SPOTLIGHTS ON NEW PUBLICATIONS
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SPOTLIGHTS ON NEW PUBLICATIONS
Vol. 6, No. 1, 2013 ISSN: 1687-7942 S P O T L I G H T S O N N E W P U B L I C AT I O N S PUJ Trichomonas vaginalis Trichomonas vaginalis is the most common curable sexually transmitted infection worldwide. In 2001, WHO claimed that more than 170 million people are infected annually with T. vaginalis. It is emerging as a serious reproductive tract pathogen, mainly affecting people living in poor or disadvantaged communities. However, serious adverse reproductive health outcomes including pregnancy complications, pelvic inflammatory disease and an increased risk of HIV acquisition have been linked to trichomoniasis. In this regard, potential mechanisms for increased susceptibility include (1) recruitment of HIV target cells (CD4+ T cells) to the genital tract as a result of the host immune response to T. vaginalis, (2) degradation of HIV-protective factors such as secretory leukocyte protease inhibitor, and (3) direct and indirect cytotoxic effects of the parasite itself. Trichomoniasis is transmitted through sexual contact or vertically through vaginal delivery. Men may present with symptoms of nongonococcal urethritis (i.e., urethral discharge, irritation, or dysuria), whereas the most common symptom in women is a malodorous vaginal discharge. Women may also report dyspareunia, dysuria, lower abdominal pain, or vulvovaginal irritation. However, the majority of the infected women and men are asymptomatic. The parasite’s genome sequence was reported in 2007, and 2 types population structure emerged. Type 1 was easier to detect by wet mount and may represent symptomatic patients with high parasite loads; while type 2 demonstrated a significantly higher minimum lethal concentration of metronidazole necessary to kill isolates compared with type 1. It was reported that a double-stranded RNA virus was detected in 73% of type 1 isolates and 2.5% of type 2 isolates. T. vaginalis viruses induced alteration of the surface expression of P270 and cysteine proteinases, which conceivably can result in modulation of its pathogenicity. There are several sensitive and specific diagnostic tests available, including a newly approved nucleic acid amplification test. Metronidazole and tinidazole can cure trichomoniasis. Systemic therapy is preferred over topical applications to achieve adequate drug concentrations in non-vaginal sites such as the urethra and periurethral glands. Metronidazole-resistant isolates are estimated to occur in 2.5-5% of cases and increasing its dose or switching to tinidazole can usually overcome the resistance. In the present issue, recent original articles concerning T. vaginalis prevalence, pathogenicity, immune response, genomics, diagnosis and treatment will be summarized. Prevalence: In Iran, various studies determined the prevalence of trichomoniasis between 2-8% according to the cultural and social status. To determine its prevalence among symptomatic and asymptomatic women in Hamadan city, Iran, M. Matini and his colleagues presented a descriptive cross-sectional study. Another objective besides prevalence was to evaluate the usefulness of the clinical examination and the value of signs and symptoms in diagnosis of trichomoniasis in gynecological and obstetrics clinics. The study was carried out on 750 women from November 2010 to July 2011 excluding cases who had used vaginal antibiotic during the past 2 weeks. Information regarding vaginal discharge (color and consistency), itching, dysuria and dyspareunia was collected, followed by clinical examination. The discharge was subjected to wet mount examination and culture technique (Dorset medium). The culture was examined daily up to 7 days until they turned positive. Clinical examination revealed 42 T. vaginalis infected women. Parasitological results showed that the city had low trichomoniasis prevalence (2.1%); culture diagnosed 16 cases while wet mount missed only 3 cases. The highest infection rate was in the age group 25-34 years with statistically significant difference. In addition, 4 asymptomatic cases were not identified by clinical examination. The sensitivity, specificity and positive and negative predictive values of clinical diagnosis compared to culture method (gold standard) were 75%, 95%, 28% and 99%, respectively. On the other hand, 550 cases (73.3%) showed one or more signs and symptoms of trichomoniasis; the vaginal discharge was the most common sign. From the previous results, it was concluded that 1) clinical signs and symptoms are not specific for trichomoniasis and are common in all sexual transmitted disease; 2) diagnosis of trichomoniasis based on only clinical symptoms is unreliable. Prevalence of Trichomonas vaginalis infection in Hamadan City, Western Iran. Iran J Parasitol; 2012, 7(2):67–72. Pathogenecity and virulence: In a review article, the Indian scientists Sehgal R, Goyal K and Sehgal A pointed out the importance of iron as an essential