Tumour Viruses and Carcinogenesis (UCL)

UCL Cancer Institute Faculty of Medical Sciences Tumour Viruses and Carcinogenesis Dr Thiru Surentheran [email protected] MSc Cancer 2 Part 1 Virus-host interactions Learning Outcomes Following this topic, students should be able to: • Understand the nature of viruses and how they inte...

UCL Cancer Institute Faculty of Medical Sciences Tumour Viruses and Carcinogenesis Dr Thiru Surentheran [email protected] MSc Cancer 2 Part 1 Virus-host interactions Learning Outcomes Following this topic, students should be able to: • Understand the nature of viruses and how they interact with the host cells • Understand what viruses have taught us about oncogenes/tumour suppressor genes and the oncogenic process 3 4 The nature of viruses • Small intracellular parasites with a diameter of <200nm • Virus particles contain either RNA or DNA • Single / double stranded genomes • Viruses depend on the host cells that they infect to reproduce • Diverse structures and replication strategies CD4+ T-lymphocyte releasing HIV particles 5 Viruses and acute diseases Smallpox virus Ebola virus Coronavirus Influenza virus Rabies virus Viruses and malignant diseases Polyomavirus Epstein-Bar Virus(EBV) Becoming prominent in both male and female Human Herpes Virus 8 Human Papilloma Virus (HHV8) (HPV) head/neck cancers 6 Hepatitis B Virus (HBV) only retrovirus that causes malignancy Human T Cell Lymphotropic/ Leukaemia Virus 1 (HTLV-1) Virus-host interactions 7 • Viruses show diverse specificity to host cells • Viruses interact with many cellular pathways to achieve their replication cycles • Small genome viruses need to activate the host cell life - limited genes so they need to activate host cycle e.g. polyoma, HPV, HBV Compact machinery • Large viral genomes encode more enzymes for themselves almost independently e.g. herpes viruses function interact with tumour surpressor genes (eg p53, PRB) • Viral proteins associate and inhibit cellular proteins that have antiviral functions 8 Consequences of viral infections • Most acute infections result in cell death and subsequent virus clearance by the host • In persistent infections – slow release of virions by budding • In latent viral infections - no new virus production (no viral DNA replication) • Virus integration - some viral proteins drive the cells for proliferation. No cell death and opportunity to become cancer cells Persistant infections needed for the transformation process as it is a very long process Can lead to the integration of virus in the human genome eg herpes 9 DNA tumour viruses • Need to activate S phase of cell cycle to replicate viral DNA in the nucleus • Full replication  cell death Not ideal for the virus either • Defective virus keeping ‘early’ genes eg E6 E7 that bind to p53  cell transformation • Non-permissive cell only expressing ‘early’ genes  cell transformation • In tumour cells, viral genomes often integrate into host DNA: Papilloma, Polyoma & HBV Genes involved in cancer 10 Many of these genes were discovered first in relation to oncogenic viruses, e.g. p53 in 1979 from SV40 polyoma virus infection. Viral oncogenesis • DNA viruses negate tumour suppressors Blind to proteins as a cellular target - don’t directly activate oncogenes • RNA viruses activate oncogenes directly 11 RNA tumour viruses (Retroviruses) Retroviruses have given molecular stranded DNA to integrate into the biologists: double human genome via integrate enzyme Except hepatitis C - they are retroviruses • Reverse transcriptase to make cDNA Protease for cleaving • Oncogenes • Vectors for gene therapy They have also given humans: • AIDS HDLV1 causes leukaemia as • Leukaemia well as neurological disease • Neurological disease • ~8% human DNA (viral genomes integrated into germ-line and hence inherited) Adapted from Eckwahl et al., 2016 12 13 Salient discoveries of Retroviruses Sarcoma in chicken extracted and injected into other chickens Rous sarcoma virus* 1911 P Rous In vitro transformation 1958 H Temin & H Rubin Retroviral oncogene src 1969 PK Vogt & S Martin Reverse transcriptase* 1970 HM Temin & D Baltimore Host origin of oncogenes* 1976 H Varmus & JM Bishop cultures