Thio- and selenosemicarbazones as antiprotozoal agents against Trypanosoma cruzi and Trichomonas vaginalis.

Herein, we report the preparation of a panel of Schiff bases analogues as antiprotozoal agents by modification of the stereoelectronic effects of the substituents on N-1 and N-4 and the nature of the chalcogen atom (S, Se). These compounds were evaluated towards Trypanosoma cruzi and Trichomonas vaginalis. Thiosemicarbazide 31 showed the best trypanocidal profile (epimastigotes), similar to benznidazole (BZ): IC50 (31)=28.72 µM (CL-B5 strain) and 33.65 µM (Y strain), IC50 (BZ)=25.31 µM (CL-B5) and 22.73 µM (Y); it lacked toxicity over mammalian cells (CC50 > 256 µM). Thiosemicarbazones 49, 51 and 63 showed remarkable trichomonacidal effects (IC50 =16.39, 14.84 and 14.89 µM) and no unspecific cytotoxicity towards Vero cells (CC50 ≥ 275 µM). Selenoisosters 74 and 75 presented a slightly enhanced activity (IC50=11.10 and 11.02 µM, respectively). Hydrogenosome membrane potential and structural changes were analysed to get more insight into the trichomonacidal mechanism.

Promising hit compounds against resistant trichomoniasis: Synthesis and antiparasitic activity of 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles.

A series of 11 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles (2-12) has been prepared starting from 1-benzyl-5-nitroindazol-3-ol 13, and evaluated against sensitive and resistant isolates of the sexually transmitted protozoan Trichomonas vaginalis. Compounds 2, 3, 6, 9, 10 and 11 showed trichomonacidal profiles with IC50 < 20 µM against the metronidazole-sensitive isolate. Moreover, all these compounds submitted to cytotoxicity assays against mammalian cells exhibited low non-specific cytotoxic effects, except compounds 3 and 9 which displayed moderate cytotoxicity (CC50 = 74.7 and 59.1 µM, respectively). Those compounds with trichomonacidal effect were also evaluated against a metronidazole-resistant culture. Special mention deserve compounds 6 and 10, which displayed better IC50 values (1.3 and 0.5 µM respectively) than that of the reference drug (IC50 MTZ = 3.0 µM). The high activity of these compounds against the resistant isolate reinforces the absence of cross-resistance with the reference drug. The remarkable trichomonacidal results against resistant T. vaginalis isolates suggest the interest of 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles to be considered as good prototypes to continue in the development of new drugs with enhanced trichomonacidal activity, aiming to increase the non-existent drugs to face clinical resistance efficiently for those patients in whom therapy with 5-nitroimidazoles is contraindicated.

Expansion of T regulatory lymphocytes by murine bone marrow dendritic cells previously stimulated with Anisakis simplex larval antigens.

BACKGROUND: Anisakis simplex antigens present immunomodulatory properties by the induction of tolerogenic dendritic cells (DCs) in mice. OBJECTIVES: To study the capacity of DCs stimulated with A. simplex excretory-secretory (ES) or crude extract (CE) to generate Tregs. To investigate in vitro effects of antigens on the metabolic activity of splenocytes induced by LPS or CpG. METHODS: Phenotypic and functional characterization of T cells co-cultured with A. simplex-pulsed DCs was performed by flow cytometry. Lymphocyte mitochondrial respiratory activity was estimated by the Alamar Blue® Assay. FINDINGS: In C57BL/6J, CD4+CD25-Foxp3+ and CD8+CD25-Foxp3+ populations increased by CE-stimulated-DCs. In BALB/c, CE-stimulated-DCs caused the expansion of CD4+CD25+Foxp3+IL-10+ and CD8+CD25+Foxp3+IL-10+. IFN-γ expression raised in BALB/c CD4+CD25+ and CD4+CD25- for CE and ES, respectively. ES-stimulated-DCs increased CD4+CD25+ Foxp3+ and CD8+CD25- Foxp3+ expression in T cells. The association of ES or CE with LPS produced the increase in splenocyte activity in C57BL/6J. The association of CE with CpG decreased the proliferation caused by CpG in C57BL/6J. MAIN CONCLUSIONS: A. simplex increase the frequency of Tregs, which in turn produce IL-10 and IFN-γ. The host genetic base is essential in the development of anti-Anisakis immune responses (Th2, Th1, Treg).

