Advanced in vitro and ex vivo models provide a suitable platform for the evaluation of antiviral small molecules against human parainfluenza virus 3

Human parainfluenza virus 3 (HPIV-3) is responsible for lower respiratory tract infections. Due to the lack of antiviral therapeutics or vaccines, infections can result in high mortality rates e.g., in immunocompromised patients. Predictive test systems are urgently needed to test new antiviral therapies. Here, we report the suitability of human airway epithelial (HAE) cells differentiated <italic>in vitro</italic> and precision-cut lung slices (PCLS) from cotton rat and human lung tissue for drug screening on the example of the hemagglutinin-neuraminidase (HN) inhibitor BCX2798. HAE cells and PCLS from cotton rat and human lung tissue were generated, infected with HPIV-3 (C‑243), and treated with BCX2798. In addition, a pre-incubation setup of the virus with the compound was tested. Focus forming assay, qPCR, and confocal laser scanning microscopy (LSM) were used to determine viral load after treatment. To evaluate possible toxicity of the treatment, LDH release was analyzed. HPIV-3 could be detected by LSM in epithelial cells from cotton rat and human lung tissue. BCX2798 effectively reduced viral load in HAE cells and both PCLS models to nearly the same level, indicating that all models are similarly predictive. The HN inhibitor reached IC₅₀ values between 10 to 100 µM and showed no signs of toxicity, as could be determined by LDH release. We have shown that cotton rat and human PCLS are a suitable model for HPIV-3 infection and for testing small molecules. The HN inhibitor BCX2798 effectively reduces viral load in PCLS from cotton rat and human lung tissue, as well as in differentiated HAE cells.