The development of Trypanosoma brucei within the tsetse fly midgut observed using green fluorescent trypanosomes

BACKGROUND: The protozoan pathogen, Trypanosoma brucei, undergoes complex cycles of differentiation and multiplication in its vector, the tsetse fly, genus Glossina. Flies are refractory to infection and resistance mechanisms operate at a number of levels and timepoints. Here we have used highly conspicuous green fluorescent trypanosomes to study the early events in establishment of infection in the fly midgut. RESULTS: Less than 10% of the bloodstream form trypanosomes in the infected feed differentiated into viable procyclics. Up to day 3, trypanosomes were found in the bloodmeal in every fly examined, and increased in number between days 1 and 3. Flies dissected on days 5 and 6 fell into 2 clearly distinct groups: those with high numbers of trypanosomes and those with undetectable infection. Trypanosomes were found in the ectoperitrophic space and proventriculus from 6 days following the infective feed. CONCLUSION: Trypanosomes that have undergone successful differentiation appear to experience an environment within the midgut suited to their unrestricted growth for the first 3 days. After this time, a process of attrition is evident in some flies, which leads to the complete elimination of infection. By day 5, flies fall into 2 groups according to the level of infection: high or undetectable. This timecourse coincides with lectin secretion, development of the PM and the digestion and movement of the bloodmeal along the gut. Further experiments are needed to discriminate between these factors

Dynamics of gamete production and mating in the parasitic protist <i>Trypanosoma brucei</i>

BACKGROUND: Sexual reproduction in Plasmodium falciparum and Trypanosoma brucei occurs in the insect vector and is important in generating hybrid strains with different combinations of parental characteristics. Production of hybrid parasite genotypes depends on the likelihood of co-infection of the vector with multiple strains. In mosquitoes, existing infection with Plasmodium facilitates the establishment of a second infection, although the asynchronicity of gamete production subsequently prevents mating. In the trypanosome/tsetse system, flies become increasingly refractory to infection as they age, so the likelihood of a fly acquiring a second infection also decreases. This effectively restricts opportunities for trypanosome mating to co-infections picked up by the fly on its first feed, unless an existing infection increases the chance of successful second infection as in the Plasmodium/mosquito system. RESULTS: Using green and red fluorescent trypanosomes, we compared the rates of trypanosome infection and hybrid production in flies co-infected on the first feed, co-infected on a subsequent feed 18 days after emergence, or fed sequentially with each trypanosome clone 18 days apart. Infection rates were highest in the midguts and salivary glands (SG) of flies that received both trypanosome clones in their first feed, and were halved when the infected feed was delayed to day 18. In flies fed the two trypanosome clones sequentially, the second clone often failed to establish a midgut infection and consequently was not present in the SG. Nevertheless, hybrids were recovered from all three groups of infected flies. Meiotic stages and gametes were produced continuously from day 11 to 42 after the infective feed, and in sequentially infected flies, the co-occurrence of gametes led to hybrid formation. CONCLUSIONS: We found that a second trypanosome strain can establish infection in the tsetse SG 18 days after the first infected feed, with co-mingling of gametes and production of trypanosome hybrids. Establishment of the second strain was severely compromised by the strong immune response of the fly to the existing infection. Although sequential infection provides an opportunity for trypanosome mating, the easiest way for a tsetse fly to acquire a mixed infection is by feeding on a co-infected host

Trypanosomes are monophyletic: evidence from genes for glyceraldehyde phosphate dehydrogenase and small subunit ribosomal RNA.

The genomes of Trypanosoma brucei, Trypanosoma cruzi and Leishmania major have been sequenced, but the phylogenetic relationships of these three protozoa remain uncertain. We have constructed trypanosomatid phylogenies based on genes for glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) and small subunit ribosomal RNA (SSU rRNA). Trees based on gGAPDH nucleotide and amino acid sequences (51 taxa) robustly support monophyly of genus Trypanosoma, which is revealed to be a relatively late-evolving lineage of the family Trypanosomatidae. Other trypanosomatids, including genus Leishmania, branch paraphyletically at the base of the trypanosome clade. On the other hand, analysis of the SSU rRNA gene data produced equivocal results, as trees either robustly support or reject monophyly depending on the range of taxa included in the alignment. We conclude that the SSU rRNA gene is not a reliable marker for inferring deep level trypanosome phylogeny. The gGAPDH results support the hypothesis that trypanosomes evolved from an ancestral insect parasite, which adapted to a vertebrate/insect transmission cycle. This implies that the switch from terrestrial insect to aquatic leech vectors for fish and some amphibian trypanosomes was secondary. We conclude that the three sequenced pathogens, T. brucei, T. cruzi and L. major, are only distantly related and have distinct evolutionary histories

Effect of Nonsteroid Anti-Inflammatory and Antipyretic Drugs on Prostaglandin Biosynthesis by Human Skin

There is increasing evidence that prostaglandins are mediators of inflammation in skin and that prostaglandins are synthesised locally in response to the inflammatory stimulus. The effect of four nonsteroid anti-inflammatory or antipyretic drugs on prostaglandin biosynthesis by human skin has therefore been studied. Aspirin (0.56 mM) and indomethacin (0.28 mM) produced a small but significant inhibition of synthesis of prostaglandin E2. Indomethacin and chloroquine, but not aspirin, inhibited synthesis of prostaglandin F2a. Acetaminophen inhibited synthesis of prostaglandin F2, but did not inhibit prostaglandin E2 synthesis. None of the drugs studied are therapeutically effective anti-inflammatory agents in human skin and it may be significant that the inhibitory effects of aspirin and indomethacin on prostaglandin synthesis by skin are small compared with the effects of the same drugs on prostaglandin synthesis in other tissues

