title: New attenuated vaccine against columnaris disease in fish: choosing the right parental strain is critical for vaccine efficacy.
abstract: Flavobacterium columnare, the causative agent of columnaris disease, is a highly diverse species comprised by three genomovars. Genomovar II strains are more virulent toward catfishes than genomovar I isolates. The objective of this study was to compare the vaccine efficacy of avirulent mutants derived from genomovars I and II using a rifampicin-resistance strategy. First, we compared the efficacy of 13 genomovar II mutants in channel catfish (Ictalurus punctatus) fingerlings and identified mutant 17-23 as the best vaccine candidate based on their relative percent survival (RPS) against a highly virulent genomovar II strain (BGFS-27). In the second experiment, we vaccinated zebrafish (Danio rerio) with two genomovar II mutants (17-23 and 16-534) and FCRR (genomovar I mutant) followed by exposure to BGFS-27 strain. RPS values were 28.4, 20.3 and 8.1% for 17-23, 16-534, and FCRR, respectively. For experiments 3 and 4, we tested both 17-23 and FCRR in channel catfish fry and Nile tilapia (Oreochromis niloticus). In both experiments, vaccinated fish were divided in two groups and each challenged with either a genomovar I (ARS-1) or a II (BGFS-27) strain. Channel catfish fry vaccinated with 17-23 and FCRR followed by challenge with BGFS-27 resulted in RPS values of 37.0% and 4.4%. When fish were challenged with ARS-1, RPS values were 90.9% and 72.7% for fish vaccinated with 17-23 and FCRR, respectively. Nile tilapia vaccinated with 17-23 and FCRR followed by challenged with BGFS-27 had RPS values of 82.1% and 16.1%, respectively. When fish were challenged with strain ARS-1, RPS values were 86.9% and 75.5%. Overall, our results demonstrated that vaccination with genomovar II mutant 17-23 confers better protection in channel catfish and Nile tilapia than FCRR against columnaris disease caused by genomovar II. Both mutants were equally protective against columnaris caused by genomovar I showing that 17-23 mutant cross-protected against both genomovars.
authors.affiliation: Aquatic Microbiology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, 203 Swingle Hall, Auburn, AL 36849, USA.
authors.forename: Haitham
authors.initials: H
authors.lastname: Mohammed
authors.forename: Oscar
authors.initials: O
authors.lastname: Olivares-Fuster
authors.forename: Stacey
authors.initials: S
authors.lastname: LaFrentz
authors.forename: Covadonga R
authors.initials: CR
authors.lastname: Arias
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D023681:Cichlids; D005393:Fish Diseases / Q000276:immunology / Q000517:prevention & control*; D045826:Flavobacteriaceae Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D005417:Flavobacterium / Q000235:genetics / Q000276:immunology*; D005838:Genotype; D007059:Ictaluridae; D016019:Survival Analysis; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology; D015027:Zebrafish
chemical_list: D001428:Bacterial Vaccines; D014613:Vaccines, Attenuated
keywords: Catfish; Columnaris disease; Flavobacterium columnare; Tilapia; Vaccine; Zebrafish