Understanding oncogenic human papillomavirus persistence and immune modulation in tonsil epithelia
Lead Research Organisation:
University of Birmingham
Department Name: Institute of Cancer and Genomic Sciences
Abstract
Viruses are obligate intracellular parasites that have evolved to manipulate the target cell and local tissue environment to facilitate replication. Some viruses can establish persistent, sub-clinical infection of target cells and these infections can evade host immune detection and exist for decades. Human papillomaviruses (HPV) are a family of viruses that infect the moist and dry surfaces of human skin. The target cell of infection is a specific type of skin cell called a keratinocyte. Infection with many different types of HPV results in the formation of warts but persistent infection with a subset of HPV types, so called high-risk HPV, is the cause of cancers of anal and genital regions of the body (including the uterine cervix), and cancers of the head and neck, specifically in the tonsils and base of tongue, collectively known as the oropharynx.
Although robust strategies exist to prevent high-risk HPV infection and to detect pre-cancerous lesions through vaccination and national cervical screening programmes, these measures are not available in all countries. Indeed, the number of HPV-associated cancers has remained at around 600,000 cases per year worldwide despite screening and vaccination. Furthermore, the incidence of HPV-driven oropharyngeal cancer is increasing in patients that are younger, predominantly male and non-smokers.
The primary site of oropharyngeal HPV infection is the tonsil, a organ rich in immune cells that serve to detect invading pathogens and prevent respiratory and gastrointestinal infection. Establishment of persistent high-risk HPV infection in the tonsil must therefore require strong suppression of local immune cell activation. The majority (greater than 90%) of HPV-positive oropharyngeal cancers are caused by HPV type 16 (HPV16). While HPV16 is also the most common HPV found in cervical cancers (~60%) the burden is much less than for oropharyngeal cancers. Another high-risk type, HPV18 accounts for ~15% of cervical cancers but is rarely found in oropharyngeal cancers. The reasons for this disparity in disease association at different body sites are not known. Our preliminary data suggest that HPV16, but not HPV18, is able to suppress the production of immune activating molecules by reprogramming gene expression of the host tonsil keratinocyte.
Using state-of-the-art primary cell-based models of HPV infection and cutting-edge DNA and gene sequencing methods, we will investigate the similarities and differences in HPV16 and HPV18 life cycles in tonsil keratinocytes. We will determine how HPV16 suppresses host immune detection through repression of key pathways that activate and attract local immune cells to the site of infection. We will then use our expertise in primary cell culture to combine primary keratinocytes with donor-matched lymphoidal tissue, which contains to tonsillar immune cells, to establish in vitro tonsil organ-like cultures that will be used to study immune cell activation and migration in response to HPV infection.
The results of this project will uncover novel mechanisms of HPV persistence in the tonsil. We will also determine the key differences in immune suppression by cancer-causing HPV16 and HPV18 and how these differences contribute to local immune cell activation and viral clearance. This is important as there is a critical need to understand how HPV16 can persist and induce cancer within the immune-rich oropharynx to enable the development of novel (immuno-) therapies to combat HPV-driven cancers.
Although robust strategies exist to prevent high-risk HPV infection and to detect pre-cancerous lesions through vaccination and national cervical screening programmes, these measures are not available in all countries. Indeed, the number of HPV-associated cancers has remained at around 600,000 cases per year worldwide despite screening and vaccination. Furthermore, the incidence of HPV-driven oropharyngeal cancer is increasing in patients that are younger, predominantly male and non-smokers.
The primary site of oropharyngeal HPV infection is the tonsil, a organ rich in immune cells that serve to detect invading pathogens and prevent respiratory and gastrointestinal infection. Establishment of persistent high-risk HPV infection in the tonsil must therefore require strong suppression of local immune cell activation. The majority (greater than 90%) of HPV-positive oropharyngeal cancers are caused by HPV type 16 (HPV16). While HPV16 is also the most common HPV found in cervical cancers (~60%) the burden is much less than for oropharyngeal cancers. Another high-risk type, HPV18 accounts for ~15% of cervical cancers but is rarely found in oropharyngeal cancers. The reasons for this disparity in disease association at different body sites are not known. Our preliminary data suggest that HPV16, but not HPV18, is able to suppress the production of immune activating molecules by reprogramming gene expression of the host tonsil keratinocyte.
