Equine immunoglobulin F(ab') fragments protect mice from Rift Valley fever virus infection.

Background: Rift Valley fever virus (RVFV) is an emerging arbovirus in Africa and the Arabian Peninsula, in which infection with RVFV poses a serious threat to humans and livestock globally. Approved treatments for RVFV infection, especially for use in humans, have not yet been developed. There is an urgent need for effective drugs to prevent RVFV disease.

Methods: In previous study, we developed RVFV virus like particles (VLPs) expressing the surface glycoproteins Gn and Gc. The morphology was shown to be similar to live RVFV under electron microscopy. In this study, we immunized horses with RVFV VLPs, prepared the immunoglobulin F(ab') fragments, and characterized its in vitro neutralization and in vivo efficacy in mice.

Results: F(ab') was found to potently neutralize RVFV in VeroE6 cells, and passive transfer of immunoglobulin F(ab') fragments resulting in reduced mortality in RVFV infected mice.

Conclusion: Our results show that passive immunotherapy with equine immunoglobulin F(ab') fragments is a promising strategy to treat RVFV infections.