nutrient for the survival of pathogenic protozoa, especially the amitochondriate ones such as Trichomonas, Giardia, and Entamoeba. These protozoa require higher extracellular iron concentration for their functional energy metabolism system. On the other hand, ferric irons are chelated by lactoferrin (Lf), which is an extracellular glycoprotein of Personal non-commercial use only. PUJ copyright © 2013. All rights reserved PUJ; 2013, 6(1):121-124 Spotlights on New Publications the host immune system, so there is a balance between the invading pathogen and the host immune response to determine the clinical outcome. This extracellular glycoprotein has a wide range of biological activities including regulation of iron absorption in addition to its antioxidant, anticarcinogenic, anti-inflammatory and antimicrobial activities. It is found in various mucosal secretions, including saliva, tears, vaginal fluids, semen, nasal and bronchial secretions, GIT fluids, urine, milk and blood. In other words, extracellular iron is bound to transferrin to be transferred to all cells and at the mucosal surfaces it is bound to Lf. Meanwhile, Lf exists in two forms; apo-Lf (without iron) and holo-Lf (saturated with iron). When apo-Lf acquires iron, it becomes saturated with iron and forms holo-Lf to be an important source of iron for microorganisms. The latter developed various strategies to acquire iron from holo-Lf to be used in replication causing acute or chronic infections and tissue damage. The reviewers described 4 strategies; expression of Lf binding receptors or proteins (Lbps) (e.g. in T. vaginalis), proteases secretion to cleave holo-Lf releasing iron (e.g. Tritrichomonas fetus and E. histolytica), reductases secretion to reduce ferric to ferrous state (e.g. Leishmania spp.), and the 4th mechanism is used by bacteria and fungi (xenosiderophores). It was observed also that trophozoites grown in iron-rich media become resistant to complement lysis, because iron regulates parasite cysteine proteinases (CPs) necessary to provide resistance to complement degradation and to recognize and bind to host cells (CPs dual role; parasite survival and tissue damage). Meanwhile, iron downregulates proteolytic activity, expression and transcription of CPs participating in T. vaginalis virulence e.g. CP65 and CP39 which are involved in cytotoxicity. So, just before menstruation with low iron concentration and decreased cytoadhesion, CP65 and CP39 are activated to help the parasite moving in search of iron to maintain its virulence. On the other hand, the major surface immunogen (P270) is a protein characterizing T. vaginalis phenotypic variation. According to P270, there are 2 genotypes, I and II; and it was shown that iron played an important role in modulating surface localization of P270 in virus-harboring parasites. Finally, the authors recommended further studies to evaluate drugs which can target the holo-Lf receptor or inhibit Lf binding sites to provide immunity against trichomoniasis. Further studies are also required to test using T. vaginalis receptor-mediated mechanism as a vaccine candidate. In the receptor mediated mechanism, T. vaginalis recognizes human holo-Lf by two surface proteins; 178 and 75 kDa. Increased Lbps activity was observed in response to iron-depleted conditions. This means increased number and affinity of Lbps in in vitro T. vaginalis cultivated under iron-depleted conditions or in vivo, keeping in mind that Lf concentration in human vaginal mucosa fluctuates from 9-200 μg/ml during the menstrual cycle. The reviewers discussed different roles of iron on growth, cytoadherence and virulence of T. vaginalis in vitro. Shorter trophozoites generation time and significant lethal effects of metronidazole in low concentration were observed in iron-rich media. For cytoadherence (as an initial step in pathogenesis), trophozoites isolated from iron-rich media showed higher level of cytoadherence in proportion to iron concentration. To colonize the vaginal epithelium, T. vaginalis trophozoites evolved several adherence factors such as adhesion proteins (APs), lipophosphoglycan, α-actinin, enolase, phosphoglucomutase, and various binding proteins (fibronectin, laminin and GTP). The majority of APs are positively regulated by iron such as the AP65-1 gene (which encodes 65 kDa malic enzyme involved in cytoadherence) and AP120 (which is involved in synthesis of a component localized to the parasite surface and participates in cytoadherence). The iron role in T. vaginalis virulence was also discussed. Trophozoites cultivated in iron-deficient media failed to produce pathological lesions while those cultivated in normal Diamond's media or iron-supplemented TYM media produced subcutaneous abscesses. Trichomoniasis and lactoferrin: Future prospects. Infect Dis Obstet Gynecol; 2012, 536037. Genomics: Previous studies documented the role of iron components such as cysteine desulfurase, the molecular scaffold protein (IscU), and cytosolic and nuclear FeS proteins (e.g. Rli1p) in hydrogenosomes (specific mitochondria-related organelles), and ribosome biogenesis and functions. These proteins are essential for the formation of FeS clusters in the catalytic centers of apoproteins, which is mediated by iron–sulfur cluster (ISC) assembly machinery. Recent studies also revealed regulation at the post-transcriptional level of 2 cysteine proteases (TVCP4 and TVCP12) by an iron response protein-like system. In addition, in vitro experiments showed the important role of iron in regulation of T. vaginalis cytoadherence to target cells and increase of its resistance to complement-mediated lysis. Hence, the role of iron in T. vaginalis gene expression and genome evolution was investigated in a collaborated study between scientists of Parasitology and Immunobiology Departments and the Bioinformatics Center in Czech Republic and Taiwan. Identification of the mechanisms underlying the iron-dependent regulation of these processes was the objective of recent work by Lenka Horváthová and her colleagues. Prior to their experiment, T1 T. vaginalis strain was cultivated in either TYM-ironrich (+Fe) or iron-restricted (−Fe) media. Total RNA was extracted, the contaminating genomic DNA was digested 122 SM Abaza Immune response: Several previous in vitro studies revealed secretion of different cytokines from human neutrophils, monocytes, macrophages and the vaginal cells as well as from murine lymphocytes on exposure of cultured cells to T. vaginalis. These cytokines included interleukins (ILs) such as IL-8, IL-2, IL-1β and IL-6 and interferon (IFN-γ) and tumor necrosis factor (TNF-α). However, few studies detected IL-10 secreted from dendritic cells and macrophages infected with T. vaginalis. It is well known that IL-10 has an important anti-inflammatory role and it is secreted by the host immune response cells, e.g. macrophages, monocytes and B and T lymphocytes. In addition, immune cells infected with HIV showed high secretion of IL-10. Meanwhile, T. vaginalis-infected patients are more likely to acquire HIV, due to increased IL-10 levels. In an attempt to determine whether T. vaginalis and T. foetus stimulated IL-10 from the cultured bovine epithelial cells, the Brazilain investigators RC VilelaI and M Benchimo published their short communication work. Bovine epithelial cells cultures (BOECs) were prepared and exposed to both JT and K strains of T. vaginalis and T. foetus (human and bovine parasite, respectively). Each culture supernatant was collected to determine IL-10 levels. Results showed high IL-10 levels were secreted from the BOECs exposed to T. foetus, compared to control cells. While on exposure to T. vaginalis, IL-10 levels remained at baseline and increased only slightly compared to controls. The investigators concluded that the host immune cell response in trichomoniasis is species-specific. and the complementary DNA was reconstructed. The investigators screened iron-regulated genes using T. vaginalis oligonucleotide microarray analysis and expressed sequence tag (EST) sequencing of cDNA libraries derived from trichomonads cultivated under +Fe and −Fe conditions. Using microarray analysis, results revealed the presence of 195 genes that were significantly regulated by iron, of which the 117 and 78 genes were upregulated in cells cultivated under +Fe and −Fe conditions, respectively. Using EST approach, 19,074 ESTs were sequenced from distinct cDNA libraries, and the results revealed 336 genes, of which 165 and 171 genes were upregulated under +Fe and −Fe conditions, respectively. The investigators discussed the major ironregulated pathways for proteins involved in carbohydrate metabolism; glycolysis and energy metabolism. As regards the former, it was shown that enzymes supplying substrates to the glycolytic pathway were significantly upregulated under +Fe conditions. For energy metabolism, malate (ME) is able to serve as a substrate for hydrogenosomal energy metabolism under +Fe conditions; while under −Fe, malate is metabolized in the cytosol via pyruvate to lactate. However, the investigators found four gene copies for ME, whose expression was not iron dependent. The majority of genes encoding amino acid metabolism were significantly upregulated under +Fe conditions. In contrast to genes encoding proteins involved in carbohydrate and amino acids metabolism, genes encoding ISCs assembly machinery and certain cysteine proteases were upregulated under −Fe conditions. The expression of 16 genes coding for cysteine proteases and metallopeptidases was found to be regulated by iron, and 9 of these genes were upregulated under −Fe conditions. For hydrogenosomal membrane proteins, only 2 proteins showed significant iron-dependent regulation; AAC-1 (upregulated under −Fe conditions) and AAC-2 (upregulated under +Fe conditions). With limited iron conditions and increased AAC-1 expression, ATP is transported from cytosol to hydrogenosomes. Finally, for the genes encoding proteins involved in the regulation of transcription and