Intestinal barrier of carp (Cyprinus carpio L.) during a cyprinid herpesvirus 3-infection: Molecular identification and regulation of the mRNA expression of claudin encoding genes Hamdan Syakuri a, d , Miko1aj Adamek a , Graham Brogden a , Krzysztof q. Rakus b, 1 , Marek Matras c , Ilgiz Irnazarow b , Dieter Steinhagen a, * a Fish Disease Research Unit, Centre of Infectious Diseases, University of Veterinary Medicine Hannover, Bünteweg 17, D-30559 Hannover, Germany b Polish Academy of Sciences, Institute of Ichthyobiology & Aquaculture in Golysz, Kalinowa 2, 43-520 Chybie, Poland c Laboratory of Fish Diseases, National Veterinary Research Institute, Partyzantow 57, 24-100 Pulawy, Poland d Department of Fisheries and Marine Science, Faculty of Science and Technology, Jenderal Soedirman University, Purwokerto, Indonesia article info Article history: Received 14 August 2012 Received in revised form 24 October 2012 Accepted 3 November 2012 Available online 26 November 2012 Keywords: Koi herpesvirus Cyprinid herpesvirus 3 Cyprinus carpio Claudin gene Barrier intestine abstract As a major part of tight junctions in the intestinal epithelium of vertebrates, claudin proteins are crucial to develop a selective permeable function and to maintain integrity of the barrier. The intestine has been reported as one of the targeted tissue of the cyprinid herpesvirus 3 (CyHV-3) or koi herpesvirus (KHV) which causes major disease problems in carp production worldwide. To analyse the impact of the disease on the epithelial barrier of the intestine, carp claudin encoding genes were cloned, their tissue expression was described, and the abundance of gene transcripts in the intestine of carp under CyHV-3 infection was determined. Some of the carp claudin genes such as claudin-7 and -11 were expressed in various tissues, whilst others, like claudin-2 and -23, showed more tissue-specific expression profiles, which may reflect specific functions of these particular claudins. Along the gut axis, a spatial distribution of claudin gene expressions was found, with a lower abundance of gene transcripts in anterior regions of the intestine and increased expression in the distal section of the intestine, which might indicate specific functions of different regions in the intestinal tract of carp. In carp under CyHV-3 infection, an up- regulation in the expression of IFN-a2, IL-1beta and iNOS was observed, together with an elevation of transcriptional levels of claudin-2, -3c, -11, and -23. The data suggest that expression of claudins is involved in the reorganisation of the intestinal epithelium in CyHV-3-infected carp, which may be responsible for changes in the paracellular permeability. An increased expression of the claudins might be a response to the disturbance of the hydromineral balance in carp under CyHV-3 infection. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Common carp (Cyprinus carpio L.) is considered as one of the most important commodities in freshwater aquaculture. In the last two decades the annual production of common carp increased exponentially and reached more than 3 millions tonnes in 2010 [1]. Currently, it represents 14% of the global freshwater aquaculture production and is mainly cultivated in Asian countries, especially in China which accounts for 70% of the total global production [1]. As a source of protein for human food this fish species is not classified as being in a high-priced class and therefore is mainly consumed by low income families. Improving carp aquaculture could be a crucial part of efforts dealing with global food security issues [2,3]. The development of the common carp industry is challenged by many factors including the protection from disease outbreaks. A main disease problem in the cultivation of common carp and its coloured variety the koi, arises from infections with koi herpesvirus (KHV) [4] also called carp interstitial nephritis and gill necrosis virus (CNGV) [5] or cyprinid herpesvirus 3 (CyHV-3) [6]. The main external clinical signs of the disease shown by fish from outbreaks were pale skin discoloration, prominent lesions of skin and fins, a high mucus production in gills, and severe gill necrosis * Corresponding author. University of Veterinary Medicine, Centre for Infection Medicine, Fish Disease Research Unit, Buenteweg 17, D-30559 Hannover, Germany. Tel.: þ49 511 953 8560; fax: þ49 511 953 8587. E-mail address: dieter.steinhagen@tiho-hannover.de (D. Steinhagen). 1 Present address: Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases (B43b), Faculty of Veterinary Medicine, University of Liège, 4000 Liège, Belgium. Contents lists available at SciVerse ScienceDirect Fish & Shellfish Immunology journal homepage: www.elsevier.com/locate/fsi 1050-4648/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fsi.2012.11.010 Fish & Shellfish Immunology 34 (2013) 305e314