most common non-viral sexually transmitted infection in the world. Since the 1960s, nitroimidazoles such as metronidazole are the drugs of choice for the treatment of trichomoniasis, but many adverse effects and allergic reactions may result from their use. Reports of metronidazole-resistant infections also highlight the importance for the search of new anti-T. vaginalis agents. Considering this, herein we report the anti-T. vaginalis evaluation of 21 synthetic monocarbonyl analogues of curcumin, which itself has been reported to possess antiparasitic potential. From the in vitro analysis of the synthetic molecules, untreated trophozoites, and metronidazole at 100 μM, it was observed that three curcumin analogues (3a, 3e, and 5e) exhibited anti-T. vaginalis activity comparable to metronidazole (no significant statistical difference). Optimal antiparasitic concentrations were determined to be 80 μM and 90 μM for propanone derivatives 3a and 3e, respectively, and 200 μM for cyclohexanone derivative 5e. Kinetic growth curves showed that, after 24 h, the trophozoites were completely inhibited. At the tested concentrations, natural curcumin did not significantly inhibit the growth of trophozoites, therefore demonstrating that the designed synthetic molecules not only have better chemical stability, but also higher anti-T. vaginalis potential. Cytotoxicity analysis, performed on VERO cells, demonstrated low, moderate and high cytotoxic effects for analogues 3e, 5e and 3a, respectively. This study suggests that these analogues possess chemical features of interest to be further explored as alternatives for the treatment of trichomoniasis.

Structural basis of interaction between dimeric cyclophilin 1 and Myb1 transcription factor in Trichomonas vaginalis

Cyclophilin 1 (TvCyP1), a cyclophilin type peptidyl-prolyl isomerase present in the human parasite Trichomonas vaginalis, interacts with Myb1 and assists in its nuclear translocation. Myb1 regulates the expression of ap65-1 gene that encodes for a disease causing cytoadherence enzyme. Here, we determined the crystal structures of TvCyP1 and its complex with the minimum TvCyP1-binding sequence of Myb1 (Myb1^104-111), where TvCyP1 formed a homodimer, unlike other single domain cyclophilins. In the complex structure, one Myb1^104-111 peptide was bound to each TvCyP1 protomer, with G106-P107 and Y105 fitting well into the active site and auxiliary S2 pocket, respectively. NMR data further showed that TvCyP1 can catalyze the cis/trans isomerization of P107 in Myb1^104-111. Interestingly, in the well-folded Myb1 protein (Myb1^35-141), the minimum binding sequence adopted a different conformation from that of unstructured Myb1^104-111 peptide, that could make P107 binding to the active site of TvCyP1 difficult. However, NMR studies showed that similar to Myb1^104-111 peptide, Myb1^35-141 also interacted with the active site of TvCyP1 and the dynamics of the Myb1^35-141 residues near P107 was reduced upon interaction. Together, the structure of TvCyP1 and detailed structural insights on TvCyP1-Myb1 interaction provided here could pave the way for newer drugs to treat drug-resistant strains.

Immunocytochemistry Improving the Diagnosis of Trichomonas vaginalis Infections

The aim of this study was to evaluate the immunocytochemistry (ICC) to diagnose trichomoniasis, particularly asymptomatic infections. By culture serial dilutions, ICC was able to detect 1 trophozoite/mL, while the culture was positive up to 100 trophozoites/mL. The ICC in vivo detection capability was assessed in vaginal secretions of mice experimentally infected and in vaginal swabs from asymptomatic HIV-positive pregnant women compared with culture. All vaginal secretion samples from mice were positive according to both methods. Swabs from fifty-five asymptomatic women were positive in four (7.27%) of them by culture. Beyond these four, another ten (25.45%) women were positive by immunocytochemistry, proving their higher sensitivity (p = 0.002), noticing 3.5 times more positives. ICC had better performance in both successive dilutions as in asymptomatic women, showing higher sensitivity and specificity. In this way, its facility of execution and cost-effectiveness support its practicality, as a routine procedure to diagnose trichomoniasis not only when the parasite load is lower but probably in all clinical scenarios.