The public health effects of interventions similar to basic income: a scoping review

Universal, unconditional basic income is attracting increasing policy and academic interest. Income is a key health determinant, and a basic income could affect health through its effect on other determinants, such as employment. However, there is little evidence of its potential effects on public health, because no studies of interventions which meet the definition of basic income have been done. However, there is evidence from studies of interventions with similarities to basic income. Therefore, we aimed to identify these studies and to consider what can be learned from them about the potential effects of such interventions on health and socioeconomic outcomes. We did a systematic scoping review of basic income-like interventions, searching eight bibliographic and eight specialist databases from inception to July, 2019, with extensive hand searching. We included publications in English of quantitative and qualitative studies done in upper-middle-income or high-income countries, of universal, permanent, or subsistence-level interventions providing unconditional payments to individuals or families. We sought to identify the range of outcomes reported by relevant studies, and report health, education, employment, and social outcomes. We extracted and tabulated relevant data and narratively reported effects by intervention and outcome. We identified 27 studies of nine heterogeneous interventions, some universal and permanent, and many evaluated using randomised controlled trials or robust quasi-experimental methods. Evidence on health effects was mixed, with strong positive effects on some outcomes, such as birthweight and mental health, but no effect on others. Employment effects were inconsistent, although mostly small for men and larger for women with young children. There was evidence of spill-over effects in studies measuring effects on large populations. In conclusion, little evidence exists of large reductions in employment, and some evidence suggests positive effects on some other outcomes, including health outcomes. Evidence for macro-level effects is scarce. Quasi-experimental and dynamic modelling approaches are well placed to investigate such effects

The Trypanosoma brucei AIR9-like protein is cytoskeleton-associated and is required for nucleus positioning and accurate cleavage furrow placement

AIR9 is a cytoskeleton-associated protein in Arabidopsis thaliana with roles in cytokinesis and cross wall maturation, and reported homologues in land plants and excavate protists, including trypanosomatids. We show that the Trypanosoma brucei AIR9-like protein, TbAIR9, is also cytoskeleton-associated and colocalises with the subpellicular microtubules. We find it to be expressed in all life cycle stages and show that it is essential for normal proliferation of trypanosomes in vitro. Depletion of TbAIR9 from procyclic trypanosomes resulted in increased cell length due to increased microtubule extension at the cell posterior. Additionally, the nucleus was re-positioned to a location posterior to the kinetoplast, leading to defects in cytokinesis and the generation of aberrant progeny. In contrast, in bloodstream trypanosomes, depletion of TbAIR9 had little effect on nucleus positioning, but resulted in aberrant cleavage furrow placement and the generation of non-equivalent daughter cells following cytokinesis. Our data provide insight into the control of nucleus positioning in this important pathogen and emphasise differences in the cytoskeleton and cell cycle control between two life cycle stages of the T. brucei parasite

Intraclonal mating occurs during tsetse transmission of Trypanosoma brucei

<p>Abstract</p> <p>Background</p> <p>Mating in <it>Trypanosoma brucei </it>is a non-obligatory event, triggered by the co-occurrence of different strains in the salivary glands of the vector. Recombinants that result from intra- rather than interclonal mating have been detected, but only in crosses of two different trypanosome strains. This has led to the hypothesis that when trypanosomes recognize a different strain, they release a diffusible factor or pheromone that triggers mating in any cell in the vicinity whether it is of the same or a different strain. This idea assumes that the trypanosome can recognize self and non-self, although there is as yet no evidence for the existence of mating types in <it>T. brucei</it>.</p> <p>Results</p> <p>We investigated intraclonal mating in <it>T. b. brucei </it>by crossing red and green fluorescent lines of a single strain, so that recombinant progeny can be detected in the fly by yellow fluorescence. For strain 1738, seven flies had both red and green trypanosomes in the salivary glands and, in three, yellow trypanosomes were also observed, although they could not be recovered for subsequent analysis. Nonetheless, both red and non-fluorescent clones from these flies had recombinant genotypes as judged by microsatellite and karyotype analyses, and some also had raised DNA contents, suggesting recombination or genome duplication. Strain J10 produced similar results indicative of intraclonal mating. In contrast, trypanosome clones recovered from other flies showed that genotypes can be transmitted with fidelity. When a yellow hybrid clone expressing both red and green fluorescent protein genes was transmitted, the salivary glands contained a mixture of fluorescent-coloured trypanosomes, but only yellow and red clones were recovered. While loss of the <it>GFP </it>gene in the red clones could have resulted from gene conversion, some of these clones showed loss of heterozygosity and raised DNA contents as in the other single strain transmissions. Our observations suggest that many recombinants are non-viable after intraclonal mating.</p> <p>Conclusion</p> <p>We have demonstrated intraclonal mating during fly transmission of <it>T. b. brucei</it>, contrary to previous findings that recombination occurs only when another strain is present. It is thus no longer possible to assume that <it>T. b. brucei </it>remains genetically unaltered after fly transmission.</p