Little is known about the host response of chickens infected with Newcastle disease virus (NDV) and the relationship between the innate immune response and the severity of clinical disease. Measurement of cytokine responses during infection in vivo can help to elucidate the mechanisms of virus pathogenesis. The transcriptional response of several cytokines from paraffin-embedded, formalin-fixed spleen of chicken naturally infected by NDV velogenic viscerotropic viruses was compared to the responses of atypical velogenic, velogenic neurotropic, and mesogenic strains during the first five days after infection. The RNA expression for IFN-γ and IL-6 was enhanced at day two 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-β RNA expression were only detected in the velogenic viscerotropic virus infected chickens (California and rZJ1 strains) at 3 days post-infection and one mesogenic strain (Anhinga) early in infection. The RNA expression levels of IL-2 did not increase upon infection with any of the viruses. A pronounced increase of RNA expression levels of IL-6 and IFN-γ was detected simultaneously with infiltration of macrophages and/or lymphoid necrosis in the histopathological analysis of the spleen and cecal tonsils. The differences in the RNA expression levels may help explain possible underlying mechanisms of clinical disease and/or immune responses in birds infected with strains of APMV-1 that cause distinct pathologic changes.
Bibliographical noteFunding Information:
R. E. was supported by the Brazilian government sponsoring agency “Conselho Nacional de Desenvolvimento Cientıfico e Tecnologico” (CNPq) and Universidade Federal de Minas Gerais (UFMG).
This work was funded by USDA CRIS project number 6612-32000-049-00D. Mention of trade names or commercial products in this manuscript is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.
- Gene expression
- Newcastle disease virus