Extensive genetic diversity, unique population structure and evidence of genetic exchange in the sexually transmitted parasite Trichomonas vaginalis

Microbial Matryoshka: Addressing the Relationship between Pathogenic Flagellated Protozoans and Their RNA Viral Endosymbionts (Family Totiviridae)

Three genera of viruses of the family Totiviridae establish endosymbiotic associations with flagellated protozoa responsible for parasitic diseases of great impact in the context of One Health. Giardiavirus, Trichomonasvirus, and Leishmaniavirus infect the protozoa Giardia sp., Trichomonas vaginalis, and Leishmania sp., respectively. In the present work, we review the characteristics of the endosymbiotic relationships established, the advantages, and the consequences caused in mammalian hosts. Among the common characteristics of these double-stranded RNA viruses are that they do not integrate into the host genome, do not follow a lytic cycle, and do not cause cytopathic effects. However, in cases of endosymbiosis between Leishmaniavirus and Leishmania species from the Americas, and between Trichomonasvirus and Trichomonas vaginalis, it seems that it can alter their virulence (degree of pathogenicity). In a mammalian host, due to TLR3 activation of immune cells upon the recognition of viral RNA, uncontrolled inflammatory signaling responses are triggered, increasing pathological damage and the risk of failure of conventional standard treatment. Endosymbiosis with Giardiavirus can cause the loss of intestinal adherence of the protozoan, resulting in a benign disease. The current knowledge about viruses infecting flagellated protozoans is still fragmentary, and more research is required to unravel the intricacies of this three-way relationship. We need to develop early and effective diagnostic methods for further development in the field of translational medicine. Taking advantage of promising biotechnological advances, the aim is to develop ad hoc therapeutic strategies that focus not only on the disease-causing protozoan but also on the virus.

Trichomonas vaginalis extracellular vesicles up-regulate and directly transfer adherence factors promoting host cell colonization

Trichomonas vaginalis, a common sexually transmitted parasite that colonizes the human urogenital tract, secretes extracellular vesicles (TvEVs) that are taken up by human cells and are speculated to be taken up by parasites as well. While the crosstalk between TvEVs and human cells has led to insight into host:parasite interactions, roles for TvEVs in infection have largely been one-sided, with little known about the effect of TvEV uptake by T. vaginalis. Approximately 11% of infections are found to be coinfections of multiple T. vaginalis strains. Clinical isolates often differ in their adherence to and cytolysis of host cells, underscoring the importance of understanding the effects of TvEV uptake within the parasite population. To address this question, our lab tested the ability of a less adherent strain of T. vaginalis, G3, to take up fluorescently labeled TvEVs derived from both itself (G3-EVs) and TvEVs from a more adherent strain of the parasite (B7RC2-EVs). Here, we showed that TvEVs generated from the more adherent strain are internalized more efficiently compared to the less adherent strain. Additionally, preincubation of G3 parasites with B7RC2-EVs increases parasite aggregation and adherence to host cells. Transcriptomics revealed that TvEVs up-regulate expression of predicted parasite membrane proteins and identified an adherence factor, heteropolysaccharide binding protein (HPB2). Finally, using comparative proteomics and superresolution microscopy, we demonstrated direct transfer of an adherence factor, cadherin-like protein, from TvEVs to the recipient parasite's surface. This work identifies TvEVs as a mediator of parasite:parasite communication that may impact pathogenesis during mixed infections.

Imidazole Carbamates as a Promising Alternative for Treating Trichomoniasis: In Vitro Effects on the Growth and Gene Expression of Trichomonas vaginalis

Metronidazole (MTZ) is the most common drug used against Trichomonas vaginalis (T. vaginalis) infections; however, treatment failures and high rates of recurrence of trichomoniasis have been reported, suggesting the presence of resistance in T. vaginalis to MTZ. Therefore, research into new therapeutic options against T. vaginalis infections has become increasingly urgent. This study investigated the trichomonacidal activity of a series of five imidazole carbamate compounds (AGR-1, AGR-2, AGR-3, AGR-4, and AGR-5) through in vitro susceptibility assays to determine the IC50 value of each compound. All five compounds demonstrated potent trichomonacidal activity, with IC50 values in the nanomolar range and AGR-2 being the most potent (IC50 400 nM). To gain insight into molecular events related to AGR-induced cell death in T. vaginalis, we analyzed the expression profiles of some metabolic genes in the trophozoites exposed to AGR compounds and MTZ. It was found that both AGR and MTZ compounds reduced the expression of the glycolytic genes (CK, PFK, TPI, and ENOL) and genes involved in metabolism (G6PD, TKT, TALDO, NADHOX, ACT, and TUB), suggesting that disturbing these key metabolic genes alters the survival of the T. vaginalis parasite and that they probably share a similar mechanism of action. Additionally, the compounds showed low cytotoxicity in the Caco-2 and HT29 cell lines, and the results of the ADMET analysis indicated that these compounds have pharmacokinetic properties similar to those of MTZ. The findings offer significant insights that can serve as a basis for future in vivo studies of the compounds as a potential new treatment against T. vaginalis.

Presence of CRISPR CAS-Like Sequences as a Proposed Mechanism for Horizontal Genetic Exchanges between Trichomonas vaginalis and Its Associated Virus: A Comparative Genomic Analysis with the First Report of a Putative CRISPR CAS Structures in Eukaryotic Cells

Introduction

Trichomonas vaginalis genome is among the largest genome size and coding capacities. Combinations of gene duplications, transposon, repeated sequences, and lateral gene transfers (LGTs) have contributed to the unexpected large genomic size and diversity. This study is aimed at investigating genomic exchange and seeking for presence of the CRISPR CAS system as one of the possible mechanisms for some level of genetic exchange. Material and Methods. In this comparative analysis, 398 publicly available Trichomonas vaginalis complete genomes were investigated for the presence of CRISPR CAS. Spacer sequences were also analyzed for their origin using BLAST.

Results

We identified a CRISPR CAS (Cas3). CRISPR spacers are highly similar to transposable genetic elements such as viruses of protozoan parasites, especially megavirals, some transposons, and, interestingly, papillomavirus and HIV-1 in a few cases. Discussion. There is a striking similarity between the prokaryotes/Archaean CRISPR and what we find as eukaryotic CRISPR. About 5-10% of the 398 T. vaginalis possess a CRISPR structure.

Conclusion

According to sequences and their organization, we assume that these repeated sequences and spacer, along with their mentioned features, could be the eukaryotic homolog of prokaryotes and Archaean CRISPR systems and may involve in a process similar to the CRISPR function.

