title: Immunostimulatory activities of a decapeptide derived from Alcaligenes faecalis FY-3 to crucian carp.
abstract: A strain was isolated from a soil sample collected from Weihe river in Shaanxi province (108°03'E 34°14'N), which was identified as Alcaligenes faecalis by 16S rRNA analysis. A compound M showing potent immune activity was isolated from secondary metabolites of the strain through bioassay-guided isolation techniques. The structure of the compound M was elucidated using FT-IR, EI-MS, 1H NMR and 13C NMR spectra and identified as cyclo-(L-Pro-Gly)5 which was first time reported as a natural product. We evaluated the immune effects of the cyclo-(L-Pro-Gly)5 on the basis of serum lysozyme activity, bacterial agglutination titre assay, superoxide anion production and phagocytic activity assay, and they were found to be significantly increased by cyclo-(L-Pro-Gly)5. The effects of cyclo-(L-Pro-Gly)5 on immune-related gene expression were further investigated. The outcomes of real-time quantitative polymerase chain reaction (RQ-PCR) proved that the transcribing level of interleukin 6β (IL-6β) and inducible nitric oxide synthase 1β (iNOS-1β) mRNA in the blood leucocytes have been augmented by cyclo-(L-Pro-Gly)5. The challenge experiment showed that crucian carp injected the cyclo-(L-Pro-Gly)5 had significantly (P < 0.05) lower cumulative mortality (13.0%) compared with the control (45.4%) after infection with live Aeromonas hydrophila. These results suggested that cyclo-(L-Pro-Gly)5 is a possible immunostimulant and may strengthen the immune response and protect the heath status of crucian carp against A. hydrophila.
authors.affiliation: Northwest A&F University, Yang ling, Xian, China. wanggaoxue@126.com
authors.forename: G-X
authors.initials: GX
authors.lastname: Wang
authors.forename: F-Y
authors.initials: FY
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Cui
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: Y-T
authors.initials: YT
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Han
authors.forename: Y
authors.initials: Y
authors.lastname: Lei
mesh_terms: D000276:Adjuvants, Immunologic / Q000737:chemistry / Q000494:pharmacology*; D042481:Alcaligenes faecalis / Q000276:immunology* / Q000302:isolation & purification; D000818:Animals; D002347:Carps / Q000276:immunology* / Q000382:microbiology; D005393:Fish Diseases / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D007109:Immunity / Q000187:drug effects; D007114:Immunization; D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology*; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000276:Adjuvants, Immunologic; D009842:Oligopeptides; D010456:Peptides, Cyclic; C560421:cyclo(prolyl-glycyl)5