PROS1 and infection: Anti-EBOV antibody levels were monitored in the treated animals using (i) a Protein A ELISA, which measures total EBOV-specific antibody responses (both equine and NHP) (Fig. 2d, top panels) and (ii) an ELISA measuring only NHP-specific anti-EBOV IgG responses, which represent endogenous antibody responses raised by the NHPs in response to infection (Fig. 2d, bottom panels).