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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Endemic Poultry Viral Diseases Research » Research » Publications at this Location » Publication #421237
Research Project: Systems Biology Approaches to Develop Medical Countermeasures to Detect, Prevent, and Control Poultry Production Viral Diseases

Location: Endemic Poultry Viral Diseases Research

Title: Determination of a suitable avian cell line for the quantification of avian orthoreovirus via plaque assays

Author
item Harrell, Telvin
item Alvarez Narvaez, Sonsiray
item Conrad, Steven

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2025
Publication Date: 5/30/2025
Citation: Harrell, T.L., Alvarez Narvaez, S., Conrad, S.J. 2025. Determination of a suitable avian cell line for the quantification of avian orthoreovirus via plaque assays. Avian Diseases. 69(2):212–216. https://doi.org/10.1637/aviandiseases-D-24-00100.
DOI: https://doi.org/10.1637/aviandiseases-D-24-00100

Interpretive Summary: Avian orthoreovirus (ARV) infections are a serious issue in poultry farming, affecting both productivity and costs despite measures like biocontainment and vaccines. Accurate measurement of ARV levels is crucial for understanding the virus's spread and impact. A plaque assay is a method used to measure the amount of infectious virus particles in a sample. In this process, a diluted virus sample is added to a layer of cells in a dish. Each virus infects a cell and spreads to neighboring cells, killing them and forming a small clear spot called a "plaque." There's a misconception that ARV doesn’t form clear plaques in culture, leading researchers to rely on other less precise methods for counting virus particles. In this study, we tested two bird-derived cell lines, LMH and QM5, to see which was better for plaque assays. LMH cells, while useful for growing the virus, had issues with syncytia (clusters of fused cells), poor attachment to the culture surface, and rapid growth that covered virus-affected areas, making them unsuitable for plaque counting. In contrast, QM5 cells showed strong contact inhibition and formed clear, countable plaques with distinct virus-induced damage. This makes QM5 cells more suitable for plaque assays, providing a clearer picture of virus quantity and growth patterns. Overall, QM5 cells allow for more accurate tracking of ARV infectivity and growth compared to LMH cells.

Technical Abstract: Avian orthoreovirus (ARV) infections pose a significant economic threat to poultry production despite biocontainment efforts and live-attenuated vaccines. Quantifying ARV load is essential for understanding infection dynamics. There is a widespread misperception that ARVs in culture do not produce countable plaques, leading most in the field to use the less-useful TCID50 quantifications. Here we compare the suitability of two well-known avian cell lines, QM5 and LMH, for their use in plaque assays for the quantification of ARV. LMH cells, which exhibit syncytia formation post-infection, proved unsuitable for plaque assays due to their poor substrate adherence, their tendency to form syncytia-like conglomerations of cells even when uninfected, and the tendency for areas of the substrate cleared by viral cytopathic effect to quickly fill in with new cell growth. In contrast, QM5 cells demonstrated clear contact inhibition and well-defined cytopathic effects (CPE), enabling distinct, countable plaques even at high virus titers. Therefore, while LMH cells are advantageous for viral propagation, QM5 cells are better suited for plaque assays to assess ARV infectivity, with QM5 enabling more precise viral growth tracking and quantification.