Trichomoniasis in a tertiary hospital of Madrid, Spain (2013-2017): prevalence and pregnancy rate, coinfections, metronidazole resistance, and endosymbiosis.

Trichomoniasis is the most prevalent curable sexually transmitted infection (STI) worldwide and a risk factor for the acquisition of other STIs and adverse pregnancy outcomes. The objectives of this study were to determine the prevalence of T. vaginalis and related coinfections in women attending a third-level hospital of Madrid (Spain). A retrospective study of 24,173 vaginal exudates from women with suspected vaginitis was conducted between 2013 and 2017. Likewise, among T. vaginalis positive samples, co-occurrence with gonorrhea, chlamydia, syphilis, VIH, Mycoplasma hominis, and Ureaplasma urealyticum was checked. Moreover, seven T. vaginalis isolates from 2017 were randomly collected for endobionts, drug resistance, and microsatellite (MS) instability determinations. The prevalence of T. vaginalis was 0.8% between 2013 and 2017. Less than 20% of patients with trichomoniasis were submitted to a complete screening for other genital pathogens. From that, two patients were coinfected with chlamydia and three with syphilis. Surprisingly, 6.4% of positive samples were diagnosed among pregnant women, showing an alarming increase from 3.2% (2014) to 10% (2017). Among the isolates randomly analyzed, five carried T. vaginalis virus, five harbored mycoplasmas, and one was metronidazole-resistant. The molecular genotyping showed a high variability in the three MS evaluated. To our knowledge, this is the first study in Spain that evaluates the prevalence of trichomoniasis in general and pregnant population and includes biomolecular determinations. These results warn about the increasing prevalence and highlight the importance of including T. vaginalis detection in routine gynecological revisions with special emphasis on childbearing age women and patients with previous STIs.

An in vitro characterisation of the Trichomonas vaginalis TATA box-binding proteins (TBPs).

The protozoan parasite Trichomonas vaginalis is a common human pathogen from one of the earliest-diverging eukaryotic lineages. At the transcriptional level, the highly conserved Inr element of RNA pol II-transcribed genes surrounds the transcription start site and is recognised by IBP39, a protein exclusive of T. vaginalis. Typical TATA boxes have not been identified in this organism but, in contrast, BLAST analyses of the T. vaginalis genome identified two genes encoding putative TATA-binding proteins (herein referred to as TvTBP1 and TvTBP2). The goal of this work was to characterise these two proteins at the molecular level. Our results show that both TvTBPs theoretically adopt the saddle-shaped structure distinctive to TBPs and both Tvtbp genes are expressed in T. vaginalis. TvTBP1 did not complement a Saccharomyces cerevisiae mutant lacking TBP; however, TvTBP1 and TvTBP2 proteins bound T. vaginalis DNA promoter sequences in EMSA assays. We propose that TvTBP1 may be part of the preinitiation transcription complex in T. vaginalis since TvTBP1 recombinant protein was able to bind IBP39 in vitro. This work represents the first approach towards the characterisation of general transcription factors in this early divergent organism.

In vitro trichomonacidal activity and preliminary in silico chemometric studies of 5-nitroindazolin-3-one and 3-alkoxy-5-nitroindazole derivatives.

