Mohammed Sajid

Publications (66) View all

• Article: Loss-of-function analyses defines vital and redundant functions of the Plasmodium rhomboid protease family.

  Jing-Wen Lin, Patrícia Meireles, Miguel Prudêncio, Sabine Engelmann, Takeshi Annoura, Mohammed Sajid, Séverine Chevalley-Maurel, Jai Ramesar, Carolin Nahar, Cristina M C Avramut, Abraham J Koster, Kai Matuschewski, Andrew P Waters, Chris J Janse, Gunnar R Mair, Shahid M Khan
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  ABSTRACT: Rhomboid-like proteases cleave membrane-anchored proteins within their transmembrane domains. In apicomplexan parasites substrates include molecules that function in parasite motility and host cell invasion. While two Plasmodium rhomboids, ROM1 and ROM4, have been examined, the roles of the remaining six rhomboids during the malaria parasite's life cycle are unknown. We present systematic gene deletion analyses of all eight Plasmodium rhomboid-like proteins as a means to discover stage-specific phenotypes and potential functions in the rodent malaria model, P. berghei. Four rhomboids (ROM4, 6, 7 and 8) are refractory to gene deletion, suggesting an essential role during asexual blood stage development. In contrast ROM1, 3, 9 and 10 were dispensable for blood stage development and exhibited no, subtle or severe defects in mosquito or liver development. Parasites lacking ROM9 and ROM10 showed no major phenotypic defects. Parasites lacking ROM1 presented a delay in blood stage patency following liver infection, but in contrast to a previous study blood stage parasites had similar growth and virulence characteristics as wild type parasites. Parasites lacking ROM3 in mosquitoes readily established oocysts but failed to produce sporozoites. ROM3 is the first apicomplexan rhomboid identified to play a vital role in sporogony.
  Molecular Microbiology 03/2013; · 5.01 Impact Factor
• Article: Screening Inhibitors of P. berghei Blood Stages Using Bioluminescent Reporter Parasites.

  Jing-Wen Lin, Mohammed Sajid, Jai Ramesar, Shahid M Khan, Chris J Janse, Blandine Franke-Fayard
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  ABSTRACT: We describe two improved assays for in vitro and in vivo screening of inhibitors and chemicals for antimalarial activity against blood stages of the rodent malaria parasite, Plasmodium berghei. These assays are based on the determination of bioluminescence in small blood samples that is produced by reporter parasites expressing luciferase. Luciferase production increases as the parasite develops in a red blood cell and as the numbers of parasites increase during an infection. In the first assay, in vitro drug luminescence (ITDL) assay, the in vitro development of ring-stage parasites into mature schizonts in the presence and absence of candidate inhibitor(s) is quantified by measuring luciferase activity after the parasites have been allowed to mature into schizonts in culture. In the second assay, the in vivo drug luminescence (IVDL) assay, in vivo parasite growth (using a standard 4-day suppressive drug test) is quantified by measuring the luciferase activity of circulating parasites in samples of tail blood of drug-treated mice.
  Methods in molecular biology (Clifton, N.J.) 01/2013; 923:507-22.
• Source

  Available from: Mohammed Sajid

  Dataset: evolution of apoptosis-like

  Szymon Kaczanowski, Mohammed Sajid, Sarah E Reece
• Article: Assessing the adequacy of attenuation of genetically modified malaria parasite vaccine candidates.

  Takeshi Annoura, Ivo H J Ploemen, Ben C L van Schaijk, Mohammed Sajid, Martijn W Vos, Geert-Jan van Gemert, Severine Chevalley-Maurel, Blandine M D Franke-Fayard, Cornelus C Hermsen, Audrey Gego, Jean-Francois Franetich, Dominique Mazier, Stephen L Hoffman, Chris J Janse, Robert W Sauerwein, Shahid M Khan
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  ABSTRACT: The critical first step in the clinical development of a malaria vaccine, based on live-attenuated Plasmodium falciparum sporozoites, is the guarantee of complete arrest in the liver. We report on an approach for assessing adequacy of attenuation of genetically attenuated sporozoites in vivo using the Plasmodium berghei model of malaria and P. falciparum sporozoites cultured in primary human hepatocytes. We show that two genetically attenuated sporozoite vaccine candidates, Δp52+p36 and Δfabb/f, are not adequately attenuated. Sporozoites infection of mice with both P. berghei candidates can result in blood infections. We also provide evidence that P. falciparum sporozoites of the leading vaccine candidate that is similarly attenuated through the deletion of the genes encoding the proteins P52 and P36, can develop into replicating liver stages. Therefore, we propose a minimal set of screening criteria to assess adequacy of sporozoite attenuation necessary before advancing into further clinical development and studies in humans.
  Vaccine 02/2012; 30(16):2662-70. · 3.77 Impact Factor
• Article: A blood fluke serine protease inhibitor regulates an endogenous larval elastase.

  Landys A Lopez Quezada, Mohammed Sajid, Kee C Lim, James H McKerrow
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  ABSTRACT: The larvae of Schistosoma mansoni invade their mammalian host by utilizing a serine protease, cercarial elastase (SmCE), to degrade macromolecular proteins in host skin. The catalytic activity of serine and cysteine proteases can be regulated after activation by serpins. SmSrpQ, one of two S. mansoni serpins found in larval secretions, is only expressed during larval development and in the early stages of mammalian infection. In vitro, (35)S-SmSrpQ was able to form an SDS-stable complex with a component of the larval lysate, but no complex was detected when (35)S-SmSrpQ was incubated with several mammalian host proteases. Formation of a complex was sensitive to the protease active site inhibitors PMSF, Z-AAPF-CMK, and Z-AAPL-CMK. Western blot analysis of parasite lysates from different life stages detected a complex of comparable size to SmCE bound to SmSrpQ using anti-SmSrpQ or anti-SmCE antibodies. SmSrpQ and SmCE are located in adjacent but discrete compartments in the secretion glands of the parasite. Fluorescence immunohistochemical analysis of simulated infection showed co-localization of SmCE and SmSrpQ in host tissue suggesting a post release regulation of parasite protease activity during skin transversal. The results of this study suggest that cercarial elastase degradation of skin tissue is carefully regulated by SmSrpQ.
  Journal of Biological Chemistry 12/2011; 287(10):7074-83. · 4.77 Impact Factor