The viruses were grown in 8C10-day-old embryonated chicken eggs (Charles River Laboratories) for 48?h at 37?C and the allantoic fluid harvested. in the hemagglutinin that are highly pathogenic in avian species and have caused human infections. In addition, an outbreak of a highly pathogenic H7N8 strain was reported in the US state of Indiana in 2016. Furthermore, an H7N2 feline computer virus strain caused an outbreak in cats in an animal shelter in New York City Splitomicin Splitomicin in 2016, resulting in one human zoonotic event. In this study, mouse monoclonal antibodies previously raised against the hemagglutinin of the A/Shanghai/1/2013 (H7N9) computer virus were tested for their (cross-) reactivity to these novel H7 viruses. Moreover, the functionality of these antibodies was assessed in vitro in hemagglutination inhibition and microneutralization assays. The therapeutic and prophylactic efficacy of the broadly reactive antibodies against novel H7 viruses was decided in vivo in mouse passive transfer-viral challenge experiments. Our results provide data about the conservation of crucial H7 epitopes and could inform the selection of pre-pandemic H7 vaccine strains. Introduction Influenza viruses are a public health concern on a global level1. Annually, influenza viruses infect millions of people worldwide resulting in 290,000 to 650,000 influenza-related deaths2. Besides globally circulating seasonal influenza strains of the H1N1 subtype, H3N2 subtype, or Rabbit Polyclonal to IKZF2 influenza B strains, avian influenza viruses of the H7 subtype can result in zoonotic Splitomicin infections3. In 2017, the fifth wave of a zoonotic H7N9 epidemic emerged in China, resulting in higher numbers of laboratory-confirmed human infections (over 1500) than in previous years, coupled with a high case fatality rate (almost 40%)4. While these viruses have not yet gained the capability of sustained human-to-human transmission, they do present a pandemic risk if the avian computer virus were to adapt to humans or undergo reassortment with seasonal viruses5,6. Human infections with highly pathogenic avian influenza (HPAI) H7N9 viruses with polybasic cleavage sites in the hemagglutinin (HA) have been reported during the most recent epidemic6. These HPAI H7N9 computer virus isolates contained dual receptor binding properties, allowing them to bind to 2,6-linked sialic acid receptors (prevalent in the human upper airways) as well as 2,3-linked sialic acid receptors (prevalent in many avian species)7. Additionally, during the 2016C2017 Northern Hemisphere winter season, the A/H7N9 computer virus developed and clustered into antigenically unique lineages7,8 the Yangtze River Delta (YRD) lineage and Pearl River Delta (PRD) lineage. When tested against ferret antisera, it was shown that these two lineages did not match H7 stockpiled vaccines well9. Outside Splitomicin Mainland China, a highly pathogenic avian H7N8 computer virus was isolated from commercial turkeys in the US state of Indiana in 2016, causing severe systemic disease and high mortality in these animals10,11. Additionally, in New York City, an outbreak of an H7N2 computer virus in cats in an animal shelter led to public health concerns at the end of 2016. The feline computer virus caused one known human zoonotic event by infecting a human healthcare worker, who subsequently experienced influenza-like illness12. Humans are immunologically naive to subtype H7 viruses13. If zoonotic H7 viruses from animal reservoirs were to adapt to humans through mutations, H7 viruses could gain pandemic potential14,15. Vaccination regimens to protect against H7 viruses often only elicit low levels of hemagglutination inhibiting antibody titers and require further development16C21. However, the hemagglutination inhibition (HI) assay may not be sufficient to measure the full extent of the antibody response against H7 viruses19,22,23. Antibodies that target other regions of the HA, such as the membrane proximal stalk domain name, can contribute to protection by mechanisms other than HI, but can only be detected in other types of assays24C26. We have previously generated a set of four murine monoclonal antibodies (mAbs) against the HA of the A/Shanghai/1/2013 H7N9 computer virus27. The panel includes two Splitomicin HI-active and neutralizing mouse.