The viral tropism was narrow in some duck respiratory and immune organs, as viral replication could only be detected in the lungs (3/3 at 1 dpi and 1/3 at 2 dpi), trachea, (1/3 at 3 dpi), and tonsil (1/3 at 3 dpi) of the ducks. and distribution in chickens and ducks after infection with H9N2 AIV by the intravenous route. Results Our results revealed that the antibody response was rapid and robust in ducks than in chickens at early time (2-3dpi) after intravenous infection with H9N2 AIVs, while Mouse monoclonal to cMyc Tag. Myc Tag antibody is part of the Tag series of antibodies, the best quality in the research. The immunogen of cMyc Tag antibody is a synthetic peptide corresponding to residues 410419 of the human p62 cmyc protein conjugated to KLH. cMyc Tag antibody is suitable for detecting the expression level of cMyc or its fusion proteins where the cMyc Tag is terminal or internal. delayed and lower antibody detected in ducks than in chickens after intranasal infection with H9N2 AIVs. The virus was detected in multiple organs tissues in chickens but not in ducks infected by the intravenous route. Conclusions Our results provide the evidence that humoral immune response could play a critical role in duck resistance for influenza, which expands our knowledge on duck anti-influenza characteristics. Keywords: Humoral immune response, Chickens, Ducks, H9N2 AIVs, Different routes Background Chickens and ducks are the two most predominant domestic bird species in China, and they are also the most economically important land fowl and waterfowl as sources of meat, eggs, and feathers. H9N2 AIV was first isolated from turkeys in Wisconsin (USA) in 1966 and was later first identified in chickens in Guangdong province, China in 1994 [1, 2]. Subsequently, viruses of the AMG319 H9N2 subtype have quickly spread to most areas of China. Currently, H9N2 AIVs have become prevalent among the domestic poultry populations in several Asian countries and are considered to be potential candidates for a future pandemic [3, 4]. Additionally, the H9N2 influenza virus has donated six internal genes to the H7N9 and H10N8 AIVs, which have recently infected humans in China [5, 6]. Furthermore, H9N2 AIVs have been reported to infect pigs and humans, resulting in severe and even lethal cases in humans [7C10]. Although there is currently no evidence of human-to-human transmission of H9N2 AIVs, the results of serological surveillance studies found higher anti-H9 antibody positive rates in serum samples collected from poultry workers [10, 11]. Moreover, there is evidence showing that the continual transmission of H9N2 AIVs between chickens and aquatic birds facilitates the generation of reassortant viruses with the potential to infect humans [12]. This emphasizes that the threat of H9N2 AIVs to public health is a growing concern [10, 13]. H9N2 AIVs continue to circulate in chickens despite the implementation of a long-term vaccination program [3]. Moreover, ducks have been reported to be tolerant to H9N2 AIV infection, since infected ducks typically do not exhibit any clinical symptoms; however, ducks are able to shed the virus and transmit AMG319 it to other species and can be for almost all types of influenza A viruses [4]. In addition, ducks typically also serve as the natural reservoir for HPAIVs and display no clinical signs following infection, whereas chickens are more susceptible to HPAIVs [14, 15]. Studies have shown that many immune-related genes are involved in the anti-influenza responses of ducks, including innate immune, cellular immune, inflammatory and chemokine genes [16C19]. Ducks have been found to mount more active and robust cellular immune responses compared to chickens exposed to H9N2 AIV by the intranasal route [20]. Following infection with HPAIVs, ducks are able to initiate a faster but lower inflammatory cytokine response followed by the activation of major pattern recognition receptors (i.e., for 10?min at 4?C. The supernatants were collected for viral titration in SPF eggs. We next intra-allantoically injected 9C11-day-old chicken embryonated eggs with 100?L of the supernatants of tissue homogenates. The viral titer for each organ was determined by the Reed and Muench method and expressed as log10 EID50/g of tissue [29]. Statistical analysis Antibody responses based on HI and blocking ELISA were analyzed by analysis of variance (ANOVA) in AMG319 GraphPad Prism version 5.0 (GraphPad software Inc., CA,USA). A value of test. Results Antibody response in birds intranasally infected with the H9N2 virus Following intranasal infection with the H9N2 virus, three out of five chickens seroconverted at 4 dpi to a positive HI titer (HI?>?log24) and all chickens (5/5) seroconverted at 6 dpi with a higher HI titer and inhibition according to the results of the blocking ELISA (PI >?25%) (Fig.?1). In contrast, none of the infected ducks seroconverted at 4 dpi and 5 dpi, until four out of five ducks (4/5) were sera positive at 6 dpi and all ducks (5/5) seroconverted at 7 dpi. Noticeably, a significantly higher antibody titer was detected in the chickens than in the ducks from 7 dpi to the experimental end point (18 dpi) (p?