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Papers by George Christophides

The Asian tiger mosquito, Aedes albopictus, is an invasive vector species. It is capable of trans... more The Asian tiger mosquito, Aedes albopictus, is an invasive vector species. It is capable of transmitting more than 20 arboviruses, and is responsible for chikungunya, dengue, and zika transmission. Urbanisation, globalisation, and climate change are expected to expand its habitable range and increase the global vector-borne disease burden in the coming decades. To plan effective control strategies, early-warning and decision support systems are urgently needed.We developed a climate- and environment-driven population dynamics model of Aedes albopictus with extensive geospatial applicability. The foundation of the model is the age- and stage-structured population dynamics model of Erguler et al. (2016)1. We replaced its rainfall- and human population density-dependent breeding site component with a large-scale mechanistic ecological model. The extension effectively created an ecological-dynamic model hybrid capable of representing niche dependence and response to changing environment...

Additional file 7: Fig. S1. (A) Pearson correlation plot of each transcriptome calculated from ge... more Additional file 7: Fig. S1. (A) Pearson correlation plot of each transcriptome calculated from genome TPM values (0.04–1.00) for each stage from each experiment. The samples were clustered by hierarchical clustering using Ward's clustering criterion ('ward.d2' setting in corrplot function [87], and six clusters are highlighted in boxes. Six clusters were chosen as most optimal with the 'elbow method' [88], as implemented through the factoextra package function 'fviz_nbclust' using k-means clustering and within cluster sums of squares. The Experiment codes are listed in Table 2.

Additional file 15. Complete sequence alignment of the pirorthologues shown in Fig. 5A.

Additional file 14. Table of contents of additional files 1–6.

Additional file 4. Statistics of P. berghei individual pir genes (DESeq).

Additional file 16: Table S1. The relationship between P. chabaudi RNA-seq samples used in this s... more Additional file 16: Table S1. The relationship between P. chabaudi RNA-seq samples used in this study and their entries in the ENA is described.

Additional file 5. P. c. chabaudi counts across the 24 hour asexual developmental cycle.

The early parasite development in the mosquito is mostly driven by previously synthesised transcr... more The early parasite development in the mosquito is mostly driven by previously synthesised transcripts in the gametocyte. However, the role of gametocyte players in later sporogonic stages in the vector is relatively unknown. The in vivo transcriptional profiling of P. berghei during the first hour in the Anopheles gambiae midgut was employed in combination with published proteome data, to identify Plasmodium gametocyte enriched genes with functions in downstream sporogonic development. Additionally, differentially regulated Plasmodium genes were also selected from a transcriptional profiling of P. falciparum during the first 24 hours of development in Anopheles gambiae and Anopheles arabiensis. This led to the identification of six genes that are essential for malaria transmission. PBANKA_1353800 and PBANKA_0720900, identified from the P. berghei array are essential for ookinete motility and oocyst sporogony respectively. P. falciparum orthologous PBANKA_0201700, PBANKA_1422900, PBA...

Ratio of ookinete to total early sporogonic stage counts in vernolide and vernodalol treated micr... more Ratio of ookinete to total early sporogonic stage counts in vernolide and vernodalol treated microplate wells.

Ratio of ookinete to total early sporogonic stage counts in microplate wells treated with Vernoni... more Ratio of ookinete to total early sporogonic stage counts in microplate wells treated with Vernonia amygdalina fractions.

Oocysts and melanised ookinetes dataset. (XLSX 195 kb)

Detailed description of the experimental procedures and statistical analyses utilized. Evaluation... more Detailed description of the experimental procedures and statistical analyses utilized. Evaluation of gene knock down efficiency. (PDF 62 kb)

dsRNA haemocyte-specific library. The main features of target genes and dsRNAs used in this study... more dsRNA haemocyte-specific library. The main features of target genes and dsRNAs used in this study are presented. DsRNA IDs, KD phenotypes in cell-based RNAi screens [5], VectorBase gene IDs, Affymetrix probe codes and previous ENSEMBL IDs are listed in columns A, B, C, D and E, respectively. Circulating haemocyte microarray information from [2] are summarized in columns F (cluster), G (normalized haemocyte value), H (normalized carcass value) and I (normalized head value). Comments (name and/or homology of An. gambiae genes) and InterPro domain data are reported in columns J and K, respectively. Drosophila melanogaster orthologs are shown in column L, and corresponding FlyBase IDs in column M. D. melanogaster KD phenotypes according to the GenomeRNAi database are reported in column N. This table is modified from Lombardo et al. 2013 [5]. (XLS 81 kb)

List of primers used in this study. (PDF 86 kb)

Additional file 3: Table S2. Reproductive fitness of gene silenced mosquitoes.

