Host cell proteins induce inflammation and immunogenicity as adjuvants in an integrated analysis of in vivo and in vitro assay systems.

•Co-administration of host cell proteins (HCPs) and biopharmaceutical induced inflammation by intravitreal administration to rabbits.•Co-administration of HCPs with biopharmaceutical produced anti-drug antibody in the vitreous fluid by intravitreal administration to rabbits.•Co-stimulation of HCPs with biopharmaceutical enhanced immnostimulatory effects in the in vitro THP-1 cells assay.•HCPs induce inflammation and immunogenicity as adjuvants when they are co-treated with biopharmaceuticals in both in vivo and in vitro systems.