The serum sample mixed with the detection antigen dissolves the gold-labeled mAb in the conjugate pad and techniques through the detection membrane from your sample end to the absorbent ones by capillary action after the solution is applied to the bLFA strip. other avian pathogens. A total of 510 clinical samples were tested for NDV antibodies. The coincidence rate between the results of the bLFA strip and HI test was 97.65%. Therefore, it is an ideal option method for assessing the clinical immunity of ND vaccines in the field in real-time. Abstract Newcastle disease (ND) is an acute septicemic infectious disease caused by Newcastle disease computer virus (NDV). Considering that vaccination is currently the main modality Acebilustat for the prevention of ND, it is essential to assess the effectiveness of clinical immunization. In this study, we have developed a blocking lateral circulation assay (bLFA) strip for the quick detection of NDV antibodies using the monoclonal antibody 9C1 against haemagglutinin-neuraminidase (HN), which allows for the determination of an NDV-specific antibody titer within 10 min at room temperature. In addition, the bLFA strip has no cross-reactivity with the positive serum of other avian pathogens including avian influenza subtypes H5, H7, and H9, MD, IBD, IB, EDS, and avian adenovirus. The ability of the bLFA strip for detecting a neutralizing antibody was also estimated. The results showed that the poultry NDV hyperimmunized serum experienced a complete blocking (100%) titer of 11 log 2, and half-blocking titer of 13 log 2, which are 4 occasions less than and the same as that VBCH of the HI test (13 log 2), and 8 and 2 times less than that Acebilustat of the VN test (14 log 2), respectively. A total of 510 clinical samples were tested for NDV antibodies. The coincidence rate between the results of the bLFA strip and HI test was 97.65%. Therefore, it is an ideal alternative method for assessing the clinical immunity of ND vaccines in the field in real-time. Keywords: Newcastle disease computer virus, blocking lateral circulation bLFA strip, neutralizing antibodies, HI, monoclonal antibodies 1. Introduction Newcastle disease computer virus (NDV) is usually a membrane-bearing, Acebilustat non-segmented, unfavorable single-stranded RNA computer virus, belonging to the genus [1]. Its genomic size is usually 15 kb, encoding six structural proteins (NP, P, M, F, HN, and L), and two non-structural proteins (V and W) [2]. F and HN are the two major vesicular membrane glycoproteins on the surface of NDV, playing important functions in viral contamination [3,4]. As a notifiable epidemic disease outlined by the World Organization for Animal Health (OIE), NDV can infect chickens of all ages with a high mortality rate, still causing ongoing damage to the poultry industry in China currently. It mainly causes respiratory distress, neurological disorders, hemorrhage, and necrosis of mucous and serous membranes in birds [5,6,7]. At present, the prevention and control of ND in China is still dominated by vaccination [8,9]. Maternal antibodies in chicks are vital to influencing the effectiveness of ND vaccines (especially attenuated vaccines). The monitoring of maternal antibody and immune antibody levels in chickens is an important basis for developing and optimizing NDV immunization programs [10,11,12]. In the mean time, the serum antibody levels in vaccinated chickens, especially neutralizing antibody levels, are important indicators for evaluating NDV vaccination [13,14,15]. The Hemagglutination inhibition (HI) test remains a common method for detecting NDV antibodies and can effectively evaluate the level of immune antibodies and immune protection against the vaccine [16,17,18,19,20]. However, the HI test is usually complex and time-consuming to perform and requires specific specialist operators. Due to the complicated process, it is usually limited to the laboratory and cannot be popularized and applied in field detection. The rapid detection technology of the lateral circulation assay (LFA) is usually specific, sensitive, simple, quick, and Acebilustat low-cost, which does not depend on laboratory conditions to achieve a foolproof operation [21,22,23,24]. Studies have shown that using NDV (LaSota strain) purified virus-labeled colloidal platinum, the strip can detect the lowest HI antibody titer of 4.