| Pigeon Paramyxovirus type Ⅰ(PPMV-1) is identified as Pigeon Newcastle Disease Virus, which could cause urgent and highly infectious disease in pigeons. PPMV-1 has high morbidity and mortality, which makes a real threat to the pigeons feeding. At present, pigeons are mainly raised in small scale in China. Due to the crude environment and irregulated immune procedure, pigeons are susceptible to be infected by virus and the other pathogenic microorganisms. The corresponding animal products carried a large number of pathogens, which could further threaten human health through the food-chain. In order to improve pigeon immune condition by exogenous measurements, reduce the risk of the pathogen infection(such as PPMV-1), and protect pigeons, it is important for us to understand the signal transduction mecha nism of host antiviral role.Fifty 1-month-old pigeons were separated randomly into two groups, 40 pigeons in group one and 10 pigeons in group two. Pigeons in group one were inoculated intranasally with PPMV-1 strain(pi/CH/LHLJ/110822). Pigeons in the control group were mock inoc ulated with phosphate-buffered saline(PBS). The pigeons were monitored for clinical signs for up to 28 days post infection(dpi), and killed at 24, 72 hpi and 7 dpi(ten individuals at each time point). Ten tissues, including liver, spleen, lung, kidney, glandular stomach, bursa of Fabricius, cecal tonsil, trachea, Harderian glands, brain, were collected from pigeons for quantitative PCR(qPCR) analysis of host genes. One Step real-time Prime Script reverse transcription-PCR(RT-PCR) was used to quantify the m RNA levels of viral loads, Toll-like receptors(TLRs), β-defensins(AvBDs), Cytokine, Apoptosis and Immune factors. In addition, serum samples were collected at 8, 12, 16, 20, 24 and 28 dpi, respectively.Pigeons inoculated with PPMV-1 showed obvious clinical signs, such as depression, anorexia and paralysis. Three pigeons died on 18, 19 and 27 dpi, respectively, and caseous exudate was observed in the trachea. Histopathological examination of pigeons inoculated with PPMV-1 indicated apparent changes in detective tissues, and mild congestion in these tissues. Moreover all pigeons inoculated with PPMV-1 showed a positive serum antibody response from 8 dpi to 28 dpi, and the antibody levels increased with time.The results showed that viral RNA was not detected in the control group. In contrast, viral RNA was found in pigeons inoculated with PPMV-1. Compared with the control, the expression level of TLR2 was significantly increased in the liver of PPMV-1 infected pigeons at 72 hpi(P<0.05). For TLR5, the expression level was decreased in the kidney of PPMV-1 infected pigeons(P<0.05). The expression level of TLR7 was significantly increased in the trachea(24 and 72 hpi) of PPMV-1 infected pigeons, compared with control group(P<0.05). TLR15 was induced in tissues of pigeons in response to PPMV-1-infection, and detected significantly increased expression in the glandular stomach and spleen(P<0.05). We observed that RIG-I was detectable in all 10 tissues investigated from both the control and infected pigeon s. Furthermore, we detected increased level of RIG-I expression in the liver of PPMV-1 infected pigeons at 72 hpi, compared with control group(P>0.05). We next evaluated the levels of AvBDs, Cytokine, Apoptosis and Immune factors. Unfortunately, we did not identify the AvBD1 and AvBD7 genes in pigeons in this study. Therefore, we analyzed AvBD2 and AvBD10 found that the expression of AvBD2 in the lung, kidney, spleen, bursa of Fabricius and cecal tonsi of the control group; AvBD10 in the brain, kidney and trachea of the control group. We did not observe any significant differences in AvBD2 or AvBD10 expression in tissues between the control and PPMV-1 infected pigeons(P>0.05). At the same time, we detected significantly higher levels of Interleukin 6(IL-6) expression in the liver(72 hpi and 7 dpi) and trachea(72 hpi) of PPMV-1 infected pigeons than in control pigeons(P<0.05). In addition, no significant differences in the expression of IL-6 was found in trachea(P>0.05). IL-8 expression was significant dereased in the kideny of PPMV-1 infected pigeons(P<0.05). Compared with the control, the expression level of IL-10 was significantly increased in the liver of PPMV-1 infected pigeons at 72 hpi(P<0.05). Interferon γ(IFN-γ) was significantly expressed in the spleen(24 h and 72 h), kidney(72 h and 7 d) and cecal tonsil(72 h and 7 d) of PPMV-1 infected pigeons(P<0.05). Compared with the control, the expression level of RNA-dependent protein kinase(PKR) was significantly increased in the liver of PPMV-1 infected pigeons at 72 hpi(P<0.05); 2’-5’ oligoadenylate synthetase(OAS) expression was dereased in the trachea(72 hpi) of PPMV-1 infected pigeons(P<0.05). The mRNA expression level of factor associated suicide ligand(FASLG) was significantly increased in the liver(P<0.05). In addition, no significant differences in the expression of B cell lymphoma/lewkmia-2(Bcl-2) was found in response to PPMV-1 infection(P>0.05). Bcl-2 Aaaociated X Protein(Bax) expression was dereased in the liver of PPMV-1 infected pigeons(P<0.05). Caspase-6 was only expressed in the spleen and cecal tonsil of PPMV-1 infected pigeons.In conclusion, this study demonstrates that specific antibody could be induced as early as 8 dpi by experimental infection with PPMV-1, and the antibody levels increased with time. The mRNA expression levels of TLRs(2, 7and 15) were significantly increased in some tissues, while TLR5 expression was decreased in some tissues of PPMV-1 infected pigeons(P<0.05). Compared to the control, interleukin 6(IL-6) and IL-10 expression were significantly increased in liver, and IFN-γ was induced in tissues of pigeons in response to PPMV-1-infection(P<0.05). Furthermore, the expression level of PKR was significantly increased in the liver by 72 hpi(P<0.05), while expression levels of IL-8, OAS and Bax were dereased in response to PPMV-1-infection(P<0.05). In addition, FASLG expression was significantly increased in liver, and Caspase-6 was induced in the spleen and cecal tonsil of pigeons in response to PPMV-1-infection(P<0.05). |
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