Structural and molecular basis for foot-and-mouth disease virus neutralization by two potent protective antibodies.

Outbreaks of Foot-and-mouth disease (FMD) caused by FMD virus result in significant economic losses. Vaccination is helpful, but the benefits are diminished with antigenic diversity within serotypes, instability of the immunogen and inability to confer protection for long durations. Here we have further dissected the mechanisms underpinning the protective efficacy of two previously reported neutralizing antibodies (NAbs), M8 and M170. The atomic details of the epitopes of M8 and M170 unveiled suggest that protection is conferred by disrupting the virus-receptor interactions. Consequently, administration of these NAbs conferred prophylactic and therapeutic benefit in guinea pigs, raising the possibility of administering NAbs before or during vaccination to confer immediate protection; well before the bolstering of the immune response by the vaccine. Differences in the residues and the conformation of elements making up the epitopes explain the differences in specificities of M8 and M170. An ability to bind 146S viral particles specifically, but not 12S degraded components, highlights a likely role for M170 in the quality control of vaccines.