Trichomonas vaginalis adherence phenotypes and extracellular vesicles impact parasite survival in a novel in vivo model of pathogenesis

Trichomonas vaginalis is a human infective parasite responsible for trichomoniasis-the most common, non-viral, sexually transmitted infection worldwide. T. vaginalis resides exclusively in the urogenital tract of both men and women. In women, T. vaginalis has been found colonizing the cervix and vaginal tract while in men it has been identified in the upper and lower urogenital tract and in secreted fluids such as semen, urethral discharge, urine, and prostatic fluid. Despite the over 270 million cases of trichomoniasis annually worldwide, T. vaginalis continues to be a highly neglected organism and thus poorly studied. Here we have developed a male mouse model for studying T. vaginalis pathogenesis in vivo by delivering parasites into the murine urogenital tract (MUT) via transurethral catheterization. Parasite burden was assessed ex-vivo using a nanoluciferase-based gene expression assay which allowed quantification of parasites pre- and post-inoculation. Using this model and read-out approach, we show that T. vaginalis can be found within MUT tissue up to 72 hrs post-inoculation. Furthermore, we also demonstrate that parasites that exhibit increased parasite adherence in vitro also have higher parasite burden in mice in vivo. These data provide evidence that parasite adherence to host cells aids in parasite persistence in vivo and molecular determinants found to correlate with host cell adherence in vitro are applicable to infection in vivo. Finally, we show that co-inoculation of T. vaginalis extracellular vesicles (TvEVs) and parasites results in higher parasite burden in vivo. These findings confirm our previous in vitro-based predictions that TvEVs assist the parasite in colonizing the host. The establishment of this pathogenesis model for T. vaginalis sets the stage for identifying and examining parasite factors that contribute to and influence infection outcomes.

Genetic Variability of the Internal Transcribed Spacer and Pyruvate:Ferredoxin Oxidoreductase Partial Gene of Trichomonas vaginalis from Female Patients

In the present study, we evaluated the genetic variability of the internal transcribed spacer (ITS) region and the pyruvate:ferredoxin oxidoreductase (pfor) A gene of Trichomonas vaginalis from female patients and its possible implications in the host-parasite relationship. Phylogenetic and genetics of populations analyses were performed by analyzing sequences of the ITS region and partial pfor A gene of clinical samples with T. vaginalis, as previously documented. Alignments of protein sequences and prediction of three-dimensional structure were also performed. Although no correlation between the main clinical characteristics of the samples and the results of phylogeny was found, a median-joining analysis of ITS haplotypes showed two main clusters. Also, pfor A, due to its phylogenetic divergence, could be used as a marker to confirm the genus and species of trichomonads. Alignment of protein sequences and prediction of three-dimensional structure showed that PFOR A had a highly conserved structure with two synonymous mutations in the PFOR domain, substituting a V for a G or a S for a P. Our results suggest that the role of genetic variability of PFOR and ITS may not be significant in the symptomatology of this pathogen; however, their utility as genus and species markers in trichomonads is promising.

Identification of Trichomonas vaginalis 5-Nitroimidazole Resistance Targets

Trichomonas vaginalis is the most common non-viral sexually transmitted infection. 5-nitroimidazoles are the only FDA-approved medications for T. vaginalis treatment. However, 5-nitroimidazole resistance has been increasingly recognized and may occur in up to 10% of infections. We aimed to delineate mechanisms of T. vaginalis resistance using transcriptome profiling of metronidazole (MTZ)-resistant and sensitive T. vaginalis clinical isolates. In vitro, 5-nitroimidazole susceptibility testing was performed to determine minimum lethal concentrations (MLCs) for T. vaginalis isolates obtained from women who had failed treatment (n = 4) or were successfully cured (n = 4). RNA sequencing, bioinformatics, and biostatistical analyses were performed to identify differentially expressed genes (DEGs) in the MTZ-resistant vs. sensitive T. vaginalis isolates. RNA sequencing identified 304 DEGs, 134 upregulated genes and 170 downregulated genes in the resistant isolates. Future studies with more T. vaginalis isolates with a broad range of MLCs are needed to determine which genes may represent the best alternative targets in drug-resistant strains.

Prevalence and Genotype of Trichomonas vaginalis among Men in Xinxiang City, Henan Province, China

Trichomonas vaginalis (T. vaginalis) could cause trichomoniasis through sexual transmission, which was globally distributed. In this study, the prevalence and phylogenetic analyses of T. vaginalis among men in Xinxiang were conducted. From October 2018 to December 2019, a total of 634 male clinical samples were collected, including 254 samples of semen, 43 samples of prostate fluid, and 337 samples of urine. These samples were examined by nested PCR and a total of 32 (5.05%) T. vaginalis-positive samples were detected. Among these samples, the positive rates of T. vaginalis in semen, prostate fluid, and urine were 7.87% (20/254), 4.65% (2/43), and 2.97% (10/337), respectively. Three actin genes were successfully isolated and sequenced from the 32 positive DNA samples, and the analysis of the sequence and phylogenetic tree showed that the three actin gene sequences exhibited 99.7%-100% homology to the published actin gene sequence (EU076580) in NCBI, and the T. vaginalis strains in the three positive samples were identified as genotype E. Our results demonstrate a notable genotype of T. vaginalis in the male population and provide insight into the performance of these genetic markers in the molecular epidemiology of trichomoniasis. However, further studies are needed to research the association between the genotype and the pathogenicity of T. vaginalis.

Molecular characterization of Trichomonas infections in women of Ilam City, southwestern Iran

Trichomoniasis is a sexually transmitted infection (STI) caused by the flagellated protozoan Trichomonas vaginalis. Little information is available on the epidemiology and genetic diversity of T. vaginalis in Ilam City, southwestern Iran. A descriptive cross-sectional investigation was carried out between July 2017 and December 2018 on the suspected women patients referred to eight gynecology clinics of Ilam City for probable Trichomonas infection. They were undergone a set of clinical, parasitological, and molecular examinations. During clinical consultation, posterior vaginal fornix secretions and urine samples were gathered from the participants. For the reasons such as physical conditions and cultural and religious constraints, most of participating women, especially young girls due to their virginity, preferred to give urine samples instead of vaginal discharge. The presence of Trichomonas was diagnosed by microscopic examination and molecular detection using conventional PCR targeting ITS1-rDNA. A total of 1765 suspected individuals were examined clinically via vaginal secretions (495 specimens) and urine samples (1270 specimens). Of them, 21 (1.18%) cases, including 13 vaginal secretions and 8 urine samples, were positive for Trichomonas infection by microscopy. Slightly more than half of the patients (11/21, 52.4%) complained of vulvar itching, burning, and frequent urination. Cervical lesions, patchy erythema, and vaginal discharge were recorded in 28.6%, 23.8%, and 19% of the patients respectively. All patients with positive microscopic identification were confirmed by amplification of 450-bp fragment of ITS1-rDNA. Phylogenetic analysis revealed a high rate of genetic homogeneity in which all our isolates together with homologous sequences from China, Philippines, Austria, and USA were clustered within the same clade. A statistically significant relationship was recorded between the patients positive for trichomoniasis and the presence of chronic disease (e.g., diabetes, immune system deficiency).

Involvement of Macrophages in Proliferation of Prostate Cancer Cells Infected with Trichomonas vaginalis

Macrophages play a key role in chronic inflammation, and are the most abundant immune cells in the tumor microenvironment. We investigated whether an interaction between inflamed prostate cancer cells stimulated with Trichomonas vaginalis and macrophages stimulates the proliferation of the cancer cells. Conditioned medium was prepared from T. vaginalis-infected (TCM) and uninfected (CM) mouse prostate cancer (PCa) cell line (TRAMP-C2 cells). Thereafter conditioned medium was prepared from macrophages (J774A.1 cell line) after incubation with CM (MCM) or TCM (MTCM). When TRAMP-C2 cells were stimulated with T. vaginalis, protein and mRNA levels of CXCL1 and CCL2 increased, and migration of macrophages toward TCM was more extensive than towards CM. Macrophages stimulated with TCM produced higher levels of CCL2, IL-6, TNF-α, their mRNAs than macrophages stimulated with CM. MTCM stimulated the proliferation and invasiveness of TRAMP-C2 cells as well as the expression of cytokine receptors (CCR2, GP130, CXCR2). Importantly, blocking of each cytokine receptors with anti-cytokine receptor antibody significantly reduced the proliferation and invasiveness of TRAMP-C2 cells. We conclude that inflammatory mediators released by TRAMP-C2 cells in response to infection by T. vaginalis stimulate the migration and activation of macrophages and the activated macrophages stimulate the proliferation and invasiveness of the TRAMP-C2 cells via cytokine-cytokine receptor binding. Our results therefore suggested that macrophages contribute to the exacerbation of PCa due to inflammation of prostate cancer cells reacted with T. vaginalis.

