Comparative analysis of differential gene expression in kidney tissues of moribund and surviving crucian carp (Carassius auratus gibelio) in response to cyprinid herpesvirus 2 infection

Abstract

Cyprinid herpesvirus 2 (CyHV-2) has recently been associated with high mortality of cultured crucian carp (Carassius auratus gibelio) in eastern China. In this study, we established a real-time PCR method to confirm viral infection of crucian carp and to quantify CyHV-2 particles obtained by sucrose gradient centrifugation from diseased fish. Virus-free crucian carp were artificially infected with CyHV-2 using an injection method, which resulted in a dose-dependent death rate. In situ hybridization analysis indicated that there was extensive viral replication and lysis in the kidneys of moribund fish, in contrast to very limited replication in surviving fish. To probe the host immune response to viral infection at the level of gene expression, we identified virus-responsive genes using suppression subtractive hybridization (SSH) in head kidney tissues, the principal immune organ of fish, from moribund and surviving crucian carps after viral challenge. From the moribund SSH library, 363 expressed sequence tags (ESTs) were clustered to 234 unigenes (including 15 singletons and 45 contigs). From the survivor SSH library, 599 ESTs was clustered to 549 unigenes (including 107 singletons and 105 contigs). We further analyzed the transcriptional levels of all immune-related genes by quantitative real-time RT-PCR, which confirmed the upregulation of 90.48 % of these genes. The significantly upregulated immune-related genes identified in this study can serve as candidate marker genes for acute CyHV-2 infection.

Distinct herpesvirus resistances and immune responses of three gynogenetic clones of gibel carp revealed by comprehensive transcriptomes

“…Owing to the highly intensifying and seriously crowding of monoculture, gibel carp has been suffered by a series of pathogens [73]. Since 2009, an epizootic with acute gill hemorrhages and high mortality has outbroken in cultured gibel carp [74]. The complete genome sequencing of the virus isolated from the tissues of diseased gibel carp showed the Ca HV was most closely related to CyHV-2 [15].…”

“…By using PCR assay, CyHV-2 was first detected in gibel carp in Hungary [81]. Recently, it has been detected in many main culture regions of gibel carp [74] and caused huge economic loss. The experimental infection of indigenous Cyprininae species in Japan, such as ginbuna C. auratus langsdorfii , nagabuna C. auratus buergeri , nigorobuna C. auratus grandoculis and common carp, suggested that Japanese Carassius fish species possess different ability to depress the replication of CyHV-2 [82].…”

“…The up-regulation of IL6 was also observed in Japanese pufferfish ( Fugu rubripes ) [98], rainbow trout [99], Japanese flounder [100], gilthead seabream ( Sparus aurata ) [101], and European sea bass ( Dicentrarchus labrax ) [102]. After LPS, poly I:C or pathogen infection, Japanese flounder, rainbow trout and gibel carp IL11 also increased expression after challenge with viral [74, 103, 104]. Rainbow trout recombinant IL6 protein can promote macrophage growth in culture and induce up-regulation of antimicrobial peptide [105].…”

“…Apparently healthy individuals were selected to gradually acclimatize in 150-l tanks with aerated water at 24(±1)°C for 2 weeks before infection and fed with commercial feed twice a day. Before infection, 5 individuals of each clone were randomly selected to perform PCR analysis as previously described [74] to confirm Ca HV free.…”

Virus genomes and virus-host interactions in aquaculture animals

“…In recent years, after cyprinid herpesvirus disease became widely reported in the world, (especially in China) [145][146][147], numerous studies on cyprinid herpesviruses and identification of immune-related genes have been conducted [148][149][150]. It is envisaged, therefore, that new insight and better understanding of these cyprinid herpesviruses will emerge and lead to efficient antiviral approaches being developed in the near future.…”