Rous’s original tumour Human T-cell Leukaemia Virus(HTLV-1) 1980 RC Gallo Human Immunodeficiency Virus(HIV)* 1983 F Barré-Sinoussi & L Montagnier Retroviral vectors: first use in human gene therapy 2003 A Fischer *Discovery recognised by Nobel Prize Retroviruses 14 v-onc is viral oncogene C-onc is host oncogene Can immediately transform the host cell - but can’t replicate A Replicating viruses without v-onc - a long incubation period before disease because many millions of host cells will be infected for one integration to occur adjacent to a cellular (c-onc) gene. Enhancer sequencers or promoters in the long terminal repeat (LTR) then activate the c-onc gene. B Acutely transforming retroviruses carry v-onc genes that can immediately transform the infected host cell, but they are usually defective for replication because the vonc disrupts viral genes. For infectious spread, a replication-competent virus is also needed to complement the missing functions. Oncogene discovery via Retroviruses • Retroviruses have hijacked v-oncs from c-oncs • >50 oncogenes in animal retroviruses • Examples of cellular oncogenes first discovered in retroviruses: src, myc, erb-B (avian retroviruses) ras, Abl1, fos (murine retroviruses) 15 Cancer activation pathways * Growth factors PDGF Cell surface receptors PDGRF EGFR viral genes * * Non-Receptor Tyrosine kinases Src, Abl Serine/Threonine kinases Mos, Akt Lipid kinases Pi3K * * first discovered through oncogenic virus research 16 What viruses have taught us? Concepts in cancer biology were advanced by research on viral oncogenesis: • Cellular origins of viral oncogenes • Genetic basis of cancer • Multistep carcinogenesis • Positive and negative regulatory genes as cancer genes proto-oncogenes and tumour suppressor genes • Unification of molecular basis of cancer 17 Summary 18 • Viruses cause acute lethal infections and malignancies • Viruses have diverse replication strategies • Some DNA viruses or retroviruses can induce transformation in cells • Oncogenic viruses have given us much insight into cancer through the discovery of oncogenes and tumour suppressor genes UCL Cancer Institute Faculty of Medical Sciences Tumour Viruses and Carcinogenesis Dr Thiru Surentheran [email protected] MSc Cancer 2 Part 2 Human oncogenic viruses Learning Outcomes Following this topic, students should be able to: • Understand the genomic structure of DNA and RNA tumour viruses • Relate tumour associated viruses to the tumour types they promote • Describe the biological functions of various viral oncogenic proteins 3 4 Infections and human cancers • Approximately 18% of human cancers are caused by infections • 27.9% of this is due to human papillomavirus (HPV) • Epstein Barr virus (EBV) causes 12.3% cases • Hepatitis C virus (HCV) and Hepatitis B virus (HBV) are responsible for 24.2% cancers • Helicobacter pylori contributes to 32% cases DNA tumour viruses: Papillomaviruses Polyomaviruses Herpesviruses Hepatitis B virus Retroviruses Hepatitis C virus Helicobacter pylori Helminths (Schistosoma hematobium) 5 Human oncogenic viruses Virus Cancers First identified Epstein-Barr virus (EBV) Nasopharyngeal carcinoma, most Burkitt’s lymphoma, some Hodgkin’s lymphoma, posttransplant lymphoma 1964 Hepatitis B virus (HBV) Hepatocellular carcinoma (liver cancer) 1965 Human T-lymphotropic virus-1 / Human T cell leukaemia virus (HTLV-1) Adult T-cell leukaemia 1980 Human immunodeficiency virus (HIV) AIDS-associated tumors via immunodeficiency (due to impaired T cell responses) Human papillomaviruses (HPV) Genital tumors & oropharyngeal carcinomas (types 16, 18 etc.), skin cancer (types 5, 8 etc.) 1983 Hepatitis C virus (HCV) Hepatocellular carcinoma (liver cancer) 1989 Kaposi’s sarcoma herpesvirus (KSHV) Kaposi’s sarcoma, primary effusion lymphoma 1994 Merkel cell polyomavirus (MCPyV) Merkel cell carcinoma 2008 6 Human papillomaviruses and cancer 405BCE: Cervical cancer is described by Hippocrates 1906: Discovery of papillomaviruses in skin warts 1943: George Papanicolaou developed cervical smear test – ‘Pap’ 1974: Fred Rapp proposed Herpes simplex virus type 2 as cause of cervical cancer 1983: Dürst … zur Hausen: A novel type