High Co-Infection Rate of Trichomonas vaginalis and Candidatus Mycoplasma Girerdii in Gansu Province, China

Trichomonas vaginalis (Tv) is a flagellated protist parasite that infects the human urogenital tract. The symbiotic relationship between Tv and Mycoplasma hominis has been reported. Recent studies have identified a new Mycoplasma strain, Candidatus Mycoplasma girerdii (Ca. M. girerdii), present in the vaginal secretions of women and have shown that this strain may be related to trichomoniasis. Here, we evaluated the presence of Tv, M. hominis and Ca. M. girerdii in 312 clinical samples from adult women diagnosed with vaginitis in Zhangye, Gansu province, China. Among these samples, 94, 153, and 48 were Tv, M. hominis and Ca. M. girerdii positive, respectively. Moreover, Tv was highly frequent in 17–30-year-old women in this region. Forty samples (83.3%) positive for Ca. M. girerdii were also positive for Tv. Six Tv isolates were successfully cultured, including five isolates that showed symbiotic relationships with Mycoplasma. This is the first report to evaluate the genetic characteristics of Ca. M. girerdii in China and may therefore provide insights into the effects of Ca. M. girerdii on the reproductive health of women.

Distribution of genotypes in relation to metronidazole susceptibility patterns in Trichomonas vaginalis isolated from South African pregnant women

Reports on metronidazole resistance of Trichomonas vaginalis strains have been on the increase. This study investigated the in vitro metronidazole resistance patterns in T. vaginalis isolates obtained from South African pregnant women and the genotypes of these isolates. This study included 362 pregnant women recruited from a hospital in Durban, South Africa. The women provided self-collected vaginal swabs for the detection of T. vaginalis by culture in Diamonds media. Cultured isolates were then subjected to anaerobic susceptibility assays to metronidazole. For the genotyping assays, the actin gene was digested by HindII, MseI, and RsaI. The banding patterns obtained after digestion was used to determine the genotypes. A total of 21/362 (5.8%) pregnant women tested positive for T. vaginalis infection. Of the 21 T. vaginalis isolates tested for metronidazole susceptibility, 9.5% (2/21) had a minimum inhibitory concentration (MIC) of 4 μg/ml (resistant), 38.1% (8/21) had a MIC of 2 μg/ml (intermediate), and 52.4% (11/21) had a MIC ≤ 1 μg/ml (susceptible). The dominant genotype that was identified across the isolates was genotype G. There was no correlation between genotype harboured and metronidazole susceptibility patterns. In this study, resistance to metronidazole was observed in clinical isolates of T. vaginalis. This study did not find a correlation between genotype harboured and metronidazole susceptibility patterns. Despite the lack of association, our study provides data on an area of research that is currently lacking in our setting.

Viruses of protozoan parasites and viral therapy: Is the time now right?

Infections caused by protozoan parasites burden the world with huge costs in terms of human and animal health. Most parasitic diseases caused by protozoans are neglected, particularly those associated with poverty and tropical countries, but the paucity of drug treatments and vaccines combined with increasing problems of drug resistance are becoming major concerns for their control and eradication. In this climate, the discovery/repurposing of new drugs and increasing effort in vaccine development should be supplemented with an exploration of new alternative/synergic treatment strategies. Viruses, either native or engineered, have been employed successfully as highly effective and selective therapeutic approaches to treat cancer (oncolytic viruses) and antibiotic-resistant bacterial diseases (phage therapy). Increasing evidence is accumulating that many protozoan, but also helminth, parasites harbour a range of different classes of viruses that are mostly absent from humans. Although some of these viruses appear to have no effect on their parasite hosts, others either have a clear direct negative impact on the parasite or may, in fact, contribute to the virulence of parasites for humans. This review will focus mainly on the viruses identified in protozoan parasites that are of medical importance. Inspired and informed by the experience gained from the application of oncolytic virus- and phage-therapy, rationally-driven strategies to employ these viruses successfully against parasitic diseases will be presented and discussed in the light of the current knowledge of the virus biology and the complex interplay between the viruses, the parasite hosts and the human host. We also highlight knowledge gaps that should be addressed to advance the potential of virotherapy against parasitic diseases.

Genotypic Variation in Trichomonas vaginalis Detected in South African Pregnant Women

Background

Trichomonas vaginalis is the causative agent of trichomoniasis. The genetic characterisation of T. vaginalis isolates reveals significant genetic diversity in this organism. Data on the prevalence of different genotypes of T. vaginalis in South African populations is lacking. This study investigated the diversity of T. vaginalis in a pregnant population in South Africa.

Methods

In this study, 362 pregnant women from the King Edward VIII Hospital in Durban, South Africa, provided vaginal swabs to be tested for the presence of T. vaginalis. T. vaginalis was detected using the TaqMan assay using commercially available primers and probes specific for this protozoan (Pr04646256_s1). The actin gene from T. vaginalis was amplified with gene-specific primers. The actin amplicons were digested with HindII, MseI, and RsaI, and the banding patterns were compared across the three digests for assignment of genotypes. Phylogenetic analysis was conducted using MEGA.

Results

The prevalence of T. vaginalis in the study population was 12.9% (47/362). Genotype G was the most frequent genotype in our study population. Genotypes H and I were detected in one sample each. According to the multiple sequence alignments and phylogenetic analysis, a level of diversity was observed across and within genotypes. Four different single-nucleotide changes in the actin gene were detected. Sample TV358 (H genotype) contained a single amino acid substitution from glutamine to lysine. Sample TV184 (G genotype) contained a single amino acid substitution from glutamic acid to arginine. Sample TV357 (G genotype) contained two amino acid substitutions, arginine to leucine and glycine to aspartic acid.

Conclusion

Three different genotypes were observed in the pregnant population. Diversity was observed across and within genotypes. The observed diversity can be challenging for future vaccine design and development of antigen-based rapid diagnostic tests for trichomoniasis.

A systematic review of the literature on mechanisms of 5-nitroimidazole resistance in Trichomonas vaginalis

BACKGROUND

Trichomonas vaginalis is the most common non-viral sexually transmitted infection. 5-Nitroimidazoles [metronidazole (MTZ) and tinidazole (TDZ)] are FDA-approved treatments. To better understand treatment failure, we conducted a systematic review on mechanisms of 5-nitroimidazole resistance.

METHODS

PubMed, ScienceDirect and EMBASE databases were searched using keywords Trichomonas vaginalis, trichomoniasis, 5-nitroimidazole, metronidazole, tinidazole and drug resistance. Non-English language articles and articles on other treatments were excluded.