Trichomonas vaginalis Repair of Iron Centres Proteins: The Different Role of Two Paralogs

Trichomonas vaginalis, the causative parasite of one of the most prevalent sexually transmitted diseases is, so far, the only protozoan encoding two putative Repair of Iron Centres (RIC) proteins. Homologs of these proteins have been shown to protect bacteria from the chemical stress imposed by mammalian immunity. In this work, the biochemical and functional characterisation of the T. vaginalis RICs revealed that the two proteins have different properties. Expression of ric1 is induced by nitrosative stress but not by hydrogen peroxide, while ric2 transcription remained unaltered under similar conditions. T. vaginalis RIC1 contains a di-iron centre, but RIC2 apparently does not. Only RIC1 resembles bacterial RICs on spectroscopic profiling and repairing ability of oxidatively-damaged iron-sulfur clusters. Unexpectedly, RIC2 was found to bind DNA plasmid and T. vaginalis genomic DNA, a function proposed to be related with its leucine zipper domain. The two proteins also differ in their cellular localization: RIC1 is expressed in the cytoplasm only, and RIC2 occurs both in the nucleus and cytoplasm. Therefore, we concluded that the two RIC paralogs have different roles in T. vaginalis, with RIC2 showing an unprecedented DNA binding ability when compared with all other until now studied RICs.

Regulation of nuclear translocation of the Myb1 transcription factor by TvCyclophilin 1 in the protozoan parasite Trichomonas vaginalis

In Trichomonas vaginalis, a Myb1 protein was previously demonstrated to repress transcription of an iron-inducible ap65-1 gene. In this study, a human cyclophilin A homologue, TvCyclophilin 1 (TvCyP1), was identified as a Myb1-binding protein using a bacterial two-hybrid library screening system. The recombinant TvCyP1 exhibited typical peptidyl-prolyl isomerase activity with kcat/Km of ∼7.1 μm(-1) s(-1). In a pulldown assay, the His-tagged Myb1 interacted with a GST-TvCyP1 fusion protein, which had an enzymatic proficiency half that of recombinant TvCyP1. Both the enzymatic proficiency of GST-TvCyP1 and its binding to His-Myb1 were eliminated by mutation of Arg(63) in the catalytic motif or inhibited by cyclosporin A. TvCyP1 was primarily localized to the hydrogenosomes by immunofluorescence assay, but it was also co-purified with Myb1 in certain vesicle fractions from differential and gradient centrifugations. Transgenic cells overexpressing HA-TvCyP1 had a higher level of nuclear Myb1 but a much lower level of Myb1 associated with the vesicles than control and those overexpressing HA-TvCyP1(R63A). Myb1 was detected at a much higher level in the HA-TvCyP1 protein complex than in the HA-TvCyP1(R63A) protein complex immunoprecipitated from P15 and P100, but not S100, fractions of postnuclear lysates. A TvCyP1-binding motif, (105)YGPKWNK(111), was identified in Myb1 in which Gly(106) and Pro(107) were essential for its binding to TvCyP1. Mutation of Gly(106) and Pro(107), respectively, in HA-Myb1 resulted in cytoplasmic retention and elevated nuclear translocation of the overexpressed protein. These results suggest that TvCyP1 may induce the release of Myb1 that is restrained to certain cytoplasmic vesicles prior to its nuclear translocation.

Iron-inducible nuclear translocation of a Myb3 transcription factor in the protozoan parasite Trichomonas vaginalis

In Trichomonas vaginalis, a novel nuclear localization signal spanning the folded R2R3 DNA-binding domain of a Myb2 protein was previously identified. To study whether a similar signal is used for nuclear translocation by other Myb proteins, nuclear translocation of Myb3 was examined in this report. When overexpressed, hemagglutinin-tagged Myb3 was localized to nuclei of transfected cells, with a cellular distribution similar to that of endogenous Myb3. Fusion to a bacterial tetracycline repressor, R2R3, of Myb3 that spans amino acids (aa) 48 to 156 was insufficient for nuclear translocation of the fusion protein, unless its C terminus was extended to aa 167. The conserved isoleucine in helix 2 of R2R3, which is important for Myb2's structural integrity in maintaining DNA-binding activity and nuclear translocation, was also vital for the former activity of Myb3, but less crucial for the latter. Sequential nuclear influx and efflux of Myb3, which require further extension of the nuclear localization signal to aa 180, were immediately induced after iron repletion. Sequence elements that regulate nuclear translocation with cytoplasmic retention, nuclear influx, and nuclear efflux were identified within the C-terminal tail. These results suggest that the R2R3 DNA-binding domain also serves as a common module for the nuclear translocation of both Myb2 and Myb3, but there are intrinsic differences between the two nuclear localization signals.

