Cross-reactive immunity against different strains of the hepatitis E virus transferable by simian and human sera.

Monkey infection with the hepatitis E virus induces protection. We confirm the humoral nature of this immunity and show that protection is effective against the homologous strain, as well as against heterologous strains isolated from Asian and African countries. However this immunity is incomplete since only the clinical disease seems to be prevented, while the virus is still excreted in stools and can even appear in blood as well after serotherapy as previous acute or occult infections. We obtained also a preliminary evidence that convalescent human sera are also efficient for the passive protection, indicating that seroprophylaxis of HEV hepatitis in pregnant women (20% of mortality during the 3rd trimester of pregnancy) should be attempted in the case of epidemics.