Antibody responses in mice protected against malaria by vaccination

Mice were vaccinated against lethal P. yoelii or P. berghei malaria and their immunofluorescent anti-parasite antibody levels followed after infection with live homologous parasites. There was a good correlation between antibody titres (especially IgG) and protection, under various experimental conditions, including: different doses of vaccine, different strains of mice, and increase or decrease of macrophage function. When antiserum was passively transferred to normal recipients, protection against challenge also correlated with antibody titre, though even with high titres only a small number of parasites could be completely eliminated. P. berghei was much more difficult to protect against than P. yoelii, despite similar antibody responses. We conclude that antibody is important in the protective effect of vaccination, but that other properties of both the host and the parasite influence its effectiveness.