Broad-range and effective detection of human noroviruses by colloidal gold immunochromatographic assay based on the shell domain of the major capsid protein

Abstract

Background: Human noroviruses (HuNoVs) are a major cause of nonbacterial gastroenteritis in all age groups worldwide. HuNoVs can be detected in vitro using molecular assays such as RT-PCR and RT-qPCR. However, these molecular-based techniques require special equipment, unique reagents, experienced personnel, and extended time to obtain results. Besides, the diversity of viral genotypes is high. Therefore, methods that are rapid, broad-range and effective in the detection of HuNoVs are desiderated for screening the feces or vomit of infected people during outbreaks.

Results: In this study, a colloidal-gold-based immunochromatographic assay (ICA) was developed for effective detection of HuNoVs in clinical samples. Monoclonal antibodies (MAbs) against the shell (S) domain in the major capsid protein of HuNoVs were used in the ICA. The limitations of detection for HuNoVs in clinical samples were 1.2 × 10⁶ genomic copies per gram of stool sample (gc/g) and 4.4 × 10⁵ gc/g for genogroup I and II (GI and GII) HuNoVs, respectively. A total of 122 clinical samples were tested for HuNoVs by ICA and compared against RT-qPCR. The relative sensitivity, specificity and agreement of ICA was 84.2% (95% CI: 83.6-84.8%), 100.0% (95% CI: 98.5-100.0%) and 87.7% (95% CI: 85.6-89.8%), respectively. No cross-reaction with other common enteric viruses or bacteria was observed. The ICA detected a broad range of genotypes, including GI.1, GI.3, GI.4, GI.6, GI.14, GII.2, GII.3, GII.4, GII.6, GII.13, and GII.17 HuNoVs.

Conclusions: This study demonstrates that ICA targeting the S domain of VP1 is a promising candidate for effectively identifying the different genotypes of HuNoVs in clinical samples with high sensitivity and specificity.

Keywords: Broad-range detection; Colloid gold; Human norovirus; Immunochromatographic assays; S domain of VP1.

Fig. 1

Schematic diagram of ICA test. MAb H9E was used as labeled antibody with colloidal gold particles (in red); MAb J5D was used as capture-antibody in the T line; goat-anti mouse MAb Ig G was used in the C line. Arrow indicates the direction of the movement of antigens (capsid protein of noroviruses)

Fig. 2

LOD of ICA for purified S domain of VP1 and clinical samples. a Sensitivity for S domain of VP1 (two-fold dilutions from 22.4 ng/ml to 0.7 ng/ml), b Sample 57,404 (GI.1) (two-fold dilutions from 5.0 × 10⁶ to 1.6 × 10⁵ gc/g) and (c) Sample 1717 (GII.4) of different virus copies (two-fold dilutions from 3.5 × 10⁶ to 1.1 × 10⁵ gc/g) were detected with test strips. PBS buffer (pH 7.4) was used as blank control

Fig. 3

Specificity of ICA. Five HuNoVs clinical samples, Rotavirus, and Salmonella cultured samples were tested with the strips