A convenient immunochromatographic test strip for rapid diagnosis of yellow head virus infection in shrimp

A simple yellow head virus (YHV) “strip test” was developed using monoclonal antibody Y19 (against the p20 structural protein) conjugated with colloidal gold as the detector antibody. Rabbit anti-recombinant p20 (rp20) protein antibody was used as a capture antibody at the test line (T) and goat anti-mouse IgG antibody (GAM) was used as the capture antibody at the control line (C). The ready-to-use strip was housed in a plastic case for convenient application and stored in the desiccated plastic bag. A sample volume of 100 μl of either haemolymph or gill or appendage homogenates in application buffer was applied to the sample chamber at one end of the strip and allowed to flow by chromatography through the nitrocellulose membrane to the other end. In test samples containing YHV, the virus would bind to colloidal gold conjugated monoclonal antibody and the resulting complex would be captured by the rabbit anti-rp20 antibody at the test line to give a reddish-purple band. Any unbound monoclonal antibody conjugated with colloidal gold moved across the test line to be captured by the GAM to form a band at the control line (C). In the sample without YHV or below the limit of detection for the kit, only the control line was demonstrated. This method was about 500 times less sensitive than that of one-step RT-PCR, but slightly more sensitive than dot blotting. Therefore, it could be used for primary screening of individual shrimp or pooled shrimp samples to confirm high levels of YHV infection or YHV disease outbreaks. This kit can be used to detect gill associated virus (GAV) infection as well since the monoclonal antibody used in this kit cross-reacted well with GAV. The beneficial features of this kit are that simple, convenient, and rapid results that can be obtained without the requirement of sophisticated tools or special skills.