A selection of 1,2-disubstituted 5-nitroindazolin-3-ones (1-19) and 3-alkoxy-5-nitroindazoles substituted at positions 1 (20-24) or 2 (25-39) from our in-house compound library were screened in vitro against the most common curable sexually transmitted pathogen, Trichomonas vaginalis. A total of 41% of the studied molecules (16/39) achieved a significant activity of more than 85% growth inhibition at the highest concentration assayed (100 µg mL(-1)). Among these compounds, 3-alkoxy-5-nitroindazole derivatives 23, 24, 25 and 27 inhibited parasite growth by more than 50% at 10 µg mL(-1). In addition, the first two compounds (23, 24) still showed remarkable activity at the lowest dose tested (1 µg mL(-1)), inhibiting parasite growth by nearly 40%. Their specific activity towards the parasite was corroborated by the determination of their non-specific cytotoxicity against mammalian cells. The four mentioned compounds exhibited non-cytotoxic profiles at all of the concentrations assayed, showing a fair antiparasitic selectivity index (SI > 7·5). In silico studies were performed to predict pharmacokinetic properties, toxicity and drug-score using Molinspiration and OSIRIS computational tools. The current in vitro results supported by the virtual screening suggest 2-substituted and, especially, 1-substituted 3-alkoxy-5-nitroindazoles as promising starting scaffolds for further development of novel chemical compounds with the main aim of promoting highly selective trichomonacidal lead-like drugs with adequate pharmacokinetic and toxicological profiles.

Trypanocidal, trichomonacidal and cytotoxic components of cultivated Artemisia absinthium Linnaeus (Asteraceae) essential oil.

Artemisia absinthium is an aromatic and medicinal plant of ethnopharmacological interest and it has been widely studied. The use ofA. absinthium based on the collection of wild populations can result in variable compositions of the extracts and essential oils (EOs). The aim of this paper is the identification of the active components of the vapour pressure (VP) EO from a selected and cultivated A. absinthium Spanish population (T2-11) against two parasitic protozoa with different metabolic pathways: Trypanosoma cruzi and Trichomonas vaginalis. VP showed activity on both parasites at the highest concentrations. The chromatographic fractionation of the VP T2-11 resulted in nine fractions (VLC1-9). The chemical composition of the fractions and the antiparasitic effects of fractions and their main compounds suggest that the activity of the VP is related with the presence of trans-caryophyllene and dihydrochamazulene (main components of fractions VLC1 and VLC2 respectively). Additionally, the cytotoxicity of VP and fractions has been tested on several tumour and no tumour human cell lines. Fractions VLC1 and VLC2 were not cytotoxic against the nontumoural cell line HS5, suggesting selective antiparasitic activity for these two fractions. The VP and fractions inhibited the growth of human tumour cell lines in a dose-dependent manner.

Selective nematocidal effects of essential oils from two cultivated Artemisia absinthium populations.

Essential oils (EOs) obtained from two crops and populations of thujone-free cultivated Artemisia absinthium were tested against two nematode models, the mammalian parasite Trichinella spiralis, and the plant parasitic root knot nematode Meloidogyne javanica. The EOs were characterized by the presence of (Z)-epoxyocimene and chrysanthenol as major components and showed time and population dependent quantitative and qualitative variations in composition. The EOs showed a strong ex vivo activity against the L1 larvae of the nematode Trichinella spiralis with a reduction of infectivity between 72 and 100% at a dose range of 0.5-1 mg/ml in absence of cytotoxicity against mammalian cells. Moreover, the in vivo activity of the EO against T. spiralis showed a 66% reduction of intestinal adults. However, these oils were not effective against M. javanica.

The Past, Present, and Future in the Diagnosis of a Neglected Sexually Transmitted Infection: Trichomoniasis.

More than one million curable sexually transmitted infections occur every day. Trichomonas vaginalis is one of the main infections responsible for these epidemiological data; however, the diagnosis of this protozoan is still mainly based on microscopic and culture identification. The commercialization of immunological tests and the development of molecular techniques have improved the sensitivity of classical methods. Nevertheless, the fact that trichomoniasis is a neglected parasitic infection hinders the development of novel techniques and their implementation in routine diagnosis. This review article shows the different methods developed to identify T. vaginalis in population and the difficulties in diagnosing male and asymptomatic patients. The importance of including this parasite in routine gynecological screening, especially in pregnant women, and the importance of considering T. vaginalis as an indicator of high-risk sexual behavior are also discussed.

