Experimental Rift Valley fever in rhesus macaques

Area of Science:

• Veterinary Medicine
• Infectious Diseases
• Virology

Background:

• Rift Valley fever (RVF) poses a significant threat to human health in endemic regions of sub-Saharan Africa and has pandemic potential.
• Previous studies in nonhuman primates have not documented severe hemorrhagic disease following RVF virus inoculation.

Purpose of the Study:

• To investigate the pathogenesis of Rift Valley fever (RVF) in rhesus macaques using a specific viral isolate.
• To evaluate the efficacy of passive antibody transfer in preventing RVF infection in a primate model.

Main Methods:

• Intravenous inoculation of rhesus macaques with a 1977 Egyptian RVF virus isolate (ZH-501).
• Observation of clinical signs, viremia, and pathological changes, including liver necrosis, disseminated intravascular coagulation, and hemolytic anemia.
• Passive transfer of serum from vaccinated rhesus monkeys to naive animals prior to virus challenge.

Main Results:

• A subset of macaques (20%) developed severe hemorrhagic fever syndrome, characterized by extensive liver necrosis, DIC, and microangiopathic hemolytic anemia.
• This severe disease manifestation was not previously reported in nonhuman primates infected with RVF virus.
• Passive transfer of as little as 0.025 ml/kg of immune serum completely prevented viremia in naive macaques.

Conclusions:

• The rhesus macaque model, particularly with the ZH-501 isolate, can recapitulate severe RVF disease, offering insights into pathogenesis.
• The study demonstrates the potential effectiveness of passive immunization for preventing RVF.
• This primate model is valuable for understanding RVF pathogenesis and developing preventative strategies for human disease.