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

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.

Effect of the silencing of the Ehcp112 gene on the in vitro virulence of Entamoeba histolytica

Background

Entamoeba histolytica is an intestinal protozoan parasite that causes amoebiasis in humans, affecting up to 50 million people worldwide each year and causing 40,000 to 100,000 deaths annually. EhCP112 is a cysteine proteinase of E. histolytica able to disrupt cell monolayers and digest extracellular matrix proteins, it is secreted by trophozoites and it can be active in a wide range of temperature and pH. These characteristics have encouraged the use of EhCP112 in the design and production of possible vaccines against amoebiasis, obtaining promising results. Nevertheless, we have no conclusive information about the role of EhCP112 in the E. histolytica pathogenesis.

Methods

A set of three specific siRNA sequences were used to silence the Ehcp112 gene via the soaking system. Silencing was evaluated by Western blot using an antibody against the EhCP112 recombinant protein. Finally, we analyzed the protease activity, the phagocytosis rate and the ability to destroy MDCK cells of the EhCP112-silenced trophozoites.

Results

The highest silencing effect on EhCP112 was detected at 16 h of treatment; time enough to perform the in vitro virulence assays, which showed that EhCP112 silencing produces a significant reduction in cytolysis and phagocytosis of target cells, indicating the participation of this proteinase in these events.

Conclusions

EhCP112 is involved in the in vitro virulence of E. histolytica.

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.

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.

Treatment of infections caused by metronidazole-resistant Trichomonas vaginalis

Infections with the sexually transmitted protozoan Trichomonas vaginalis are usually treated with metronidazole, a 5-nitroimidazole drug derived from the antibiotic azomycin. Metronidazole treatment is generally efficient in eliminating T. vaginalis infection and has a low risk of serious side effects. However, studies have shown that at least 5% of clinical cases of trichomoniasis are caused by parasites resistant to the drug. The lack of approved alternative therapies for T. vaginalis treatment means that higher and sometimes toxic doses of metronidazole are the only option for patients with resistant disease. Clearly, studies of the treatment and prevention of refractory trichomoniasis are essential. This review describes the mechanisms of metronidazole resistance in T. vaginalis and provides a summary of trichomonicidal and vaccine candidate drugs.

Trichomoniasis in pregnant human immunodeficiency virus-infected and human immunodeficiency virus-uninfected congolese women: prevalence, risk factors, and association with low birth weight

OBJECTIVE

We sought to assess the prevalence of and risk factors for vaginal trichomoniasis in human immunodeficiency virus-infected and human immunodeficiency virus-uninfected pregnant Congolese women and its relationship to pregnancy outcomes.

STUDY DESIGN

We performed a nested case-control study of 215 infected and 206 uninfected mothers who responded to questionnaires, underwent sexually transmitted disease testing (including culture for trichomoniasis shortly after delivery), and underwent assessment of infant outcomes. Maternal variables and birth outcomes were assessed according to presence or absence of trichomoniasis and human immunodeficiency virus.

RESULTS

Trichomoniasis was present in 18.6% of human immunodeficiency virus-positive and 10.2% of human immunodeficiency virus-negative women, respectively (odds ratio, 2.0; 95% confidence interval, 1.1-3.6), and was significantly associated with low birth weight (odds ratio, 2.4; 95% confidence interval, 1.2-4.5). In multivariate analyses trichomoniasis remained associated with low birth weight, and adjustments were made for other risk factors associated with low birth weight.

CONCLUSION

These findings suggest an association between trichomoniasis and low birth weight independent of human immunodeficiency virus infection and other risk factors. Further studies are needed to assess the impact of antenatal screening and treatment for trichomoniasis on pregnancy outcomes.

Trichomonad invasion of the mucous layer requires adhesins, mucinases, and motility

BACKGROUND/OBJECTIVE

Trichomonas vaginalis, the causal agent of trichomonosis, is a flagellated parasitic protozoan that colonises the epithelial cells of the human urogenital tract. The ability of T vaginalis to colonise this site is in part a function of its ability to circumvent a series of non-specific host defences including the mucous layer covering epithelial cells at the site of infection. Mucin, the framework molecule of mucus, forms a lattice structure that serves as a formidable physical barrier to microbial invasion. The mechanism by which trichomonads traverse the mucous covering is unknown. Proteolytic degradation of mucin, however, may provide for a mechanism to penetrate this layer. The goal, therefore, was to determine how trichomonads cross through a mucous layer.

METHODS

Secreted trichomonad proteinases were analysed for mucinase activity by mucin substrate-sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The importance of trichomonad mucinases for traversing the mucous layer was examined on an artificial mucin layer in invasion chambers. Adherence to mucin and tissue culture cells was measured using a microtitre plate assay.

RESULTS

Trichomonad isolate 24402 secreted five proteinases when incubated in PBS. All five proteinases were shown to possess mucinase activity. These mucinases were able to degrade bovine submaxillary mucin and to a lesser extent porcine stomach mucin. These enzymes were active over a pH range of 4.5-7.0 and were inhibited with cysteine proteinase inhibitors. Furthermore, T vaginalis was shown to bind to mucin possibly via a lectin-like adhesin. Adherence to mucin was increased threefold when parasites were grown in iron deficient medium. Adherence to soluble mucin prevented attachment to HeLa cells. Proteinase activity, adherence, and motility were required for trichomonads to traverse a mucin layer in vitro.

CONCLUSIONS

These results show that trichomonads can traverse the mucous barrier first by binding mucin followed by its proteolytic degradation. The data further underscore the importance of trichomonad proteinases in the pathogenesis of trichomonosis. Finally, this study suggests that interference with trichomonad mucin receptors and proteinases may be a strategy to prevent colonisation by this parasite.