Q2Despite their diversity in structures and functions, all 60 isoprenoids are derived from the common precursor isopentenyl di-61 phosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). 62Until recently, it was assumed that IPP and DMAPP were solely syn-63 thesized through the mevalonic acid (MVA) pathway (Chappell, 64 1995). However, it is now well established that they can also be pro-65 duced by the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway 66 (Lichtenthaler, 1999;Rodriguez-Concepcion and Boronat, 2002 81Another mechanism known to provide plasticity to plant metabolic 82 responses is provided by functional diversification of specific enzymes. 83Enzymes involved in secondary metabolic pathways are commonly

SUMOylation is a post‐translational modification that positively regulates monoallelic expression of the trypanosome variant surface glycoprotein (VSG). The presence of a highly SUMOylated focus associated with the nuclear body, where the VSG gene is transcribed, further suggests an important role of SUMOylation in regulating VSG expression. Here, we show that SNF2PH, a SUMOylated plant homeodomain (PH)‐transcription factor, is upregulated in the bloodstream form of the parasite and enriched at the active VSG telomere. SUMOylation promotes the recruitment of SNF2PH to the VSG promoter, where it is required to maintain RNA polymerase I and thus to regulate VSG transcript levels. Further, ectopic overexpression of SNF2PH in insect forms, but not of a mutant lacking the PH domain, induces the expression of bloodstream stage‐specific surface proteins. These data suggest that SNF2PH SUMOylation positively regulates VSG monoallelic transcription, while the PH domain is required for the expression of bloodstream‐specific surface proteins. Thus, SNF2PH functions as a positive activator, linking expression of infective form surface proteins and VSG regulation, thereby acting as a major regulator of pathogenicity.

Asymptomatic Leishmania infections have been the main cause of transfusion transmission in endemic areas. Polymerase chain reaction has been used to detect L. infantum DNA in the peripheral blood of asymptomatic Leishmania carriers. In our region, the prevalence of asymptomatic L. infantum infection in donors is markedly high (5·9% of donors studied). We investigated the ability of pathogen inactivation technology, using amotosalen and UVA illumination, to eliminate L. infantum in a blood component collected from an asymptomatic L. infantum infected donor. This is the first report of the INTERCEPT system being used to eliminate a parasite from a component collected from a donor.

Catalase is one of the most abundant enzymes on Earth. It decomposes hydrogen peroxide, thus protecting cells from dangerous reactive oxygen species. The catalase-encoding gene is conspicuously absent from the genome of most representatives of the family Trypanosomatidae. Here, we expressed this protein from the Leishmania mexicana Β-TUBULIN locus using a novel bicistronic expression system, which relies on the 2A peptide of Teschovirus A . We demonstrated that catalase-expressing parasites are severely compromised in their ability to develop in insects, to be transmitted and to infect mice, and to cause clinical manifestation in their mammalian host. Taken together, our data support the hypothesis that the presence of catalase is not compatible with the dixenous life cycle of Leishmania , resulting in loss of this gene from the genome during the evolution of these parasites.

Neglected tropical diseases such as human African trypanosomiasis (HAT) are prevalent primarily in tropical climates and among populations living in poverty. Historically, the lack of economic incentive to develop new treatments for these diseases has meant that existing therapeutics have serious shortcomings in terms of safety, efficacy, and administration, and better therapeutics are needed. We now report a series of 3,5-disubstituted-7-azaindoles identified as growth inhibitors of Trypanosoma brucei, the parasite that causes HAT, through a high-throughput screen. We describe the hit-to-lead optimization of this series and the development and preclinical investigation of 29d, a potent anti-trypanosomal compound with promising pharmacokinetic (PK) parameters. This compound was ultimately not progressed beyond in vivo PK studies due to its inability to penetrate the blood-brain barrier (BBB), critical for stage 2 HAT treatments. Targeted Value NEU-1207 NEU-1208 NEU-1209 T.b.b. pEC50 ≥7 7.0 7.2 6.5 HepG2 pTC50 ≤pEC50-2 4.5 5.0 4.0 cLogP ≤3 2.6 2.8 2.2 TPSA (Å 2 ) 4010 2 18 † 12 † PPB (%) <95 95 nd nd

Leishmaniasis is a parasitic vector-borne disease caused by the protistan flagellates of the genus Leishmania. Leishmania (Viannia) guyanensis is one of the most common causative agents of the American tegumentary leishmaniasis. It has previously been shown that L. guyanensis strains that carry the endosymbiotic Leishmania RNA virus 1 (LRV1) cause more severe form of the disease in a mouse model than those that do not. The presence of the virus was implicated into the parasite’s replication and spreading. In this respect, studying the molecular mechanisms of cellular control of viral infection is of great medical importance. Here, we report ~30.5 Mb high-quality genome assembly of the LRV1-positive L. guyanensis M4147. This strain was turned into a model by establishing the CRISPR-Cas9 system and ablating the gene encoding phosphatidate phosphatase 2-like (PAP2L) protein. The orthologue of this gene is conspicuously absent from the genome of an unusual member of the family Trypanosomatidae, Vickermania ingenoplastis, a species with mostly bi-flagellated cells. Our analysis of the PAP2L-null L. guyanensis showed an increase in the number of cells strikingly resembling the bi-flagellated V. ingenoplastis, likely as a result of the disruption of the cell cycle, significant accumulation of phosphatidic acid, and increased virulence compared to the wild type cells.

Novymonas esmeraldas is a parasitic flagellate of the family Trypanosomatidae representing the closest insect-restricted relative of the human pathogen Leishmania . It bears symbiotic bacteria in its cytoplasm, the relationship with which has been established relatively recently and independently from other known endosymbioses in protists.

Leishmania spp. represent human pathogens that cause leishmaniasis, a widespread parasitic disease with mild to fatal clinical manifestations. Some strains of leishmaniae bear leishmaniaviruses (LRVs), and this has been shown to aggravate disease course.