Phosphoproteome profiling of the sexually transmitted pathogen Trichomonas vaginalis

Persistent Trichomonas vaginalis infections and the pseudocyst form

Recent studies have proposed that Trichomonas vaginalis, the causative agent of trichomoniasis [the most common nonviral sexually transmitted infection (STI) in humans] can establish persistent infections in the vagina. T. vaginalis infections are often asymptomatic but can have adverse consequences such as increased risk of HIV-1 infection and cervical cancer. Despite this, it remains an understudied infection. A potential agent of persistent infections is the 'pseudocyst', a spherical form of T. vaginalis identified by several laboratories and linked to persistence in related species such as the avian parasite Trichomonas gallinae and cattle parasite Tritrichomonas foetus. Additional robust and reproducible research on pseudocysts and persistent T. vaginalis infections is required, which may ultimately shed light on how to better diagnose and treat trichomoniasis.

Establishment of suitable reference genes for studying relative gene expression during the transition from trophozoites to cyst-like stages and first evidences of stress-induced expression of meiotic genes in Trichomonas vaginalis

Trichomonas vaginalis is a parasite of the human urogenital tract and the causative agent of trichomoniasis, a sexually transmitted disease of worldwide importance. This parasite is usually found as a motile flagellated trophozoite. However, when subjected to stressful microenvironmental conditions, T. vaginalis trophozoites can differentiate into peculiar cyst-like stages, which exhibit notable physiological resistance to unfavourable conditions. Although well documented in morphological and proteomic terms, patterns of gene expression changes involved in the cellular differentiation into cyst-like stages are mostly unknown. The real-time reverse transcription polymerase chain reaction (RT-qPCR) is recognized as a sensitive and accurate method for quantification of gene expression, providing fluorescence-based data that are proportional to the amount of a target RNA. However, the reliability of relative expression studies depends on the validation of suitable reference genes, which RNAs exhibit a minimum of variation between tested conditions. Here, we attempt to determine suitable reference genes to be used as controls of invariant expression during cold-induced in vitro differentiation of T. vaginalis trophozoites into cyst-like forms. Furthermore, we reveal that the mRNA from the meiotic recombinase Dmc1 is upregulated during this process, indicating that cryptic sexual events may take place in cyst-like stages of T. vaginalis.

Trichomonas vaginalis: Pathogenesis, Symbiont Interactions, and Host Cell Immune Responses

The parasite Trichomonas vaginalis (Tv) causes a highly prevalent sexually transmitted infection. As an extracellular pathogen, the parasite mediates adherence to epithelial cells to colonize the human host. In addition, the parasite interfaces with the host immune system and the vaginal microbiota. Modes of Tv pathogenesis include damage to host tissue mediated by parasite killing of host cells, disruption of steady-state vaginal microbial ecology, and eliciting inflammation by activating the host immune response. Recent Tv research has uncovered new players that contribute to multifactorial mechanisms of host-parasite adherence and killing, and has examined the relationship between Tv and vaginal bacteria. Mechanisms that may lead to parasite recognition and killing, or the evasion of host immune cells, have also been revealed.

Metabolomic profiling and stable isotope labelling of Trichomonas vaginalis and Tritrichomonas foetus reveal major differences in amino acid metabolism including the production of 2-hydroxyisocaproic acid, cystathionine and S-methylcysteine

