Molecular characterization, tissue tropism, and genetic variability of the novel Mupapillomavirus type HPV204 and phylogenetically related types HPV1 and HPV63

HPV Infections-Classification, Pathogenesis, and Potential New Therapies

To date, more than 400 types of human papillomavirus (HPV) have been identified. Despite the creation of effective prophylactic vaccines against the most common genital HPVs, the viruses remain among the most prevalent pathogens found in humans. According to WHO data, they are the cause of 5% of all cancers. Even more frequent are persistent and recurrent benign lesions such as genital and common warts. HPVs are resistant to many disinfectants and relatively unsusceptible to external conditions. There is still no drug available to inhibit viral replication, and treatment is based on removing lesions or stimulating the host immune system. This paper presents the systematics of HPV and the differences in HPV structure between different genetic types, lineages, and sublineages, based on the literature and GenBank data. We also present the pathogenesis of diseases caused by HPV, with a special focus on the role played by E6, E7, and other viral proteins in the development of benign and cancerous lesions. We discuss further prospects for the treatment of HPV infections, including, among others, substances that block the entry of HPV into cells, inhibitors of viral early proteins, and some substances of plant origin that inhibit viral replication, as well as new possibilities for therapeutic vaccines.

An Improved Protocol for Comprehensive Etiological Characterization of Skin Warts and Determining Causative Human Papillomavirus Types in 128 Histologically Confirmed Common Warts

Human papillomaviruses (HPVs) are etiologically associated with various benign and malignant neoplasms of cutaneous and mucosal epithelia. We describe an improved diagnostic protocol for comprehensive characterization of causative HPV types in common warts, in which broad-spectrum PCRs followed by Sanger sequencing, two previously described and seven newly developed type-specific quantitative real-time PCRs (qPCRs) coupled with the human beta-globin qPCR were used for: (i) diagnosis of HPV infection in warts; (ii) estimation of cellular viral loads of all HPV types detected; and (iii) determination of their etiological role in 128 histologically confirmed fresh-frozen common wart tissue samples. A total of 12 different causative HPV types were determined in 122/126 (96.8%) HPV-positive warts, with HPV27 being most prevalent (27.0%), followed by HPV57 (26.2%), HPV4 (15.1%), HPV2 (13.5%), and HPV65 (7.9%). The cellular viral loads of HPV4 and HPV65 were estimated for the first time in common warts and were significantly higher than the viral loads of HPV2, HPV27, and HPV57. In addition, we showed for the first time that HPV65 is etiologically associated with the development of common warts in significantly older patients than HPV27 and HPV57, whereas HPV4-induced warts were significantly smaller than warts caused by HPV2, HPV27, HPV57, and HPV65.

Principles of epithelial homeostasis control during persistent human papillomavirus infection and its deregulation at the cervical transformation zone

Human papillomaviruses establish a reservoir of infection in the epithelial basal layer. To do this they limit their gene expression to avoid immune detection and modulate epithelial homeostasis pathways to inhibit the timing of basal cell delamination and differentiation to favour persistence. For low-risk Alpha papillomaviruses, which cause benign self-limiting disease in immunocompetent individuals, it appears that cell competition at the lesion edge restricts expansion. These lesions may be considered as self-regulating homeostatic structures, with epithelial cells of the hair follicles and sweat glands, which are proposed targets of the Beta and Mu papillomaviruses, showing similar restrictions to their expansion across the epithelium as a whole. In the absence of immune control, which facilitates deregulated viral gene expression, such lesions can expand, leading to problematic papillomatosis in afflicted individuals. By contrast, he high-risk Alpha HPV types can undergo deregulated viral gene expression in immunocompetent hosts at a number of body sites, including the cervical transformation zone (TZ) where they can drive the formation of neoplasia. Homeostasis at the TZ is poorly understood, but involves two adjacent epithelial cell population, one of which has the potential to stratify and to produce a multilayed squamous epithelium. This process of metaplasia involves a specialised cell type known as the reserve cell, which has for several decades been considered as the cell of origin of cervical cancer. It is becoming clear that during evolution, HPV gene products have acquired functions directly linked to their requirements to modify the normal processes of epithelial homestasis at their various sites of infection. These protein functions are beginning to provide new insight into homeostasis regulation at different body sites, and are likely to be central to our understanding of HPV epithelial tropisms.

Determination of Causative Human Papillomavirus Type in Tissue Specimens of Common Warts Based on Estimated Viral Loads

Background: Assessment of human papillomavirus (HPV) type-specific viral load (VL) is a valid tool for determining the etiology of HPV-related skin tumors, especially when more than one HPV type is detected within one lesion.

Methods: The causative HPV type was determined in 185 fresh-frozen tissue specimens of histologically confirmed common warts (CWs) collected from 121 immunocompetent patients. All tissues were tested using the type-specific quantitative real-time polymerase chain reactions (PCR) for the most common wart-associated Alpha-PV (HPV2/27/57) and Mu-PV types (HPV1/63/204). The presence of 23 additional low-risk HPVs was evaluated using a conventional wide-spectrum PCR.

Results: HPV DNA was detected in 176/185 (95.1%) CWs and multiple HPV types in 71/185 (38.4%) lesions. Using the VL approach and a robust cutoff of one viral copy/cell established in this study, HPV2/27/57 were determined as causative agents in 41/53 (77.3%) and 53/71 (74.7%) CWs with single and multiple HPVs, respectively.

Conclusions: CWs are mostly etiologically associated with HPV2/27/57 and only rarely with HPV1. In the majority of CWs containing multiple HPVs, a single HPV type was present in high concentration, indicating etiological association. No significant differences in VLs of lesion-causing HPV types in CWs containing single or multiple HPVs were found.