Impact of COVID-19 Pandemic on the Trends of Trichomonas vaginalis Infection in a Tertiary Hospital of Madrid, Spain.

More than one million sexually transmitted infections (STIs) occur every day, and Trichomonas vaginalis is responsible for more than 156 million cases each year worldwide. Nevertheless, epidemiological studies of this parasite in Europe are scarce. The aim of this study was to evaluate the impact that the COVID-19 pandemic may have had in the diagnosis and epidemiology of trichomoniasis. All available data from January 2018 to December 2021 for T. vaginalis isolation on gynecologic patients attending a Spanish Tertiary Hospital were analyzed. Pre-pandemic results (2018-2019) were compared to pandemic results (2020-2021). The pre-pandemic T. vaginalis prevalence in women was 1.15% (95% Confidence Interval, CI: 0.94-1.41), and significantly decreased in 2020-2021 (0.77%, 95% CI: 0.57-1.03; p = 0.025). Demographic nor clinical characteristics of women diagnosed with trichomoniasis did not statistically differ between the periods, although an increase in chlamydia co-infected patients was observed in the latest (from 8% in 2018-2019 to 19% in 2020-2021). This study has detected a decrease in the diagnosis of trichomoniasis; however, this is probably due to the increase in the healthcare pressure triggered by the pandemic. More than 75% of the cases diagnosed in 2021 occurred in the second half, which suggests that special attention should be given to the evolution in the coming years once normality has been restored in hospitals. Moreover, these results warn of the lack of routine diagnosis of trichomoniasis during pregnancy and the absence of specific protocols for possible co-infections, which could become a strategy to reduce the growing trend of STIs, including T. vaginalis detection, as an interesting marker of sexual risk behaviors.

Antibacterial, Trichomonacidal, and Cytotoxic Activities of Pleopeltis crassinervata Extracts.

Pleopeltis crassinervata is a fern documented in ethnobotanical records for its use in Mexican traditional medicine to treat gastric disorders and mouth ulcers. Consequently, conducting biological and pharmacological assays is crucial to validate the therapeutic efficacy of this plant within the context of traditional medicine. In the present study, we investigated the biological activity of extracts and fractions obtained from P. crassinervata organs against bacteria (Salmonella typhimurium, Salmonella typhi, Staphylococcus aureus, Proteus mirabilis, Shigella flexneri, Bacillus subtilis, Escherichia coli) and Trichomonas vaginalis using in vitro models. The precipitate fraction obtained from the frond methanolic extract showed significant antibacterial activity (minimal inhibitory concentration [MIC] 120 µg/mL) against the Staphylococcus aureus strain and was effective against both Gram-positive and Gram-negative bacteria. The hexane fraction also obtained from frond methanolic extract, showed a trichomonacidal effect with an IC50 of 82.8 µg/mL and a low cytotoxic effect. Hsf6 exhibited the highest activity against T. vaginalis, and the GC-MS analysis revealed that the predominant compound was 16-pregnenolone. The remaining identified compounds were primarily terpene-type compounds.

Synthesis and Biophysical and Biological Studies of N-Phenylbenzamide Derivatives Targeting Kinetoplastid Parasites.

The AT-rich mitochondrial DNA (kDNA) of trypanosomatid parasites is a target of DNA minor groove binders. We report the synthesis, antiprotozoal screening, and SAR studies of three series of analogues of the known antiprotozoal kDNA binder 2-((4-(4-((4,5-dihydro-1H-imidazol-3-ium-2-yl)amino)benzamido)phenyl)amino)-4,5-dihydro-1H-imidazol-3-ium (1a). Bis(2-aminoimidazolines) (1) and bis(2-aminobenzimidazoles) (2) showed micromolar range activity against Trypanosoma brucei, whereas bisarylimidamides (3) were submicromolar inhibitors of T. brucei, Trypanosoma cruzi, and Leishmania donovani. None of the compounds showed relevant activity against the urogenital, nonkinetoplastid parasite Trichomonas vaginalis. We show that series 1 and 3 bind strongly and selectively to the minor groove of AT DNA, whereas series 2 also binds by intercalation. The measured pKa indicated different ionization states at pH 7.4, which correlated with the DNA binding affinities (ΔTm) for series 2 and 3. Compound 3a, which was active and selective against the three parasites and displayed adequate metabolic stability, is a fine candidate for in vivo studies.