RESULTS

The search yielded 606 articles, of which 550 were excluded, leaving 58 articles. Trichomonas vaginalis resistance varies and is higher with MTZ (2.2-9.6%) than TDZ (0-2%). Resistance can be aerobic or anaerobic and is relative rather than absolute. Differential expression of enzymes involved in trichomonad energy production and antioxidant defenses affects 5-nitroimidazole drug activation; reduced expression of pyruvate:ferredoxin oxidoreductase, ferredoxin, nitroreductase, hydrogenase, thioredoxin reductase and flavin reductase are implicated in drug resistance. Trichomonas vaginalis infection with Mycoplasma hominis or T. vaginalis virus has also been associated with resistance. Trichomonas vaginalis has two genotypes, with greater resistance seen in type 2 (vs type 1) populations.

DISCUSSION

5-Nitroimidazole resistance results from differential expression of enzymes involved in energy production or antioxidant defenses, along with genetic mutations in the T. vaginalis genome. Alternative treatments outside of the 5-nitroimidazole class are needed.

Molecular characterisation of Trichomonas vaginalis isolates in Southwest Turkey with multilocus sequence typing and genetic structure analysis in relation to different countries

Trichomonas vaginalis, a flagellated protozoan parasite, is among the most common sexually transmitted pathogens in the world. The present study aimed to identify the genetic profiles of T. vaginalis in the southwest of Turkey with multilocus sequence typing (MLST) and to analyse the genetic structure of the parasite in a collection of isolates from different countries. The study included 27 T. vaginalis isolates from symptomatic females in Aydin, Turkey. Seven housekeeping genes of T. vaginalis were partially amplified and sequenced after genomic DNA extraction from in vitro cultures. The allele profiles and sequence types (STs) of the isolates were determined by using the MLST database (https://pubmlst.org/tvaginalis). The genetic structure and differentiation of the parasite were analysed in relation to findings from other countries by assembling the available MLST sequences. When referred to the database, a total of 22 STs, including 18 new STs were found; besides, there were two new allele types. The genetic analysis of MLST data demonstrated the presence of two main genetic structures: Type I and Type II. In addition, the neighbor-joining method also revealed that the isolates were clustered into two groups. The genetic types distributed almost equally in the Netherlands and the USA, however, the predominance of Type I was noted in Turkey and the UK. The genetic differentiation among four countries was significant (p < .05), the gene flow was relatively high between the Netherlands and the USA, in contrast to Turkey. Finally, genetic variations were originated within populations (93.8%) rather than among populations (6.2%). In conclusion, we studied the genetic diversity of T. vaginalis isolates with MLST in the southwest of Turkey and showed the origin of genetic differentiation of the parasite among different countries. The presentation of MLST profiles and genetic variance of T. vaginalis isolates will contribute to the development of new diagnostic and treatment options for the parasite.

Population structure and genetic diversity of Trichomonas vaginalis clinical isolates in Australia and Ghana

Population genetic studies of Trichomonas vaginalis have detected high genetic diversity associated with phenotypic differences in clinical presentations. In this study, microscopy and next generation-multi-locus sequence typing (NG-MLST) were used to identify and genetically characterise T. vaginalis isolates from patients in Australia and Ghana. Seventy-one polymorphic nucleotide sites, 36 different alleles, 48 sequence types, 24 of which were novel, were identified among 178 isolates, revealing a geneticallly diverse T. vaginalis population. Polymorphism was found at most loci, clustering genotypes into eight groups among both Australian and Ghanaian isolates, although there was some variation between countries. The number of alleles for each locus ranged from two to nine. Study results confirmed geographic expansion and diversity of the T. vaginalis population. Two-type populations in almost equal frequencies and a third unassigned group were identified in this study. Linkage disequilibrium was observed, suggesting T. vaginalis population is highly clonal. Multillocus disequilibrium was observed even when analysing clades separately, as well as widespread clonal genotypes, suggesting that there is no evidence of recent recombination. A more comprehensive study to assess the extent of genetic diversity and population structure of T. vaginalis and their potential impact on varied pathology observed among infected individuals is recommended.

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.

'Meiotic genes' are constitutively expressed in an asexual amoeba and are not necessarily involved in sexual reproduction

The amoebae (and many other protists) have traditionally been considered as asexual organisms, but suspicion has been growing that these organisms are cryptically sexual or are at least related to sexual lineages. This contention is mainly based on genome studies in which the presence of 'meiotic genes' has been discovered. Using RNA-seq (next-generation shotgun sequencing, identifying and quantifying the RNA species in a sample), we have found that the entire repertoire of meiotic genes is expressed in exponentially growing Acanthamoeba and we argue that these so-called meiotic genes are involved in the related process of homologous recombination in this amoeba. We contend that they are only involved in meiosis in other organisms that indulge in sexual reproduction and that homologous recombination is important in asexual protists as a guard against the accumulation of mutations. We also suggest that asexual reproduction is the ancestral state.

Prevalence and Correlates of Trichomonas vaginalis Infection Using the OSOM Rapid Point-of-Care Test Among Women Attending New York City Sexual Health Clinics, May-July 2016

Using electronic medical record data and OSOM Trichomonas Rapid Tests, Trichomonas vaginalis prevalence was 9.3% among women attending New York City sexual health clinics in 2016. Positivity was associated with black race (adjusted odds ratios 3.73; 95% confidence interval, 1.9-7.1) and vaginal pH of 4.5 or greater (adjusted odds ratios, 1.9; 95% CI, 1.2-3.3).

Trichomonas vaginalis virus: a review of the literature

Trichomonas vaginalis (TV) is a parasitic protozoan responsible for the sexually transmitted infection trichomoniasis. Trichomonas vaginalis virus (TVV) is a nonsegmented, 4.5-5 kbp, double-stranded RNA virus, from the Totiviridae family, which inhabits TV. A capsid protein consisting of 120 subunits is covered in channels aiding in RNA release. TVV is closely associated with the Golgi complex and is transmitted vertically. TVV has four subspecies, TVV1, TVV2, TVV3, and TVV4. The clinical significance of TVV and its effect on the pathogenicity of TV is not well known. We performed a systematic review of the literature on TVV to better understand its clinical significance and its role in the pathogenesis of TV.

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.

Genetic Indicators of Drug Resistance in the Highly Repetitive Genome of Trichomonas vaginalis

Trichomonas vaginalis, the most common nonviral sexually transmitted parasite, causes ∼283 million trichomoniasis infections annually and is associated with pregnancy complications and increased risk of HIV-1 acquisition. The antimicrobial drug metronidazole is used for treatment, but in a fraction of clinical cases, the parasites can become resistant to this drug. We undertook sequencing of multiple clinical isolates and lab derived lines to identify genetic markers and mechanisms of metronidazole resistance. Reduced representation genome sequencing of ∼100 T. vaginalis clinical isolates identified 3,923 SNP markers and presence of a bipartite population structure. Linkage disequilibrium was found to decay rapidly, suggesting genome-wide recombination and the feasibility of genetic association studies in the parasite. We identified 72 SNPs associated with metronidazole resistance, and a comparison of SNPs within several lab-derived resistant lines revealed an overlap with the clinically resistant isolates. We identified SNPs in genes for which no function has yet been assigned, as well as in functionally-characterized genes relevant to drug resistance (e.g., pyruvate:ferredoxin oxidoreductase). Transcription profiles of resistant strains showed common changes in genes involved in drug activation (e.g., flavin reductase), accumulation (e.g., multidrug resistance pump), and detoxification (e.g., nitroreductase). Finally, we identified convergent genetic changes in lab-derived resistant lines of Tritrichomonas foetus, a distantly related species that causes venereal disease in cattle. Shared genetic changes within and between T. vaginalis and Tr. foetus parasites suggest conservation of the pathways through which adaptation has occurred. These findings extend our knowledge of drug resistance in the parasite, providing a panel of markers that can be used as a diagnostic tool.