A highly organized structure mediating nuclear localization of a Myb2 transcription factor in the protozoan parasite Trichomonas vaginalis

Nuclear proteins usually contain specific peptide sequences, referred to as nuclear localization signals (NLSs), for nuclear import. These signals remain unexplored in the protozoan pathogen, Trichomonas vaginalis. The nuclear import of a Myb2 transcription factor was studied here using immunodetection of a hemagglutinin-tagged Myb2 overexpressed in the parasite. The tagged Myb2 was localized to the nucleus as punctate signals. With mutations of its polybasic sequences, 48KKQK51 and 61KR62, Myb2 was localized to the nucleus, but the signal was diffusive. When fused to a C-terminal non-nuclear protein, the Myb2 sequence spanning amino acid (aa) residues 48 to 143, which is embedded within the R2R3 DNA-binding domain (aa 40 to 156), was essential and sufficient for efficient nuclear import of a bacterial tetracycline repressor (TetR), and yet the transport efficiency was reduced with an additional fusion of a firefly luciferase to TetR, while classical NLSs from the simian virus 40 T-antigen had no function in this assay system. Myb2 nuclear import and DNA-binding activity were substantially perturbed with mutation of a conserved isoleucine (I74) in helix 2 to proline that altered secondary structure and ternary folding of the R2R3 domain. Disruption of DNA-binding activity alone by point mutation of a lysine residue, K51, preceding the structural domain had little effect on Myb2 nuclear localization, suggesting that nuclear translocation of Myb2, which requires an ordered structural domain, is independent of its DNA binding activity. These findings provide useful information for testing whether myriad Mybs in the parasite use a common module to regulate nuclear import.

Glyceraldehyde-3-phosphate dehydrogenase is a surface-associated, fibronectin-binding protein of Trichomonas vaginalis

Trichomonas vaginalis colonizes the urogenital tract of humans and causes trichomonosis, the most prevalent nonviral sexually transmitted disease. We have shown an association of T. vaginalis with basement membrane extracellular matrix components, a property which we hypothesize is important for colonization and persistence. In this study, we identify a fibronectin (FN)-binding protein of T. vaginalis. A monoclonal antibody (MAb) from a library of hybridomas that inhibited the binding of T. vaginalis organisms to immobilized FN was identified. The MAb (called ws1) recognized a 39-kDa protein and was used to screen a cDNA expression library of T. vaginalis. A 1,086-bp reactive cDNA clone that encoded a protein of 362 amino acids with identity to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was obtained. The gapdh gene was cloned, and recombinant GAPDH (rGAPDH) was expressed in Escherichia coli cells. Natural GAPDH and rGAPDH bound to immobilized FN and to plasminogen and collagen but not to laminin. MAb ws1 inhibited binding to FN. GAPDH was detected on the surface of trichomonads and was upregulated in synthesis and surface expression by iron. Higher levels of binding to FN were seen for organisms grown in iron-replete medium than for organisms grown in iron-depleted medium. In addition, decreased synthesis of GAPDH by antisense transfection of T. vaginalis gave lower levels of organisms bound to FN and had no adverse effect on growth kinetics. Finally, GAPDH did not associate with immortalized vaginal epithelial cells (VECs), and neither GAPDH nor MAb ws1 inhibited the adherence of trichomonads to VECs. These results indicate that GAPDH is a surface-associated protein of T. vaginalis with alternative functions.

Genetic identity and differential gene expression between Trichomonas vaginalis and Trichomonas tenax

BACKGROUND

Trichomonas vaginalis is a human urogenital pathogen responsible for trichomonosis, the number-one, non-viral sexually transmitted disease (STD) worldwide, while T. tenax is a commensal of the human oral cavity, found particularly in patients with poor oral hygiene and advanced periodontal disease. The extent of genetic identity between T. vaginalis and its oral commensal counterpart is unknown.

