A Novel Point-of-Care Immunochromatographic Strip for Lumpy Skin Disease Virus: Leveraging P32-Specific Monoclonal Antibodies for Enhanced Field Surveillance

Lumpy skin disease (LSD) is a transboundary viral disease of cattle for which rapid antigen detection could support field surveillance and outbreak investigations. This study aimed to develop and preliminarily evaluate a colloidal gold immunochromatographic strip targeting the P32 protein of lumpy skin disease virus (LSDV). Recombinant P32 proteins were expressed in Escherichia coli, and two P32-specific monoclonal antibodies, 5B1 and 7H4, were generated using hybridoma technology. Indirect ELISA with truncated P32 fragments showed that both antibodies reacted predominantly with P32-1 (amino acids 13–60), although their precise epitopes were not determined. Of four antibody combinations tested, gold-conjugated 5B1 paired with immobilized 7H4 produced the strongest test-line signal and was selected for strip development. Using recombinant His-tagged P32, the lowest concentration consistently detected in three replicate tests was 40 μg/mL, with results read after 15 min. The strip reacted with LSDV suspension and LSDV-positive skin nodule tissue, while no positive reactions were observed with the selected heterologous viral preparations or negative controls. In an evaluation of 30 bovine clinical specimens, the strip detected 9 of 11 qPCR-positive samples and correctly classified all 19 qPCR-negative samples. Using qPCR as the comparator method, positive percent agreement was 81.82% (95% CI, 48.22–97.72%), negative percent agreement was 100% (95% CI, 82.35–100%), and overall agreement was 93.33%. These findings demonstrate the feasibility of a P32-based antigen detection strip, although its diagnostic performance requires further evaluation in larger and more representative sample sets.