Genital re-excretion of Murid gammaherpesvirus 4 following intranasal infection

Gammaherpesviruses are the archetypes of persistent viruses that have been identified in a range of animals from mice to man. As the human gammaviruses have no well-established in vivo infection model, related animal gammaherpesviruses are an important source of information. We are studying Murid herpesvirus 4 (MuHV-4) in inbred laboratory mouse strains which are commonly accepted as a good model for studying gammaherpesviruses in vivo. To date, it has however never been possible to monitor viral reexcretion and virus transmission in this species. In order to identify potential re-excretion sites, intranasally infected mice were followed through global luciferase imaging for up to six months after infection. Surprisingly, we detected transient viral replication in mice genital tract at various times after latency establishment. Ex vivo imaging, quantitative PCR and immunohistochemistry revealed that virus genomes were present in high quantity in the vaginal tissue and that viral replication occurred mainly at the vaginal external border. Moreover, we highlighted the presence of free infectious viruses in the vaginal cavity at the moment of the observation of viral replication. As this ephemeral viral reexcretion could reveal a link with reproductive cycle, we compared reexcretion in normal and ovariectomized mice. Interestingly, no viral reactivation was observed in absence of hormonal cycle. In conclusion, we experimentally indentified for the first time a reexcretion site for MuHV-4 in mice that had been intranasaly infected. In the future, these results could help us to better understand the biology of gammaherpesviruses but should also allow us to develop strategies that could prevent the spread of these viruses in natural populations.