Prevalence and genetic diversity of Trichomonas vaginalis clinical isolates in a targeted population in Xinxiang City, Henan Province, China

Background

Trichomonas vaginalis (TV) is a protozoan parasite that causes trichomoniasis, a sexually transmitted disease, worldwide. In this study, we investigated the prevalence and genetic characterization of T. vaginalis and contrasted the most prevalent strains of T. vaginalis isolated from Xinxiang City, Henan Province, China.

Results

In Xinxiang from September 2015 to September 2017, a total of 267 (1.64%, 95% confidence interval, CI: 1.45–1.85) clinical T. vaginalis-positive samples from vaginal secretions were observed by wet mount microscopy from 16,294 women with some clinical symptoms of trichomoniasis. We found that trichomoniasis frequently occurred in the 21- to 40-year-old age group and in winter. After the 267 clinical T. vaginalis positive samples were cultured, 68 isolates of T. vaginalis were harvested and identified as genotype E (58.82%), H (17.65%), mixed 1 (17.65%) and mixed 2 (5.88%) using a sensitive and reliable polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) typing method on the actin gene. The phylogenetic diversity analysis showed that the genotype E samples fell within a separate clade compared to the other T. vaginalis isolates, while the samples of the genotype H separated into two clades.

Conclusions

Our results demonstrate a notable gene polymorphism of clinical isolates from the targeted population and provide insight into the performance of these genetic markers in the molecular epidemiology of trichomoniasis. However, further studies are needed to clarify the association between a certain genotype and the pathogenicity of T. vaginalis.

Humoral and T cell-mediated immune response against trichomoniasis

Trichomonas vaginalis (T. vaginalis) infection leads to the synthesis of specific antibodies in the serum and local secretions. The profile of T. vaginalis-specific antibodies and T cell-mediated immune responses may influence the outcome of infection, towards parasite elimination, persistence or pathological reactions. Studies have indicated that Th1-, Th17- and Th22 cell-related cytokines may be protective or pathogenic, whereas Th2- and Treg cell-related cytokines can exert anti-inflammatory effects during T. vaginalis infection. A number of T. vaginalis-related components such as lipophosphoglycan (TvLPG), α-actinin, migration inhibitory factor (TvMIF), pyruvate:ferredoxin oxidoreductase (PFO), legumain-1 (TvLEGU-1), adhesins and cysteine proteases lead to the induction of specific antibodies. T. vaginalis has acquired several strategies to evade the humoral immune responses such as degradation of immunoglobulins by cysteine proteases, antigenic variation and killing of antibody-producing B cells. The characterization of the T. vaginalis-specific antibodies to significant immunogenic molecules and formulation of strategies to promote their induction in vaginal mucosa may reveal their potential protective effects against trichomoniasis. In this review, we discuss the current understanding of antibody and T cell-mediated immune responses to T. vaginalis and highlight novel insights into the possible role of immune responses in protection against parasite.

CRISPR/Cas9-mediated gene modification and gene knock out in the human-infective parasite Trichomonas vaginalis

The sexually-transmitted parasite Trichomonas vaginalis infects ~1/4 billion people worldwide. Despite its prevalence and myriad adverse outcomes of infection, the mechanisms underlying T. vaginalis pathogenesis are poorly understood. Genetic manipulation of this single-celled eukaryote has been hindered by challenges presented by its complex, repetitive genome and inefficient methods for introducing DNA (i.e. transfection) into the parasite. Here, we have developed methods to increase transfection efficiency using nucleofection, with the goal of efficiently introducing multiple DNA elements into a single T. vaginalis cell. We then created DNA constructs required to express several components essential to drive CRISPR/Cas9-mediated DNA modification: guide RNA (gRNA), the Cas9 endonuclease, short oligonucleotides and large, linearized DNA templates. Using these technical advances, we have established CRISPR/Cas9-mediated repair of mutations in genes contained on circular DNA plasmids harbored by the parasite. We also engineered CRISPR/Cas9 directed homologous recombination to delete (i.e. knock out) two non-essential genes within the T. vaginalis genome. This first report of the use of the CRISPR/Cas9 system in T. vaginalis greatly expands the ability to manipulate the genome of this pathogen and sets the stage for testing of the role of specific genes in many biological processes.

A review on metronidazole: an old warhorse in antimicrobial chemotherapy

The 5-nitroimidazole drug metronidazole has remained the drug of choice in the treatment of anaerobic infections, parasitic as well as bacterial, ever since its development in 1959. In contrast to most other antimicrobials, it has a pleiotropic mode of action and reacts with a large number of molecules. Importantly, metronidazole, which is strictly speaking a prodrug, needs to be reduced at its nitro group in order to become toxic. Reduction of metronidazole, however, only takes place under very low concentrations of oxygen, explaining why metronidazole is exclusively toxic to microaerophilic and anaerobic microorganisms. In general, resistance rates amongst the pathogens treated with metronidazole have remained low until the present day. Nevertheless, metronidazole resistance does occur, and for the treatment of some pathogens, especially Helicobacter pylori, metronidazole has become almost useless in some parts of the world. This review will give an account on the current status of research on metronidazole's mode of action, metronidazole resistance in eukaryotes and prokaryotes, and on other 5-nitroimidazoles in use.

CRISPR-like sequences in Helicobacter pylori and application in genotyping

Background

Many bacteria and archaea possess a defense system called clustered regularly interspaced short palindromic repeats (CRISPR) associated proteins (CRISPR-Cas system) against invaders such as phages or plasmids. This system has not been demonstrated in Helicobacter pylori. The numbers of spacer in CRISPR array differ among bacterial strains and can be used as a genetic marker for bacterial typing.

Results

A total of 36 H. pylori isolates were collected from patients in three hospitals located in the central (PBH) and southern (SKH) regions of Thailand. It is of interest that CRISPR-like sequences of this bacterium were detected in vlpC encoded for VacA-like protein C. Virulence genes were investigated and the most pathogenic genotype (cagA vacA s1m1) was detected in 17 out of 29 (58.6%) isolates from PBH and 5 out of 7 (71.4%) from SKH. vapD gene was identified in each one isolate from PBH and SKH. CRISPR-like sequences and virulence genes of 20 isolates of H. pylori obtained in this study were analyzed and CRISPR-virulence typing was constructed and compared to profiles obtained by the random amplification of polymorphic DNA (RAPD) technique. The discriminatory power (DI) of CRISPR-virulence typing was not different from RAPD typing.

Conclusion

CRISPR-virulence typing in H. pylori is easy and reliable for epidemiology and can be used for inter-laboratory interpretation.

Electronic supplementary material

The online version of this article (10.1186/s13099-017-0215-8) contains supplementary material, which is available to authorized users.

Molecular typing of Trichomonas vaginalis isolates by actin gene sequence analysis and carriage of T. vaginalis viruses

Background

The protozoan parasite Trichomonas vaginalis is the most common non-viral, sexually transmitted pathogen. Although T. vaginalis is highly prevalent among women in Kenya, there is lack of data regarding genetic diversity of isolates currently in circulation in Kenya.