5-Nitroindazole-based compounds: further studies for activity optimization as anti-Trypanosoma cruzi agents.

In this study, a new series of eleven 5-nitroindazole derivatives (10-20) and a related 6-nitroquinazoline (21) was synthesized and tested in vitro against different forms of the kinetoplastid parasite Trypanosoma cruzi, etiological agent of Chagas disease. Among these compounds, derivatives 11-14 and 17 showed trypanocidal profiles on epimastigotes (IC50 = 1.00-8.75 µM) considerably better than that of the reference drug benznidazole, BZ (IC50 = 25.22 µM). Furthermore, the lack of cytotoxicity observed for compounds 11, 12, 14, 17 and 18 over L929 fibroblasts, led to a notable selectivity (SI) on the extracellular replicative form of the parasite: SIEPI > 12.41 to > 256 µM. Since these five derivatives overpassed the cut-off value established by BZ (SIEPI ≥ 10), they were moved to a more specific assay against the intracellular and replicative form of T. cruzi, i.e, amastigotes. These molecules were not as active as BZ (IC50 = 0.57 µM) against this parasite form; however, all of them showed remarkable IC50 values lower than 7 µM. Special mention deserve compounds 12 and 17, whose SIAMA were > 246.15 and > 188.23, respectively. The results compiled in the present work, point to a positive impact over the trypanocidal activity of the electron withdrawing substituents introduced at position 2 of the N-2 benzyl moiety of these compounds, especially fluorine, i.e., derivatives 12 and 17. These outcomes, supported by the in silico prediction of good oral bioavailability and suitable risk profile, reinforce the 5-nitroindazole scaffold as an adequate template for preparing potential antichagasic agents.

Antiparasitic Properties of Cantharidin and the Blister Beetle Berberomeloe majalis (Coleoptera: Meloidae).

Cantharidin (CTD) is a toxic monoterpene produced by blister beetles (Fam. Meloidae) as a chemical defense against predators. Although CTD is highly poisonous to many predator species, some have evolved the ability to feed on poisonous Meloidae, or otherwise beneficially use blister beetles. Great Bustards, Otis tarda, eat CTD-containing Berberomeloe majalis blister beetles, and it has been hypothesized that beetle consumption by these birds reduces parasite load (a case of self-medication). We examined this hypothesis by testing diverse organisms against CTD and extracts of B. majalis hemolymph and bodies. Our results show that all three preparations (CTD and extracts of B. majalis) were toxic to a protozoan (Trichomonas vaginalis), a nematode (Meloidogyne javanica), two insects (Myzus persicae and Rhopalosiphum padi) and a tick (Hyalomma lusitanicum). This not only supports the anti-parasitic hypothesis for beetle consumption, but suggests potential new roles for CTD, under certain conditions.

Drug repositioning for novel antitrichomonas from known antiprotozoan drugs using hierarchical screening.

AIM: Metronidazole is the most widely used drug in trichomoniasis therapy. However, the emergence of metronidazole-resistant Trichomonas vaginalis isolates calls for the search for new drugs to counter the pathogenicity of these parasites. RESULTS: Classification models for predicting the antitrichomonas activity of molecules were built. These models were employed to screen antiprotozoal drugs, from which 20 were classified as active. The in vitro experiments showed moderate to high activity for 19 of the molecules at 10 µg/ml, while 3 compounds yielded higher activity than the reference at 1 µg/ml. The 11 most active chemicals were evaluated in vivo using Naval Medical Research Institute (NMRI) mice. CONCLUSION: Benznidazole showed similar results as metronidazole, and can thus be considered as a potential candidate in antitrichomonas therapy.

Antichagasic, Leishmanicidal, and Trichomonacidal Activity of 2-Benzyl-5-nitroindazole-Derived Amines.

