Cellular and molecular immune responses of the sea bass (Dicentrarchus labrax) experimentally infected with betanodavirus.
Naïve sea bass juveniles (38.4 + or - 4.5 g) were intramuscularly infected with a sublethal dose of betanodavirus isolate 378/I03, followed after 43 days by a similar boosting. This infection resulted in an overall mortality of 7.6%. At various intervals, sampling of fish tissues was performed to investigate: i) B and T lymphocyte content in organs and tissues; ii), proliferation of leucocytes re-stimulated in vitro with inactivated virus; iii) presence of serum antibody specific for betanodavirus; iv) expression of genes coding for the following immunoregulatory molecules involved in innate and acquired responses: type I IFN, Mx, IL-1, Cox-2; IL-10, TGF-beta, TCRbeta, CD4, CD8alpha, IgM, by using a quantitative PCR array system developed for sea bass. The obtained results showed a detectable increase of T cells and B cells in PBL during betanodavirus infection. Furthermore, leucocytes obtained from blood, head kidney, and gills showed a detectable "in vitro" increase in viability upon addition of inactivated viral particles, as determined by measuring intracellular ATP concentration. ELISA analysis of sera showed that exposure to nodavirus induced a low, but specific antibody titer measured 43 days after infection, despite the presence of measurable levels of natural antibody. Finally, a strong upregulation of genes coding for type I IFN, Mx, and IgM was identified after both infection and boosting. Interestingly, an upregulation of Cox-2 until boosting, and of TGF-beta and IL-10 after boosting was also observed, while the other tested genes did not show any significant variations with respect to mock-treated fish. Overall, our work represents a first comprehensive analysis of cellular and molecular immune parameters in a fish species exposed to a pathogenic virus.
Scapigliati
G
G
Dipartimento di Scienze Ambientali, Largo dell'Università, Università degli Studi della Tuscia, Viterbo 01100, Italy. scapigg@unitus.it
Buonocore
F
F
Randelli
E
E
Casani
D
D
Meloni
S
S
Zarletti
G
G
Tiberi
M
M
Pietretti
D
D
Boschi
I
I
Manchado
M
M
Martin-Antonio
B
B
Jimenez-Cantizano
R
R
Bovo
G
G
Borghesan
F
F
Lorenzen
N
N
Einer-Jensen
K
K
Adams
S
S
Thompson
K
K
Alonso
C
C
Bejar
J
J
Cano
I
I
Borrego
J J
JJ
Alvarez
M C
MC
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001492:Bass / Q000276:immunology* / Q000821:virology*; D002460:Cell Line; D049109:Cell Proliferation; D004797:Enzyme-Linked Immunosorbent Assay; D005393:Fish Diseases / Q000276:immunology* / Q000821:virology; D008214:Lymphocytes / Q000166:cytology; D030381:Nodaviridae / Q000276:immunology*; D016133:Polymerase Chain Reaction; D012327:RNA Virus Infections / Q000276:immunology / Q000662:veterinary*
D000914:Antibodies, Viral