Methods

Typing was performed on 22 clinical isolates of T. vaginalis collected from women attending the antenatal care clinic at Kilifi County Hospital, Kenya, in 2015. Genotyping followed a previously proposed restriction fragment length polymorphism (RFLP) scheme, which involved in silico cleavage of the amplified actin gene by HindII, MseI and RsaI restriction enzymes. Phylogenetic analysis of all the sequences was performed to confirm the results obtained by RFLP-analysis and to assess the diversity within the RFLP genotypes. Additionally, we determined carriage of the four different types of Trichomonas vaginalis viruses (TVVs) by polymerase chain reaction.

Results

In silico RFLP-analysis revealed five actin genotypes; 50.0% of the isolates were of actin genotype E, 27.3% of actin genotype N, 13.6% of actin genotype G and 4.5% of actin genotypes I and P. Phylogenetic analysis was in agreement with the RFLP-analysis, with the different actin genotypes clustering together. Prevalence of TVVs was 43.5% (95% confidence interval, CI: 23.2–65.5). TVV1 was the most prevalent, present in 39.1% of the strains and 90% of the T. vaginalis isolates which harbored TVVs had more than one type of TVV. None of the isolates of actin genotype E harbored any TVV.

Conclusion

The presence of five actin genotypes in our study suggests notable diversity among T. vaginalis isolates occurring among pregnant women in Kilifi, Kenya. Isolates of the most prevalent actin genotype E lacked TVVs. We found no association between T. vaginalis genotype, carriage of TVVs and symptoms. Further studies with higher number of strains should be conducted in order to corroborate these results.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2496-7) contains supplementary material, which is available to authorized users.

The genetic diversity of metronidazole susceptibility in Trichomonas vaginalis clinical isolates in an Egyptian population

Trichomoniasis is the most common curable sexually transmitted disease worldwide. Resistance to metronidazole in treating trichomoniasis is a problematic health issue. We aimed to determine the minimum lethal concentration (MLC) of metronidazole for Trichomonas vaginalis isolates detected in Mansoura, Egypt and studied the genotypic profile of these isolates. Vaginal swab specimens were obtained from 320 symptomatic and 100 asymptomatic females, for whom clinical examination, vaginal discharge wet mount, Giemsa stain, and culture in modified Diamond's media were performed. Metronidazole susceptibility testing by an aerobic tube assay was performed. Both sensitive and resistant isolates were examined by PCR amplification followed by restriction fragment length polymorphism (RFLP). Trichomonas vaginalis was identified in 49/420 (11.7%) using either culture or PCR, while wet mount and Giemsa stain detected the parasite in 8.1 and 7.6% of participants, respectively. After 48 h incubation, most isolates were sensitive to metronidazole with a minimal lethal concentration (MLC) of 1 μg/ml. Mild resistance was observed in two isolates with MLCs of 64 μg\ml and mild to moderate resistance was observed in an additional two isolates with MLCs of 128 μg/ml. The four isolates that demonstrated low to moderate metronidazole resistance displayed a unique genotype band pattern by RFLP compared to the other 45 samples that were metronidazole sensitive. Our results highlight the presence of in vitro metronidazole tolerance in a few T. vaginalis isolates in Mansoura, Egypt that may lead to the development of drug resistance as well as the possibility of an identifying RFLP pattern in the isolates.

Unique Trichomonas vaginalis gene sequences identified in multinational regions of Northwest China

Trichomonas vaginalis (T. vaginalis) is a flagellated protozoan parasite that infects humans worldwide. This study determined the sequence of the 18S ribosomal RNA gene of T. vaginalis infecting both females and males in Xinjiang, China. Samples from 73 females and 28 males were collected and confirmed for infection with T. vaginalis, a total of 110 sequences were identified when the T. vaginalis 18S ribosomal RNA gene was sequenced. These sequences were used to prepare a phylogenetic network. The rooted network comprised three large clades and several independent branches. Most of the Xinjiang sequences were in one group. Preliminary results suggest that Xinjiang T. vaginalis isolates might be genetically unique, as indicated by the sequence of their 18S ribosomal RNA gene. Low migration rate of local people in this province may contribute to a genetic conservativeness of T. vaginalis. The unique genetic feature of our isolates may suggest a different clinical presentation of trichomoniasis, including metronidazole susceptibility, T. vaginalis virus or Mycoplasma co-infection characteristics. The transmission and evolution of Xinjiang T. vaginalis is of interest and should be studied further. More attention should be given to T. vaginalis infection in both females and males in Xinjiang.

Considerable Genetic Diversity of Trichomonas vaginalis Clinical Isolates in a Targeted Population in South of Iran

BACKGROUND

The present study aimed to characterize genetically and to compare the most frequently occurring strains of Trichomonas vaginalis isolated from southern Iran.

METHODS

Totally, 150 vaginal swab and urine specimens were collected from symptomatic and asymptomatic women from May 2012 to Jun 2013. This study implemented a sensitive and reliable PCR-restriction fragment length polymorphism (RFLP) typing method on the actin gene. Moreover, one representative sample of each identified genotype was subjected to sequencing.

RESULTS

Twenty-four T. vaginalis isolates were positive and 6 distinct electrophoretic patterns (H, E, G, I, M, N) were identified. Genotypes H and I were found to be more prevalent (50 and 37.5%) in Kerman and Shiraz, respectively. The phylogenetic analysis showed that two isolates were located as a separated clade with the other T. vaginalis isolates.

CONCLUSION

The obtained findings showed a considerable genetic polymorphism of clinical isolates from the population studied. More studies may be warranted in future as to unveiling any possible links between a given genotype/cluster and pathogenic behavior of T. vaginalis.

Trichomonas vaginalis infection in symbiosis with Trichomonasvirus and Mycoplasma

Trichomonas vaginalis is a protozoan with an extracellular obligatory parasitic lifestyle exclusively adapted to the human urogenital tract and responsible for nearly a quarter billion sexually transmitted infections worldwide each year. This review focuses on symbiotic Trichomonasvirus and mycoplasmas carried by the protozoan, their molecular features and their role in altering the human vaginal microbiome and the immunopathogenicity of the parasite. Improved diagnostics and larger clinical interventional studies are needed to confirm the causative role of protozoan symbionts in the variable clinical presentation of trichomoniasis and its morbid sequelae, including adverse reproductive outcome, susceptibility to viral infections and cancer.

Multilocus sequence typing of Trichomonas vaginalis clinical samples from Amsterdam, the Netherlands

OBJECTIVES

In this cross-sectional epidemiological study we aimed to identify molecular profiles for Trichomonas vaginalis and to determine how these molecular profiles were related to patient demographic and clinical characteristics.

SETTING

Molecular typing methods previously identified two genetically distinct subpopulations for T. vaginalis; however, few molecular epidemiological studies have been performed. We now increased the sensitivity of a previously described multilocus sequence typing (MLST) tool for T. vaginalis by using nested PCR. This enabled the typing of direct patient samples.

PARTICIPANTS

From January to December 2014, we collected all T. vaginalis positive samples as detected by routine laboratory testing. Samples from patients either came from general practitioners offices or from the sexually transmitted infections (STI) clinic in Amsterdam. Epidemiological data for the STI clinic patients were retrieved from electronic patient files.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was the success rate of genotyping direct T. vaginalis positive samples. The secondary outcome was the relation between T. vaginalis genotypes and risk factors for STI.