RESULTS

Genes that were differentially expressed in T. vaginalis were identified by screening three independent subtraction cDNA libraries enriched for T. vaginalis genes. The same thirty randomly selected cDNA clones encoding for proteins with specific functions associated with colonization were identified from each of the subtraction cDNA libraries. In addition, a T. vaginalis cDNA expression library was screened with patient sera that was first pre-adsorbed with an extract of T. tenax antigens, and seven specific cDNA clones were identified from this cDNA library. Interestingly, some of the clones identified by the subtraction cDNA screening were also obtained from the cDNA expression library with the pre-adsorbed sera. Moreover and noteworthy, clones identified by both the procedures were found to be up-regulated in expression in T. vaginalis upon contact with vaginal epithelial cells, suggesting a role for these gene products in host colonization. Semi-quantitative RT-PCR analysis of select clones showed that the genes were not unique to T. vaginalis and that these genes were also present in T. tenax, albeit at very low levels of expression.

CONCLUSION

These results suggest that T. vaginalis and T. tenax have remarkable genetic identity and that T. vaginalis has higher levels of gene expression when compared to that of T. tenax. The data may suggest that T. tenax could be a variant of T. vaginalis.

Entamoeba histolytica: effect on virulence, growth and gene expression in response to monoxenic culture with Escherichia coli 055

Monoxenic cultivation of pathogenic Entamoeba histolytica trophozoites with Escherichia coli serotype 055 which binds strongly to the Gal/GalNAc amoebic lectin, markedly improved the growth of E. histolytica and produced a significant decrease in cysteine proteinase activity and a lower cytopathic activity on monolayer cells after 3 months of monoxenic culture. However, after long term monoxenic culture (12 months) the proteolytic and cytopathic activities were recovered and the amoebic growth reached the maximum yield. Employing the GeneFishing(R) technology and DNA macroarrays we detected differentially gene expression related to the amoebic interaction with bacteria. A number of differentially expressed genes encoding metabolic enzymes, ribosomal proteins, virulence factors and proteins related with cytoskeletal and vesicle trafficking were found. These results suggest that E. coli 055 has a nutritional role that strongly supports the amoebic growth, and is also able to modulate some biological activities related with amoebic virulence.

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.

Characterization of the Trichomonas vaginalis surface-associated AP65 and binding domain interacting with trichomonads and host cells

Background

AP65 is a prominent adhesin of Trichomonas vaginalis that mediates binding of parasites to host vaginal epithelial cells (VECs). AP65 with no secretion signal sequence, membrane targeting peptide, and anchoring motif was recently found to be secreted.

Results

We first wanted to demonstrate surface association of AP65 to the parasite followed by the identification of the binding epitope interacting with both organisms and VECs. AP65 was found to bind to trichomonads, but not to trypsin-treated parasites, in an auto-ligand assay, suggesting the existence of a surface protein associating with AP65. Since rabbit antiserum IgG antibodies reactive with epitopes localized to the N-terminal region of AP65 inhibit the attachment of live parasites to VECs, we hypothesized that the binding domain was localized to this region. We subcloned five overlapping fragments of AP65 called c1 through c5, and expression of recombinant clones was confirmed with antibodies to AP65. Each purified recombinant protein was then tested for binding activity using an established ligand assay, and fragment c1 with the first twenty-five amino acids in the N-terminal domain was required for binding to VECs and, surprisingly, also to parasites. Importantly, c1 competed with the binding of AP65 to both cells types.

Conclusion

T. vaginalis AP65 is a secreted, surface-associated protein and a model is proposed to explain how this secreted protein functions as an adhesin.