translation (including ribosomal proteins and proteins affecting DNA metabolism), only five genes were significantly regulated by iron. One gene was upregulated under +Fe conditions, and the other 4 were upregulated under −Fe conditions. The investigators concluded that iron has broad critical effects on T. vaginalis’s transcriptome as iron regulated the expression of a single gene, whereas the expression of other paralogous copies of the gene was iron independent. Short communication: IL-10 release by bovine epithelial cells cultured with Trichomonas vaginalis and Tritrichomonas foetus. Mem Inst Oswaldo Cruz (Rio de Janeiro); 2013 Feb, 108(1):110-2. Diagnosis: The estimated prevalence of trichomoniasis in men ranges from 0-58% in asymptomatic men and highrisk adolescents. In symptomatic men, trichomoniasis was associated with urethritis and prostatitis. Chronic prostatitis or chronic pelvic pain syndrome (CP/CPPS) is the most common form of prostatitis, with no existing reference standard for diagnosis (so, the condition is mostly recurrent). One of the most common causes of infection in chronic prostatitis is trichomoniasis (15%). Trichomoniasis also was incriminated in 13% of patients with non-gonococcal urethritis (NGU). Diagnosis of T. vaginalis in men using PCR was the main objective of a study conducted in Korea by Jong Jin Lee and his colleagues. They used primers based on a repetitive sequence cloned from T. vaginalis (TV-E650). These primars were used previously by the same investigators and proved 100% (sensitivity and specificity) to detect T. Transcriptomic identification of iron-regulated and iron-independent gene copies within the heavily duplicated Trichomonas vaginalis genome. Genome Biol Evol; 2012, 4(10):1017–29. 123 Spotlights on New Publications Treatment: Metronidazole (MTZ) is considered as a drug of choice for trichomoniasis with a cure rate of approximately 95%; but clinical resistance was reported since 1962. In their work, the Iranian investigator Hossein A. Youse and his colleagues investigated herbal plants in treatment of trichomoniasis in vitro in comparison to MTZ. They used TYIS culture medium containing isolated T. vaginalis with different concentrations of alcoholic and watery extracts of Iranian plants; Stachys lavanduifolia, Echinophora platyloba and Eucalyptus camaldulensis. The parasite number in each test tube was counted after 24, 48 and 72 h incubation. The results showed that MTZ (5 μg/ml), E. camaldulensis (60 or 90 μg) had significant effects on parasite count after 72 h, while no significant effect on T. vaginalis growth was observed on using alcoholic or watery extract of either S. lavandulifolia or E. platyloba. The authors discussed the antibacterial and antifungal effects of Eucaliptus spp. essential oil against several microorganisms such as Staphylococcus aureus, Esherichia coli and Candida albicans; in addition to its anti trypanosomal activity in vitro. Accordingly, the investigators concluded that E. camaldulensis could be used as an alternative drug for T. vaginalis treatment. They recommended further studies to recognize the efficient components of this plant to be used with unique efficiency against infective vaginitis; whatever the cause, bacterial, fungal or parasitic. vaginalis in vaginal discharge fluid at low concentration of 1 cell/per PCR mixture. In the present study, PCR was used to diagnose trichomoniasis in 33 male patients with chronic recurrent prostatitis and/or urethritis as well as in 84 male outpatients without lower urinary tract symptoms. Specimens used in the study were expressed prostatic secretion (EPS) and first-void urine and midstream urine samples of pre- (VB1 and Pre-M), and post-prostatic massage (VB3 and Post-M). Chronic prostatitis or urethritis were diagnosed by Pre-M and Post-M urine specimens, while EPS, VB1 and VB3 urine sediments were used for culture in TYM media. In a PCR technique, the specificity of the primers was tested against DNA extracted from Candida albicans, Chlamydia trachomatis, Neisseria gonorrhea, and Escherichia coli. Results showed that culture failed to diagnose trichomoniasis, whereas PCR identified 7 cases (21.2%), 5 of whom were diagnosed with prostatitis and 2 with urethritis. Positive PCR results were reported in bothVB1 and VB3 in all prostatitis cases and only in VB1 for urethritis patients. All the control patients (No. 84) gave no positive results for T. vaginalis neither by PCR nor by culture. The investigators concluded that PCR using urine specimens is more sensitive than culture for diagnosis of trichomoniasis, and recommended PCR screening among men with recurrent prostatitis and urethritis as a part of routine checking in public health units to control trichomoniasis. Effect of Echinophora platyloba, Stachys lavandulifolia, and Eucalyptus camaldulensis plants on Trichomonas vaginalis growth in vitro. Adv Biomed Res; 2012, 1: 79. PCR for diagnosis of male Trichomonas vaginalis infection with chronic prostatitis and