Trichomonas vaginalis and Tritrichomonas foetus are pathogens that parasitise, respectively, human and bovine urogenital tracts causing disease. Using LC-MS, reference metabolomic profiles were obtained for both species and stable isotope labelling with D-[U-13C6] glucose was used to analyse central carbon metabolism. This facilitated a comparison of the metabolic pathways of T. vaginalis and T. foetus, extending earlier targeted biochemical studies. 43 metabolites, whose identities were confirmed by comparison of their retention times with authentic standards, occurred at more than 3-fold difference in peak intensity between T. vaginalis and T. foetus. 18 metabolites that were removed from or released into the medium during growth also showed more than 3-fold difference between the species. Major differences were observed in cysteine and methionine metabolism in which homocysteine, produced as a bi-product of trans-methylation, is catabolised by methionine γ-lyase in T. vaginalis but converted to cystathionine in T. foetus. Both species synthesise methylthioadenosine by an unusual mechanism, but it is not used as a substrate for methionine recycling. T. vaginalis also produces and exports high levels of S-methylcysteine, whereas only negligible levels were found in T. foetus which maintains significantly higher intracellular levels of cysteine. 13C-labeling confirmed that both cysteine and S-methylcysteine are synthesised by T. vaginalis; S-methylcysteine can be generated by recombinant T. vaginalis cysteine synthase using phosphoserine and methanethiol. T. foetus contained higher levels of ornithine and citrulline than T. vaginalis and exported increased levels of putrescine, suggesting greater flux through the arginine dihydrolase pathway. T. vaginalis produced and exported hydroxy acid derivatives of certain amino acids, particularly 2-hydroxyisocaproic acid derived from leucine, whereas negligible levels of these metabolites occurred in T. foetus.

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

ETIOLOGY

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

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.

The biology of Trichomonas vaginalis in the light of urogenital tract infection

The human pathogen Trichomonas vaginalis is a parasitic protist. It is a representative of the eukaryotic supergroup Excavata that includes a few other protist parasites such as Leishmania, Trypanosoma and Giardia. T. vaginalis is the agent of trichomoniasis and in the US alone, one in 30 women tests positive for this parasite. The disease is easily treated with metronidazole in most cases, but resistant strains are on the rise. The biology of Trichomonas is remarkable: it includes for example the biggest protist genome currently sequenced, the expression of about 30,000 protein-encoding genes (and thousands of lncRNAs and pseudogenes), anaerobic hydrogenosomes, rapid morphogenesis during infection, the secretion of exosomes, the manipulation of the vaginal microbiota through phagocytosis and a rich strain-dependent diversity. Here we provide an overview of Trichomonas biology with a focus on its relevance for pathogenicity and summarise the most recent advances. With some respect this parasite offers the opportunity to serve as a model system to study certain aspects of cell and genome biology, but tackling the complex biology of T. vaginalis is also important to better understand the effects that accompany infection and direct symptoms.

Gene-expression analysis of cold-stress response in the sexually transmitted protist Trichomonas vaginalis

BACKGROUND

Trichomonas vaginalis is the etiologic agent of trichomoniasis, the most common nonviral sexually transmitted disease in the world. This infection affects millions of individuals worldwide annually. Although direct sexual contact is the most common mode of transmission, increasing evidence indicates that T. vaginalis can survive in the external environment and can be transmitted by contaminated utensils. We found that the growth of T. vaginalis under cold conditions is greatly inhibited, but recovers after placing these stressed cells at the normal cultivation temperature of 37 °C. However, the mechanisms by which T. vaginalis regulates this adaptive process are unclear.

METHODS

An expressed sequence tag (EST) database generated from a complementary DNA library of T. vaginalis messenger RNAs expressed under cold-culture conditions (4 °C, TvC) was compared with a previously published normal-cultured EST library (37 °C, TvE) to assess the cold-stress responses of T. vaginalis.

RESULTS

A total of 9780 clones were sequenced from the TvC library and were mapped to 2934 genes in the T. vaginalis genome. A total of 1254 genes were expressed in both the TvE and TvC libraries, and 1680 genes were only found in the TvC library. A functional analysis showed that cold temperature has effects on many cellular mechanisms, including increased H2O2 tolerance, activation of the ubiquitin-proteasome system, induction of iron-sulfur cluster assembly, and reduced energy metabolism and enzyme expression.

CONCLUSION

The current study is the first large-scale transcriptomic analysis in cold-stressed T. vaginalis and the results enhance our understanding of this important protist.