of Papillomavirus DNA (HPV16) detected in HeLa cells and in cervical cancer biopsy samples. HPV-18 and other oncogenic types soon followed. History of cervical cancer 1842: Domenico Rigoni-Stern suggested a sexually transmitted factor for cervical cancer 1933-4: Richard Shope, Peyton Rous & Joe Beard: Papillomavirus causes malignant tumours in rabbits 1952: Margaret and George Gye in Baltimore developed the Hela cell line from a cervical cancer biopsy from Henrietta Lacks 1970s: Stefania Jabłonska, Gerard Orth: HPV-5 was linked to human squamous cell carcinoma in heritable EV patients 2006: HPV vaccines licensed 2008: Harald zur Hausen was awarded the Nobel Prize 7 HPV genome and life cycle HPV genome replicates outside the host DNA Virus infects primitive basal keratinocytes Adapted from Lazarczyk et al., 2009 Epithelial cell differentiation episomal replication Persistent HPV infection & cervical cancer • Some HPV infections can persist for many years e.g. HPV-16, HPV-18 • HPV infection can lead to the growth of pre-cancerous cells in the cervix - if untreated, may progress to cancer • HPV types 16 and 18 associated with 70% of cancers; the remaining 30% is caused by other types • Two of the proteins (E6 & E7) made by high-risk HPVs interfere with normal cellular functions • Molecular mechanisms of HPV oncogenesis will be covered in detail by Dr Lechner 8 Persistent HPV infection & cervical cancer Cervical cancer develops at the transition zone between squamous and columnar epithelium 9 Hepatitis viruses and liver cancer 10 • Two viruses – Hepatitis B virus (HBV) and Hepatitis Cvirus virus (HCV) RNA Double stranded DNA virus • HBV causes the most common chronic viral infection (approx. 257 millions) and the leading cause of hepatocellular carcinoma (HCC) • HCV – a virus with high mutation rate which accounts for 140 million cases worldwide, however only a minority of HCVinfected individuals develop cancer • HCC represents approximately 90% of all primary liver cancer cases • Chronic HBV and HCV infections are linked 60-70% HCCs 11 Hepatitis B virus HBV genome Biological activities of HBx Adapted from White et al., 2014 • Partially double stranded, circular DNA • 4 overlapping open reading frames (ORFs) S, P, C and X 12 Hepatitis C virus • Destruction of mature hepatocytes • Regeneration of hepatocytes from stem cells that may carry oncogenic mutations • HCV core protein has many cellular targets Schematic representation of signalling by HCV core protein Adapted from White et al., 2014 Epstein Barr virus (EBV) • First tumour virus discovered • Associated with a wide range of human cancers originating from epithelial cells, lymphocytes and mesenchymal cells • EBV causes malignancies in both immunocompetent and immunosuppressed individuals • EBV infection results in extensive methylation of both the host and viral genome, which alters cellular functions that promote viral persistence and propagation • Development of tumours are dependent on environmental factors and genetic susceptibility to viral infection - more detail in multifactorial carcinogenesis 13 14 Kaposi’s sarcoma herpesvirus (KSHV/HHV8) Genome A a large DNA γvOx-2 Herpes virus LNA-1 vCyclin vFLIP Kaposins 72 K15 vGPCR 74 73 K14 TR K1 CBP ssDBP gB 4 75 6 7 8 9 71 DR2 K12 DR1 69 68 65-67 >70 genes DNA Pol vIL-6 DHFR K2 TS K3 vMIP-II 70 K4 vMIP-III K4.1 K4.2 vMIP-I K5 10 11 K6 Tegument proteins K7 16 17 18 64 105kb Ribonucleotide reductase DNA replication protein KSHV Episome 140kb 63 62 61 19 20 21 22 23 24 60 59 Schematic representation of signalling by KSHV latencyassociated nuclear antigen (LANA) vBcl-2 Tegument protein TK gH 35kb 25 58 26 27 28 29b K11 K10.1 K10 vIRFs ? 