Intra-specific variation in avian malaria : Linking infection dynamics to haplotypes

Avian Malaria infects thousands of species of birds across the Aves class. The most widespread (geographically and phylogenetically)morphological species is Plasmodium relictum, and of that, the mitochondrial lineage of SGS1 is the most common and invasive. It infects146 bird species, with large differences in infection outcome, from low intensity chronic disease to shorter, highly virulent infections. InPaper 1, I studied the gene expression of SGS1 in experimentally infected birds pre and post maximum parasitemia. The parasitemiavaried widely between birds and especially over the course of the infection. These differences were significantly linked to genes relatedto cell replication and cellular movement in high parasitemia infections and cellular metabolism in low parasitemia infections. We foundthat over time, variation in gene expression increased between samples, possibly illustrating individual responses of the parasites to theirhosts, and a desynchronisation in their lifecycles. Paper 2 explored the phylogeography of SGS1, and its related lineage GRW11, in thepalearctic region. Because the lineage system is defined by a highly conserved single mitochondrial gene, the nuclear polymorphic cellinvasion gene, merozoite surface protein 1 (msp1), was selected to study the genetic variation present in infected resident and migrant hostpopulations. We found extremely little variation, suggesting SGS1and GRW11 in Europe have an epidemic population structure, or thereis strong purifying selection pressure on the msp1 gene despite the wide host range. Paper 3 developed a genomic sequence capture methodusing 1035 probes designed for SGS1, and tested it on a range of SGS1, GRW11, and GRW4 samples. The probes effectively isolatedDNA from all three lineages, but sequencing success was low for samples with less than 1% parasitemia. We selected 25 genes to describethe higher-than-expected variation within SGS1 and with GRW11 and GRW4 samples. In Paper 4, two different host sources of SGS1infected blood were used to infect two groups of canaries. The groups differed in parasitemia and mortality, and from each group the threebirds with largest differences in infection outcome were selected for RNA sequencing to survey the underlying genomic variation. Thesource of the infection reliably separated the samples phylogenetically, with relatively less variation observed within the groups. Thissuggests that an infection is made up of a population of genetically diverse parasites. Paper 5 expanded on this idea by using the genomicsequence capture method from Paper 3 and refined bioinformatic methods from Paper 4 on some of the same samples from Paper 1.Samples collected at the same time points (8 and 20 days post infection) were sequenced. This allowed analyses of how the predominanthaplotypes change during an infection, and then link those haplotypes to the disease severity. We found that the least suppressed/mostvirulent haplotypes had genetic variants in genes related to cell invasion and immune evasion. The combined results of my thesis havefar-reaching implications that extend beyond the particular organism under investigation. The notion of genetic diversity within a singleinfections and the resulting parasite population dynamics offers exciting prospects for future research

Shifts in gene expression variability in the blood-stage of Plasmodium relictum

Avian malaria is a common and widespread disease of birds caused by a diverse group of pathogens of the genera Plasmodium. We investigated the transcriptomal profiles of one of the most common species, Plasmodium relictum, lineage SGS1, at multiple timepoints during the blood stages of the infection under experimental settings. The parasite showed well separated overall transcriptome profiles between day 8 and 20 after the infection, shown by well separated PCA profiles. Moreover, gene expression becomes more heterogenous within the experimental group late in the infection, either due to adaptations to individual differences between the experimental hosts, or due to desynchronisation of the life-cycle of the parasite. Overall, this study shows how the avian malaria system can be used to study gene expression of the avian Plasmodium parasite under controlled experimental settings, thus allowing for future comparative analysis of gene responses of parasite with different life-history traits and host effects

Immune gene expression in the mosquito vector <i>Culex quinquefasciatus</i> during an avian malaria infection

International audiencePlasmodium relictum is the most widespread avian malaria parasite in the world. It is listed as one of the 100 most dangerous invasive species, having been responsible for the extinction of several endemic bird species, and the near-demise of several others. Here we present the first transcriptomic study focused on the effect of P. relictum on the immune system of its vector (the mosquito Culex quinquefasciatus) at different times post-infection. We show that over 50% of immune genes identified as being part of the Toll pathway and 30%–40% of the immune genes identified within the Imd pathway are overexpressed during the critical period spanning the parasite's oocyst and sporozoite formation (8–12 days), revealing the crucial role played by both these pathways in this natural mosquito–Plasmodium combination. Comparison of infected mosquitoes with their uninfected counterparts also revealed some unexpected immune RNA expression patterns earlier and later in the infection: significant differences in expression of several immune effectors were observed as early as 30 min after ingestion of the infected blood meal. In addition, in the later stages of the infection (towards the end of the mosquito lifespan), we observed an unexpected increase in immune investment in uninfected, but not in infected, mosquitoes. In conclusion, our work extends the comparative transcriptomic analyses of malaria-infected mosquitoes beyond human and rodent parasites and provides insights into the degree of conservation of immune pathways and into the selective pressures exerted by Plasmodium parasites on their vectors

Durability of Synthetic Fibers in Fiber-Cement Building Materials

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84746/1/Lhoneux2003.pd

Development of High Tenacity Polypropylene Fibers for Cementitious Composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84811/1/LhoneuxDFRCC2002.pd

Genomic sequence capture of Plasmodium relictum in experimentally infected birds

Background: Sequencing parasite genomes in the presence of host DNA is challenging. Sequence capture can overcome this problem by using RNA probes that hybridize with the parasite DNA and then are removed from solution, thus isolating the parasite DNA for efficient sequencing. Methods: Here we describe a set of sequence capture probes designed to target 1035 genes (c. 2.5 Mbp) of the globally distributed avian haemosporidian parasite, Plasmodium relictum. Previous sequence capture studies of avian haemosporidians from the genus Haemoproteus have shown that sequencing success depends on parasitemia, with low-intensity, chronic infections (typical of most infected birds in the wild) often being difficult to sequence. We evaluate the relationship between parasitemia and sequencing success using birds experimentally infected with P. relictum and kept under laboratory conditions. Results: We confirm the dependence of sequencing success on parasitemia. Sequencing success was low for birds with low levels of parasitemia (< 1% infected red blood cells) and high for birds with higher levels of parasitemia. Plasmodium relictum is composed of multiple lineages defined by their mitochondrial DNA haplotype including three that are widespread (SGS1, GRW11, and GRW4); the probes successfully isolated DNA from all three. Furthermore, we used data from 25 genes to describe both among- and within-lineage genetic variation. For example, two samples of SGS1 isolated from different host species differed by 11 substitutions across those 25 genes. Conclusions: The sequence capture approach we describe will allow for the generation of genomic data that will contribute to our understanding of the population genetic structure and evolutionary history of P. relictum, an extreme host generalist and widespread parasite. Graphical : [Figure not available: see fulltext.]