Lysyl-tRNA synthetase as a drug target in malaria and cryptosporidiosis

Malaria and cryptosporidiosis, caused by apicomplexan parasites, remain major drivers of global child mortality. New drugs for the treatment of malaria and cryptosporidiosis, in particular, are of high priority; however, there are few chemically validated targets. The natural product cladosporin is active against blood- and liver-stage; Plasmodium falciparum; and; Cryptosporidium parvum; in cell-culture studies. Target deconvolution in; P. falciparum; has shown that cladosporin inhibits lysyl-tRNA synthetase (; Pf; KRS1). Here, we report the identification of a series of selective inhibitors of apicomplexan KRSs. Following a biochemical screen, a small-molecule hit was identified and then optimized by using a structure-based approach, supported by structures of both; Pf; KRS1 and; C. parvum; KRS (; Cp; KRS). In vivo proof of concept was established in an SCID mouse model of malaria, after oral administration (ED; 90; = 1.5 mg/kg, once a day for 4 d). Furthermore, we successfully identified an opportunity for pathogen hopping based on the structural homology between; Pf; KRS1 and; Cp; KRS. This series of compounds inhibit; Cp; KRS and; C. parvum; and; Cryptosporidium hominis; in culture, and our lead compound shows oral efficacy in two cryptosporidiosis mouse models. X-ray crystallography and molecular dynamics simulations have provided a model to rationalize the selectivity of our compounds for; Pf; KRS1 and; Cp; KRS vs. (human); Hs; KRS. Our work validates apicomplexan KRSs as promising targets for the development of drugs for malaria and cryptosporidiosis

Identification and Characterization of Two Novel RNA Viruses from Anopheles gambiae Species Complex Mosquitoes

Mosquitoes of the Anopheles gambiae complex display strong preference for human blood-meals and are major malaria vectors in Africa. However, their interaction with viruses or role in arbovirus transmission during epidemics has been little examined, with the exception of O'nyong-nyong virus, closely related to Chikungunya virus. Deep-sequencing has revealed different RNA viruses in natural insect viromes, but none have been previously described in the Anopheles gambiae species complex. Here, we describe two novel insect RNA viruses, a Dicistrovirus and a Cypovirus, found in laboratory colonies of An. gambiae taxa using small-RNA deep sequencing. Sequence analysis was done with Metavisitor, an open-source bioinformatic pipeline for virus discovery and de novo genome assembly. Wild-collected Anopheles from Senegal and Cambodia were positive for the Dicistrovirus and Cypovirus, displaying high sequence identity to the laboratory-derived virus. Thus, the Dicistrovirus (Anopheles C virus, AnCV) and Cypovirus (Anopheles Cypovirus, AnCPV) are components of the natural virome of at least some anopheline species. Their possible influence on mosquito immunity or transmission of other pathogens is unknown. These natural viruses could be developed as models for the study of Anopheles-RNA virus interactions in low security laboratory settings, in an analogous manner to the use of rodent malaria parasites for studies of mosquito anti-parasite immunity

Conflict and cooperation in the mutualism between ants and aphids.

