Expression and serological application of recombinant epitope-repeat protein carrying an immunodominant epitope of Newcastle disease virus nucleoprotein

Gaikwad, Satish S.; Lee, Hyun-Jeong; Kim, Ji-Ye; Choi, Kang-Seuk

Western blot analysis showed the purified rERP was recognized by chicken anti-NDV serum with a specific band at approximately 20 kDa (lanes 1-6 in Fig. 2) , while no specific band was observed when using negative control serum. This indicates that the expressed rERP has the molecular weight as expected. We employed the indirect ELISA to evaluate the specificity and sensitivity of the expressed rERP using confirmed positive and negative sera samples. rERP could react specifically with the anti-NDV serum and showed no reactivity towards anti-IBV, anti-IBDV, anti-AIV, and normal sera. It suggests that rERP can specifically recognize anti-NDV antibodies. The potential of rERP ELISA to serve as discriminatory test in combination with the IDE deleted marker vaccine was investigated using three panels of sera. The test correctly classified the marker vaccinated and SPF chicken sera as antibody negative but sera from wildtype NDV immunized chickens as antibody positive. These results revealed that rERP possessed good reactivity, specificity and sensitivity.