Ketamine-Mediated Inhibition of Rabies Virus Infection in vitro and in Rat Brain

Abstract

SummaryThis report describes the effect of the dissociative anaesthetic ketamine, a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, on the infectivity of the neurotropic rabies virus, in neuronal culture systems and in vivo. produced an approximate 10Q-1000-fold decrease in the production of rabies virus in neuronal cell cultures. Rabies virus infection was also inhibited in non-neuronal cell lines (Baby Hamster Kidney fibroblasts) but the inhibitory effects appeared better expressed in cells of neuronal origin (neuroblastoma and primary neuronal cultures). The kalnate/quisqualate competitive antagonist CNQX did not modify the course of rabies virus infection and modulators of known NMDA regulatory sites (Mg 2 + , Zn 2 + , HA-966) failed to antagonize the ketamine-rnediated inhibition of rabies virus production in neuroblastoma cells. Furthermore, Ca 2 +-mobilization does not appear to be involved because Ca 2 +-depleted and EGTA-treated medium did not affect the normal production of rabies virus. The action of ketamine on rabies virus infection in vivo was also investigated; peripheral treatment ofrats with this drug inhibited rabies virus infection in the thalamus, cortex and hippocampal formation (in particular the pyramidal layer of the CA1 region). Taken together, these data suggest that the ketamine-mediated inhibition of rabies virus production in vitro, although highly selective, is not acting via classic NMDA receptor-mediated mechanisms. However, the ketaminemediated retardation of rabies virus infection in vivo may offer new prospects for post-exposure rabies antiviral therapy.

Modification of tritiated -amino-n-butyric acid transport in rabies virus-infected primary cortical cultures

“…Cortical neurons were prepared in 24-well poly-Lornithine-coated (3 ~tg/ml, Sigma) dishes from 15-day-old rat embryos as previously described (Lockhart et at., 1991) with the following changes. On the fourth day in culture 5-fluoro-2"-deoxyuridine (10 ~tg/ml) and uridine (25 gg/ml) were added to the F-10 medium for 24 h to control non-neural cell proliferation.…”

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).…”

“…Vehicle (footpad, n ϭ 8; intracerebral, n ϭ 3) and ketamine (footpad, n ϭ 11; intracerebral, n ϭ 6) treatment groups were compared using an unpaired t test ( * , statistical significance, P Ͻ 0.05; error bars, standard errors of the means). (16). Virus entry using footpad inoculation better evaluates viral spread through the neuroaxis, and it is highly doubtful that there is a species-specific difference in the therapeutic effect of ketamine.…”

Why does the prognosis remain so poor in human rabies?

“…The recommendation for therapy with ketamine was based on animal work that was performed at the Institut Pasteur in Paris, France, in the early 1990s [7]. Like current therapies for cancer, HIV infection and chronic hepatitis C infection, it was felt that a combination of therapies might be effective where specific therapies had failed in the past.…”