The Biology of Papillomavirus Latency



Gareth Adam Maglennon1, John Doorbar*, 2
1 Pathology & Infectious Diseases, The Royal Veterinary College, North Mymms, AL9 7TA, UK
2 Division of Virology, National Institute for Medical Research, Mill Hill, London, NW7 1AA, UK


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© Maglennon and Doorbar; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Division of Virology, National Institute for Medical Research, Mill Hill, London, NW7 1AA, UK; Tel +44 20 8816 2623; Fax +44 20 8906 4477; E-mail: jdoorba@nimr.mrc.ac.uk


Abstract

The presence of viral DNA in the absence of disease has suggested that papillomaviruses, like many other viruses, can exist as latent infections in the skin or other epithelial sites. In animal models, where detailed investigation has been carried out, papillomavirus DNA can be found at sites of previous infection following immune regression, with the site of latent infection being the epithelial basal layer. Such studies suggest that immune surveillance can restrict viral gene expression in the basal and parabasal layers without efficiently suppressing viral genome replication, most probably through the action of memory T-cells in the skin or dermis. Although gradual papillomavirus genome loss appears to occur over time at latent sites, immunosuppression can arrest this, and can lead to an elevation in viral genome copy number in experimental systems. In addition to immune-mediated latency, it appears that a similar situation can be achieved following infection at low virus titres and/or infection at epithelial sites where the virus life cycle is not properly supported. Such silent of asymptomatic infections do not necessarily involve the host immune system and may be controlled by different mechanisms. It appears that virus reactivation can be triggered by mechanical irritation, wounding or by UV irradiation which changes the local environment. Although the duration of papillomavirus latency in humans is not yet known, it is likely that some of the basic principles will resemble those elucidated in these model systems, and that persistence in the absence of disease may be the default outcome for at least some period of time following regression.

Keywords: Papillomavirus, HPV, latency, basal cell, stem cell, immune regression, immunosuppression..