This HEK 293 HCP ELISA Kit, 3G, Cat. No. F650S, replaces the previous F650R kit while incorporating several improvements in performance. Expression of viral vectors in HEK 293 cells is a widely used procedure for obtaining sufficient quantities of a desired virus. The manufacturing and purification process of these products leaves the potential for impurities by host cell proteins (HCPs) from HEK 293 cells. HCP impurities can result in adverse toxic or immunological reactions and thus it is desirable to reduce these impurities to the lowest levels practical. The polyclonal antibodies used in this kit have been generated against and affinity-purified using a mild lysate of HEK 293 cells to obtain HCPs typically encountered in initial product recovery steps. This kit can be used as a process development tool to monitor the optimal removal of host cell impurities as well as in routine final product release testing when comprehensively characterized using samples from your process. Antibody Affinity Extraction (AAE) was used to determine reactivity to individual HCPs in a mild lysate of HEK 293. AAE indicated reactivity to ~74% of the individual 2-D PAGE fractionated spots presumed to be HCP.