Volume 23, Issue 12, Dec. 2024
Volume 23, Issue 10, Oct. 2024
Virus neutralization (VN) antibody is deffned as a critical immune correlate for avian inffuenza vaccines. However, particular types of vaccines induce low levels of VN antibodies but can protect against avian inffuenza viruses, indicating novel mechanisms of protection. In our study, we reported that H7N9 avian inffuenza vaccine based on Newcastle disease virus vector (NDVvecH7N9) elicited low VN antibody titers but high levels of non-neutralizing antibodies against H7N9 virus in chickens. Passive transfer of these antibodies to chickens conferred complete protection from H7N9 virus challenge. The NDVvecH7N9 immune serum can induce strong lysis of H7N9 virus-infected cells and signiffcantly inhibit H7N9 virus infectivity. These activities of the serum were dependent on the engagement of the complement system as well as recognition of the epitope 150-SGS-152 in the hemagglutinin by the antibodies. Our ffndings suggest that activation of the complement system by antibodies elicited by NDVvecH7N9 contributes to protection in chickens. Our study unveils a previously-unidentiffed role of the complement system in protection conferred by NDVvecH7N9 in chickens, providing novel insights into the immune mechanism of H7N9 vaccines. The cover illustration depicts the mechanism of antibody-dependent complement-mediated protection of NDVvecH7N9, which is provided by Prof. Xiufan Liu and Dr. Zenglei Hu from Yangzhou University, China. See pages 2052–2064 for more details.