30-33 K9 vIRF -1 57 34-38 56 29a K8.1 55 54 40 39 43 41 5352 K8 5049 48 45-47 44 42 Major capsid protein Minor capsid protein Kinase Packaging Proteins DNA replication Alkaline exonuclease gM protein Rta-like UDG Helicase-primase ZEBRA-like 70kb From Sharp & Boshoff Life, 2000 Adapted from White et al., 2014 • Causes Kaposi’s sarcoma - more detail in multifactorial carcinogenesis Adult T-cell Leukaemia (ATL) 15 Flower leukaemia cells (Jain and Prabhash, 2012) •ThatA malignancy of CD4+ CD25+ T-cells transformation usually takes around 50 years to occur but when it does, the survival isn’t very high • Mean survival from diagnosis ~5 months • Commonest adult leukaemia in Japan • Also prevalent in the West Indies and West Africa Uchiyama et al., Blood 1977: ATL cases plotted where patients were born Adult T-cell Leukaemia (ATL) and HTLV-1 16 • Caused by HTLV-1 infection decades before appearance of tumour in only ~5% infected subjects breast • Transmitted via milk and by leukocytes • Spread by blood transfusions, sexual contact and sharing needles • HTLV-1 also causes degenerative neurological disease tropical spastic paraparesis (TSP) / HTLV-1 associated myelopathy (HAM) in ~1% infected subjects, more frequent after acquisition via blood transfusion • Others are asymptomatic throughout their lives 17 Transformation by HTLV-1 Cis-activation • Animal retroviruses Cis-activation of cellular oncogenes • HTLV-1 Trans-activates host genes HBZ HTLV-1 genome Trans-activation Adapted from Matsuoka & Bangham (2017) • Viral transcription factors Tax and HBZ activate some host genes and viral LTR • HBZ may act differently to promote viral persistence A novel polyomavirus & Merkel cell carcinoma 18 Merkel Cell Polyoma virus (MCPyV) genome • An aggressive rare skin cancer of Merkel cells (sense of touch cells) • Occurs in the elderly and immunosuppressed individuals (e.g. transplant recipients and AIDS patients) • An ‘age-old’ virus of humans but not discovered until 2008 19 Biological functions of viral oncoproteins Block p53 Papilloma virus Adenovirus Polyomavirus KSHV E6 E1a Large T LANA Signal transduction HPV EBV KSHV E5 LMP-1 K1, K15, vIL-6 Sequester Rb Papilloma virus Adenovirus Polyomavirus KSHV E7 E1b Large T LANA, v-Cyclin Tyrosine kinase signalling Polyomavirus Middle T Retroviral oncogenes: Src, Abl, Erb-B Summary • Seven human tumour viruses are responsible almost 15% of the total cancer incidence • DNA viruses are oncogenic and their oncoproteins are essential for transformation (HPV, EBV, HBV, MCPyV). • Retroviruses (RNA viruses) have the oncogenes (v-onc) – these have cellular counterparts (c-onc) which can be activated to induce malignancy. • Different proteins of oncogenic viruses target common cellular pathways 20 UCL Cancer Institute Faculty of Medical Sciences Tumour Viruses and Carcinogenesis Dr Thiru Surentheran [email protected] MSc Cancer 2 Part 3 Multifactorial nature of viral tumours Learning Outcomes Following this topic, students should be able to: • Discuss the multifactorial nature that increases the risk of these viral tumours 3 4 Relative risk of viral cancer development Virus Tumour % lifetime risk of cancer among infected persons HPV Cervical Cancer ~10 HBV Hepatocellular carcinoma (HCC) ~25? HCV Hepatocellular carcinoma (HCC) ~15? HTLV-1 Adult T Cell leukaemia ~5 EBV Nasopharyngeal carcinoma Lymphoma <1 <1 KSHV Kaposi’s sarcoma (KS) ~1.4 • Is cancer a relatively rare outcome of frequent infection? • Should we regard viral cancer as a 'side effect' of viral persistence? • Which co-factors increase the chances of cancer development? Viral malignancies and co-factors • Host genetic predisposition • Immune defects • Environmental and lifestyle factors other than the virus • Bad luck (random somatic mutation) 5 Epidermodysplasia verruciformis (EV) • A rare autosomal recessive skin disease – a defect in DNA repair gene • EV patients develop keratotic skin lesions that display a high rate of progression to squamous cell carcinoma (SCC) • Persistent multiple flat lesions may become malignant on sun exposed areas 6 HPV and skin cancer • A number of HPV types found – HPV 5, 8, 9, 10, 12, 14, 15, 17, 19, 38, 47, 49, etc. - EV HPV types. • Most studied HPV types are 5, 8 and 38. • HPVs 5 and 8 are determined as potentially carcinogenic by IARC (International Agency for Research on Cancer) • A combination of factors lead to SCCs – HPV as the underlying cause, UV as the environmental carcinogen and the defective gene to form warts. 