Cutaneous beta human papillomavirus (HPV) types are suspected to be involved, together with ultraviolet (UV) radiation, in the development of non-melanoma skin cancer (NMSC). Studies in in vitro and in vivo experimental models have highlighted the transforming properties of beta HPV E6 and E7 oncoproteins. However, epidemiological findings indicate that beta HPV types may be required only at an initial stage of carcinogenesis, and may become dispensable after full establishment of NMSC. Here, we further investigate the potential role of beta HPVs in NMSC using a Cre-loxP-based transgenic (Tg) mouse model that expresses beta HPV38 E6 and E7 oncogenes in the basal layer of the skin epidermis and is highly susceptible to UV-induced carcinogenesis. Using whole-exome sequencing, we show that, in contrast to WT animals, when exposed to chronic UV irradiation K14 HPV38 E6/E7 Tg mice accumulate a large number of UV-induced DNA mutations, which increase proportionally with the severity of the skin lesions. The mutation pattern detected in the Tg skin lesions closely resembles that detected in human NMSC, with the highest mutation rate in p53 and Notch genes. Using the Cre-lox recombination system, we observed that deletion of the viral oncogenes after development of UV-induced skin lesions did not affect the tumour growth. Together, these findings support the concept that beta HPV types act only at an initial stage of carcinogenesis, by potentiating the deleterious effects of UV radiation. Many epidemiological and biological findings support the hypothesis that beta HPV types cooperate with UV radiation in the induction of NMSC, the most common form of human cancer. We have previously shown that K14 HPV38 E6/E7 Tg mice, when exposed to long-term UV radiation, developed NMSC, whereas WT animals subjected to identical treatments did not develop any type of skin lesions. Here, we show that the high skin cancer susceptibility of these Tg animals tightly correlates with their tendency to accumulate UV-induced mutations in genes that are frequently mutated in human NMSC. Importantly, deletion of the HPV38 E6 and E7 genes in existing skin lesions did not affect the further growth of the cancer cells. Together, these findings support the model that beta HPV infection is a co-factor in skin carcinogenesis, facilitating the accumulation of the UV-induced DNA mutations.

Human papillomavirus type 16 (HPV16) and other oncoviruses have been shown to block innate immune responses and to persist in the host. However, to avoid viral persistence, the immune response attempts to clear the infection. IL-1β is a powerful cytokine produced when viral motifs are sensed by innate receptors that are members of the inflammasome family. Whether oncoviruses such as HPV16 can activate the inflammasome pathway remains unknown. Here, we show that infection of human keratinocytes with HPV16 induced the secretion of IL-1β. Yet, upon expression of the viral early genes, IL-1β transcription was blocked. We went on to show that expression of the viral oncoprotein E6 in human keratinocytes inhibited IRF6 transcription which we revealed regulated IL-1β promoter activity. Preventing E6 expression using siRNA, or using E6 mutants that prevented degradation of p53, showed that p53 regulated IRF6 transcription. HPV16 abrogation of p53 binding to the IRF6 promoter was shown by ChIP in tissues from patients with cervical cancer. Thus E6 inhibition of IRF6 is an escape strategy used by HPV16 to block the production IL-1β. Our findings reveal a struggle between oncoviral persistence and host immunity; which is centered on IL-1β regulation. Oncoviruses block innate immune responses to persist in the host. However, to avoid viral persistence, the immune response attempts to clear the infection. IL-1β is a pro-inflammatory cytokine produced by the inflammasome pathway. Whether oncoviruses such as human papillomavirus (HPV) can activate the inflammasome remains to be explored. We demonstrated that keratinocytes, the host cell type for papillomaviruses, when infected with HPV16 induced IL-1β transcription and secretion. Yet, upon expression of the viral oncoprotein E6, IL-1β transcription was blocked. E6 expression inhibited IRF6 transcriptional regulation of the IL-1β promoter. Preventing E6 expression, or its ability to degrade p53, restored the ability of IRF6 to bind to the IL-1β promoter. HPV16 abrogation of p53, IRF6 and IL-1β expression was fully confirmed in cervical cancer cells and tissues from patients. These data highlight the equilibrium between the host innate immune rheostat and viral immune escape.

