Repurposing the orphan drug nitisinone to control the transmission of African trypanosomiasis

Tsetse transmit African trypanosomiasis, which is a disease fatal to both humans and animals. A vaccine to protect against this disease does not exist so transmission control relies on eliminating tsetse populations. Although neurotoxic insecticides are the gold standard for insect control, they negatively impact the environment and reduce populations of insect pollinator species. Here we present a promising, environment-friendly alternative to current insecticides that targets the insect tyrosine metabolism pathway. A bloodmeal contains high levels of tyrosine, which is toxic to haematophagous insects if it is not degraded and eliminated. RNA interference (RNAi) of either the first two enzymes in the tyrosine degradation pathway (tyrosine aminotransferase (TAT) and 4-hydroxyphenylpyruvate dioxygenase (HPPD)) was lethal to tsetse. Furthermore, nitisinone (NTBC), an FDA-approved tyrosine catabolism inhibitor, killed tsetse regardless if the drug was orally or topically applied. However, oral administration of NTBC to bumblebees did not affect their survival. Using a novel mathematical model, we show that NTBC could reduce the transmission of African trypanosomiasis in sub-Saharan Africa, thus accelerating current disease elimination programmes

Alignment of the RdRp4 domain from PMeV and related viruses.

<p>Alignment of the RdRp4 domain (pfam02123) identified in ORF2 of papaya meleira virus (PMeV) with the corresponding regions of the most closely related totivirid-like viruses (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155240#pone.0155240.s003" target="_blank">S2 Table</a> for full virus names and GenBank access numbers). Sequences were aligned with MUSCLE (Edgar, 2004). The numbers in parenthesis indicate the number of amino acid residues separating individual motifs. Amino acid residues highlighted in black are conserved among all aligned sequences.</p

The dsRNA Virus Papaya Meleira Virus and an ssRNA Virus Are Associated with Papaya Sticky Disease

<div><p>Papaya sticky disease, or “meleira”, is one of the major diseases of papaya in Brazil and Mexico, capable of causing complete crop loss. The causal agent of sticky disease was identified as an isometric virus with a double stranded RNA (dsRNA) genome, named papaya meleira virus (PMeV). In the present study, PMeV dsRNA and a second RNA band of approximately 4.5 kb, both isolated from latex of papaya plants with severe symptoms of sticky disease, were deep-sequenced. The nearly complete sequence obtained for PMeV dsRNA is 8,814 nucleotides long and contains two putative ORFs; the predicted ORF1 and ORF2 display similarity to capsid proteins and RdRp's, respectively, from mycoviruses tentatively classified in the family <i>Totiviridae</i>. The sequence obtained for the second RNA is 4,515 nucleotides long and contains two putative ORFs. The predicted ORFs 1 and 2 display 48% and 73% sequence identity, respectively, with the corresponding proteins of papaya virus Q, an umbravirus recently described infecting papaya in Ecuador. Viral purification in a sucrose gradient allowed separation of particles containing each RNA. Mass spectrometry analysis indicated that both PMeV and the second RNA virus (named papaya meleira virus 2, PMeV2) were encapsidated in particles formed by the protein encoded by PMeV ORF1. The presence of both PMeV and PMeV2 was confirmed in field plants showing typical symptoms of sticky disease. Interestingly, PMeV was detected alone in asymptomatic plants. Together, our results indicate that sticky disease is associated with double infection by PMeV and PMeV2.</p></div

Schematic representation of the genomic organization of papaya umbraviruspapaya meleira virus 2 (PpUVPMeV2).

<p>The viral ssRNA contains two ORFs. ORF1 encodes a hypothetical protein and ORF2 encodes a putative RdRp.</p

Phylogenetic relationship between PMeV and related viruses.

<p>Phylogenetic tree based on an alignment of deduced amino acid sequences of the RdRp proteins from PMeV and members of the family <i>Totiviridae</i>, obtained using Bayesian inference. The numbers at the branch nodes indicate Bayesian posterior probabilities. The names of the viruses used in the analysis and their respective GenBank access numbers are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155240#pone.0155240.s003" target="_blank">S2 Table</a>.</p

Phylogenetic relationship between PpUVPMeV2 and related viruses.

<p>Phylogenetic tree based on an alignment of the deduced amino acid sequences of PpUVPMeV2 and members of the family <i>Tombusviridae</i>, obtained using Bayesian inference. The numbers at the branch nodes indicate Bayesian posterior probabilities. The names of the viruses used in the analysis and their respective GenBank access numbers are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155240#pone.0155240.s003" target="_blank">S2 Table</a>.</p

Genome organization and molecular features of papaya meleira virus (PMeV).

<p>(a) Schematic representation of the PMeV genomic organization. The viral dsRNA contains two ORFs. ORF1 encodes the putative coat protein (CP) and ORF2 encodes a putative RNA-dependent RNA polymerase (RdRp). The position of a putative slippery sequence for -1 translational frameshift is indicated at the 3'-end of ORF1. (b) Predicted pseudoknot structure located downstream of the slippery sequence.</p

Genome of Rhodnius prolixus, an insect vector of Chagas disease, reveals unique adaptations to hematophagy and parasite infection

Rhodnius prolixus not only has served as a model organism for the study of insect physiology, but also is a major vector of Chagas disease, an illness that affects approximately seven million people worldwide. We sequenced the genome of R. prolixus, generated assembled sequences covering 95% of the genome (∼ 702 Mb), including 15,456 putative protein-coding genes, and completed comprehensive genomic analyses of this obligate blood-feeding insect. Although immune-deficiency (IMD)-mediated immune responses were observed, R. prolixus putatively lacks key components of the IMD pathway, suggesting a reorganization of the canonical immune signaling network. Although both Toll and IMD effectors controlled intestinal microbiota, neither affected Trypanosoma cruzi, the causal agent of Chagas disease, implying the existence of evasion or tolerance mechanisms. R. prolixus has experienced an extensive loss of selenoprotein genes, with its repertoire reduced to only two proteins, one of which is a selenocysteine-based glutathione peroxidase, the first found in insects. The genome contained actively transcribed, horizontally transferred genes from Wolbachia sp., which showed evidence of codon use evolution toward the insect use pattern. Comparative protein analyses revealed many lineage-specific expansions and putative gene absences in R. prolixus, including tandem expansions of genes related to chemoreception, feeding, and digestion that possibly contributed to the evolution of a blood-feeding lifestyle. The genome assembly and these associated analyses provide critical information on the physiology and evolution of this important vector species and should be instrumental for the development of innovative disease control methods

Repurposing the orphan drug nitisinone to control the transmission of African trypanosomiasis

Tsetse transmit African trypanosomiasis, which is a disease fatal to both humans and animals. A vaccine to protect against this disease does not exist so transmission control relies on eliminating tsetse populations. Although neurotoxic insecticides are the gold standard for insect control, they negatively impact the environment and reduce insect pollinator species. Here we present a promising, environment-friendly alternative that targets insect tyrosine metabolism pathway. A bloodmeal contains high levels of tyrosine, which is toxic to haematophagous insects if it is not degraded. RNAi silencing of either the first two enzymes in the tyrosine degradation pathway (TAT and HPPD) was lethal to tsetse. Furthermore, nitisinone (NTBC), an FDA-approved tyrosine catabolism inhibitor, killed tsetse regardless if the drug was orally or topically applied. However, it did not affect bumblebee survival. A mathematical model shows that NTBC could reduce the transmission of African trypanosomiasis in sub-Saharan Africa, thus accelerating current elimination programmes.Centro Regional de Estudios Genómico