Amit Pal

Biography

Dr. Amit Pal is a Scientist D at the Division of Pathophysiology, National Institute of Cholera and Enteric Diseases (NICED) in Kolkata. He joined NICED in March 1999 as a Senior Research Officer. He did his Bachelors and Masters in Physiology from Kolkata University. He completed his doctoral thesis related to enteric toxins at Division of Microbiology, NICED in 1992. He did his postdoctoral research on molecular characterization of V. cholerae O1 strains under Dr Y Takeda at the Department of Microbiology, Kyoto University from 1992 to 1994. He was a Research Associate at the Department of Molecular Biology at the Indian Institute of Chemical Biology, Jadavpur, Kolkata from 1994 to 1995. He did his next postdoctoral research from 1995 to 1997 at the National Children's Hospital, Tokya, Japan under Dr T. Takeda working on molecular epidemiological studies on E. coli O157:H7 strains. He was a pool officer at the Department of Microbiology, NICED from 1997-1999. Since 1999 he has joined NICED working as a Senior Research Officer at the Division of Pathophysiology. He has been working on the enterotoxigenicity of cholera toxin gene negative V. cholerae non-O1, non-O139 strains. He has three Ph. D students working under him. At present he is working as a visiting researcher at the Department of Molecular Biology Umea University, Sweden. He is also the main partner in the Swedish Foundation for International Cooperation in Research and Higher Education along with Dr Sun Nyunt Wai, Associate Professor, Department of Molecular Biology, Umea University. The STINT project is related to work on molecular pathogenesis of V. cholerae O1 strains.

Research Interest

Studies on enterotoxigenicity of 45-kDa matured and 35-kDa processed forms of hemagglutinin protease purified from a cholera toxin gene negative Vibrio cholerae non-O1, non-O139 strain. Cholera toxin gene negative Vibrio cholerae non-O1, non-O139 strain PL-21 is the etiologic agent of cholera like syndrome. Hemagglutinin protease (HAP) is one of the major secretary proteins of PL-21. The 45-kDa matured and the 35-kDa processed forms of HAP were purified in the presence and absence of EDTA from culture supernatants of PL-21. Enterotoxigenicities of both forms of HAP were tested in the rabbit ileal loop (RIL), Ussing's chamber and tissue culture assay. The 35-kDa HAP showed hemorrhagic fluid response in a dose-dependent manner in the RIL assay. Histopathological examination of 20 µ g of purified protease treated rabbit ileum showed presence of erythrocytes and neutrophils in the upper part of the villus lamina propria. The 35-kDa HAP, when added to the luminal surface of rat ileum loaded in Ussing's chamber, showed a decrease in the intestinal short circuit current and a cell rounding effect on HeLa cells. The mature 45-kDa form of HAP showed an increase in intestinal short circuit current in Ussing's chamber and a cell distending effect on HeLa cells. These results show that HAP may play a role in the pathogenesis of PL-21. Pathogenesis and outer membrane vesicle mediated transport of hemagglutinin protease of Vibrio cholerae O1. Hemagglutinin protease (HAP), a major secreted proteolytic enzyme, was purified from the culture supernatant of Vibrio cholerae O1 strain C6709 after removal of outer membrane vesicles (OMVs) using a single step ion-exchange chromatography. The purified HAP or the culture supernatant of C6709 when injected subcutaneously into suckling mouse, showed distinct in vivo hemorrhagic response and histopathological changes including presence of moderate number of erythrocytes diffusely scattered throughout the skin, capillary necrosis, acute myofiber degeneration and necrosis of muscle layer. However, when the culture supernatant of an isogenic ?hapA strain CHA6.8 was used the hemorrhagic effects in suckling mouse was not detectable. Themajor protein components, laminin and collagen, of basement membrane comprising of vascular endothelial cells, are degraded by HAP and this may cause destruction of the basement membrane, breakdown of capillary blood vessels and leakage of erythrocytes. Purified HAP or OMVs of C6709 showed cell distending and rounding effects on Int407 cells. In this study we show that the HAP may be exported through OMVs. Confocal microscopical studies indicated that OMVs of C6709 bind to the cell surface of Int407 followed by release of HAP in the cytoplasm.