TY - JOUR
T1 - Differential immune response of rainbow trout (Oncorhynchus mykiss) at early developmental stages (larvae and fry) against the bacterial pathogen Yersinia ruckeri
AU - Chettri, Jiwan Kumar
AU - Raida, Martin Kristian
AU - Kania, Per Walter
AU - Buchmann, Kurt
PY - 2012/2
Y1 - 2012/2
N2 - Innate immune factors play a crucial role in survival of young fish especially during early stages of life when adaptive immunity is not fully developed. In the present study, we investigated the immune response of rainbow trout (Oncorhynchus mykiss) larvae and fry at an early stage of development. We exposed 17 and 87° days post hatch larvae and fry (152 and 1118 degree days post hatch; avg. wt. 70 and 770. mg, respectively) to the bacterial pathogen, Yersinia ruckeri for 4. h by bath challenge. Samples were taken at 4, 24, 72 and 96. h post exposure for qPCR and immunohistochemical analyses to elucidate the immune response mounted by these young fish. Larvae showed no mortality although infected larvae at 48. h post exposure showed hyperaemia in the mouth region and inflammation on the dorsal side of the body. Gene expression studies showed an up-regulation of iNOS and IL-22 in infected larvae 24. h post exposure but most of the investigated genes did not show any difference between infected and uninfected larvae. Immunohistochemical studies demonstrated a high expression of IgT molecules in gills and CD8 positive cells in thymus of both infected and uninfected larvae. Infection of rainbow trout fry with Y. ruckeri, in contrast, induced a cumulative mortality of 74%. A high expression of cytokines (IL-1β, TNF-α, IL-22, IL-8 and IL-10), acute phase proteins (SAA, hepcidin, transferrin and precerebellin), complement factors (C3, C5 and factor B), antimicrobial peptide (cathelicidin-2) and iNOS was found in infected fry when compared to the uninfected control. IgT molecules and mannose binding lectins in gills of both infected and uninfected fry were detected by immunohistochemistry. The study indicated that early life stages (yolk-sac larvae), merely up-regulate a few genes and suggests a limited capacity of larvae to mount an immune response by gene regulation at the transcriptional level. Based on the observed clearance of bacteria and lack of mortality it could be speculated that larvae may be covered by protective shield of different immune factors providing protection against broad range of pathogens. However, the increased susceptibility of older fry suggests that Y. ruckeri may utilize some of the immune elements to enter the naive fish. The up-regulation of iNOS and IL-22 in the infected larvae implicates an important role of these molecules in immune response at early developmental stages. A dense covering of surfaces of gill filaments by IgT antibody in the young fish suggest a role of this antibody as innate immune factor at early developmental stages.
AB - Innate immune factors play a crucial role in survival of young fish especially during early stages of life when adaptive immunity is not fully developed. In the present study, we investigated the immune response of rainbow trout (Oncorhynchus mykiss) larvae and fry at an early stage of development. We exposed 17 and 87° days post hatch larvae and fry (152 and 1118 degree days post hatch; avg. wt. 70 and 770. mg, respectively) to the bacterial pathogen, Yersinia ruckeri for 4. h by bath challenge. Samples were taken at 4, 24, 72 and 96. h post exposure for qPCR and immunohistochemical analyses to elucidate the immune response mounted by these young fish. Larvae showed no mortality although infected larvae at 48. h post exposure showed hyperaemia in the mouth region and inflammation on the dorsal side of the body. Gene expression studies showed an up-regulation of iNOS and IL-22 in infected larvae 24. h post exposure but most of the investigated genes did not show any difference between infected and uninfected larvae. Immunohistochemical studies demonstrated a high expression of IgT molecules in gills and CD8 positive cells in thymus of both infected and uninfected larvae. Infection of rainbow trout fry with Y. ruckeri, in contrast, induced a cumulative mortality of 74%. A high expression of cytokines (IL-1β, TNF-α, IL-22, IL-8 and IL-10), acute phase proteins (SAA, hepcidin, transferrin and precerebellin), complement factors (C3, C5 and factor B), antimicrobial peptide (cathelicidin-2) and iNOS was found in infected fry when compared to the uninfected control. IgT molecules and mannose binding lectins in gills of both infected and uninfected fry were detected by immunohistochemistry. The study indicated that early life stages (yolk-sac larvae), merely up-regulate a few genes and suggests a limited capacity of larvae to mount an immune response by gene regulation at the transcriptional level. Based on the observed clearance of bacteria and lack of mortality it could be speculated that larvae may be covered by protective shield of different immune factors providing protection against broad range of pathogens. However, the increased susceptibility of older fry suggests that Y. ruckeri may utilize some of the immune elements to enter the naive fish. The up-regulation of iNOS and IL-22 in the infected larvae implicates an important role of these molecules in immune response at early developmental stages. A dense covering of surfaces of gill filaments by IgT antibody in the young fish suggest a role of this antibody as innate immune factor at early developmental stages.
KW - Former LIFE faculty
KW - Early life stages
KW - Larvae
KW - Innate immunity
KW - I&T
KW - CD8
KW - Cytokines
KW - Acute phase proteins
KW - IL-22
KW - iNOS
U2 - 10.1016/j.dci.2011.08.014
DO - 10.1016/j.dci.2011.08.014
M3 - Journal article
SN - 0145-305X
VL - 36
SP - 463
EP - 474
JO - Developmental and Comparative Immunology
JF - Developmental and Comparative Immunology
IS - 2
ER -