7 Liver cancer and co-factors • Aflatoxins; a group of naturally occurring mycotoxins produced by Aspergillus. It occurs on grain and groundnuts in hot humid climates. • Aflatoxin B1 (AFB1) - one of the most potent chemical liver carcinogens • 5–28% of global HCC cases are attributable to aflatoxin exposure: HBV + aflatoxin: ~5-fold greater relative risk – a potential synergistic interaction between chronic HBV infection and AFB1 exposure. 8 Burkitt's Lymphoma in children • First described by Denis Burkitt in 1958 in Uganda • Tumours in jaw during 2⁰ dentition • Boys > girls (five times) • Histology: lymphoma not carcinoma • Analysis of biopsies via cell culture resulted in the isolation of a new virus transmitted via saliva: gamma herpes virus – EpsteinBarr Virus (EBV) • Tumours are 100% positive for EBV 9 Malaria and Burkitt's Lymphoma in children • Plasmodium falciparum - the causative agent of severe malaria • Burkitt lymphoma in tropical Africa apparently associated with intense and repeated exposure to Plasmodium falciparum infections Risk factor is the parasite • Limited immunity against malaria parasite, hence the immune system is under relentless pressure in children <5 years due to changing of antigens 10 Malaria belt and Burkitt’s Lymphoma Malaria belt BL cases Possible mechanisms of Burkitt's lymphoma 11 • Extensive expansion of a monoclonal EBV-infected B cell population due to immunosuppression caused by malaria • Malaria parasite induces deregulated expression of the DNA mutating and cutting enzyme (AID) which leads to DNA damage and translocations in EBV-infected B cells • Malaria infection is another risk factor • AID-dependent C-myc translocation to Ig heavy or light chain gene loci (t8;14, 8;2 or 8;22) were found in all cases 12 Kaposi's sarcoma (KS) • KSHV / HHV8 is the primary cause • Classic KS is rare and occurs in elderly individuals; affects the skin on the lower legs and feet • Iatrogenic KS is common in immunosuppressed transplant patients. • Endemic or African Kaposi's sarcoma is common in certain parts of Africa. • The KS lesion is due to the increased proliferation of latently KSHV-infected spindle cells. Spindle cells AIDS associated Kaposi's sarcoma (AIDS-KS) • KSHV infection alone is generally not sufficient to cause KSHV-associated cancers. • KS incidence increases dramatically in HIV-infected individuals. • HIV/AIDS is a potent co-factor for KSHV oncogenesis. • Role of HIV – immunosuppression, HIV secretory proteins (HIV Tat has been found to synergise with KSHV lytic proteins to induce angiogenesis) 13 Skin lesions on AIDS patient (each lesion is probably a different clone) Immunosuppression and viral tumours 14 • Transplant recipients are at increased risk of developing viral tumours. • Most common transplant associated cancers are non-Hodgkin lymphoma (NHL), lung cancer, kidney cancer, liver cancer and nonmelanoma skin cancer (NMSC). • NHL is caused by EBV infection, and liver cancer by chronic HBV and HCV infections. • HIV/AIDS also increases the risk of cancers that are caused by EBV, KSHV, HPV, HBV and HCV. • HPV’s role NMSC has been suggested and investigated for many years – however still remains controversial. Immunosuppression and viral tumours • In the tumour cells, oncogenic viruses persist and express viral antigens • In immunocompetent individuals, the T-cell arm of the immune system recognises these foreign antigens and suppresses tumour growth. • Non-viral tumours with higher incidence in AIDS also tend to express tumour antigens, e.g. melanoma (or is there an unknown virus?) • Tumours with viral antigens tend to have better prognosis after chemo- or radio- therapy, e.g. HPV +ve versus HPV -ve oral squamous carcinoma 15 16 Relative risk due to immunosuppression Transplant Known viral tumours HIV / AIDS Kaposi’s sarcoma (KS) 310 ~50 Non-Hodgkin’s lymphoma (NHL) 110 ~34 Cervical carcinoma (HPV-16, -18) 43.4 34 Anal carcinoma (HPV-16, -18) 26 ? Other malignancies Relative risk Melanoma 1.8 4.3 Brain tumours (includes brain lymphoma?) 