Abstract
BackgroundWe have recently developed several homozygous families of transgenic rainbow trout harbouring cecropin P1 transgene. These fish exhibit resistance characteristic to infection by Aeromonas salmonicida and infectious hematopoietic necrosis virus (IHNV). In our earlier studies we have reported that treatment of a rainbow trout macrophage cell line (RTS11) with a linear cationic α-helical antimicrobial peptide (e.g., cecropin B) resulted in elevated levels of expression of two pro-inflammatory relevant genes (e.g., IL-1β and COX-2). Therefore, we hypothesized that in addition to the direct antimicrobial activity of cecropin P1 in the disease resistant transgenic rainbow trout, this antimicrobial peptide may also affect the expression of immune relevant genes in the host. To confirm this hypothesis, we launched a study to determine the global gene expression profiles in three immune competent organs of cecropin P1 transgenic rainbow trout by using a 44k salmonid microarray.ResultsFrom the microarray data, a total of 2480 genes in the spleen, 3022 in the kidney, and 2102 in the liver were determined as differentially expressed genes (DEGs) in the cecropin P1 transgenic rainbow trout when compared to the non-transgenics. There were 478 DEGs in common among three tissues. Enrichment analyses conducted by two different bioinformatics tools revealed a tissue specific profile of functional pathway perturbation. Many of them were directly related to innate immune system such as phagocytosis, lysosomal processing, complement activation, antigen processing/presentation, and leukocyte migration. Perturbation of other biological functions that might contribute indirectly to host immunity was also observed.ConclusionsThe gene product of cecropin P1 transgene produced in the disease resistant transgenic rainbow trout not only can kill the pathogens directly but also exert multifaceted immunomodulatory properties to boost host immunity. The identified genes involved in different pathways related to immune function are valuable indicators associated with enhanced host immunity. These genes may serve as markers for selective breeding of rainbow trout or other aquaculture important fish species bearing traits of disease resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-887) contains supplementary material, which is available to authorized users.
Highlights
We have recently developed several homozygous families of transgenic rainbow trout harbouring cecropin P1 transgene
In the present study, using disease resistant transgenic rainbow trout harbouring cecropin P1 as experimental animals, we investigated the effect of antimicrobial peptide (AMP) on global gene expression profiles at the organism level by DNA microarray analysis on a 44K oligo salmonid array platform [11]
Preliminary analysis and an overview of microarray datasets Tissue samples of spleen, kidney, and liver were collected from two different families of cecropin P1 transgenic or non-transgenic fish of equal body sizes and sexes
Summary
We have recently developed several homozygous families of transgenic rainbow trout harbouring cecropin P1 transgene. We hypothesized that in addition to the direct antimicrobial activity of cecropin P1 in the disease resistant transgenic rainbow trout, this antimicrobial peptide may affect the expression of immune relevant genes in the host. During the past few decades, different strategies including vaccination, good husbandry practice, and use of antibiotics or breeding strains less susceptible to specific diseases through conventional genetic selection have been practiced for fish disease prevention and control These strategies, effective to a certain extent, suffer from various drawbacks such as the high cost, labour intensiveness, emergence of antibiotics-resistant microbial strains, absence of effective cure for certain types of viral pathogens, and unsatisfactory degree of protection. First identified in Cecrpoia moth, are members of the antimicrobial peptide (AMP) family that constitute a main part of the cell-free immunity of insects [2] They are initially identified in a number of insect species and were later isolated from porcine small intestine, named cecropin P1 [3]. These basic peptides, 31 to 37 amino acid residues in length and consisting of mainly alpha helices, attack bacterial membrane by forming pores or ion channels and cause cell lysis [4]
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