Development and evaluation of a gold nanoparticle-based immunochromatographic strip test for the detection of canine parvovirus

Canine parvovirus (CPV) is the leading viral cause of enteritis in dogs and occurs mainly in 6- to 8-week-old pups. Rapid diagnosis of CPV under field conditions is now possible due to commercially available immunochromatographic (IC) assays. However, these commercial kits are somewhat expensive because they utilize a minimum of two monoclonal antibodies (mAbs) targeting different epitopes as capture and detector antibodies. Using only a single mAb for both capture and detection purpose may reduce the sensitivity of the assay. In the present study, efforts were made to develop an economical assay that can be utilized for diagnosis of CPV under Indian conditions with a high level of confidence. Rabbit polyclonal antibodies (pAbs) generated against recombinant truncated VP2 proteins of CPV were used as capture antibodies because they can be produced economically, while a commercial anti-CPV mAb was used as the detector antibody. The detection limit of the test strip was 6.6×10⁵ TCID₅₀/ml, and it specifically detected CPV-2, CPV-2a and CPV-2b while displaying no cross-reactivity with other common canine enteric pathogens. The relative sensitivity/specificity of pAb based strip test was 71%/92% and 71%/100% in relation to the hemagglutination test and a commercial IC kit, respectively, with substantial agreement. In addition, two commercially available mAbs targeting different epitopes were also used for development of another IC assay, which showed sensitivity, and specificity of 82%/87% and 90%/98% in relation to the hemagglutination test and commercial kit. Hence, the present strip test based on a combination of mAb and pAb provides an acceptable alternative for onsite and cost-effective diagnosis of CPV infection.