In contrast, the ND50 values produced from the serum samples of Pekin ducks in Inner Mongolia autonomous region ranged from 25 to 200, significantly lower than those obtained in Hubei and Shandong provinces (< 0.001) (Physique 3). Open in a separate window Figure 3 Screening of sera of ducks showing drops in egg production by using PRNT. plaque-purified computer virus of the PS TMUV isolate (PS180) in combined with immunization-challenge experiments revealed that ND50 titer of ~1,258 is the minimum capable of providing adequate protection against challenge with virulent TMUV. In the investigation of serum samples collected from three flocks infected by TMUV and four flocks vaccinated with a licensed attenuated vaccine (the 120th passage computer virus), ND50 titers peaked at 1 week after both disease onset (7,943C125,893) and vaccination (3,612C79,432), and high levels of ND50 titer were detected in sera collected at 15 weeks after disease onset (5,012C63,095) and 17 weeks after vaccination (3,981C25,119). Together these findings exhibited that spontaneous and experimental infections by TMUV and vaccination with the licensed TMUV attenuated vaccine elicit high, long-lasting neutralizing antibodies. The highest ND50 titer of neutralizing antibodies elicited by PS180 was decided to be 3,162, MK-0679 (Verlukast) suggesting that attenuation of TMUV by more passages has a dramatic impact on the neutralizing antibody response of the computer virus. Keywords: duck, Tembusu computer virus, TMUV contamination, TMUV attenuated vaccine, humoral immune response, neutralizing antibody, plaque reduction neutralization test Introduction Humoral immune response plays a significant role in protection of the host from flavivirus infections (1). Generally, neutralizing antibodies are thought to be the key mediators of protection against flaviviruses following both contamination and vaccination (2, 3). Under some circumstances, however, antibodies may enhance flavivirus contamination, a phenomenon called antibody-dependent enhancement (ADE) of contamination (4, 5). In the case of MK-0679 (Verlukast) dengue computer virus (DENV), the ADE phenomenon most frequently occurs in secondary infections with different DENV serotypes and in children with maternal antibodies declined to sub-neutralizing concentrations (6, 7). In fact, any antibody that neutralizes at sufficiently high concentrations can enhance flavivirus infectivity at sub-neutralizing concentrations (3). Therefore, high levels of neutralizing antibody are crucial to exerting a protective effect, especially in the context of vaccine-mediated humoral immunity. For assessing the host’s specific immune response to flaviviruses, many useful serological assessments have been developed, such as hemagglutination inhibition, match fixation, enzyme-linked immunosorbent assay (ELISA), and plaque reduction neutralization test (PRNT) (8). However, flavivirus serological assessments may present a classical challenge in differential diagnosis owing to strong cross-reactivity between antibodies and heterologous viral antigens (9, 10). PRNT steps neutralizing antibodies, and is the most virus-specific serological test. Thus, this test is considered the platinum standard for the differentiation of flavivirus infections and the measurement of immunity to flaviviruses although it is usually time-consuming to perform (2, 8, 11C18). Tembusu computer virus (TMUV) is currently classified within the genus of the family (https://talk.ictvonline.org/taxonomy). Based on the mode of transmission and serological cross-reactivity, TMUV is also classified within the Ntaya group of the mosquito-borne flavivirus group, along with Bagaza computer virus (BAGV), Ntaya computer MK-0679 (Verlukast) virus (NTAV), and Zika computer virus (ZIKV) (8). TMUV-related disease in ducks emerged in 2010 2010, which affects mainly ducks during egg-laying periods. The disease is usually characterized by sudden onset, quick spread, severe drops in egg production, and degenerate ovaries with hemorrhagic lesions (19C22). In affected flocks, the egg production rate may reduce to 10% or less within ~1 week after disease onset (23). To control the disease, several vaccine candidates have been developed, DKFZp686G052 including live-attenuated (24), inactivated (25, 26), and subunit-based (27C31) vaccine candidates. Live-attenuated and inactivated vaccines have been licensed to use in ducks in China (32, 33). It has been shown previously that humoral immune response to TMUV can be developed in ducks following vaccination.