One of the best examples of a trophic mutualism in social insects is that between ants and aphids, whereby aphids secrete a sugary-rich food source termed honeydew, and the ants protect the aphids in return against natural enemies (Hölldobler & Wilson, 1990). Conflict, however, can occur when either the ants or the aphids exploit the mutualism by not returning their services. The aphids, for example, could gain a selfish advantage by secreting less or lower quality honeydew, but still take advantage of the protective services of the ants. Here we use the native Lasius niger-Aphis fabae ant-aphid system as a model to test whether such cheating occurs, and what processes could help to prevent it. One possibility is that aphid clones secreting little or low-quality honeydew are sanctioned by the ants relative to more cooperative clones. Evidence in this direction is provided by the fact that when Lasius niger ants have a choice of aphid species it preferentially tends those species that produce most honeydew, and kills the others (Fischer et al., 2001). In our study we plan to test whether such a preference also exists within one species (Aphis fabae fabae, black bean aphid) if the ants are presented with different aphid clones producing different amounts or qualities of honeydew. In order to do this, we collected A. fabae clones around Leuven and in Antwerp. Then, we chemically analyzed their honeydew using HPLC. Preliminary data show high variations in the quality and quantity of sugars secreted by the aphids. Therefore we will conduct more chemical analyses to confirm these results and average the plant influence on the aphids secretions. The second part of the study will consist in behavioural experiments where low- and high-producing clones will be presenting to the ants in binary choice experiments to test whether the ants will sanction uncooperative aphid clones. Another side of the study will be to evaluate clonal mixing in the field. Indeed, genetic data have highlighted the presence of clonal mixing in Aphis fabae. However the sample set was small and only from the beginning of the season. Therefore more sampling will be conduct during the next season to evaluate the importance of clonal mixing and its possible changes in time. These data on Aphis fabae fabae clonal mixing will be completed with data on Aphis fabae cirsiiacanthoides which can be found on thistle and Aphis rumicis which can be found on sorrel. Microsatellites from Aphis fabae have been used for these two species and have shown the presence of clonal mixing too. These species are easily found around Leuven and are ant-attended too, therefore it will permit to compare clonal mixing in the field between different species and subspecies of aphids. The laboratory of Entomology has a long working experience in social insects, and this project fits into the lines of research of behavioural ecology and evolutionnary biology developped by Dr Tom Wenseleers. One problem in evolutionary biology is to explain how competition and conflict is repressed in the evolution of more complex, cooperative groups. Previous and current work on this subject by Dr Tom Wenseleers and colleagues has focused on the case of conflicts occurring in animal societies. This project will explore another aspect of this problem using the example of interspecific mutualisms. Hölldobler B & Wilson EO (1990) The Ants Springer-Verlag, Berlin, Heidel berg. Fischer MK, Hoffmann KH, Völkl W (2001) Competition for mutualists in an ant homopteran interaction mediated by hierarchies of ant attendance. Oikos 92, 531-541.status: publishe

Dataset of the study on field evidence for manipulation of mosquito host selection by the human malaria parasite

<p>This repository contains the dataset from host preferences assays to determine odour-mediated mosquito host preference as well as mosquito host selection determination through identification of the blood meal origin from indoor-resting blood-fed mosquito females in Burkina Faso.</p

Levels of clonal mixing in the black bean aphid Aphis fabae, a facultative ant mutualist

Aphids are a worldwide pest and an important model in ecology and evolution. Little is known, however, about the genetic structure of their colonies at a microgeographic level. For example, it remains largely unknown whether most species form monoclonal or polyclonal colonies. Here, we present the first detailed study on levels of clonal mixing in a nonsocial facultative ant mutualist, the black bean aphid Aphis fabae. In contrast to the earlier suggestion that colonies of this species are generally monoclonal, we found that across two subspecies of the black bean aphid, A. fabae cirsiiacanthoidis and A. fabae fabae, 32% and 67% of the aphid colonies were in fact polyclonal, consisting of a mix of up to four different clones, which resulted in an overall average relatedness within colonies of 0.90 and 0.79 in the two subspecies. Data further show that the average relatedness in A. f. cirsiiacanthoidis remained relatively constant throughout the season, which means that clonal erosion due to clonal selection more or less balanced with the influx of new clones from elsewhere. Nevertheless, relatedness tended to decrease over the lifetime of a given colony, implying that clonal mixing primarily resulted from the joining of pre-existing colonies as opposed to via simultaneous host colonisation by several foundresses. Widespread clonal mixing is argued to affect the ecology and evolution of the aphids in various important ways, for example with respect to the costs and benefits of group living, the evolution of dispersal and the interaction with predators as well as with the ant mutualists.status: publishe