Theranostics 2017, Vol. 7, Issue 7 http://www.thno.org 1835 Theranostics 2017; 7(7): 1835-1846. doi: 10.7150/thno.18857 Research Paper Rapid Detection of Avian Influenza Virus by Fluorescent Diagnostic Assay using an Epitope-Derived Peptide Duong Tuan Bao 1* , Do Thi Hoang Kim 1* , Hyun Park 1* , Bui Thi Cuc 1 , Nguyen Minh Ngoc 1 , Nguyen Thi Phuong Linh 1 , Nguyen Chien Huu 1 , Trinh Thi Thuy Tien 1 , Nguyen Thi Viet Anh 1 , Tung Dao Duy 1 , Chom-Kyu Chong 2 , Seung-Taek Yu 3 , Do-Young Choi 3 , Seon-Ju Yeo 1 1. Zoonosis Research Center, Department of Infection Biology, School of Medicine, Wonkwang University, 460, Iksan-daero, Iksan, 54538, Republic of Korea; 2. GenBody Inc, No.206, Biotech Business IC, DanKook University, San-29, Anseo-dong, Dongnam-gu, Cheonan, Republic of Korea; 3. Department of Pediatrics, School of Medicine, Wonkwang University, 460, Iksan-daero, Iksan, 54538, Republic of Korea. * These authors contributed equally to this manuscript.  Corresponding author: Seon-Ju Yeo, Ph.D., Zoonosis Research Center, Department of Infection Biology, School of Medicine, Wonkwang University, 460, Iksan-daero, Iksan, 54538, Republic of Korea. Tel +82-63-850-6777 Fax +82-63-857-0342 Email: yeosj@wku.ac.kr © Ivyspring International Publisher. This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/). See http://ivyspring.com/terms for full terms and conditions. Received: 2016.12.21; Accepted: 2017.02.20; Published: 2017.04.10 Abstract Currently, the point of care testing (POCT) is not fully developed for subtype-specific avian influenza virus detection. In this study, an H5N1 hemaglutinin 1 (HA1) epitope (P0: KPNDAINF) and three modified peptides (P1: KPNTAINF, P2: KPNGAINF, P3: KPNDAINDAINF) were evaluated as POCT elements for rapid detection of avian influenza virus. Based on modeling predictions by Autodock Vina, binding affinity varied depending on alteration of one amino acid in these peptides. The binding energy of P2 indicated its potential for a strong interaction with HA. Fluorescence-linked immunosorbent assay experimentally demonstrated the interaction between these peptides and virus. The four peptides interacted with HA1 of H5N3 with different binding affinities with P2 showing the strongest binding affinity. When P0 and P2 peptides were used in rapid fluorescent immunochromatographic test (FICT) as detection elements, the inter-assay coefficients of variation (CV) indicated that P2–linked FICT was more acceptable than the P0-linked FICT in the presence of human specimens. Antibody pair-linked FICT was influenced by clinical samples more than the P2-linked FICT assay, which showed a 4-fold improvement in the detection limit of H5N3 and maintained H5 subtype-specificity. Compared to the rapid diagnostic test (RDT) which is not specific for influenza subtypes, P2-linked FICT could increase virus detection. In conclusion, results of this study suggest that HA epitope-derived peptides can be used as alternatives to antibodies for a rapid fluorescent diagnostic assay to detect avian influenza virus. Key words: Epitope-derived peptide, H5 subtype influenza A virus, Rapid fluorescent immunochromatographic test, Haemagglutinin 1. Introduction Avian influenza (AI) A virus with a hemagglutinin (HA) 5 protein and a neuraminidase (NA) 1 protein (subtype H5N1) is a highly pathogenic virus. It causes lower respiratory tract infections associated with a mortality rate of higher than 60% [1]. H5N1 diagnosis should be included in differential diagnosis of acute febrile respiratory illness in areas where H5N1 has been identified in animals [2]. However, rapid point-of-care detection tests (POCT) are not performed for influenza due to sensitivity limitations in detecting H5N1 using the POCT developed by the Centers for Disease Control and Prevention (CDC) [2]. A commercialized H5 subtype-specific rapid diagnostic system is not yet available. HA has been used to categorize influenza A viruses into various subtypes. It shares high amino acid (aa) sequence homologies among all subtypes [3], making the development of subtype-specific antibody based on HA antigen difficult. This is also the reason for the lack of H5 subtype-specific rapid diagnostic Ivyspring International Publisher