Rhesus monkeys infected with hepatitis E virus (HEV) from the former USSR are immune to subsequent challenge with an Indian strain of HEV.

Two rhesus monkeys (M. mullata) of approximately two years of age were inoculated intravenously with a 10% suspension of hepatitis E virus (HEV) positive stool from Kirghistan as evidenced by immuno-electron microscopy. Evidence of HEV infection was demonstrated by rise in serum alanine transaminase (ALT) levels and seroconversion of these monkeys to anti-HEV after 1-1/2 months post-inoculation as evidenced by immunoblot. One year after the primary inoculation, these monkeys were challenged with an Indian strain of HEV. No rise in serum ALT levels was noted during an observation period of 6 months. The same inoculum produced HE in two rhesus monkeys. The results showed that strains from India and Kirghistan were antigenically closely related and rhesus monkeys infected with one strain of virus were immune to another strain.