urethritis. Korean J Parasitol; 2012 June, 50(2):157–9. Compiled by Prof. Dr. Sherif M. Abaza Parasitology Department, Faculty of Medicine Suez Canal University, Ismailia, Egypt. Email: [email protected] 124 Vol. 6, No. 1, 2013 ISSN: 1687-7942 PA R A S I TO L O G I C A L R E S O U R C E S 1. TropEduWeb-Swiss tropical Institute: Web-basedLearning Tools for Tropical Medicine and Parasitology: http://www.tropeduweb.ch/: This web site is maintained by the Swiss Tropical Institute (STI) which undertakes research, teaching/training and provides services in the fields of tropical medicine, travel medicine and international health. STI is an associated institute of the University of Basel. Many members of the STI staff hold teaching posts (professors, senior lecturers) at the University of Basel in the faculties of Sciences, Medicine, and Arts (Ethnology). The site is intended to provide interactive web-based learning with continuous auto-evaluation and formal assessments based on the specific teaching and learning objectives. The learning process is user-driven and covers the full spectrum from acquiring information/knowledge to conceptualising and conceptualising complex systems based on theories and case studies. PUJ diagnosis and treatment. The second page has pictures and videos. 5. John Hopkins School of Public Health Malariology Course: http://ocw.jhsph.edu/index.cfm/go/viewCourse/ course/malariology/coursePage/index/: This is a free web course which presents issues related to malaria as a major public health problem. It emphasizes the biology of malaria parasites and factors affecting their transmission to humans by anopheline vectors. Topics include host-parasite-vector relationships; diagnostics; parasite biology; vector biology; epidemiology; host immunity; risk factors associated with infection, human behavior, chemotherapy, and drug resistances; antivector measures; vaccine development; and management and policy issues. 2. Schistosomiasis Research Group-University of Cambridge: http://www.path.cam.ac.uk/~schisto/index.htm: This site is intended to convey information not only on the research that is carried out by Schistosomiasis Research Group at Cambridge University, but also all aspects of schistosomiasis as a tropical parasitic disease. Other helminth infections are also covered, although in less detail. 6. History of Parasitology and Tropical Medicine: http://dna.kdna.ucla.edu/parasite_course-old/intro_files/ intro1.htm: This website shows the history of eminent Parasitologists who contributed to the discovery of parasites starting from the 17th century when the Dutch amateur scientist Anton van Leeuwenhoek discovered the first protozoan parasite, Giardia, till the late seventies of the 20th century when Trager and Jensen, at Rockefeller University in New York, discovered a simple method to grow the pathogenic human malaria, Plasmodium falciparum, in continuous culture inside red blood cells. 3. PLOS Neglected Tropical Diseases Journal: http:// www.plosntds.org/ PLOS Neglected Tropical Diseases (eISSN 1935-2735) is an open-access journal devoted to the world's most neglected tropical diseases (NTDs), such as elephantiasis, river blindness, leprosy, hookworm, schistosomiasis, and African sleeping sickness. The journal publishes high-quality, peer-reviewed research on all scientific, medical, and public-health aspects of these forgotten diseases affecting the world's forgotten people. PLOS Neglected Tropical Diseases is published online by PLOS, a nonprofit organization. The journal's start-up phase is supported by a grant from the Bill and Melinda Gates Foundation. PLOS Neglected Tropical Diseases is indexed in PubMed, PubMed Central, Scopus, Google Scholar, and the Web of Science. 7. Introduction to Diagnostic Medical Parasitology: Swiss Tropical and Public Health Institute: http:// www.parasite-diagnosis.ch/: This learning software allows beginners to gain experience in diagnosing the most important helminth and protozoan diseases of humans. For this purpose, one can gain basic knowledge through short overviews of parasites, diseases, diagnostic methods and strategies. Even more important, one can train diagnostic capabilities using a virtual microscope. The course leads the student from basic training to more complicated diagnostic exercises. The underlined purpose is to facilitate a first approach to Diagnostic Medical Parasitology. This programme cannot replace working with a real microscope or consulting diagnostic textbooks and atlases. 4. Parasites in Humans Organization: http://www. parasitesinhumans.org/ This website is all about parasitic infections caused by worms, protozoa and skin parasites. Each parasite species has two pages. The first of the two contains basic information such as: life cycle, symptoms, Compiled by Prof. Dr. Khalifa E. Khalifa Parasitology Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt. Email: [email protected] Personal non-commercial use only. PUJ copyright © 2013. All rights reserved PUJ; 2013, 6(1): 125