Viral Neuro-Immunology - CNRS U3015  

  HEADMonique LAFON /
  MEMBERSChercheurs permanents: Monique LAFON, Chef de Laboratoire Institut Pasteur, Dr PhD / Françoise MEGRET Ingénieure de Recherche, Institut Pasteur / Christophe PREHAUD, Chargé de Recherche Institut Pasteur Dr PhD
Techniciens, administratifs: Corinne BARAN, Secrétaire Institut Pasteur / Edmond BELLANCE, Agent de laboratoire Institut Pasteur / Mireille LAFAGE, Technicienne Supérieure Institut Pasteur
Etudiants: Damien CHOPY, Master II and PhD student / Pauline MENAGER, PhD Student

  Annual Report

Rabies remains an important public health problem in the world due to uncontrolled enzootic rabies, lack of vaccines and poor information. Globally there are over 70 000 cases of rabies reported each year. Rabies is becoming a re-emerging disease in several parts of the world including China where epidemics are currently exploding. Rabies virus, which is transmitted by bites of rabid animals, replicates in nervous tissues- only in neurons-, causing fatal encephalitis in nearly all the cases. In the absence of post-exposure treatment, rabies is one of the very few human infections with nearly a 100 % mortality rate. Intriguingly, once the rabies virus has entered the CNS, its progression is interrupted neither by destruction of the infected neuron nor by the immune response. Therefore the classical strategies developed by the host to battle infection are inefficient.

We aimed to elucidate how rabies virus can avoid functional neuron impairment and host immune mechanisms. By using purified post mitotic human neurons in culture and appropriate animal models, we demonstrated that rabies virus has selected unique strategies to favour neuronal survival and paralyze the host immune response. Particularly, the up-regulation by rabies virus of immunosubversive molecules such as FasL, HLA-G and B7-H1 which protect the infected neurons from the control by the host immune response was demonstrated (Baloul et al, 2004, Lafon et al, 2005, Lafon et al, 2008 ).

Rabies virus has also developed strategies to escape the innate immune response which represents the first line of host defence against pathogens. Nevertheless, this escape may not be complete since in the few hours following infection, r abies virus triggers strong interferon, inflammatory, chemo attractive and anti-viral responses in human neurons (Prehaud et al, 2005, Lafon et al, 2006). These analyses allowed us to show, for the first time, that human neurons express several Toll-like receptors including TLR3 which recognizes and responds to double stranded RNA. Moreover, TLR3 is a central element of Negri Bodies and appears critical for the rabies virus infection both in vivo and in vitro (Menager et al, 2009).

The rabies virus has also evolved intrinsic neuroprotective molecular mechanisms that contribute to the protection of the infected neurons from virus-mediated burden. Identifying the specific proteins that induce apoptosis as well as the precise roles of these proteins was therefore critical for improving the knowledge of virus pathogenicity and virulence. Rabies virus-induced apoptosis is inversely correlated with pathogenicity (Sarmento et al., 2005, Thoulouze et al, 2004). Induction of apoptosis is largely determined (Faber et al., 2002) by the nature of the G-protein (Prehaud et al., 2003). Recent evidence revealed that rabies virus containing the G-protein from an attenuated virus strain (“G death”) was able to trigger apoptosis of human cells, whereas expression of the pathogenic rabies virus G-protein (“G survival”) was not (Prehaud et al., 2003). The cytoplasmic portions of viral G death and G survival, possess a PDZ binding site.We observed that their host cell partners exhibit a PDZ domain. By biochemical means and rabies virus reverse genetic analysis we demonstrated the importance of the glycoprotein C domain and the PDZ protein-protein interaction (in collaboration with N. Wolff, H. Buc, Institut Pasteur; and M. Schnell, Thomas Jefferson University, USA). We are currently investigating the molecular basis of the balance between death or survival control by the virus.

Keywords: Rabies virus, neuron survival, neuronal apoptosis, TLR3, B7-H1, HLA-G


Negri bodies (arrow) composed with an internal TLR3 core (red) embedded in a corona of viral nucleocapsid (green) in rabies virus-infected human neuroblastoma cells (nuclei in blue).


PREHAUD C., MEGRET F., LAFAGE, M., and LAFON, M. (2005). Virus infection switches TLR-3 positive human neurons into high producers of interferon-beta. Journal of Virology, 79 : 12893-904

LAFON M., PREHAUD C., MEGRET F., LAFAGE M., MOUILLOT G., ROA M., MOREAU P., ROUAS-FREISS, N.and CAROSELLA, E. (2005). Modulation of HLA-G expression in human neural cells after neurotropic viral infections Journal of Virology, 79 :15226-37.

JACKSON, AC, ROSSITER JP ANDM LAFON (2006).Expression of Toll-like receptor 3 in the human cerebellar cortex in rabies, herpes simplex encephalitis, and other neurological diseases. Journal of Neurovirology,12 : 229-234.

MEGRET F., PREHAUD C., LAFAGE M., MOREAU P., MOUILLOT G., ROUASS-FREISS N., CAROSSELA E.D. andLAFON M. (2007). Modulation of HLA-G and HLA-E expression in human neuronal cells after rabies virus or HSV-1 infection. Human Immunology, 68 : 294-302

LAFON M, MEGRET F, MEUTH SG, OLE S, VELANDIA ROMERO LM,LAFAGEM, CHENL, ALEXOPOULOU L, FLAVELL RA, PREHAUDC and WIENDLH.(2008) Detrimental contribution of the immuno-inhibitor B7-H1 to rabies virus encephalitis. Journal of Immunology, 180 : 7506-15

Activity Reports 2009 - Institut Pasteur
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