Using state-of-the-art primary cell-based models of HPV infection and cutting-edge DNA and gene sequencing methods, we will investigate the similarities and differences in HPV16 and HPV18 life cycles in tonsil keratinocytes. We will determine how HPV16 suppresses host immune detection through repression of key pathways that activate and attract local immune cells to the site of infection. We will then use our expertise in primary cell culture to combine primary keratinocytes with donor-matched lymphoidal tissue, which contains to tonsillar immune cells, to establish in vitro tonsil organ-like cultures that will be used to study immune cell activation and migration in response to HPV infection.
The results of this project will uncover novel mechanisms of HPV persistence in the tonsil. We will also determine the key differences in immune suppression by cancer-causing HPV16 and HPV18 and how these differences contribute to local immune cell activation and viral clearance. This is important as there is a critical need to understand how HPV16 can persist and induce cancer within the immune-rich oropharynx to enable the development of novel (immuno-) therapies to combat HPV-driven cancers.
Technical Summary
Human papillomaviruses (HPV) can infect epithelia in the anogenital and oropharyngeal tracts and drive carcinogenesis. Certain HPV types are classed as high-risk (HR) owing to their ability to drive carcinogenesis. However, there are major differences in HR-HPV prevalence in cancers at different anatomical sites. Cervical cancer (CC) is commonly caused by HR-HPV types 16 (~60%) and 18 (~15%) but oropharyngeal squamous cell carcinoma (OPSCC) is predominantly caused by HPV16 (>90%) and rarely by HPV18 (~3%). The reasons for this discrepancy are unknown.
Preliminary findings show that both HPV16 and HPV18 successfully replicate in human tonsil keratinocytes (HTK) while HPV16 establishment, but not HPV18, results in robust transcriptional repression of host immune signalling. We therefore hypothesise that the persistence and oncogenic potential of these closely related HR-HPV types in immune-rich tonsil epithelia is dictated by the differential manipulation of host keratinocyte-immune cell interactions.
We will use cutting-edge primary HTK models that faithfully recapitulate the HPV life cycle in the oropharynx to identify and characterise key differences in HPV16 and HPV18 manipulation of immune signalling pathways. Development of these models into 3D tonsil organoids derived from donor-matched HTK and mononuclear immune cells (MNC) will allow us to unpick the specific HTK-MNC interactions at play in the tonsil and how HPV16 and HPV18 differentially manipulate these interactions. We will integrate innovative state-of-the-art technologies (long-read RNA-seq, ATAC-seq, ChIP-seq, single cell RNA-seq and digital pathology) to provide unprecedented insight into HTK-immune cell interactions in tonsil organoids.
The findings will define mechanisms of HPV16 persistence in immune-rich tonsil epithelia and will be important for the development of novel diagnostic and prognostic biomarkers and targeted therapeutics for HPV-OPSCC.
Preliminary findings show that both HPV16 and HPV18 successfully replicate in human tonsil keratinocytes (HTK) while HPV16 establishment, but not HPV18, results in robust transcriptional repression of host immune signalling. We therefore hypothesise that the persistence and oncogenic potential of these closely related HR-HPV types in immune-rich tonsil epithelia is dictated by the differential manipulation of host keratinocyte-immune cell interactions.
We will use cutting-edge primary HTK models that faithfully recapitulate the HPV life cycle in the oropharynx to identify and characterise key differences in HPV16 and HPV18 manipulation of immune signalling pathways. Development of these models into 3D tonsil organoids derived from donor-matched HTK and mononuclear immune cells (MNC) will allow us to unpick the specific HTK-MNC interactions at play in the tonsil and how HPV16 and HPV18 differentially manipulate these interactions. We will integrate innovative state-of-the-art technologies (long-read RNA-seq, ATAC-seq, ChIP-seq, single cell RNA-seq and digital pathology) to provide unprecedented insight into HTK-immune cell interactions in tonsil organoids.
The findings will define mechanisms of HPV16 persistence in immune-rich tonsil epithelia and will be important for the development of novel diagnostic and prognostic biomarkers and targeted therapeutics for HPV-OPSCC.
