Inhibition of rabies virus transcription in rat cortical neurons with the dissociative anesthetic ketamine

Abstract

In a previous study (B. P. Lockhart, H. Tsiang, P. E. Ceccaldi, and S. Guillemer, Antiviral Chem. Chemother. 2:9-15, 1991), we demonstrated an antiviral effect of the general anesthetic ketamine for rabies virus in neuronal cultures and in rat brain. This report describes an attempt to determine at what level ketamine acts on the rabies virus cycle in rat cortical neuron cultures. Immunofluorescence and [35S]methionine labelling of infected neurons showed that ketamine (1 to 1.5 mM) inhibited viral nucleoprotein and glycoprotein syntheses. Northern (RNA) blots of total RNA from drug-treated neurons, hybridized with 32P-labelled oligonucleotide probes for rabies virus nucleoprotein, matrix protein, and glycoprotein genes, showed a marked reduction (5-to 11-fold) in the levels of rabies virus mRNAs, relative to those in untreated neurons. No significant change in the levels of cellular 13-actin mRNA were detected in ketamine-treated cells.A similar antiviral effect was observed with MK-801; however, no inhibition of rabies virus synthesis was observed with the general anesthetic chloral hydrate. The antiviral effect was not complete; a time-dependent recovery of viral transcription and rabies virus protein synthesis was observed, but no infectious virus was released into the culture supernatant. The lack of any modification of cellular protein or mRNA synthesis by ketamine suggests an antiviral mechanism acting at the level of rabies virus genome transcription.Rabies virus, a member of the Rhabdoviridae family, contains an unsegmented negative-stranded RNA genome that codes sequentially for five proteins: nucleoprotein N, phosphoprotein M1, matrix protein M2, glycoprotein G, and RNA-dependent RNA polymerase L (29). The virus is highly neurotropic (38) and produces dramatic clinical symptoms leading invariably to death (12). Despite widespread and effective vaccination programs, rabies is still believed responsible for up to 20,000 human fatalities per year (35). The classical postexposure treatment for rabies infection consists of vaccination and, in cases of severe and advanced exposure, vaccination is combined with immunotherapy with either equine or human antirabies immunoglobulins (37). However, the limited availability of serum, combined with the potential risk of hepatitis B and human immunodeficiency virus contamination from human sera, has restricted its application and partly contributed to failures of postexposure treatment for rabies (2,6,36). It is for these reasons as well as for the lack of efficient anti-rabies virus agents (8, 11) that we were prompted to assess alternative potential drugs for effective postexposure treatment for rabies.We previously showed that the dissociative anesthetic ketamine, a noncompetitive antagonist of the N-methyl-Daspartate (NMDA) receptor, inhibited the production (100-to 1,000-fold) of rabies virus in a dose-dependent manner and that the inhibitory effect was unrelated to any mechanism operating through high-affinity NMDA receptor sites (20). The antiviral effect was...

Rabies Virus Infection of Primary Neuronal Cultures and Adult Mice: Failure To Demonstrate Evidence of Excitotoxicity

“…The findings indicate that caution should be taken before subjecting future human rabies patients to therapy with ketamine on the basis of the previous experimental work (15,16,20). There have been at least four patients treated with ketamine after the survivor received ketamine in 2004, and all of these patients progressed to fatal outcomes (7).…”

“…The events in rabies virus infection that lead to CNS disease and a fatal outcome are still not well understood (6). Studies with rat cortical neurons and with a rat model suggested the possibility that the noncompetitive Nmethyl-D-aspartate acid (NMDA) antagonists ketamine and MK-801 might be effective therapeutic agents for human rabies (15,16,20) and that ketamine inhibits viral RNA genome transcription (15). Consequently, a working group recommended that ketamine be considered for the therapy of human patients with rabies (12).…”

Perspectives in Diagnosis and Treatment of Rabies Viral Encephalitis: Insights from Pathogenesis

“…Ketamine is an anesthetic agent that is considered a potential therapeutic agent in the management of human rabies on account of its inhibitory effect on RNA transcription and Nmethyl D-aspartate receptor antagonistic function that might limit viral spreading in tissue [140,149]. Its ability to rapidly cross the BBB is of potential advantage in reaching the rabies virus within the CNS.…”

Encefalitis rábica humana por mordedura de murciélago en un área urbana de Colombia

“…Por otra parte, la ketamina es un antagonista del receptor de N-metil-D-aspartato con actividad específica contra la rabia en los modelos animales (43). Por todo lo anterior, se diseñó este protocolo como una estrategia para tratar de proteger el cerebro de la lesión, mientras se le permitía al sistema inmune desarrollar una respuesta natural y acabar con el virus.…”