Making Rift Valley Fever Viral Particles Fluorescent.

Rift Valley fever virus (RVFV) is a mosquito-borne pathogen that represents a significant threat to both human and veterinary public health. Since its discovery in the Great Rift Valley of Kenya in the 1930s, the virus has spread across Africa and beyond, now posing a risk of introduction into Southern Europe and Asia. Despite recent progresses, early RVFV-host cell interactions remain largely uncharacterized. In this method chapter, we delineate the procedure for labeling RVFV particles with fluorescent organic dyes. This approach makes it feasible to visualize single viral particles in both fixed and living cells and study RVFV entry into host cells. We provide additional examples with two viruses closely related to RVFV, namely, Toscana virus and Uukuniemi virus. Furthermore, we illustrate how to utilize fluorescent viral particles to examine and quantify each step of the cell entry program of RVFV, which includes state-of-the-art fluorescence-based detection techniques such as fluorescence microscopy, flow cytometry, and fluorimetry.