title: Antigenicity of Streptococcus agalactiae extracellular products and vaccine efficacy.
abstract: Streptococcus agalactiae is a major bacterial pathogen that is the cause of serious economic losses in many species of freshwater, marine and estuarine fish worldwide. A highly efficacious S. agalactiae vaccine was developed using extracellular products (ECP) and formalin-killed whole cells of S. agalactiae. The vaccine efficacy following storage of S. agalactiae ECP and formalin-killed S. agalactiae cells at 4 degrees C for 1 year was determined. The stored ECP containing S. agalactiae formalin-killed cells failed to prevent morbidity and mortality among the vaccinated fish, and the relative percentage survival was 29. Serum antibody responses of the stored ECP and freshly prepared ECP against soluble whole cell extract of S. agalactiae indicated that significantly less antibody was produced in fish immunized with stored ECP and S. agalactiae cells than in those fish immunized with freshly prepared ECP and S. agalactiae cells at day 31 post-vaccination. Silver staining of sodium dodecyl sulphate-polyacrylamide gels and immunostaining of Western blots with tilapia antiserum to S. agalactiae revealed that predominant 54 and 55 kDa bands were present in the freshly prepared ECP fraction. The 55 kDa band was absent from the stored ECP and new bands below 54 kDa appeared on the Western blot. The results of this study on S. agalactiae ECP provide evidence for a correlation between protection and antibody production to ECP and for the importance of the 55 kDa ECP antigen for vaccine efficacy.
authors.affiliation: Aquatic Animal Health Research Laboratory, United States Department of Agriculture, Agricultural Research Service, Chestertown, MD 21620, USA. dpasnik@msa-stoneville.ars.usda.gov
authors.forename: D J
authors.initials: DJ
authors.lastname: Pasnik
authors.forename: J J
authors.initials: JJ
authors.lastname: Evans
authors.forename: V S
authors.initials: VS
authors.lastname: Panangala
authors.forename: P H
authors.initials: PH
authors.lastname: Klesius
authors.forename: R A
authors.initials: RA
authors.lastname: Shelby
authors.forename: C A
authors.initials: CA
authors.lastname: Shoemaker
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology*; D001428:Bacterial Vaccines / Q000276:immunology*; D015153:Blotting, Western; D023681:Cichlids; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D016326:Extracellular Matrix Proteins / Q000276:immunology; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology*; D007106:Immune Sera / Q000276:immunology; D013290:Streptococcal Infections / Q000276:immunology / Q000662:veterinary*; D013292:Streptococcus agalactiae / Q000276:immunology*; D013997:Time Factors
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D016326:Extracellular Matrix Proteins; D007106:Immune Sera