en aquaculture aquaculture پژوهشي Orginal research papers <a name="OLE_LINK81"></a><a name="OLE_LINK80"></a><a name="OLE_LINK76"></a><a name="OLE_LINK71">Tight junction protein, occludin, plays an important role in intestinal health of fish. To study the function of occludin in the intestinal barrier at the protein level, a rabbit occludin polyclonal antibody was prepared against heterologously expressed <em>Cyprinus carpio</em> A fragment of the <em>occludin</em> gene containing antigenic determinants was first ligated into the pET-21a, which is an expression vector and transformed into <em>E. coli </em>BL21 (DE3) strain. Expression of the target fusion protein was induced by </a><a name="OLE_LINK83"></a><a name="OLE_LINK82"></a><a name="OLE_LINK6"></a><a name="OLE_LINK4">isopropyl-beta-D-thiogalactopyranoside (IPTG</a>). The purified fusion protein was used as an antigen to immunize New Zealand long-eared rabbits (<em>Oryctolagus cuniculus</em>) through ear margin vein and subcutaneous injection to obtain rabbit anti-carp polyclonal antibodies against occludin. Enzyme-linked immunosorbent assay (<a name="OLE_LINK53"></a><a name="OLE_LINK52">ELISA</a>) was used to evaluate the antibody titre, and the antibody was used to determine the distribution and expression of occludin in the intestine of carp after infection with <em>Aeromonas hydrophila</em>. The target fusion protein had a molecular weight of approximately 31.7 ku, the antibody titre was 2.4 &times; 10⁶, and the integrity of occludin protein was lower in various intestinal segments after <a name="OLE_LINK77"></a><a name="OLE_LINK36"></a><a name="OLE_LINK35"><em>A. hydrophila</em> infection</a>. The results indicated that the prepared antibody had a high titre, affinity, and specificity and can be applied to study the expression and distribution of occludin in <em>C. carpio</em>. The availability of this polyclonal antibody laid the foundation for the systematic study of the intestinal barrier of <em>Cyprinus carpio</em> . Additionally, this polyclonal antibody could also be used for explorative studies of the biological function of occludin in other fishes. Cyprinus carpio, Occludin, Prokaryotic expression, Antibody titre, Immunohistochemistry 343 357 http://jifro.ir/browse.php?a_code=A-10-3026-1&slc_lang=en&sid=1 J.C. Feng fjc15290022@126.com 100319475328460039256 100319475328460039256 No College of Fisheries X.R. Guo 2530981656@qq.com 100319475328460039257 100319475328460039257 No College of Fisheries X.L. Chang 359072413@qq.com 100319475328460039258 100319475328460039258 No College of Fisheries Y.R. Zhang zyuru_2004@163.com 100319475328460039259 100319475328460039259 No College of Fisheries X.L. Meng xuzhu288482@163.com 100319475328460039260 100319475328460039260 No College of Fisheries R.H. Lu laoaiyika@aliyun.com 100319475328460039261 100319475328460039261 No College of Fisheries M.Y. Huang 2929018025@qq.com 100319475328460039262 100319475328460039262 No College of Fisheries G.X. Nie niegx@htu.cn 100319475328460039263 100319475328460039263 No College of Fisheries J.X. Zhang 450938518@qq.com 100319475328460039264 100319475328460039264 Yes College of Fisheries