Humo ral Immune Responses After Rabies Infection

Implications of the antiviral drug favipiravir on rabies immunoglobulin for post-exposure prophylaxis of rabies in mice model with category III-like exposures

Rabies is a fatal zoonotic disease caused by the rabies virus (RABV), with almost 100% mortality if proper post-exposure prophylaxis (PEP), consisting of rabies immunoglobulin (RIG) and rabies vaccine, is not applied in a timely manner. However, this is challenged by the limited availability of RIG, especially in resource-constrained countries. In this study, we assessed the scope of the antiviral drug favipiravir to treat rabies-infected mice as an alternative to RIG. Category III-like wounds were induced in RABV-challenged mice treated with favipiravir instead of RIG in the PEP regimen. The use of favipiravir followed by rabies vaccine provided complete protection against rabies-related death in 100% of mice, even after RABV propagated to the central nervous system during infection. Additionally, the virus-neutralizing antibody titer in the favipiravir and vaccine group was significantly higher than that of the RIG and vaccine recipients. The use of favipiravir with rabies vaccine seemingly prevents fatal outcomes and even rescues the cases that already express clinical symptoms. A clinical trial of this approach is warranted, especially in countries with low RIG availability.

Viewpoint: Management of human rabies

Rabies remains a serious public health problem in many developing countries. A case in the West received media attention with the recovery of an American teenager who had not received rabies post-exposure prophylaxis. This case confirmed that rabies is not an invariably fatal disease. Review of the literature revealed only two survivors with good neurological status in nearly 40 years. Both had neutralizing antibodies in cerebrospinal fluid at or shortly after presentation, but the usual diagnostic tests for rabies were negative, a rather unique finding. It is highly probable that these two children managed to mount an unusually effective early immune response to the infection that contributed to, or was responsible for, recovery. Curative efforts for human rabies using critical care resources should especially target patients who show early neutralizing antibody. More basic research is needed to develop effective therapies for human rabies.