BioDataAnalysis GmbH 1 article published in JoVE Immunology and Infection Microscopy-based Assays for High-throughput Screening of Host Factors Involved in Brucella Infection of Hela Cells Alain Casanova*1, Shyan H. Low*1, Mario Emmenlauer*1,4, Raquel Conde-Alvarez*1,3, Suzana P. Salcedo2, Jean-Pierre Gorvel2, Christoph Dehio1 1Focal Area Infection Biology, Biozentrum, University of Basel, 2Centre d’Immunologie de Marseille-Luminy, Université de la Méditérannée UM2, INSERM U1104 CNRS UM7280, 3Departmento de Microbiologìa and Instituto de Salud Tropical, Universidad de Navarra, 4BioDataAnalysis GmbH Two assays for microscopy-based high-throughput screening of host factors involved in Brucella infection are described. The entry assay detects host factors required for Brucella entry and the endpoint assay those required for intracellular replication. While applicable for alternative approaches, siRNA screening in HeLa cells is used to illustrate the protocols.