Three different series of new 5-nitroindazole derivatives-1-(ω-aminoalkyl)-2-benzylindazolin-3-ones (series A; ten compounds), 3-(ω-aminoalkoxy)-2-benzylindazoles (series B; four compounds) and 3-alkylamino-2-benzylindazoles (series C; five compounds)-have been synthesized and evaluated against the protozoan parasites Trypanosoma cruzi, Leishmania amazonensis, and Trichomonas vaginalis: etiological agents of Chagas disease, cutaneous leishmaniasis, and trichomoniasis, respectively. Many indazoles of series A, B, and C were efficient against T. cruzi. Some compounds in series A, after successfully passing the preliminary screening for epimastigotes, exhibited activity values against amastigotes of several T. cruzi strains that were better than or similar to those shown by the reference drug benznidazole and displayed low nonspecific toxicity against mammalian cells. On the other hand, preliminary studies against promastigotes of L. amazonensis showed high leishmanicidal activity for some derivatives of series A and C. With regard to activity against T. vaginalis, some indazoles of series B and C were rather efficient against trophozoites of a metronidazole-sensitive isolate and showed low nonspecific toxicities toward Vero cell cultures. Additionally, some of these compounds displayed similar activity against metronidazole-sensitive and resistant isolates, showing the absence of cross-resistance between these derivatives and the reference drug.

Expansion of T regulatory lymphocytes by murine bone marrow dendritic cells previously stimulated with Anisakis simplex larval antigens

BACKGROUND Anisakis simplex antigens present immunomodulatory properties by the induction of tolerogenic dendritic cells (DCs) in mice. OBJECTIVES To study the capacity of DCs stimulated with A. simplex excretory-secretory (ES) or crude extract (CE) to generate Tregs. To investigate in vitro effects of antigens on the metabolic activity of splenocytes induced by LPS or CpG. METHODS Phenotypic and functional characterization of T cells co-cultured with A. simplex-pulsed DCs was performed by flow cytometry. Lymphocyte mitochondrial respiratory activity was estimated by the Alamar Blue® Assay. FINDINGS In C57BL/6J, CD4+CD25-Foxp3+ and CD8+CD25-Foxp3+ populations increased by CE-stimulated-DCs. In BALB/c, CE-stimulated-DCs caused the expansion of CD4+CD25+Foxp3+IL-10+ and CD8+CD25+Foxp3+IL-10+. IFN-γ expression raised in BALB/c CD4+CD25+ and CD4+CD25- for CE and ES, respectively. ES-stimulated-DCs increased CD4+CD25+ Foxp3+ and CD8+CD25- Foxp3+ expression in T cells. The association of ES or CE with LPS produced the increase in splenocyte activity in C57BL/6J. The association of CE with CpG decreased the proliferation caused by CpG in C57BL/6J. MAIN CONCLUSIONS A. simplex increase the frequency of Tregs, which in turn produce IL-10 and IFN-γ. The host genetic base is essential in the development of anti-Anisakis immune responses (Th2, Th1, Treg).

Antichagasic and trichomonacidal activity of 1-substituted 2-benzyl-5-nitroindazolin-3-ones and 3-alkoxy-2-benzyl-5-nitro-2H-indazoles.

