title: 9- O-acetylated sialic acids enhance entry of virulent Leishmania donovani promastigotes into macrophages.
abstract: Distribution of 9-O-acetylated sialic acids (9-O-AcSA) on Leishmania donovani has been previously reported. Considering their role in recognition, the differential distribution of sialic acids especially 9-O-acetylated sialic acids in avirulent (UR6) versus virulent (AG83 and GE1) promastigotes of Leishmania donovani and its role in entry into macrophages was explored. Fluorimetric-HPLC, fluorimetric determination and ELISA revealed 14-, 8- and 5-fold lower sialic acids in UR6 as compared to AG83. Interestingly, on UR6, flow cytometry indicated lower (alpha2-->6)-linked sialoglycoproteins along with minimal 9-O-acetylated sialoglycoproteins by Scatchard analysis. Further, UR6 demonstrated a 9- and 14.5-fold lower infectivity and phagocytic index than AG83. Additionally, de-O-acetylation and de-sialylation of AG83 demonstrated a 3- and 1.5-fold reduced phagocytic index. The role of 9-O-AcSA in entry was further confirmed by pre-blocking the macrophage surface with a cocktail of sugars followed by microscopic quantification. The phagocytic index of AG83 exclusively through 9-O-AcSA was significantly high. Interestingly, AG83 produced higher metacyclic promastigotes containing increased 9-O-AcSA as compared to avirulent UR6 supporting its virulent nature. Taken together; our results conclusively demonstrate the increased presence of 9-O-acetylated sialic acid on promastigotes of virulent Leishmania donovani as compared to avirulent UR6 and their subsequent role in entry within macrophages.
authors.affiliation: Infectious Disease and Immunology Division, Indian Institute of Chemical Biology, Jadavpur, Kolkata, India.
authors.forename: A
authors.initials: A
authors.lastname: Ghoshal
authors.forename: S
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: A K
authors.initials: AK
authors.lastname: Chava
authors.forename: G J
authors.initials: GJ
authors.lastname: Gerwig
authors.forename: J P
authors.initials: JP
authors.lastname: Kamerling
authors.forename: M
authors.initials: M
authors.lastname: Chatterjee
authors.forename: C
authors.initials: C
authors.lastname: Mandal
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D004950:Esterases / Q000378:metabolism; D005434:Flow Cytometry; D005470:Fluorometry; D037102:Lectins / Q000302:isolation & purification / Q000378:metabolism; D007893:Leishmania donovani / Q000166:cytology / Q000378:metabolism* / Q000472:pathogenicity*; D008264:Macrophages / Q000469:parasitology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D009439:Neuraminidase / Q000378:metabolism / Q000494:pharmacology; D012794:Sialic Acids / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D037102:Lectins; D012794:Sialic Acids; D037521:Virulence Factors; C050704:achatinin(H); C025676:9-O-acetyl-N-acetylneuraminic acid; D004950:Esterases; D009439:Neuraminidase