Antibody function predicts viral control in newborn monkeys immunised with an influenza virus HA stem nanoparticle.

The lack of an approved influenza vaccine for infants <6 months, coupled with the requirement for annual updates of current vaccines, warrants the development of a universal vaccine that can confer protection in young infants. Here we test the ability of a ferritin nanoparticle universal influenza vaccine (H1ssF) containing the stem region of hemagglutinin (HA) adjuvanted with AddaVax to elicit responses in newborn African green monkeys (AGM). Vaccinated newborns show robust HA stem-specific IgG responses but, despite the high antibody levels, viral load in the lung following H1N1 Ca09 challenge is variable among animals. Further analysis indicates that viral clearance is correlated with the presence of antibodies with neutralizing and antibody-dependent cellular phagocytosis activity. Our findings show that newborn AGM can generate functional HA stem-specific antibodies for viral clearance following vaccination with H1ssF+AddaVax and support further investigation of H1ssF as a universal vaccine for this vulnerable human population.