Tropism of Newcastle disease virus strains for chicken neurons, astrocytes, oligodendrocytes, and microglia

Authors: BUTT, SALMAN - University Of Georgia; MOURA, VERIDIANA - Federal University Of Goias; SUSTA, LEONARDO - Ontario Veterinary College; MILLER, PATTI - University Of Georgia; HUTCHESON, JESSICA - University Of Georgia; CARDENAS, GARCIA STIVALIS - University Of Georgia; BROWN, CORRIE - University Of Georgia; WEST, FRANKLIN - University Of Georgia; Afonso, Claudio; STANTON, J. B. - University Of Georgia

Submitted to: BMC Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2019
Publication Date: 9/4/2019
Citation: Butt, S.L., Moura, V., Susta, L., Miller, P.J., Hutcheson, J.M., Cardenas, G., Brown, C., West, F., Afonso, C.L., Stanton, J. 2019. Tropism of Newcastle disease virus strains for chicken neurons, astrocytes, oligodendrocytes, and microglia. BMC Veterinary Research. 15:317. https://doi.org/10.1186/s12917-019-2053-z.
DOI: https://doi.org/10.1186/s12917-019-2053-z

Interpretive Summary: Newcastle disease virus (NDV) is an important, worldwide poultry disease responsible for major panzootics and extensive poultry mortality. Neurotropic forms of the replicate in the central nervous system and cause significant damage leading to mortality. Understanding the pathogenic mechanism of the virus could lead to the development of more effective vaccines. Based on the data reported in the literature, it is likely that NDV infects glial cells; however, the extent of infection of glial cells and the types of affected glial cells remain unknown. Furthermore, it is unclear if the differential ability of certain NDV strains to replicate in the cellular subsets of the neuroparenchyma (e.g., neurons, astrocytes and oligodendrocytes) contributes to neuroinvasion and overall neuropathogenesis in chickens. Here, the permissibility of these mixed neural cells to infection was assessed by measuring viral titers produced at 24 hours post-inoculation in culture by double immunofluorescence for NDV and cellular markers (neurons, astrocytes, and oligodendrocytes). Immunofluorescence for NDV and for cellular markers showed that vaccine and virulent strains of NDV infected at least 20% of each of the cell types in culture (neurons, astrocytes, and oligodendrocytes). However, at 24 hours post-inoculation of cultures, neurotropic viruses replicated significantly more than vaccine viruses in mixed cell cultures. In vivo, the tropism of three different virulent strains [viscerotropic, neurotropic, and mesogenic]) was demonstrated with neurons, astrocytes, microglia, becoming infected by all of these viruses. The data indicate that similar to other paramyxoviruses, glial cells are susceptible to vNDV infection, and suggest that factors other than cellular tropism are likely the major determinant of the neurotropic phenotype.

Technical Abstract: Background Newcastle disease (ND), which is caused by infections of poultry species with virulent strains of Avian orthoavulavirus-1, also known as avian paramyxovirus 1 (APMV-1), and formerly known as Newcastle disease virus (NDV), may cause neurological signs and encephalitis. Neurological signs are often the only clinical signs observed in birds infected with neurotropic strains of NDV. Experimental infections have shown that the replication of virulent NDV (vNDV) strains is in the brain parenchyma and is possibly confined to neurons and ependymal cells. However, little information is available on the ability of vNDV strains to infect subset of glial cells (astrocytes, oligodendrocytes, and microglia). The objective of this study was to evaluate the ability of NDV strains of different levels of virulence to infect a subset of glial cells both in vitro and in vivo. Thus, neurons, astrocytes and oligodendrocytes from the brains of day-old White Leghorn chickens were harvested, cultured, and infected with both non-virulent (LaSota) and virulent, neurotropic (TxGB) NDV strains. To confirm these findings in vivo, the tropism of three vNDV strains with varying pathotypes (SA60 [viscerotropic], TxGB [neurotropic], and Tx450 [mesogenic]) was assessed in archived formalin-fixed material from day-old chicks inoculated intracerebrally. Results Double immunofluorescence for NDV nucleoprotein and cellular markers showed that both strains infected at least 20% of each of the cell types (neurons, astrocytes, and oligodendrocytes). At 24'h post-inoculation, TxGB replicated significantly more than LaSota. Double immunofluorescence (DIFA) with markers for neurons, astrocytes, microglia, and NDV nucleoprotein detected the three strains in all three cell types at similar levels. Conclusion These data indicate that similar to other paramyxoviruses, neurons and glial cells (astrocytes, oligodendrocytes, and microglia) are susceptible to vNDV infection, and suggest that factors other than cellular tropism are likely the major determinant of the neurotropic phenotype.