Evasion of host immune defenses by human papillomavirus

Abstract

A majority of human papillomavirus (HPV) infections are asymptomatic and self-resolving in the absence of medical interventions. Various innate and adaptive immune responses, as well as physical barriers, have been implicated in controlling early HPV infections. However, if HPV overcomes these host immune defenses and establishes persistence in basal keratinocytes, it becomes very difficult for the host to eliminate the infection. The HPV oncoproteins E5, E6, and E7 are important in regulating host immune responses. These oncoproteins dysregulate gene expression, protein-protein interactions, posttranslational modifications, and cellular trafficking of critical host immune modulators. In addition to the HPV oncoproteins, sequence variation and dinucleotide depletion in papillomavirus genomes has been suggested as an alternative strategy for evasion of host immune defenses. Since anti-HPV host immune responses are also considered to be important for antitumor immunity, immune dysregulation by HPV during virus persistence may contribute to immune suppression essential for HPV-associated cancer progression. Here, we discuss cellular pathways dysregulated by HPV that allow the virus to evade various host immune defenses.

Generalized papillomatosis in three horses associated with a novel equine papillomavirus (EcPV8)

“…Persistent and severe papillomatosis, features of our cases, are often associated with immunodeficiency, immunosuppression and/or viral virulence factors . Contact horses, including immature horses at a breeding facility, did not develop similar papillomatosis, which further suggested altered individual immune function.…”

“…EcPV8‐associated papillomas were epithelial plaque type, as occurs with genital papillomas and auricular plaques . Hyperkeratosis was common, similar to auricular plaques, but unlike genital papillomas, where it is usually not a feature but rarely it is pronounced .…”

Immune evasion mechanisms of human papillomavirus: An update

“…E7 has been shown to directly block the MHC‐I heavy chain promoter . HLA‐A and ‐B can be retained by an HPV16 E5‐mediated mechanism within the cell . On the contrary, HLA‐C and HLA‐E are not influenced by E5.…”

Proportion of Transcriptionally Active Dna Virus Integrants: A Meta-Analysis

“…In addition, since the reactivation would appear a long time after the infection, it is plausible to assume that no specific tests targeting oncoviruses would be implemented and the presence of the integrants might remain undetected. The immune response, in particular the action of interferon, is able to deplete viral episomes from the infected cells [86]; however integrants cannot be removed by this mechanism and can therefore persist after viral clearance. Interestingly, it has been reported that interferon can facilitate viral integration [87].…”