Tumor suppressors can exert pro-proliferation functions in specific contexts. In the beta human papillomavirus type 38 (HPV38) experimental model, the viral proteins E6 and E7 promote accumulation of a wild-type (WT) p53 form in human keratinocytes (HKs), promoting cellular proliferation. Inactivation of p53 by different means strongly decreases the proliferation of HPV38 E6/E7 HKs. This p53 form is phosphorylated at S392 by the double-stranded RNA-dependent protein kinase PKR, which is highly activated by HPV38. PKR-mediated S392 p53 phosphorylation promotes the formation of a p53/DNMT1 complex, which inhibits expression of integrin alpha 1 (ITGA1), a repressor of epidermal growth factor receptor (EGFR) signaling. Ectopic expression of ITGA1 in HPV38 E6/E7 HKs promotes EGFR degradation, inhibition of cellular proliferation, and cellular death. Itga1 expression was also inhibited in the skin of HPV38 transgenic mice that have an elevated susceptibility to UV-induced skin carcinogenesis. In summary, these findings reveal the existence of a specific WT p53 form that displays pro-proliferation properties. This study shows that beta HPV38 can convert p53 functions from a tumor suppressor to an oncoprotein via the formation of a transcriptionally repressive complex, which in turn represses ITGA1 expression, promoting cellular proliferation and UV-induced skin carcinogenesis.

Background: The detection of known human papillomaviruses (PVs) from targeted wet-lab approaches has traditionally used PCR-based methods coupled with Sanger sequencing. With the introduction of next-generation sequencing (NGS), these approaches can be revisited to integrate the sequencing power of NGS. Although computational tools have been developed for metagenomic approaches to search for known or novel viruses in NGS data, no appropriate tool is available for the classification and identification of novel viral sequences from data produced by amplicon-based methods. Results: We have developed PVAmpliconFinder, a data analysis workflow designed to rapidly identify and classify known and potentially new Papillomaviridae sequences from NGS amplicon sequencing with degenerate PV primers. Here, we describe the features of PVAmpliconFinder and its implementation using biological data obtained from amplicon sequencing of human skin swab specimens and oral rinses from healthy individuals. Conclusions: PVAmpliconFinder identified putative new HPV sequences, including one that was validated by wet-lab experiments. PVAmpliconFinder can be easily modified and applied to other viral families. PVAmpliconFinder addresses a gap by providing a solution for the analysis of NGS amplicon sequencing, increasingly used in clinical research. The PVAmpliconFinder workflow, along with its source code, is freely available on the GitHub platform: https://github.com/IARCbioinfo/PVAmpliconFinder.

Background: Mucormycosis is a rapidly progressive and often fatal invasive fungal infection in immunocompromised patients. Diagnosis remains challenging because microscopy and culture have limited sensitivity, while targeted molecular assays may fail to detect uncommon Mucorales species. Case Presentation: We report a fatal case of disseminated Mucor indicus infection with pulmonary and cerebral involvement in a heart transplant recipient receiving immunosuppressive therapy and posaconazole prophylaxis. Initial microscopy of bronchial secretions demonstrated broad pauciseptate hyphae consistent with Mucorales, whereas targeted PCR assays remained negative. Species identification was subsequently achieved by culture, MALDI-TOF mass spectrometry, and internal transcribed spacer (ITS) sequencing. Following neurological deterioration, brain biopsy confirmed cerebral involvement histopathologically, and ITS sequencing detected M. indicus. Comparative DNA- and RNA-based metagenomic sequencing identified Mucorales sequences, although read abundance remained unexpectedly low despite extensive histopathological fungal burden. Nevertheless, independent mapping of metagenomic reads against databases comprising all genomic viral and fungal reference sequences readily identified Mucor indicus as the sole pathogen receiving significant scores. Conclusions: This case illustrates that targeted Mucorales PCR may fail to detect an uncommon species despite evidence of invasive fungal infection. Microscopy, culture, histopathology, ITS sequencing, and comprehensive metagenomic analyses provided complementary evidence for disseminated Mucor indicus infection. Integrated diagnostics combining histopathology, culture, and complementary molecular methods remain essential for accurate diagnosis of invasive mucormycosis.