Field-usable lateral flow immunoassay for the rapid detection of a macluravirus, large cardamom chirke virus.

A simple and rapid lateral flow immunoassay (LFIA) was developed by utilizing gold nanoparticles conjugated to a polyclonal antibody against coat protein of large cardamom chirke virus (LCCV). The LFIA based on the principle of sandwich immunoassay detected LCCV within ∼10 min and the result could be evaluated visually. The colloidal gold (CG) was made using 1% gold chloride solution. The LCCV IgG (1 μg/μl) and Mouse IgG (0.5 μg/μl) were conjugated with CG individually and coated onto a conjugate pad at 1:1 ratio. A sample extraction procedure was optimized in order to get adequate clear leaf sap of large cardamom leaf within few minutes. The sensitivity limit of the detection was 1:40 dilution of LCCV infected leaf sap. The diagnostic performance of LFIA was compared with ELISA using field samples. The LFIA was free from false positive as no visible test line was developed with healthy and potyviruses such as papaya ringspot virus and potato virus Y. The diagnostic specificity and sensitivity of LFIA was 100% and 90%, respectively. The Cohen's kappa coefficient (0.701) suggested a very good agreement between the ELISA and LFIA. Receiver operating characteristic analysis indicated that LFIA was a robust method as the area under the curve (0.950) is significantly (P <0.0001) broader.