AUTHOR=Wang Jinhui , He Kangxin , Wu Zhengjiao , Jin Weikun , Wu Wende , Guo Yanfeng , Zhang Weiyu , Di Wenda 

TITLE=Development of a colloidal gold immunochromatographic strip for the rapid detection of antibodies against Fasciola gigantica in buffalo

JOURNAL=Frontiers in Veterinary Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2022.1004932

DOI=10.3389/fvets.2022.1004932

ISSN=2297-1769

ABSTRACT=<sec><title>Background</title><p><italic>Fasciola gigantica</italic>, a tropical liver fluke, infects buffalo in Asian and African countries, causing significant economic losses and posing public health threats. The diagnostic of buffalo fascioliasis caused by <italic>F. gigantica</italic> is vital in fascioliasis control and preventation. The 22nd gel filtration chromatography fraction of <italic>F. gigantica</italic> Excretory-Secretory Products (<italic>Fg</italic>ESP), namely <italic>Fasciola</italic> 22 (F22), which was used as a diagnostic antigen in indirect ELISA, has demonstrated great potential for fascioliasis diagnosing. In the absence of rapid diagnostic methods, the use of a colloidal gold immunochromatographic strip based on F22 was applied to detect <italic>F. gigantica</italic> infection in buffalo.</p></sec><sec><title>Methods</title><p>In the present study, the 22<sup>nd</sup> gel filtration chromatography fraction of <italic>Fg</italic>ESP (F22) was used as an antigen to establish the colloidal gold-based immunochromatographic strip (ICS). The nitrocellulose membrane was incubated with F22 at the test line (T line) and goat anti-mouse secondary antibody at the control line (C line). The mouse anti-buffalo secondary antibody 2G7 conjugated to colloidal gold particles was used as the detection system for line visualization. The strip was assembled and developed by optimizing reaction conditions. The sensitivity, specificity, stability, and early diagnostic value of the strip were evaluated employing buffalo-derived sera.</p></sec><sec><title>Results</title><p>An immunochromatographic strip for the rapid detection of antibodies against <italic>F. gigantica</italic>-<italic>Fg</italic>ICS was developed. The strip demonstrated high sensitivity and specificity. Sensitivity tests confirmed positive results even when the positive reference serum was diluted 4,096 times. Except for one <italic>Schistosoma japonicum</italic>-positive serum that tested positive via <italic>Fg</italic>ICS, specificity tests confirmed no cross-reactivity with other positive sera of <italic>Schistosoma japonicum</italic> and <italic>Babesia bovis</italic>. The strip remained stable after storage at 4°C for up to 3 months. In infected buffalo, antibodies could be detected as early as 14–21 days post-infection. The detection of 17 positive sera yielded an 82.4% positive rate via <italic>Fg</italic>ICS vs. a 100.0% positive rate via ELISA based on <italic>Fg</italic>ESP. For <italic>Fg</italic>ICS, the 95% confidence interval of sensitivity was 84.8–95.4%, while specificity was 4.2–14.7%.</p></sec><sec><title>Conclusion</title><p>The immunochromatographic strip <italic>Fg</italic>ICS developed in this study provides a simple and rapid method of <italic>F. gigantica</italic> antibody detection and infected buffalo monitoring in the field.</p></sec>