RESULTS

All 7 MLST loci were successfully typed for 71/87 clinical samples. The 71 typed samples came from 69 patients, the majority of whom were women (n=62; 90%) and half (n=34; 49%) were STI clinic patients. Samples segregated into a two population structure for T. vaginalis representing genotypes I and II. Genotype I was most common (n=40; 59.7%). STI clinic patients infected with genotype II reported more sexual partners in the preceding 6 months than patients infected with genotype I (p=0.028). No other associations for gender, age, ethnicity, urogenital discharge or co-occurring STIs with T. vaginalis genotype were found.

CONCLUSIONS

MLST with nested PCR is a sensitive typing method that allows typing of direct (uncultured) patient material. Genotype II is possibly more prevalent in high-risk sexual networks.

Bulky Trichomonad Genomes: Encoding a Swiss Army Knife

The trichomonads are a remarkably successful lineage of ancient, predominantly parasitic protozoa. Recent molecular analyses have revealed extensive duplication of certain genetic loci in trichomonads. Consequently, their genomes are exceptionally large compared to other parasitic protozoa. Retention of these large gene expansions across different trichomonad families raises the question: do these duplications afford an advantage? Many duplicated genes are linked to the parasitic lifestyle and some are regulated differently to their paralogues, suggesting they have acquired new functions. It is proposed that these large genomes encode a Swiss army knife of sorts, packed with a multitude of tools for use in many different circumstances. This may have bestowed trichomonads with the extraordinary versatility that has undoubtedly contributed to their success.

Recent Advances in the Trichomonas vaginalis Field

The microaerophilic protist parasite Trichomonas vaginalis is occurring globally and causes infections in the urogenital tract in humans, a condition termed trichomoniasis. In fact, trichomoniasis is the most prevalent non-viral sexually transmitted disease with more than 250 million people infected every year. Although trichomoniasis is not life threatening in itself, it can be debilitating and increases the risk of adverse pregnancy outcomes, HIV infection, and, possibly, neoplasias in the prostate and the cervix. Apart from its role as a pathogen, T. vaginalis is also a fascinating organism with a surprisingly large genome for a parasite, i. e. larger than 160 Mb, and a physiology adapted to its microaerophilic lifestyle. In particular, the hydrogenosome, a mitochondria-derived organelle that produces hydrogen, has attracted much interest in the last few decades and rendered T. vaginalis a model organism for eukaryotic evolution. This review will give a succinct overview of the major advances in the T. vaginalis field in the last few years.

Trichomonas vaginalis: An Updated Overview Towards Diagnostic Improvement

The protozoan Trichomonas vaginalis (TV) is responsible for trichomonosis, a sexually transmitted disease (STD) with a significant incidence worldwide. This infection is one of the most common non-viral STDs, representing almost 50% of all curable STDs. Trichomonosis has an incidence of 180 million new cases worldwide. Nowadays, the 'gold standard' for TV diagnosis remains the use of in vitro cultures combined with daily visual microscopic evaluations, which is a time-consuming and low sensitive method. Recent diagnostic methodologies include imunocromatographic assays and molecular biology techniques. The use of the latter has improved enormously the sensitivity and specificity of TV diagnosis, despite, however, none being unable to identify the presence of live parasites. By understanding the biology, the pathogenesis, the proteomic profile and its relation with the parasite's virulence mechanisms, new possibilities towards diagnostic techniques can arise. This review covers various important aspects of vaginal trichomonosis from the parasite's biology and virulence to recent improvements in diagnostic techniques and also metabolic and protein discoveries.

Trichomonas vaginalis: pathogenicity and potential role in human reproductive failure

PURPOSE

Trichomonas vaginalis, which colonizes the genitourinary tract of men and women, is a sexually transmitted parasite causing symptomatic or asymptomatic trichomoniasis. The host-parasite relationship is very complex, and clinical symptoms cannot likely be attributed to a single pathogenic effect. Among the many factors responsible for interactions between T. vaginalis and host tissues, contact-dependent and contact-independent mechanisms are important in pathogenicity, as is the immune response.

METHODS

This review focuses on the potential virulence properties of T. vaginalis and its role in female and male infertility.

RESULTS

It highlights the association between T. vaginalis infection and serious adverse health consequences experienced by women, including infertility, preterm birth and low-birth-weight infants. Long-term clinical observations and results of in vitro experimental studies indicate that in men, trichomoniasis has been also associated with infertility through inflammatory damage to the genitourinary tract or interference with sperm function.

CONCLUSION

These results contribute significantly to improving our knowledge of the role of parasitic virulence factors in the development of infection and its role in human infertility.

Anti-Retroviral Lectins Have Modest Effects on Adherence of Trichomonas vaginalis to Epithelial Cells In Vitro and on Recovery of Tritrichomonas foetus in a Mouse Vaginal Model

Trichomonas vaginalis causes vaginitis and increases the risk of HIV transmission by heterosexual sex, while Tritrichomonas foetus causes premature abortion in cattle. Our goals were to determine the effects, if any, of anti-retroviral lectins, which are designed to prevent heterosexual transmission of HIV, on adherence of Trichomonas to ectocervical cells and on Tritrichomonas infections in a mouse model. We show that Trichomonas Asn-linked glycans (N-glycans), like those of HIV, bind the mannose-binding lectin (MBL) that is part of the innate immune system. N-glycans of Trichomonas and Tritrichomonas bind anti-retroviral lectins (cyanovirin-N and griffithsin) and the 2G12 monoclonal antibody, each of which binds HIV N-glycans. Binding of cyanovirin-N appears to be independent of susceptibility to metronidazole, the major drug used to treat Trichomonas. Anti-retroviral lectins, MBL, and galectin-1 cause Trichomonas to self-aggregate and precipitate. The anti-retroviral lectins also increase adherence of ricin-resistant mutants, which are less adherent than parent cells, to ectocervical cell monolayers and to organotypic EpiVaginal tissue cells. Topical application of either anti-retroviral lectins or yeast N-glycans decreases by 40 to 70% the recovery of Tritrichomonas from the mouse vagina. These results, which are explained by a few simple models, suggest that the anti-retroviral lectins have a modest potential for preventing or treating human infections with Trichomonas.

Genetic diversity of Trichomonas vaginalis clinical isolates from Henan province in central China

Trichomonas vaginalis is a flagellated protozoan parasite that infects the human urogenital tract, causing the most common non-viral, sexually transmitted disease worldwide. In this study, genetic variants of T. vaginalis were identified in Henan Province, China. Fragments of the small subunit of nuclear ribosomal RNA (18S rRNA) were amplified from 32 T. vaginalis isolates obtained from seven regions of Henan Province. Overall, 18 haplotypes were determined from the 18S rRNA sequences. Each sampled population and the total population displayed high haplotype diversity (Hd), accompanied by very low nucleotide diversity (Pi). In these molecular genetic variants, 91.58% genetic variation was derived from intra-regions. Phylogenetic analysis revealed no correlation between phylogeny and geographic distribution. Demographic analysis supported population expansion of T. vaginalis isolates from central China. Our findings showing moderate-to-high genetic variations in the 32 isolates of T. vaginalis provide useful knowledge for monitoring changes in parasite populations for the development of future control strategies.