Immunogenic and plasminogen-binding surface-associated alpha-enolase of Trichomonas vaginalis

Trichomonas vaginalis is a protist that causes the most common human sexually transmitted infection. A T. vaginalis cDNA expression library was screened with pooled sera from patients with trichomoniasis. A highly reactive cDNA clone of 1,428 bp encoded a trichomonad protein of 472 amino acids with sequence identity to alpha-enolase (tv-eno1). The sequence alignment confirmed the highly conserved nature of the enzyme with 65% to 84% identity among organisms. The expression of tv-eno1 was up-regulated by contact of parasites with vaginal epithelial cells, and this is the first report demonstrating up-regulation by cytoadherence of a plasminogen-binding alpha-enolase in T. vaginalis. Immunofluorescence with monoclonal antibody of nonpermeabilized trichomonads showed tv-ENO1 on the surface. The recombinant tv-ENO1 was expressed in Escherichia coli as a glutathione S-transferase (GST)::tv-ENO1 fusion protein, which was cleaved using thrombin to obtain affinity-purified recombinant tv-ENO1 protein (tv-rENO1) detectable in immunoblots by sera of patients. Immobilized tv-rENO1 bound human plasminogen in a dose-dependent manner, and plasminogen binding by tv-rENO1 was confirmed in a ligand blot assay. The plasminogen-specific inhibitor epsilon-aminocaproic acid blocked the tv-rENO1-plasminogen association, indicating that lysines play a role in binding to tv-rENO1. Further, both parasites and tv-rENO1 activate plasminogen to plasmin that is mediated by tissue plasminogen activator. These data indicate that as with other bacterial pathogens, tv-ENO1 is an anchorless, surface-associated glycolytic enzyme of T. vaginalis.

Antisense RNA and RNAi in protozoan parasites: working hard or hardly working?

The complex life cycles of many protozoan parasites require the ability to respond to environmental and developmental cues through regulated gene expression. Traditionally, parasitologists have investigated these mechanisms by identifying and characterizing proteins that are necessary for the regulated expression of the genetic material. Although often successful, it is clear that protein-mediated gene regulation is only part of a complex story in which RNA itself is endowed with regulatory functions. Herein, we review both the known and potential regulatory roles of two types of RNA pathways within protozoan parasites: the RNA interference pathway and natural antisense transcripts. A better understanding of the native role of these pathways will not only enhance our understanding of the biology of these organisms but also aid in the development of more robust tools for reverse genetic analysis in this post-genomic era.

Antisense RNA decreases AP33 gene expression and cytoadherence by T. vaginalis

BACKGROUND

Host parasitism by Trichomonas vaginalis is complex. Adherence to vaginal epithelial cells (VECs) is mediated by surface proteins. We showed before that antisense down-regulation of expression of adhesin AP65 decreased amounts of protein, which lowered levels of T. vaginalis adherence to VECs. We now perform antisense down-regulation of expression of the ap33 gene to evaluate and confirm a role for AP33 in adherence by T. vaginalis. We also used an established transfection system for heterologous expression of AP33 in T. foetus as an additional confirmatory approach.

RESULTS

We successfully select stable trichomonads with sense (S) and antisense (AS) plasmids. RT-PCR confirmed decreased amounts of ap33 mRNA in AS-transfected parasites, and decreased amounts of AP33 had no effect on growth and viability when compared to wild-type (wt) trichomonads. Immunoblots of proteins from AS-transfectants gave significant decreased amounts of functional AP33 capable of binding to host cells compared to wt- and S-transfected trichomonads. As expected, AS-transfectants had lower levels of adherence to VECs, which was related to reduction in surface expression of AP33. Stable expression of T. vaginalis AP33::HA fusion in T. foetus was confirmed by immunoblots and fluorescence. The episomally-expressed surface AP33::HA fusion increased adherence of trichomonads to human VECs, which was abrogated with anti-AP33 serum.

CONCLUSION

These results using both antisense inhibition of gene expression and AP33 synthesis and the heterologous expression of AP33 in T. foetus confirms a role for this protein as an adhesin in T. vaginalis.

The proteins secreted by Trichomonas vaginalis and vaginal epithelial cell response to secreted and episomally expressed AP65

We showed recently that contact of human vaginal epithelial cells (VECs) by Trichomonas vaginalis and incubation with trichomonad proteins in conditioned medium induced expression of VEC genes. We performed 2-D SDS-PAGE followed by MALDI-TOF to identify the major secreted proteins. Based on protein abundance and separation of spots in 2-D gels, 32 major secreted proteins were examined, which gave 19 proteins with accession numbers. These proteins included known secreted cysteine proteinases. In addition, other secreted proteins were enzymes of carbohydrate metabolism, adhesin protein AP65, heat shock proteins, thioredoxin reductase and coronins. We confirmed that the secreted trichomonad proteins induced expression of VEC genes, including interleukin 8 (IL-8), COX-2 and fibronectin. Purified AP65 added to VECs had a pronounced effect only on IL-8 gene expression, which was inhibited in the presence of 12G4 monoclonal antibody to AP65. Moreover, AP65 expressed episomally within epithelial cells was found to enhance the expression of IL-8 and COX-2. This may be the first report of analysis of the secreted proteins of T. vaginalis and of the host epithelial cell response to these proteins and to the prominent adhesin AP65.

