Jiahai Lu from Sun Yat-Sen University in Guangzhou, China and colleagues from other institutions in China infected dog kidney cells in vitro with a lethal dose of H5N1 and simultaneously exposed the cells to horse antibodies against H5N1. Lu et al.'s results show that horse antibodies to H5N1 protected cells against H5N1 in vitro - the cells simultaneously infected with H5N1 and exposed to horse antibodies did not die.
Lu et al. then injected horse antibodies into 40 mice that had been infected with a lethal dose of H5N1 24 hours earlier. The authors also injected horse serum without H5N1 antibodies into a group of mice that acted as controls.
The authors found that 50μg of antibody protected 70% of the mice against death by H5N1 and 100 μg of antibody protected 100% of the mice. The mice in the control group died nine hours after receiving the normal horse serum.