Differential gene expression in black tiger shrimp, Penaeus monodon, following administration of oxytetracycline and oxolinic acid Fernand F. Fagutao a , Motoshige Yasuike a , Mudjekeewis D. Santos a , Lila Ruangpan b , Kulvara Sangrunggruang c , Anchalee Tassanakajon d , Yuikinori Takahashi e , Ryuji Ueno f , Hidehiro Kondo a , Ikuo Hirono a , Takashi Aoki a, * a Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan b Department of Fisheries, Chatuchak, Bangkok 10900, Thailand c Coastal Aquatic Animal Health Research Institute, Songkhla Province 90100, Thailand d Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand e Department of Fishery Science and Technology, National Fisheries University, Shimonoseki 759-6595, Japan f Faculty of Bioresources, Mie University, Tsu 514-8507, Japan 1. Introduction Pathogenic microorganisms are responsible for the heavy losses suffered by shrimp farms worldwide [1,2]. Diseases caused by Vibrio species and bacilliform virus, such as the White Spot Syndrome Virus (WSSV) for instance, can rapidly spread resulting in low survival rates in both hatchery and grow-out ponds [3]. Cumulative mortalities from these pathogens can reach 100% within days after the onset of infection [4]. Since shrimps are thought to have only their innate immune mechanisms to combat diseases, measures have been developed not only to prevent the spread of disease- causing pathogens but also to enhance the shrimp’s immune system. Such interventions include the use of immunostimulants [5,6], probiotics [7], vaccines [8] and antibiotics [9]. Antibiotics are used in shrimp culture for both therapeutic and prophylactic purposes [10]. Two of the most common antibiotics used in shrimp are oxytetracycline and oxolinic acid. Oxytetracy- cline (OTC) is active against a wide variety of bacterial species including Gram-negative and Gram-positive aerobic and anaerobic bacteria. Its popularity is due to its effectiveness, relative safety, low rate of accumulation in edible tissue and short tissue elimination time [11]. OTC is also one of the only four antimicrobial agents approved by the US Food and Drug Administration for use in food fish and only one of the few drugs approved for use in invertebrates [12]. It is used against many bacterial diseases including vibriosis and necrotizing hepatopancreatitis infections [13]. Oxolinic acid (OA), a quinolone, on the other hand is an antibiotic effective against a variety of Gram-negative bacteria and works primarily by inhibiting the synthesis of bacterial DNA [14]. It is used mainly in shrimp farms in Asia to treat vibriosis [9,10,15]. The effects of antibiotics on innate immunity, specifically on the expression of shrimp genes, have yet to be reported. There are, however, certain chemicals which were reported to suppress the shrimp immune system making shrimp vulnerable to pathogens [16]. Microarray technology has been used to analyze the changes in gene expression after DNA vaccination [17], stimulation [18], exposure to a chemical pollutant [19], and during larval develop- ment [20] of various fish species. In shrimp, previous reports have highlighted the use of microarray in identifying the genes that Developmental and Comparative Immunology 33 (2009) 1088–1092 ARTICLE INFO Article history: Received 3 April 2009 Received in revised form 25 May 2009 Accepted 26 May 2009 Available online 12 June 2009 Keywords: Black tiger shrimp Gene expression Oxytetracycline Oxolinic acid Microarray ABSTRACT The intensification of shrimp farming systems has led to the spreading of a variety of bacterial and viral diseases that continue to plague the shrimp industry worldwide. Efforts to combat these pathogenic organisms include the use of immunostimulants, probiotics, vaccines and antibiotics. Although a few studies have already reported on the effects of various stimuli on shrimp, the effect of antibiotics, particularly on the changes in the shrimp transcriptomic profile have yet to be reported. Here we show that injecting shrimp with oxytetracycline and oxolinic acid alters the expression of genes in the black tiger shrimp, Penaeus monodon, lymphoid organ. These antibiotics, especially oxylinic acid, down- regulated the expression of a few immune-related genes, most notably penaeidin, proPO, clotting protein, profilin and whey acidic protein. ß 2009 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +81 3 5463 0556; fax: +81 3 5463 0690. E-mail address: aoki@kaiyodai.ac.jp (T. Aoki). Contents lists available at ScienceDirect Developmental and Comparative Immunology journal homepage: www.elsevier.com/locate/dci 0145-305X/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.dci.2009.05.010