The transmission of the malaria parasite Plasmodium is governed by a complex developmental cycle.... more The transmission of the malaria parasite Plasmodium is governed by a complex developmental cycle. This PhD thesis describes the transcriptional profiling of the rodent malaria parasite Plasmodium berghei developmental migration through its A. gambiae vector. The study was conducted in vivo, using a near complete P. berghei genome microarray platform. Emphasis was placed on the oocyst stage, as little is known about the genes implicated in the ookinete to oocyst transition, and oocyst maturation. The data presented here provide novel transcriptional information about Plasmodium transmission. The analysis revealed a large shift in gene utilisation as the parasite makes its transition from the motile ookinete to the sessile oocyst. Furthermore, this work has shown that different sets of co-regulated genes are important for early and late oocyst development. In addition, this PhD thesis outlines the characterisation of a novel Plasmodium formin-like protein essential for rodent malaria transmission named the male inherited sporulation factor important for transmission (misfit). MISFIT is expressed in the early mosquito stages, where the protein localises to the parasite nucleus. Misfit exhibits an absolute requirement for paternal inheritance, which is in accordance with an observed male-biased expression pattern. pbmisfitΔ ookinetes display significant ultrastructural and gene expression defects and fail to complete zygotic meiosis. However, pbmisfitΔ ookinetes retain functionality and can successfully cross the midgut epithelial barrier. In contrast, mosquito infections with pbmisfitΔ resulted in an arrest immediately upon ookinete-oocyst transformation, where defective oocysts fail to sporulate. An essential role in chromosome segregation during mitosis / meiosis is postulated for MISFIT. In conclusion, the work presented in this thesis has established the ookinete-oocyst transition as a major cell cycle check point during malaria transmission and identified misfit as the first male inherited Plasmodium gene known [...]

Malaria Journal, 2021

Background Plasmodium interspersed repeat (pir) is the largest multigene family in the genomes of... more Background Plasmodium interspersed repeat (pir) is the largest multigene family in the genomes of most Plasmodium species. A variety of functions for the PIR proteins which they encode have been proposed, including antigenic variation, immune evasion, sequestration and rosetting. However, direct evidence for these is lacking. The repetitive nature of the family has made it difficult to determine function experimentally. However, there has been some success in using gene expression studies to suggest roles for some members in virulence and chronic infection. Methods Here pir gene expression was examined across the life cycle of Plasmodium berghei using publicly available RNAseq data-sets, and at high resolution in the intraerythrocytic development cycle using new data from Plasmodium chabaudi. Results Expression of pir genes is greatest in stages of the parasite which invade and reside in red blood cells. The marked exception is that liver merozoites and male gametocytes produce a ve...

Vector Biology Journal, 2017

Background: The bacterial microbiota which colonize the mosquito midgut play an important role in... more Background: The bacterial microbiota which colonize the mosquito midgut play an important role in vector-parasite interactions and consequently can modulate the level of malaria transmission. Their characterization may contribute to new control strategies of malaria transmission. However, these bacteria may also be eliminated in areas of high antibiotics usage. In this study, we identified paratransgenesis bacteria candidate in the gut of adults female Anopheles in Burkina Faso. Methods: The gut of 73 semi-field mosquitoes and 28 laboratoryreared mosquitoes from two villages in Burkina Faso were analyzed by conventional in vitro culture techniques to isolate and identify bacteria of the microbiota. The gene 16S sequencing was used to confirm the presence of bacteria of paratransgenesis interest. Due to the effect of antibiotics on bacteria, we evaluated in vitro their susceptibility to antibiotics generally used for infectious diseases treatment.

Malaria parasites develop and grow as oocysts in the mosquito for several days before being able ... more Malaria parasites develop and grow as oocysts in the mosquito for several days before being able to infect another human. During this time, mosquitoes take regular bloodmeals to replenish their nutrient and energy reserves needed for flight and reproduction. We hypothesized that supplemental bloodmeals are critical for oocyst growth and that experimental infection protocols, typically involving a single bloodmeal, cause nutritional stress to developing oocysts. Therefore, enumerating oocysts independently of their growth and differentiation state may lead to erroneous conclusions regarding the efficacy of malaria transmission blocking interventions. We tested this hypothesis in Anopheles coluzzii mosquitoes infected with human and rodent parasites Plasmodium falciparum and Plasmodium berghei, respectively. We find that oocyst growth rates decrease at late developmental stages as infection intensities increase; an effect exacerbated at very high infection intensities. Oocyst growth a...

First generation CRISPR-based gene drives have now been tested in the laboratory in a number of o... more First generation CRISPR-based gene drives have now been tested in the laboratory in a number of organisms including malaria vector mosquitoes. A number of challenges for their use in the area-wide genetic control of vector-borne disease have been identified. These include the development of target site resistance, their long-term efficacy in the field, their molecular complexity, and the practical and legal limitations for field testing of both gene drive and coupled anti-pathogen traits. To address these challenges, we have evaluated the concept of Integral Gene Drive (IGD) as an alternative paradigm for population replacement. IGDs incorporate a minimal set of molecular components, including both the drive and the anti-pathogen effector elements directly embedded within endogenous genes – an arrangement which we refer to as gene “hijacking”. This design would allow autonomous and non-autonomous IGD traits and strains to be generated, tested, optimized, regulated and imported indep...