Contributed by Azarene Foutouhi
Herpesviridae is a large family of Herpesviruses which are named for their tendency to result in recurrent infections. After clearance of lytic infections, these viruses enter latency, a mechanism which allows them to resist elimination and establish recurrent lifelong infections. More than 90% of people have become infected with one of these viruses, and latent forms result in most people.
While studying host response to latent Beta and Gamma-Herpesvirus infections, Barton et al. found that Herpesvirus latency confers protection from bacterial infection. In fact, mice latently infected with the Gammaherpesvirus HV68 had a nearly complete survival rate post L. monocytogenes challenge, while all control or mice with acute HV68 infections died by day 5.
MacDuff et al. found similar results while using HOIL-1 KO mice, and found that these genetically immunodeficient mice were rescued from Listeria lethality by latent HV68 infection. The HV68 latency protected the HOIL-1 KO mice from a dose of Listeria 1000-fold higher than the LD50 for HV68 negative mice, suggesting the metagenome (including virome) can help link phenotype and genotype.
Barton et al. repeated their study on the effect of HV68 latency on bacterial infection by depleting the CD4+ and CD8+ cells of latently infected and Listeria inoculated mice prior to Listeria challenge. The Listeria immune mice showed levels of Listeria equal to that of control, as the lack of CD4+ and CD8+ cells rendered them unprepared to combat the infection. However, even when depleted of CD4+ and CD8+ cells the HV68 latently infected mice showed levels of listeria similar to that of the undepleted Listeria immune mice, suggesting HV68 latency confers protection in an unexpected way. These data suggest latent herpesvirus infections could be offering the host long-term protection (up to three months) from bacterial infection independently of the adaptive immune system.
- Barton, Erik S., Douglas W. White, and Herbert W. Virgin. “Herpesvirus Latency and Symbiotic Protection from Bacterial Infection.” Viral Immunology22.1 (2009): 3–4. PMC. Web. 11 July 2017.
- MacDuff, Donna A et al. “Phenotypic Complementation of Genetic Immunodeficiency by Chronic Herpesvirus Infection.” Ed. Stephen P Goff. eLife4 (2015): e04494. PMC. Web. 11 July 2017.