Activation of Multifarious Transcription of an Adhesion Protein ap65-1 Gene by a Novel Myb2 Protein in the Protozoan Parasite Trichomonas vaginalis

Multifarious transcription of the adhesion protein ap65-1 gene in the human pathogen, Trichomonas vaginalis, is critically regulated by the coordination of two similar but opposite oriented DNA regulatory regions, MRE-1/MRE-2r and MRE-2f, both of which are binding sites for multiple Myb-like proteins. In the present study, MRE-1/MRE-2r was demonstrated to be composed of multiple overlapping promoter elements, among which the entire region is required for growth-related ap65-1 transcription, and the 5'-MRE-1 antagonizes the suppressive activity of the 3'-MRE-2r in iron-inducible transcription. The recombinant Myb2 protein derived from a previously identified myb2 gene was demonstrated to recognize distinct sequence contexts in MRE-2r and MRE-2f, whereas Myb2 in the nuclear lysate preferentially binds to MRE-2f to MRE-2r. Iron repletion resulted in persistent repression of the myb2 gene, and temporal activation/deactivation of Myb2 promoter entry, which was also activated by prolonged iron depletion. The hemagglutinintagged Myb2 when overexpressed during iron-depleted conditions facilitated basal and growth-related ap65-1 transcription to a level that was achieved in iron-replete cells, whereas ironinducible ap65-1 transcription was abolished with knockdown of Myb2. These findings demonstrated that Myb2 is involved in activation of growth-related and iron-inducible transcription of the ap65-1 gene, possibly through differential promoter selection in competition with other Myb proteins.

Adherence to human vaginal epithelial cells signals for increased expression of Trichomonas vaginalis genes

Host parasitism by Trichomonas vaginalis is complex, and the adhesion to vaginal epithelial cells (VECs) by trichomonads is preparatory to colonization of the vagina. Since we showed increased synthesis of adhesins after contact with VECs (A. F. Garcia, et al., Mol. Microbiol. 47:1207-1224, 2003) and more recently demonstrated up-regulated gene expression in VECs after parasite attachment (A. S. Kucknoor, et al., Cell. Microbiol. 7:887-897, 2005), we hypothesized that enhanced expression of adhesin and other genes would result from signaling of trichomonads following adherence. In order to identify the genes that are up-regulated, we constructed a subtraction cDNA library enriched for differentially expressed genes from the parasites that were in contact with the host cells. Thirty randomly selected cDNA clones representing the differentially regulated genes upon initial contact of parasites with host cells were sequenced. Several genes encoded functional proteins with specific functions known to be associated with colonization, such as adherence, change in morphology, and gene transcription and translation. Interestingly, genes unique to trichomonads with unknown functions were also up-regulated. Semiquantitative reverse transcription-PCR (RT-PCR) confirmed expression of select genes. An increased amount of protein was demonstrated by immunoblotting with monoclonal antibody. Finally, we showed the transcriptional regulation of some genes by iron by using RT-PCR. To our knowledge, this is the first report addressing the differential regulation of T. vaginalis genes immediately upon contact with VECs.

