NEWCASTLE DISEASE EPIDEMIOLOGY, PATHOGENESIS, AND CONTROL
Location: Exotic and Emerging Avian Viral Diseases Research Unit
Title: In vivo transcriptional cytokine responses and association with clinical and pathological outcomes in chickens infected with different Newcastle disease virus isolates using formalin-fixed paraffin-embedded samples
Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2011
Publication Date: May 1, 2011
Citation: Ecco, R., Brown, C.C., Susta, L., Cagle, C.A., Edwards, I.C., Pantin Jackwood, M.J., Miller, P.J., Afonso, C.L. 2011. In vivo transcriptional cytokine responses and association with clinical and pathological outcomes in chickens infected with different Newcastle disease virus isolates using formalin-fixed paraffin-embedded samples. Veterinary Immunology and Immunopathology. 141:221-229.
Interpretive Summary: Newcastle disease (ND) is a highly contagious problem of recurring concern to poultry industries internationally because of its worldwide distribution, extensive flock losses and/or trade restrictions. The World Organization for Animal Health defines ND as a "notifiable" disease. Virus strains causative of ND are classified into three pathotypes depending on the severity of disease (mesogen, velogen, and lentogen). Despite extensive research characterizing the pathogenesis of different isolates, little is known about the chicken response to infection and its relationship to the severity of clinical disease, lesions and death. Quantitative measuring of cytokine levels during acute infection by viruses that cause different type of damage was used to increase the understanding of the mechanisms of pathogenesis. The RNA expression levels of four cytokines in chicken spleen was related to clinical signs and pathogenesis during infection.
Little is known about the host response to Newcastle Disease Virus (NDV) infection in chickens and the relationship between the innate immune response and the severity of clinical disease. Innate responses are considered important during the earliest phases of microbial invasion because they can limit the spread of the pathogens. However, it has been suggested that excessive innate immune responses can cause deleterious effects on the host. Measurement of cytokine responses during infection in vivo can help to elucidate the mechanisms of virus pathogenesis. The transcriptional response of several cytokines in the spleen of chicken naturally infected by NDV velogenic viscerotropic viruses was compared to the response of atypical velogenic, velogenic neurotropic, and mesogenic NDV’s during the first five days after challenge. The RNA expression for IFN-Gamma and IL-6 was enhanced at day 2 in the highly virulent velogenic viscerotropic viruses (California and rZJ1 strains) and corresponded with the presence of the virus in tissues. However, in one atypical velogenic viscerotropic virus (Australia strain), two velogenic neurotropic viruses (Turkey ND and Texas GB) and, a mesogenic virus (Anhinga strain) the cytokine responses to infection were delayed or reduced. Increased levels of IFN-Beta RNA expression were only detected in one velogenic viscerotropic virus infected chicken (California strain) and one neurotropic virus infected chicken (Texas GB strain). The levels of IL-2 did not increase significantly upon infection with any of the viruses. A pronounced increase of IL-6 and IFN-Gamma was detected simultaneously with infiltration of macrophages and/or lymphoid necrosis in the histopathological analysis of the spleen and cecal tonsils.