[Viruses and the neuroendocrine system: model of murine obesity induced by cerebral infection by canine distemper virus].

It is currently well established that the nervous, endocrine and immune systems inter-communicate using biologically active soluble factors, synthesised and produced by these three systems themselves (e.g. immunomodulator effect of hormones, effect of substances secreted by immune cells on endocrine function.). In addition, these systems jointly express receptors for hormones, peptides, growth factors and cytokines. Immuno-neuroendocrine interactions therefore underlie physiological processes and their deregulation can result in various pathological states. By entering into complex relationships with the specialized and differentiated cells of these three systems viruses can alter inter-cellular communication and result in the appearance of pathological processes directly linked to these disturbances. In order to understand the role of viruses in the genesis of neuroimmunoendocrine pathologies, we have developed a cerebral infection model using canine distemper virus (CDV). In infected mice, this paramyxovirus, closely related to the human measles virus, induces early neurological pathologies (encephalitis) which are associated with active viral replication. Mice surviving the acute phase of infection exhibit motor deficits (paralysis and turning behaviour) or obesity during the viral persistence phase, despite the fact that the virus is no longer detectable. The obesity is characterised by hyperinsulinaemia, hyperleptinaemia and hyperplasia of the adipocytes, associated with decreased expression of the OB-Rb hypothalamic leptin receptor and modulated expression of hypothalamic monoamines and neuropeptides. These results support the viral "hit and run" theory, since the initial viral impact in the hypothalamus may be the origin of the changes in later immunoneuroendocrine communication. Thus, certain human neurodegenerative or neuroendocrine diseases may have a previous viral infection aetiology without it being possible to clearly identify the agent responsible.