The Transcriptome Sequence of Dientamoeba fragilis Offers New Biological Insights on its Metabolism, Kinome, Degradome and Potential Mechanisms of Pathogenicity

Dientamoeba fragilis is a human bowel parasite with a worldwide distribution. Dientamoeba was once described as a rare and harmless commensal though recent reports suggest it is common and potentially pathogenic. Molecular data on Dientamoeba is scarce which limits our understanding of this parasite. To address this, sequencing of the Dientamoeba transcriptome was performed. Messenger RNA was extracted from cultured Dientamoeba trophozoites originating from clinical stool specimens, and sequenced using Roche GS FLX and Illumina HiSeq technologies. In total 6,595 Dientamoeba transcripts were identified. These sequences were analysed using the BLAST2GO software suite and via BLAST comparisons to sequences available from TrichDB, GenBank, MEROPS and kinase.com. Several novel KEGG pathway maps were generated and gene ontology analysis was also performed. These results are thoroughly discussed guided by knowledge available for other related protozoa. Attention is paid to the novel biological insights afforded by this data including peptidases and kinases of Dientamoeba, as well as its metabolism, novel chemotherapeutics and possible mechanisms of pathogenicity. Currently, this work represents the largest contribution to our understanding of Dientamoeba molecular biology and also represents a major contribution to our understanding of the trichomonads generally, many of which are important pathogens of humans and animals.

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.

Molecular genetic diversity and characterization of conjugation genes in the fish parasite Ichthyophthirius multifiliis

Ichthyophthirius multifiliis is the etiologic agent of "white spot", a commercially important disease of freshwater fish. As a parasitic ciliate, I. multifiliis infects numerous host species across a broad geographic range. Although Ichthyophthirius outbreaks are difficult to control, recent sequencing of the I. multifiliis genome has revealed a number of potential metabolic pathways for therapeutic intervention, along with likely vaccine targets for disease prevention. Nonetheless, major gaps exist in our understanding of both the life cycle and population structure of I. multifiliis in the wild. For example, conjugation has never been described in this species, and it is unclear whether I. multifiliis undergoes sexual reproduction, despite the presence of a germline micronucleus. In addition, no good methods exist to distinguish strains, leaving phylogenetic relationships between geographic isolates completely unresolved. Here, we compared nucleotide sequences of SSUrDNA, mitochondrial NADH dehydrogenase subunit I and cox-1 genes, and 14 somatic SNP sites from nine I. multifiliis isolates obtained from four different states in the US since 1995. The mitochondrial sequences effectively distinguished the isolates from one another and divided them into at least two genetically distinct groups. Furthermore, none of the nine isolates shared the same composition of the 14 somatic SNP sites, suggesting that I. multifiliis undergoes sexual reproduction at some point in its life cycle. Finally, compared to the well-studied free-living ciliates Tetrahymena thermophila and Paramecium tetraurelia, I. multifiliis has lost 38% and 29%, respectively, of 16 experimentally confirmed conjugation-related genes, indicating that mechanistic differences in sexual reproduction are likely to exist between I. multifiliis and other ciliate species.

Antibiotic resistance in prevalent bacterial and protozoan sexually transmitted infections

The emergence of multi-drug resistant sexually transmitted infections (STIs) is causing a treatment crisis across the globe. While cephalosporin-resistant gonorrhea is one of the most pressing issues, extensively antibiotic resistant Chlamydia trachomatis and Mycoplasma hominis are also becoming commonplace. Experts have suggested that the failure of current treatment regimens are "largely inevitable" and have called for entirely new classes of antimicrobial agents. With the exception of several new classes of drugs primarily targeting nosocomial infections, progress has been slow. While pharmaceutical companies continue to introduce new drugs, they are based on decade-old discoveries. While there is disagreement about what constitutes new classes of antibiotics, many experts suggest that the last truly new family of antimicrobials was discovered in 1987. This review summarizes the existing literature on antibiotic resistance in common bacterial and protozoal STIs. It also briefly discusses several of the most promising alternatives to current therapies, and further examines how advances in drug delivery, formulation, concentration, and timing are improving the efficacy of existing treatments. Finally, the paper discusses the current state of pharmaceutical development for multidrug-resistant STI.

Antibiotic resistance in prevalent bacterial and protozoan sexually transmitted infections

The emergence of multi-drug resistant sexually transmitted infections (STIs) is causing a treatment crisis across the globe. While cephalosporin-resistant gonorrhea is one of the most pressing issues, extensively antibiotic resistant Chlamydia trachomatis and Mycoplasma hominis are also becoming commonplace. Experts have suggested that the failure of current treatment regimens are "largely inevitable" and have called for entirely new classes of antimicrobial agents. With the exception of several new classes of drugs primarily targeting nosocomial infections, progress has been slow. While pharmaceutical companies continue to introduce new drugs, they are based on decade-old discoveries. While there is disagreement about what constitutes new classes of antibiotics, many experts suggest that the last truly new family of antimicrobials was discovered in 1987. This review summarizes the existing literature on antibiotic resistance in common bacterial and protozoal STIs. It also briefly discusses several of the most promising alternatives to current therapies, and further examines how advances in drug delivery, formulation, concentration, and timing are improving the efficacy of existing treatments. Finally, the paper discusses the current state of pharmaceutical development for multidrug-resistant STI.

Sexual reproduction and genetic exchange in parasitic protists

A key part of the life cycle of an organism is reproduction. For a number of important protist parasites that cause human and animal disease, their sexuality has been a topic of debate for many years. Traditionally, protists were considered to be primitive relatives of the ‘higher’ eukaryotes, which may have diverged prior to the evolution of sex and to reproduce by binary fission. More recent views of eukaryotic evolution suggest that sex, and meiosis, evolved early, possibly in the common ancestor of all eukaryotes. However, detecting sex in these parasites is not straightforward. Recent advances, particularly in genome sequencing technology, have allowed new insights into parasite reproduction. Here, we review the evidence on reproduction in parasitic protists. We discuss protist reproduction in the light of parasitic life cycles and routes of transmission among hosts.

Immunity in urogenital protozoa

Innate and adaptive immunity play a significant role in urogenital infections. Innate immunity is provided by the epithelial cells and mucus lining along with acidic pH, which forms a strong physical barrier against the pathogens in female reproductive tract. Cells of innate immune system, antimicrobial peptides, cytokines, chemokines and adaptive immunity in the reproductive tract are evolved during infection, and a pro-inflammatory response is generated to fight against the invading pathogen Trichomonas vaginalis, a primary urogenital protozoa, the etiological agent of human trichomoniasis, a curable sexually transmitted infection. The involvement of the urogenital tract by other protozoal infections such as P. falciparum, Trypanosoma, Leishmania, Toxoplasma, Entamoeba histolytica and Acanthamoeba infection is rarely reported. Trichomonas induce pro-inflammatory and immunosuppressive responses in infected subjects. Multifactorial pathogenic mechanisms including parasite adherence, cysteine proteases, lipophosphoglycan, free radical, cytokine generation and Toll-like receptors appear to interplay with the induction of local and systemic immune responses that ultimately determine the outcome of the infection. However, the involvement of urogenital pathogen-specific immune mechanisms and effect of normal local resident flora on the outcome (symptomatic vs. asymptomatic) of infection are poorly understood. Moreover, immune interactions in trichomoniasis subjects co-infected with bacterial and viral pathogens need to be elucidated.