Fig. 4From: Nanobody-horseradish peroxidase fusion protein as an ultrasensitive probe to detect antibodies against Newcastle disease virus in the immunoassayIdentification of NDV-Nb5-HRP fusion protein expression and secretion in the HEK293T cells. a Detection of NDV-Nb5-HRP expressed in the HEK293T cells with the anti-HA mAb as the first antibody by IFA. b Detection of the HRP activity in the NDV-Nb5-HRP fusions secreted into the culture medium of HEK293T cells. c Detection of the NDV-Nb5-HRP reaction with the NDV-NP protein using indirect ELISABack to article page