Prevention of Rift Valley fever in rhesus monkeys with interferon-alpha.

Prophylactic and therapeutic efficacy of recombinant leukocyte A interferon (rIFN-alpha A) and Sendai virus-induced human leukocyte interferon (HuIFN-alpha) administered intramuscularly to Rift Valley fever virus (RVFV)-infected rhesus monkeys was studied. Clinical, virologic, immunologic, and hemostatic parameters were monitored. Five daily inoculations of 5 X 10(5) units of either interferon product per kilogram of body weight, initiated 24 hours before or 6 hours after RVFV infection, prevented or greatly suppressed viremia. No clinical signs of disease or laboratory evidence of impaired hemostasis was observed. Serum neutralizing antibody to RVFV was detected within 6 days of virus inoculation. Prophylactic administration of 5 X 10(4) or 5 X 10(3) units of rIFN-alpha A per kilogram also limited viremia, hepatocellular damage, and hemostatic derangement. Untreated, RVFV-infected, control monkeys developed high-titered viremia, clinical disease, and impaired hemostasis. These data suggest that rIFN-alpha A and HuIFN-alpha are effective in protecting RVFV-infected rhesus monkeys from viremia and hepatocellular damage and may be beneficial in human RVF infection.