Gene cloning and induced expression pattern of IRF4 and IRF10 in the Asian swamp eel(Monopterus albus)

The Asian swamp eel(Monopterus albus) is one of the most economically important freshwater fish in East Asia,but data on the immune genes of M.albus are scarce compared to other commercially important fish.A better understanding of the eel's immune responses may help in developing strategies for disease management,potentially improving yields and mitigating losses.In mammals,interferon regulatory factors(IRFs) play a vital role in both the innate and adaptive immune system; though among teleosts IRF4 and IRF10 have seldom been studied.In this study,we characterized IRF4 and IRF10 from M.albus(maIRF4 and maIRF10) and found that maIRF4 cDNA consists of 1 716 nucleotides encoding a 451 amino acid(aa) protein,while maIRF10 consists of 1 744 nucleotides including an open reading frame(ORF) of 1 236 nt encoding 411 aa.The maIRF10 gene was constitutively expressed at high levels in a variety of tissues,while maIRF4 showed a very limited expression pattern.Expression of maIRF4 and maIRF10 in head kidney,and spleen tissues was significantly up-regulated from 12 h to 48 h post-stimulation with polyinosinic: polycytidylic acid(poly I:C),lipopolysaccharide(LPS) and a common pathogenic bacteria Aeromonas hydrophila.These results suggest that IRF4 and IRF10 play roles in immune responses to both viral and bacterial infections in M.albus.

Immunogenic proteins and their vaccine development potential evaluation in outer membrane proteins(OMPs)of Flavobacterium columnare

Flavobacterium columnare is a Gram-negative bacterium that causes columnaris disease in freshwater fish worldwide.Many studies have focused on the identification of protective antigens to aid in the development of novel vaccines against the disease.In this study,an immunoblotting approach was employed to identify immunogenic outer membrane proteins(OMPs)from F.columnare in two-dimensional electrophoresis(2-DE)map gels using antibacterial sera obtained from grass carp(Ctenopharyngodon idella),and anti-grass carp-recombinant Ig(rIg)monoclonal antibodies.Five unique immunogenic proteins,including the gliding motility lipoprotein GldJ(GldJ),hypothetical protein FCOL_13420(Fco1),lipoprotein(Lip),F0F1 ATP synthase subunit beta(F0f1)and outer membrane efflux protein precursor(Omep),were characterized.Over-expression of these proteins in Escherichia coli DE3,and their immunogenicity and protective efficacy were evaluated in grass carp.The relative percent survival(RPS)of the groups immunized separately with recombinant GldJ,Lip and Omep was 72%,64%and 68%,respectively when compared to control fish.Up-regulation of immuno-related genes and specific antibodies were detected in immunized fish and sera of immunized fish inhibited the growth of F.columnare.The results suggest that GldJ,Lip and Omep are major protective antigens and may be considered as novel candidates in the development of vaccines against columnaris disease in fish.

Cryptic genetic diversity and host specificity of Bothriocephalus acheilognathi Yamaguti,1934(Eucestoda:Bothriocephalidea)

In this report, genetic variation and phylogeny of B. acheilognathi were analyzed based on 96 samples collected from 20 fish host species in 29 different localities by using the rDNA internal transcribed spacer （ITS） sequences. The ITS1 and ITS2 sequences of B. acheilognathi varied among 561-639 bp and 559-648 bp, and ten simple sequence repeat loci （microsatellites） were detected in the ITS regions, which contributed to significant sequence length variation. Phylogenetic analyses revealed 4 genetic clades （A, B, C, D） in samples with significantly different fish host spectra and geographic distribution. Clade A possessed a wide host range and geographic distribution, including all the samples ofB. acheilognathi determined in previous report. Clades B, C, and D only infected the small cyprinid fishes Opsariichthys bidens and Zacco platypus, and were limited to different locality. Interesting, Clades A and D were detected coexisting in same water body, and even in same fish host O. bidens in Danjiangkou Reservoir. The relatively higher genetic divergence and wide geographic distribution orB. acheilognathi parasitic in O. bidens indicated that O. bidens is likely to be the primary host. Sympatric occurrence of the two genetically distinct clades suggests the possibility of allopatric speciation and second encounter events.