Two series of new 5-nitroindazole derivatives, 1-substituted 2-benzylindazolin-3-ones (6-29, series A) and 3-alkoxy-2-benzyl-2H-indazoles (30-37, series B), containing differently functionalized chains at position 1 and 3, respectively, have been synthesized starting from 2-benzyl-5-nitroindazolin-3-one 5, and evaluated against the protozoan parasites Trypanosoma cruzi and Trichomonas vaginalis, etiological agents of Chagas disease and trichomonosis, respectively. Many indazolinones of series A were efficient against different morphological forms of T. cruzi CL Brener strain (compounds 6, 7, 9, 10 and 19-21: IC50 = 1.58-4.19 µM for epimastigotes; compounds 6, 19-21 and 24: IC50 = 0.22-0.54 µM for amastigotes) being as potent as the reference drug benznidazole. SAR analysis suggests that electron-donating groups at position 1 of indazolinone ring are associated with an improved antichagasic activity. Moreover, compounds of series A displayed low unspecific toxicities against an in vitro model of mammalian cells (fibroblasts), which were reflected in high values of the selectivity indexes (SI). Compound 20 was also very efficient against amastigotes from Tulahuen and Y strains of T. cruzi (IC50 = 0.81 and 0.60 µM, respectively), showing low toxicity towards cardiac cells (LC50 > 100 µM). In what concerns compounds of series B, some of them displayed moderate activity against trophozoites of a metronidazole-sensitive isolate of T. vaginalis (35 and 36: IC50 = 9.82 and 7.25 µM, respectively), with low unspecific toxicity towards Vero cells. Compound 36 was also active against a metronidazole-resistant isolate (IC50 = 9.11 µM) and can thus be considered a good prototype for the development of drugs directed to T. vaginalis resistant to 5-nitroimidazoles.

Sequestration of host-CD59 as potential immune evasion strategy of Trichomonas vaginalis.

Trichomonas vaginalis is known to evade complement-mediated lysis. Because the genome of T. vaginalis does not possess DNA sequence with homology to human protectin (CD59), a complement lysis restricting factor, we tested the hypothesis that host CD59 acquisition by T. vaginalis organisms mediates resistance to complement killing. This hypothesis was based on the fact that trichomonads are known to associate with host proteins. No CD59 was detected on the surface of T. vaginalis grown in serum-based medium using as probe anti-CD59 monoclonal antibody (MAb). We, therefore, infected mice intraperitoneally with live T. vaginalis, and trichomonads harvested from ascites were tested for binding of CD59. Immunofluorescence showed that parasites had surface CD59. Furthermore, as mouse erythrocytes (RBCs) possess membrane-associated CD59, and trichomonads use RBCs as a nutrient source, organisms were co-cultured with murine RBCs for one week. Parasites were shown to have detectable surface CD59. Importantly, live T. vaginalis with bound CD59 were compared with batch-grown parasites without surface-associated CD59 for sensitivity to complement in human serum. Trichomonads without surface-bound CD59 had a higher level of killing by complement than did parasites with surface CD59. These data show that host CD59 acquired onto the surface by live T. vaginalis may be an alternative mechanism for complement evasion. We describe a novel strategy by T. vaginalis consistent with host protein procurement by this parasite to evade the lytic action of complement.

Synthesis and in vitro and in vivo biological evaluation of substituted nitroquinoxalin-2-ones and 2,3-diones as novel trichomonacidal agents.

Two series of ten novel 7-nitroquinoxalin-2-ones and ten 6-nitroquinoxaline-2,3-diones with diverse substituents at positions 1 and 4 were synthesized and evaluated against the sexually transmitted parasite Trichomonas vaginalis. Furthermore, diverse molecular and drug-likeness properties were analyzed to predict the oral bioavailability following the Lipinski's "rule of five". 7-Nitroquinoxalin-2-one derivatives displayed moderate to high in vitro activity while the efficiency of most nitroquinoxaline-2,3-diones was rather low; both kinds of compounds did not show cytotoxic effects in mammalian cells. 7-Nitro-4-(3-piperidinopropyl)quinoxalin-2-one 9 achieved the highest trichomonacidal activity (IC50 = 18.26 µM) and was subsequently assayed in vivo in a murine model of trichomonosis. A 46.13% and a 50.70% reduction of pathogenic injuries were observed in the experimental groups treated orally during 7 days with 50 mg/kg and 100 mg/kg doses. The results obtained in the biological assays against T. vaginalis indicate that compounds with ω-(dialkylamino)alkyl substituents and a keto group at positions 4 and 2 of quinoxaline ring, respectively, provide interesting structural cores to develop novel prototypes to enhance the nitroquinoxalinones activity as trichomonacidal agents with interesting ADME properties according to virtual screening analysis.