Trichomonas vaginalis adherence mediates differential gene expression in human vaginal epithelial cells

Trichomonas vaginalis, an ancient protist, colonizes the vaginal mucosa causing trichomonosis, a vaginitis that sometimes leads to severe health complications. Preparatory to colonization of the vagina is the adhesion to vaginal epithelial cells (VECs) by trichomonads. We hypothesized that VECs alter the gene expression to form a complex signalling cascade in response to trichomonal adherence. In order to identify the genes that are upregulated, we constructed a subtraction cDNA library after contact with parasites that is enriched for differentially expressed genes from the immortalized MS-74 VECs. Sixty cDNA clones were sequenced and to our knowledge for the first time, differentially regulated genes were identified in response to early trichomonal infection. The identified genes were found to encode functional proteins with specific functions associated with cell structure maintenance and extracellular matrix components, proinflammatory molecules and apoptosis. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) confirmed expression of selected genes. Further, cyclooxygenase 2 (COX-2) protein expression was analysed using Western blot and immunofluorescence assays. Data suggest that p38 mitogen-activated protein (MAP) kinase and tyrosine kinases play a role in COX-2 induction. Finally, T. vaginalis and Tritrichomonas foetus but not Pentatrichomonas hominis induce expression of COX-2. This is a first attempt at elucidating the basis of interaction of trichomonads with host cells and the corresponding host responses triggered by the parasites.

Trichomonas vaginalis polyamine metabolism is linked to host cell adherence and cytotoxicity

Trichomonas vaginalis secretes putrescine that is readily detected in vaginal secretions. We wanted to examine the effect of decreased putrescine synthesis by inhibition of ornithine decarboxylase (ODC) on T. vaginalis. One reason is because inhibition of Tritrichomonas foetus ODC results in growth arrest, destruction of hydrogenosomes, and decreased amounts of hydrogenosomal enzymes. Treatment of T. vaginalis T016 with >/=20 mM 1,4-diamino-2-butanone (DAB) to inhibit ODC resulted in growth arrest, which was reversed by addition of exogenous putrescine. No similar reversal of growth arrest was achieved with the polyamines spermine or spermidine or with iron. Electron microscopic examination of control versus DAB-treated trichomonads did not reveal any adverse effects on the number and integrity of hydrogenosomes. Further, the adhesins AP65, AP51, and AP33 mediating binding to immortalized vaginal epithelial cells (VECs) share identity to enzymes of the hydrogenosome organelle, and there was no difference in amounts of adhesins between control versus DAB-treated T. vaginalis parasites. Likewise, similar patterns and extent of fluorescence were evident for the prominent AP65 adhesin. Surprisingly, DAB treatment increased by 4- to 20-fold above untreated trichomonads handled identically the level of adherence mediated by adhesins. Interestingly, the enhanced attachment to VECs was reversed by exogenous putrescine added to DAB-treated trichomonads. Equally noteworthy was that DAB-treated T. vaginalis with enhanced adherence did not possess the previously reported ability to kill host cells in a contact-dependent fashion mediated by cysteine proteinases, and total cysteine proteinase activity patterns were identical between control and DAB-treated trichomonads. Overall, these data suggest that polyamine metabolism and secreted putrescine are linked to host cell adherence and cytotoxicity.

Heterologous expression in Tritrichomonas foetus of functional Trichomonas vaginalis AP65 adhesin

Background

Trichomonosis, caused by Trichomonas vaginalis, is the number one, nonviral sexually transmitted infection that has adverse consequences for the health of women and children. The interaction of T. vaginalis with vaginal epithelial cells (VECs), a step preparatory to infection, is mediated in part by the prominent surface protein AP65. The bovine trichomonad, Tritrichomonas foetus, adheres poorly to human VECs. Thus, we established a transfection system for heterologous expression of the T. vaginalis AP65 in T. foetus, as an alternative approach to confirm adhesin function for this virulence factor.

Results

In this study, we show stable transfection and expression of the T. vaginalis ap65 gene in T. foetus from an episomal pBS-ap65-neo plasmid. Expression of the gene and protein was confirmed by RT-PCR and immunoblots, respectively. AP65 in transformed T. foetus bound to host cells. Specific mAbs revealed episomally-expressed AP65 targeted to the parasite surface and hydrogenosome organelles. Importantly, surface-expression of AP65 in T. foetus paralleled increased levels of adherence of transfected bovine trichomonads to human VECs.

Conclusion

The T. vaginalis AP65 adhesin was stably expressed in T. foetus, and the data obtained using this heterologous system strongly supports the role of AP65 as a prominent adhesin for T. vaginalis. In addition, the heterologous expression in T. foetus of a T. vaginalis gene offers an important, new approach for confirming and characterizing virulence factors.