Human metapneumovirus infection of organoid-derived human bronchial epithelium represents cell tropism and cytopathology as observed in in vivo models.

Human metapneumovirus (HMPV), a member of the Pneumoviridae family, causes upper and lower respiratory tract infections in humans. In vitro studies with HMPV have mostly been performed in monolayers of undifferentiated epithelial cells. In vivo studies in cynomolgus macaques and cotton rats have shown that ciliated epithelial cells are the main target of HMPV infection, but these observations cannot be studied in monolayer systems. Here, we established an organoid-derived bronchial culture model that allows physiologically relevant studies on HMPV. Inoculation with multiple prototype HMPV viruses and recent clinical virus isolates led to differences in replication among HMPV isolates. Prolific HMPV replication in this model caused damage to the ciliary layer, including cilia loss at advanced stages post-infection. These cytopathic effects correlated with those observed in previous in vivo studies with cynomolgus macaques. The assessment of the innate immune responses in three donors upon HMPV and RSV inoculation highlighted the importance of incorporating multiple donors to account for donor-dependent variation. In conclusion, these data indicate that the organoid-derived bronchial cell culture model resembles in vivo findings and is therefore a suitable and robust model for future HMPV studies. IMPORTANCE: Human metapneumovirus (HMPV) is one of the leading causative agents of respiratory disease in humans, with no treatment or vaccine available yet. The use of primary epithelial cultures that recapitulate the tissue morphology and biochemistry of the human airways could aid in defining more relevant targets to prevent HMPV infection. For this purpose, this study established the first primary organoid-derived bronchial culture model suitable for a broad range of HMPV isolates. These bronchial cultures were assessed for HMPV replication, cellular tropism, cytopathology, and innate immune responses, where the observations were linked to previous in vivo studies with HMPV. This study exposed an important gap in the HMPV field since extensively cell-passaged prototype HMPV B viruses did not replicate in the bronchial cultures, underpinning the need to use recently isolated viruses with a controlled passage history. These results were reproducible in three different donors, supporting this model to be suitable to study HMPV infection.

Filamentous fungus-produced human monoclonal antibody provides protection against SARS-CoV-2 in hamster and non-human primate models.

Monoclonal antibodies are an increasingly important tool for prophylaxis and treatment of acute virus infections like SARS-CoV-2 infection. However, their use is often restricted due to the time required for development, variable yields and high production costs, as well as the need for adaptation to newly emerging virus variants. Here we use the genetically modified filamentous fungus expression system Thermothelomyces heterothallica (C1), which has a naturally high biosynthesis capacity for secretory enzymes and other proteins, to produce a human monoclonal IgG1 antibody (HuMab 87G7) that neutralises the SARS-CoV-2 variants of concern (VOCs) Alpha, Beta, Gamma, Delta, and Omicron. Both the mammalian cell and C1 produced HuMab 87G7 broadly neutralise SARS-CoV-2 VOCs in vitro and also provide protection against VOC Omicron in hamsters. The C1 produced HuMab 87G7 is also able to protect against the Delta VOC in non-human primates. In summary, these findings show that the C1 expression system is a promising technology platform for the development of HuMabs in preventive and therapeutic medicine.