title: Expression of immune-related genes in rainbow trout (Oncorhynchus mykiss) induced by probiotic bacteria during Lactococcus garvieae infection.
abstract: The aim of the present study was to investigate the effect of lactic acid bacteria (LAB) on the control of lactococcosis as well as to assess the impact of probiotics on the expression of immune-related genes in the head kidney and intestine of rainbow trout (Oncorhynchus mykiss). Lactobacillus plantarum, Lactococcus lactis and Leuconostoc mesenteroides, were administered orally at 10⁶ CFU g⁻¹ feed to fish for 36 days. Twenty-one days after the start of the feeding period, fish were challenged with Lactococcus garvieae. Only the fish fed the diet containing Lb. plantarum showed significantly (P < 0.05) improved protection against L. garvieae compared to the control. Subsequently, real-time PCR was employed to determine the mRNA levels of IL-1β, IL-8, IL-10 and TNF-α in the head kidney, and IL-8, Tlr5 and IgT in the intestine of the control and Lb. plantarum groups. IL-1β, IL-10 and TNF-α gene expression were significantly up-regulated by Lb. plantarum. Moreover, the mRNA levels of IL-10, IL-8 and IgT were significantly higher in the Lb. plantarum group after L. garvieae infection, suggesting that Lb. plantarum can stimulate the immune response of rainbow trout. PCR-DGGE revealed no detectable levels of the probiotics or the pathogen present on the distal intestinal mucosa. These findings demonstrate that direct probiotic-host interactions with the intestine are not always necessary to induce host stimulatory responses which ultimately enhance disease resistance. Furthermore, as L. garvieae did not colonise the intestinal tract, and therefore likely did not infect via this route, the antagonistic properties of the probiotic candidate towards L. garvieae were likely of little influence in mediating the improved disease resistance which could be attributed to the elevated immunological response.
authors.affiliation: Laboratory of Fish Pathology, Faculty of Veterinary, Universidad de Zaragoza, c/. Miguel Servet 177, 50013 Zaragoza, Spain. taniaper@unizar.es
authors.forename: Tania
authors.initials: T
authors.lastname: Pérez-Sánchez
authors.forename: José Luis
authors.initials: JL
authors.lastname: Balcázar
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Merrifield
authors.forename: Oliana
authors.initials: O
authors.lastname: Carnevali
authors.forename: Giorgia
authors.initials: G
authors.lastname: Gioacchini
authors.forename: Ignacio
authors.initials: I
authors.lastname: de Blas
authors.forename: Imanol
authors.initials: I
authors.lastname: Ruiz-Zarzuela
mesh_terms: D000821:Animal Feed; D000818:Animals; D016207:Cytokines / Q000235:genetics / Q000276:immunology; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology / Q000517:prevention & control; D016908:Gram-Positive Bacterial Infections / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*; D007113:Immunity, Innate; D007136:Immunoglobulins / Q000235:genetics / Q000276:immunology; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology; D007668:Kidney / Q000276:immunology / Q000382:microbiology; D048191:Lactiplantibacillus plantarum / Q000502:physiology; D017045:Lactococcus / Q000187:drug effects / Q000276:immunology* / Q000502:physiology; D007934:Leuconostoc / Q000502:physiology; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D019936:Probiotics / Q000008:administration & dosage; D012333:RNA, Messenger / Q000235:genetics / Q000276:immunology; D051198:Toll-Like Receptor 5 / Q000235:genetics / Q000276:immunology
chemical_list: D016207:Cytokines; D007136:Immunoglobulins; D012333:RNA, Messenger; D051198:Toll-Like Receptor 5