High sensitivity immunochromatographic strip test (ICP11 strip test) for white spot syndrome virus detection using monoclonal antibodies specific to ICP11 non-structural protein

Two monoclonal antibodies (MAbs) specific to different epitopes on ICP11, a non-structural protein of white spot syndrome virus (WSSV), were employed to develop a highly sensitive immunochromatographic strip test (ICP11 strip test). One MAb (WI-11) was conjugated to colloidal gold to bind to ICP11 and another MAb (WI-16) was used to capture colloidal gold MAb-protein complexes at the test line (T) on the nitrocellulose strip. A downstream control line (C) of goat anti-mouse immunoglobulin G (GAM) antibody was used to capture the free colloidal gold conjugated MAb to validate the test performance. Homogenate of shrimp sample in application buffer could be applied directly to the application well and the test result was obtained within 15 min. The sensitivity of the kit is 40 times more sensitive than the detection limit of previously reported strip test using MAbs specific to VP28, and approximately 400 times more sensitive than that of Shrimple®, but approximately 50 times less sensitive than that of one-step PCR. For experimentally WSSV-infected shrimps, the ICP11 strip could detect WSSV as early as 12-18 h post infection. Due to its high specificity, simplicity and no requirement on sophisticated equipment or specialized skills, the strip test could be adopted to surveillance of early WSSV infection at the pond site.