biostudies-literatureMarcink TCNIAID NIH HHSDivision of Intramural Research, National Institute of Allergy and Infectious DiseasesDivision of Intramural Research, National Institute of Allergy and Infectious Diseases (Division of Intramural Research of the NIAID)8831https://www.ebi.ac.uk/biostudies/studies/S-EPMC11470942biostudies-literatureUnknown15(1)Paramyxoviruses including measles, Nipah, and parainfluenza viruses are public health threats with pandemic potential. Human parainfluenza virus type 3 (HPIV3) is a leading cause of illness in pediatric, older, and immunocompromised populations. There are no approved vaccines or therapeutics for HPIV3. Neutralizing monoclonal antibodies (mAbs) that target viral fusion are a potential strategy for mitigating paramyxovirus infection, however their utility may be curtailed by viral evolution that leads to resistance. Paramyxoviruses enter cells by fusing with the cell membrane in a process mediated by a complex consisting of a receptor binding protein (HN) and a fusion protein (F). Existing atomic resolution structures fail to reveal physiologically relevant interactions during viral entry. We present cryo-ET structures of pre-fusion HN-F complexes in situ on surfaces of virions that evolved resistance to an anti-HPIV3 F neutralizing mAb. Single mutations in F abolish mAb binding and neutralization. In these complexes, the HN protein that normally restrains F triggering has shifted to uncap the F apex. These complexes are more readily triggered to fuse. These structures shed light on the adaptability of the pre-fusion HN-F complex and mechanisms of paramyxoviral resistance to mAbs, and help define potential barriers to resistance for the design of mAbs.Nature communicationsHow a paramyxovirus fusion/entry complex adapts to escape a neutralizing antibody.PMC11470942R01 AI121349AI160961U19 AI181984AI160953R01 AI160953AI114736AI121349AI152275R01 AI114736R01 AI160961F32 AI152275Golub KMoscona AZipursky GStearns KHerman EGreninger ALMarcink TCSobolik EBPorotto MfalseHow a paramyxovirus fusion/entry complex adapts to escape a neutralizing antibody.Paramyxoviruses including measles, Nipah, and parainfluenza viruses are public health threats with pandemic potential. Human parainfluenza virus type 3 (HPIV3) is a leading cause of illness in pediatric, older, and immunocompromised populations. There are no approved vaccines or therapeutics for HPIV3. Neutralizing monoclonal antibodies (mAbs) that target viral fusion are a potential strategy for mitigating paramyxovirus infection, however their utility may be curtailed by viral evolution that leads to resistance. Paramyxoviruses enter cells by fusing with the cell membrane in a process mediated by a complex consisting of a receptor binding protein (HN) and a fusion protein (F). Existing atomic resolution structures fail to reveal physiologically relevant interactions during viral entry. We present cryo-ET structures of pre-fusion HN-F complexes in situ on surfaces of virions that evolved resistance to an anti-HPIV3 F neutralizing mAb. Single mutations in F abolish mAb binding and neutralization. In these complexes, the HN protein that normally restrains F triggering has shifted to uncap the F apex. These complexes are more readily triggered to fuse. These structures shed light on the adaptability of the pre-fusion HN-F complex and mechanisms of paramyxoviral resistance to mAbs, and help define potential barriers to resistance for the design of mAbs.2024-01-01T00:00:00Z2024 Oct2025-04-04T23:51:09.822Z2025-04-04T23:51:09.822ZS-EPMC114709423939605310.1038/s41467-024-53082-y