LAUSR

The present study describes the development of a truncated recombinant peste des petits ruminants (PPR) virus (PPRV) nucleoprotein (rPPRV-NPN) and its polyclonal antibodies-based immuno-diagnostic assay, Avidin-Biotin (AB) recombinant competitive ELISA (ABrC-ELISA) for the detection of PPRV antibodies in the sheep and goats. The PPRV N-terminal immunogenic region (1-266 aa) of nucleoprotein (NPN) coding sequence was amplified and cloned into the pETite vector. The rPPRV-NPN with a molecular weight of ∼ 30 kDa was expressed in E. coli, purified, and characterized by SDS-PAGE and immunoblot using standard PPRV specific sera. The Ni-NTA affinity-purified rPPRV-NPN as coating antigen and its hyperimmune serum as competitive antibodies raised in guinea pigs were evaluated as diagnostic reagents in ABrC-ELISA using the known standard panel of sera. The threshold (cut-off) Percentage Inhibition (PI) value was determined as 45 (mean ± 3 SD) based on the reactivity of the known sheep and goats sera to PPRV antibodies [negative (n = 140) and positive (n = 98)] and the assay had a sensitivity of 97 % (95% Confidence Interval (CI): 91.3 to 99.4) and specificity of 100 % (95% CI: 97.4-100%) with an excellent Area under curve (AUC) of 0.997 (95% CI: 0.993 to 1.0). On evaluation of diagnostic performance of the assay using the sheep and goats sera (n = 391) from vaccinated, infected, and non-vaccinated animals, the ABrC-ELISA showed the relative diagnostic sensitivity of 95.88 % (95% CI: 92.56 to 98.01 %) & 98.77 % (95% CI: 96.43- 99.74%) and diagnostic specificity of 97.97 % (95% CI: 94.19-99.58 %) & 90.54% (95% CI: 84.64-94.73%) against indigenous PPR competitive ELISA kit & IDvet Screen® PPR Competition kit, respectively. The study showed that ABrC-ELISA is rapid, sensitive, and specific and can be a better alternative assay for the detection of the PPRV antibodies in the sera of small ruminants for serosurveillance / seromonitoring of PPR not only at the eradication and post-eradication phases in the disease-controlled endemic countries but also in the PPR non-endemic countries.