Identification of the phosphorylated residues in TveIF5A by mass spectrometry

The initiation factor eIF5A in Trichomonas vaginalis (TveIF5A) is previously shown to undergo hypusination, phosphorylation and glycosylation. Three different pI isoforms of TveIF5A have been reported. The most acidic isoform (pI 5.2) corresponds to the precursor TveIF5A, whereas the mature TveIF5A appears to be the most basic isoform (pI 5.5). In addition, the intermediary isoform (pI 5.3) is found only under polyamine-depleted conditions and restored with exogenous putrescine. We propose that differences in PI are due to phosphorylation of the TveIF5A isoforms. Here, we have identified phosphorylation sites using mass spectrometry. The mature TveIF5A contains four phosphorylated residues (S3, T55, T78 and T82). Phosphorylation at S3 and T82 is also identified in the intermediary TveIF5A, while no phosphorylated residues are found in the precursor TveIF5A. It has been demonstrated that eIF5A proteins from plants and yeast are phosphorylated by a casein kinase 2 (CK2). Interestingly, a gene encoding a protein highly similar to CK2 (TvCK2) is found in T. vaginalis, which might be involved in the phosphorylation of TveIF5A in T. vaginalis.

Archaeal signal transduction: impact of protein phosphatase deletions on cell size, motility, and energy metabolism in Sulfolobus acidocaldarius

In this study, the in vitro and in vivo functions of the only two identified protein phosphatases, Saci-PTP and Saci-PP2A, in the crenarchaeal model organism Sulfolobus acidocaldarius were investigated. Biochemical characterization revealed that Saci-PTP is a dual-specific phosphatase (against pSer/pThr and pTyr), whereas Saci-PP2A exhibited specific pSer/pThr activity and inhibition by okadaic acid. Deletion of saci_pp2a resulted in pronounced alterations in growth, cell shape and cell size, which could be partially complemented. Transcriptome analysis of the three strains (Δsaci_ptp, Δsaci_pp2a and the MW001 parental strain) revealed 155 genes that were differentially expressed in the deletion mutants, and showed significant changes in expression of genes encoding the archaella (archaeal motility structure), components of the respiratory chain and transcriptional regulators. Phosphoproteome studies revealed 801 unique phosphoproteins in total, with an increase in identified phosphopeptides in the deletion mutants. Proteins from most functional categories were affected by phosphorylation, including components of the motility system, the respiratory chain, and regulatory proteins. In the saci_pp2a deletion mutant the up-regulation at the transcript level, as well as the observed phosphorylation pattern, resembled starvation stress responses. Hypermotility was also observed in the saci_pp2a deletion mutant. The results highlight the importance of protein phosphorylation in regulating essential cellular processes in the crenarchaeon S. acidocaldarius.

Trichomonas vaginalis virulence factors: an integrative overview

The elusive nature of Trichomonas vaginalis, the most common, non-viral, sexually transmitted pathogen has hampered our knowledge of its significance for human health for over 150 years. The combination of epidemiology, molecular cell biology, immunology and more recently genomics and other allied omics data, are all contributing at shedding new light onto what is increasingly recognised as a significant human pathogen leading to important health sequelae due to multifaceted interactions with its human host, the human microbiota, bacterial pathogens and viruses. The integrations of these various data are contributing in important ways to refining our understanding of the parasite pathobiology and virulent factors. Indeed, it is increasingly recognised that to rationalise the development of effective prophylactic and therapeutic treatments for human pathogens it is important to integrate the broadest possible spectrum of human-microbial-parasite-virus interactions in relation to qualitative and quantitative variations in the human innate and adaptive defence responses. This short review aims at providing an integrative overview of T vaginalis virulent factors by taking into account the importance of the human-microbiota-parasite-virus interplay in human health. It also highlights selected cellular characteristics of the parasite often overlooked in the biological and medical literature.