Development of a one-step diagnostic and differential immunochromatographic method for mpox and chickenpox

Mpox and chickenpox are highly contagious diseases with similar clinical symptoms and co-infection, and diagnostic tests are extremely useful in their differentiation. Mpox virus and chickenpox virus are the main causative pathogens of mpox and chickenpox respectively. This study aims to develop a rapid diagnostic immunochromatographic trip for differential diagnosis of mpox and chickenpox viruses.

An immunochromatographic assay (ICA) based on the double-antibody sandwich format was developed. First, the paired monoclonal antibodies (MAbs) were prepared: for mpox, the detecting MAb1 and capture MAb2; for chickenpox, the detecting MAb3 and capture MAb4. These MAbs were against the recombinant antigens (AR/gE) of mpox and chickenpox viruses. Then, the detecting MAbs were conjugated to gold nanoparticles and coated onto the conjugate pads. The capture MAbs were immobilized onto a nitrocellulose membrane at two detection zones to form the Test 1 (T1, to test AR) line and Test 2 (T2, to test gE) line, respectively. Goat anti-mouse IgG antibodies were immobilized onto the nitrocellulose membrane to form the control (C, to verify the effectiveness of the strip) line as the control. Finally, it was assembled into a one-step double T-line colloidal gold immunochromatographic test strip for the differential diagnosis of mpox and chickenpox viruses. The sensitivity, specificity, precision and methodology comparison were evaluated using mpox pseudovirus and clinical samples.

A dual-index ICA strips for the simultaneous detection of mpox and chickenpox were successfully prepared. The sensitivity of the dual-index ICA strips to AR antigen was 0.125 ng/mL, to gE antigen was 0.25 ng/mL, with high specificity, precision and reproducibility. The results can be judged within 10-15 min. Methodology comparison study (PCR vs. ICA strips) of 56 clinical samples found there was no statistically significant difference between the ICA strips and PCR method.

The dual-index ICA strips had good sensitivity, specificity, simple procedure and rapid detection. This protocol is very suitable for early diagnosis and differentiation of mpox and chickenpox in medical institutions and individuals.