Stephen M. Beverley, Ph.D.
Marvin A. Brennecke Professor and Head
Molecular Microbiology and Microbial Pathogenesis Program
Molecular Genetics and Genomics Program
9240 McDonnell Pediatric Research Building
parasites, viruses, microbial pathogenesis, macrophage, virulence, glycobiology, vaccination
Molecular genetics of protozoan parasite virulence
We study the protozoan parasite Leishmania, infecting more than 10 million people in tropical regions. We want to understand how the parasite carries out its infectious cycle, which comprises an intracellular phagolysosomal stage within vertebrate macrophages and an extracellular stage within the gut of a sand fly vector.
The development and application of new methods to parasite virulence. Experimentally, Leishmania is EASY to work with. Genetic manipulations are fast and routine, and one can plate them and generate many independent colonies. Parasites can be grown readily in culture under conditions where they differentiate well, and there are excellent mouse models enabling dissection of host defenses.
We have developed and/or applied in parasites powerful methods such as functional genetic rescue, gene knockouts, transposon mutagenesis, expression profiling via microarrays or RNA sequencing, and genome sequencing. We have identified many genes with ‘interesting’ functions, expression patterns and/or database relationships, and now are in the process of assessing their role in virulence using a variety of genetic and biochemical methods.
Genetics/genomics. In 2009 we showed for the first time that genetic crossing is possible in Leishmania. This opens the way to genetic analysis of important traits including tropisms related to different forms of leishmaniasis (cutaneous, mucocutaneous or visceral). We are resequencing several Leishmania genomes to provide SNP markers for this purpose as well as to create the first Leishmania genetic map.
In conjunction with an NHGRI/NIAID sponsored white paper initiative we are working with a consortium of scientists and the Genome Sequencing Center of Washington University to sequence over 50 new trypanosomatid genomes. Comparative analysis will permit identification of genes associated with phylogenetically with different manifestations of Leishmania pathology and virulence.
RNAi interference. In 2010 we showed that while most Leishmania species lack the RNA interference pathway, species belonging to the L. braziliensis group have retained it. This permits the application of RNAi-based methods for functional genomics in this group of species, and towards this end we are developing L. braziliensis (the agent of mucocutaneous leishmaniasis) into a superb experimental system for microbial pathogenesis. Examples include live animal imaging of infection and host response and in vitro systems for differentiation to the pathogenic amastigote stage.
The loss of RNAi in most Leishmania raises the interesting evolutionary question of what forces contribute to the loss of a pathway of such fundamental importance in other organisms. This is being pursued in several ways, through the study of RNAi-deficient L. braziliensis null mutants as well as attempts to restore RNAi to those Leishmania lacking it.
Leishmania virology and mucocutaneous leishmaniasis. In collaboration with the group of Nicolas Fasel in Lausanne Switzerland, we showed in 2011 that enigmatic dsRNA Leishmaniavirus (LRV) was associated causally with increased virulence and increased metastasis. LRV-infected Leishmania induce a hyperimmune response to the parasite responsible for the increased pathogenicity, through a dsRNA and TLR3-dependent pathway. Notably, L. braziliensis and related species of Viannia are responsible for a severe form of leishmaniasis called mucocutaneous leishmaniasis; the LRV represents the first parasite-associated factor implicated in this terrible disease. Our groups are now working to together to better understand how and where LRV contributes to human disease. We are surveying strains across South America for LRVs in an effort to associate LRV with human disease manifestations, and developing experimental Leishmania LRV ‘virology’ to assess in the laboratory how LRV contributes to pathology. The role of RNAi in LRV biology and LRV-dependent virulence is a subject of considerable interest as well.
The Leishmania surface glycocalyx. A long term project in our lab has been the study of the surface of pathogens, as the point of first contact with the host. The Leishmania surface is composed of a dense glycocalyx of glycolipids. One fruitful genetic screen involves a surface glycoconjugate, lipophosphoglycan (LPG), an essential virulence determinant involved in adhesion and survival. LPG genes encode proteins involved in biosynthesis, compartmentalization of LPG intermediates within the eukaryotic secretory pathway, and regulation. We are especially interested in understanding the role of the parasite surface interactions in manipulating host cell signal transduction, which is radically altered in Leishmania infections, and in sand fly transmission and co-evolution.
