Automated Counting of Chikungunya Virus-Formed Plaques.

The cytopathic effect (CPE) is a key to understanding the pathogenicity of the chikungunya virus (CHIKV) and is useful for evaluating viral infectivity in vitro. The plaque assay, based on the CPE induced by viral infection, provides an infectious virus titer for test samples. Additionally, the assay is simple, quantitative, and cost-effective. Thus, the plaque assay remains the gold standard for determining the infectivity of CHIKV. However, manually counting of virus-induced plaques with the naked eye or under the microscope is often time-consuming and labor-intensive. Therefore, automated plaque-counting software would improve the consistency and efficiency of plaque counting. We recently developed plaQuest, a stand-alone Windows software that enables rapid, reliable plaque counting for CHIKV. In this chapter, we describe the basic procedure for detecting and counting the CHIKV-formed plaques in a 24-well plate.