Malaria Parasite Research Laboratory
Head: Dr Danny Wilson
Plasmodium falciparum malaria is a mosquito borne parasite that causes the majority of the ≈600,000 malaria related deaths that occur each year, mainly of children under the age of 5 in Africa. Although Australia has been ‘malaria free' since the 1980's, our nearest neighbours (Indonesia, East Timor, Papua New Guinea) still have some of the highest malaria incidence and mortality rates in Asia. Malaria has a critical bottleneck in its lifecycle, namely, the invasion of oxygen carrying red blood cells (RBCs) by the small merozoite form that initiates the disease causing cycle of replication inside these host cells. Host-cell invasion by malaria is an ideal drug target because (i) extracellular parasites are directly exposed to antimalarials in the bloodstream, (ii) many proteins required for invasion are not shared with host cells, and (iii) failure to invade immediately ends the parasite lifecycle, thereby preventing disease. My research is focussed on developing new antimalarial drugs against this essential step in disease progression. I apply a breakthrough P. falciparum merozoite purification method (#Boyle MJ, #Wilson DW et al., PNAS, 2010, #joint primary authors) that is superior to alternatives for studying malaria parasite invasion biology, opening up new opportunities to study this previously intractable lifecycle stage (Figure 1).
Figure 1: Highly reproducible purification of viable P. falciparum daughter merozoites (examples blue arrow) from mature schizonts (examples green arrow) and assessment of newly invaded ring stage parasites that have established an infection of a new human red blood cell (red arrow) by microscopy (Boyle and Wilson et al. PNAS. 2010).
The invasion inhibitory activity of drugs is assessed using a highly reproducible flow cytometry based approach (Wilson et al. Antimicrobial Agents Chemotherapy, 2013; Figure 2 A & B). Using this approach I have screened traditional antimalarial therapies, protease inhibitors, kinase inhibitors, a range of antibiotics and identified several compounds and there analogues that rapidly inhibit merozoite invasion. The mechanisms by which these compounds inhibit invasion is the subject of ongoing research. To understand how compounds inhibit the essential process of merozoite invasion I apply mutation analysis of gene targets, live filming (in collaboration with Dr. Paul Gilson, The Burnet Institute Melbourne), phenotypic screens of related Apicomplexan parasites (in collaboration with Dr. Dean Goodman and Professor Geoff McFadden, The University of Melbourne), modifications and screens of analogues (in collaboration Dr. Brad Sleebs, WEHI Melbourne and Prof. James Beeson, The Burnet Institute Melbourne) and fluorescence microscopy (Figure 2C, in collaboration with Dr. Jake Baum, Imperial College London & WEHI Melbourne). By applying these state of the art methods I aim to develop invasion inhibitory antimalarials as viable alternative or partner drugs in a climate of increasing drug resistance to current frontline treatments.
Flow cytometry assessment of invasion inhibitory compounds clearly identifies newly invaded rings (population in box) in the non-inhibitory control (Figure 2A) but not in after treatment with an invasion inhibitory compound (Figure 2B, Wilson et al. AAC. 2013). Using state of the art fluorescence microscopy techniques (Figure 2C; example from Riglar and Richards et al. Cell Host & Microbe. 2011; merozoite invading a red blood cell indicated by white arrow) and live filming it is possible to examine the stage of merozoite invasion that is inhibited by an inhibitor, such as a drug, using purified merozoites (Boyle and Wilson et al. PNAS. 2010).
Wilson DW, Goodman CD, Sleebs BE, Weiss GE, de Jong NW, Angrisano F, Langer C, Baum J, Crabb BS, Gilson PR, McFadden GI, and Beeson JG. 2015. Macrolides rapidly inhibit red blood cell invasion by the human malaria parasite, Plasmodium falciparum. BMC Biology 13:52.
Boyle MJ#, Wilson DW#, Richards JS, Riglar DT, Tetteh KK, Conway DJ, Ralph SA, Baum J, Beeson JG, 2010. Isolation of viable Plasmodium falciparum merozoites to define erythrocyte invasion events and advance vaccine and drug development. Proc Natl Acad Sci U S A 107: 14378-83. # joint primary authors. (93 cites: Citations-Google Scholar 28/03/2015).
Wilson DW*, Langer C, Goodman CD, McFadden GI, Beeson JG, 2013. Defining the timing of action of anti-malarial drugs against Plasmodium falciparum. Antimicrob Agents Chemother 57: 1455-1467. * joint corresponding author. (15 cites)
Riglar DT, Richard D, Wilson DW, Boyle MJ, Dekiwadia C, Turnbull L, Angrisano F, Marapana DS, Rogers KL, Whitchurch CB, Beeson JG, Cowman AF, Ralph SA, Baum J, 2011. Super-resolution dissection of coordinated events during malaria parasite invasion of the human erythrocyte. Cell Host Microbe 9: 9-20.
Tham WH, Wilson DW, Lopaticki S, Schmidt CQ, Tetteh-Quarcoo PB, Barlow PN, Richard D, Corbin JE, Beeson JG, Cowman AF, 2010. Complement receptor 1 is the host erythrocyte receptor for Plasmodium falciparum PfRh4 invasion ligand. Proc Natl Acad Sci U S A 107: 17327-32.
Bell DR, WILSON DW, Martin LB, 2005. False-positive results of a Plasmodium falciparum histidine-rich protein 2-detecting malaria rapid diagnostic test due to high sensitivity in a community with fluctuating low parasite density. AM J TROP MED HYG 73: 199-203. (101 cites).
Marapana DS, Wilson DW, Zuccala ES, Dekiwadia CD, Beeson JG, Ralph SA, Baum J, 2012. Malaria parasite signal peptide peptidase is an ER-resident protease required for growth but not invasion. Traffic 13: 1457-65.
Wilson DW, Fowkes FJ, Gilson PR, Elliott SR, Tavul L, Michon P, Dabod E, Siba PM, Mueller I, Crabb BS, Beeson JG, 2011. Quantifying the importance of MSP1-19 as a target of growth-inhibitory and protective antibodies against Plasmodium falciparum in humans. PLoS One 6: e27705. (15 cites).
Wilson DW, Crabb BS, Beeson JG, 2010. Development of fluorescent Plasmodium falciparum for in vitro growth inhibition assays. Malar J 9: 152. (39 cites).
Chen N, Wilson DW, Pasay C, Bell D, Martin LB, Kyle D, Cheng Q, 2005. Origin and dissemination of chloroquine-resistant Plasmodium falciparum with mutant pfcrt alleles in the Philippines. Antimicrob Agents Chemother 49: 2102-5. (38 cites).
Auliff A, Wilson DW, Russell B, Gao Q, Chen N, Anh le N, Maguire J, Bell D, O'Neil MT, Cheng Q, 2006. Amino acid mutations in Plasmodium vivax DHFR and DHPS from several geographical regions and susceptibility to antifolate drugs. Am J Trop Med Hyg 75: 617-21. (55 cites).