Host metabolism, virulence and chemotherapy. Another focus involves novel biochemical pathways implicated in chemotherapy and drug resistance. Leishmania are auxotrophic for folates and pteridines, and we are characterizing this pathway genetically, biochemically and structurally. Remarkably, biopterin metabolism was recently implicated in the control of Leishmania virulence.
One recent example is the study of TOR kinases, which in other organisms play critical roles in controlling cell growth and organization. In Leishmania this family has expanded to include a new member, TOR3, which controls the function of a novel parasite organelle called the acidocalcisome, which plays important roles in energy metabolism in the infectious stages residing in the mammal. Notably TOR and related PI3 kinases are good targets for future efforts towards chemotherapy. Other interests of the lab include molecular evolution of parasitism and virulence, and the use of genetically modified parasites as vaccines.
Adaui, V., L-F. Lye, N. S. Akopyants, M. Zimic, A. Llanos-Cuentas, L. Garcia, I. Maes, S. De Doncker, D. E. Dobson, J-C. Dujardin, J. Arevalo & S.M. Beverley (2016; e-publication June 2015), “Association of endobiont dsRNA virus LRV1 with treatment failure of human leishmaniasis caused by Leishmania braziliensis in Peru and Bolivia”, J. Infectious Diseases 213: 112-21. PMCID: PMC4676543
Eren, R.O., M. Reverté, M. Rossi, M-A. Hartley, P. Castiglioni, F. Prevel, R. Martin, C. Desponds, L-F. Lye, S. K. Drexler, W. Reith, S. M. Beverley, C. Ronet, and N. Fasel, “Antiviral response promotes Leishmania parasite persistence by inducing macrophage survival”, Cell Host Microbe (in press).
Mandell, M.A., and S.M. Beverley (2016), “Concomitant immunity induced by persistent Leishmania major does not preclude secondary re-infection: implications for genetic exchange, diversity and vaccination”, PLoS Neglected Tropical Diseases 10(6):e0004811. PMCID: PMC4924822.
Valdivia, H.O., J. L. Reis Cunha, G. F. Rodriguez-Luiz. R. P. Baptista. G. C. Baldeviano, R. V. Gerbasi, D. E. Dobson, F. Pratlong, P. Bastien, A.G. Lescano, S. M. Beverley, & D. C. Bartholomeu, “Comparative genomic analysis of Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis” (2015), BMC Genomics 16:715. PMCID: PMC4575464.
Beverley, S.M. (2015), “CRISPR for Cryptosporidium”, Nature 523: 413-414. PMCID: PMC4620987.
Ives, A., C. Ronet, F. Prevel, G. Ruzzante, S. Fuertes-Marraco, F. Schutz, H. Zangger, M. Revaz-Breton, L-F. Lye, S.M. Hickerson, S.M. Beverley, H. Acha-Orbea, P. Launois, N. Fasel and S. Masina (2011), Leishmania RNA Virus controls the severity of Leishmaniasis Science 331: 775-778.
Lye, L-F., K. L. Owens, H. Shi, S.M.F. Murta, A.C. Vieira, S.J. Turco, C. Tschudi, E. Ullu, and S.M. Beverley (2010), Retention and loss of RNA interference pathways in Trypanosomatid protozoans, PLoS Pathogens 6: e1001161.
Akopyants* N, Kimblin* N, SecondinoN, Patrick R, Lawyer P, Dobson DE, Beverley* SM and Sacks* DL. Demonstration of genetic exchange during cyclical development of Leishmania in the sand fly vector, Science 2009 324: 265-268. (*1st two authors contributed equally; last two authors contributed equally). (See commentary Leishmania exploit sex, Miles MA, Yeo M and Mauricio IL. Science 2009 324: 187-189).
Madeira da Silva L, Owens KL, Murta SFM and Beverley SM. (2009) Regulated expression of the Leishmania major surface virulence factor lipophosphoglycan using conditionally destabilized fusion proteins. Proc. Natl. Acad. Sci. USA 2009 106: 7583-7588.
Last Updated: 8/23/2016 1:35:45 PM