5.2 2.4 Testicular tumours (seminoma) 2.9 2.7 Conjunctival carcinoma (Africa) 15.8 ? (Data from IARC, 2005, Newton 2009, Pierangeli et al., 2015) Paradox: viruses with oncogenic potential Some human viruses with oncogenic potential don't cause cancer in their natural host • Adenoviruses: AdV 2, 5 & 12 Highly oncogenic in newborn rats due to E1A, E1B, E4 & E5 viral genes • Polyomaviruses: BKV and JCV in >90% of humans Highly oncogenic in baby hamsters due to large T and small t antigen transformation • HTLV-2: immortalises human T-cells in culture 17 Possible viral aetiology for human cancers Are more human oncogenic viruses to be discovered? • Epidemiology suggests an unknown virus in conjunctival carcinoma in HIV+ East Africans (Newton, 2001). HPV was linked in some studies. • Cutavirus (protoparvovirus) in cutaneous malignant melanoma (Mollerup et al., 2017). Is cutavirus a passenger or participant? 18 Known virus, new cancer associations 19 • HPV-16 in anal and oropharyngeal cancers; Anal: in women > men Oropharyngeal: in men > women Occur at squamous-columnar junction (similar to cervical cancer) • EBV: Discovered in Burkitt’s lymphoma 1964 Infectious mononucleosis 1968 Nasopharyngeal carcinoma 1972 Other lymphomas 1980s Stomach cancer 2003 Summary 20 • Oncogenic viruses persist and express viral antigens in the tumour cells • Viruses alone may not be sufficient to cause tumours • Immune deficiencies increase incidence of virus-linked cancers • New viral links to human cancers may come into light in the future UCL Cancer Institute Faculty of Medical Sciences Tumour Viruses and Carcinogenesis Dr Thiru Surentheran [email protected] MSc Cancer 2 Part 4 Treatment and prevention of viral tumours Learning Outcomes Following this topic, students should be able to: • Highlight the clinical importance of cancers caused by viruses • Discuss the strategies involved in the treatment and prevention of viral tumours 3 Global cancer burden due to infections 4 2,216,920 new cases annually = 20.6% of total cancer incidence EBV 12.3% Helicobacter pylori 32.0% HBV + HCV 24.2% HPV 27.9% This pie chart excludes the remaining 3.6%:  Adult T cell leukemia (HTLV-1)  Kaposi sarcoma and KSHV lymphomas  Merkel cell carcinoma (MCPyV)  Cancers linked to helminth infections >99% cancer of the cervix (HPV) 55% oropharyngeal cancers (HPV) 80% hepatocellular carcinoma (HBV 50%, HCV 30%) 80% gastric cancer (H. pylori) 10% gastric cancer (EBV) >99% undifferentiated nasopharyngeal carcinoma (EBV) 10% non-Hodgkin lymphoma (EBV) 30% Hodgkin lymphoma (EBV) (adapted from Parkin et al., 2006) Treatment and prevention strategies • Antiviral therapy before tumours develop • Early screening for viruses and virus-induced tumours • Screening for the virus in order to prevent transmission • Immunisation - prophylactic vaccines 5 Antiviral therapy • Anti-HBV treatment with nucleos(t)ide analogues (NAs), e.g. lamivudine, entecavir, and tenofovir improved the survival of patients with chronic HBV and reduced the incidence of HCC, however the risk for HCC persists even after long period of viral suppression • Direct acting antivirals (e.g. simeprevir, sofosbuviare) used to treat HCV – effective in >90% patients • There are no directed small molecule therapy as antivirals against EBV; clinical trials have been largely ineffective 6 7 Treatment of AIDS-KS • Anti-Cancer Cytotoxic Drugs CT scan lung images of a KS patient Adriamycin, Vincristine, etc. • Anti-Herpesviral Therapy Foscarnet, Cidofovir • Anti-Retroviral Therapy (ART) Before ART Zidovudine, Lamivudine, etc. • Significant success of ART in reducing Kaposi’s sarcoma in HIV positive patients combination of drugs for successful treatment 3 months after treatment Prevention of viral cancer by screening • Early screening for HTLV-1 and HPV • Serology (EIA; ELISA)– detection of antibodies against HTLV-1 • Endemic countries - routine HTLV-1 antenatal screening and formula feeding of babies of HTLV-1-positive mothers, which decreased the prevalence from 7·2% to 1·0% • Screening of blood donors to avoid the risk of transmission – UK and the other developed countries 8 9 Cervical Cancer Screening • National screening programme: • For women aged 25 to 49 - 3 years interval • For women aged 50 to 64 – 5 years interval • Samples (Transformation Zone) usually taken in GP practice • Most popular staining method for wet-fixed preparation is Papanicolaou technique –Pap smear (George Papanicolaou in 1940s) • If high-risk HPV types are found, further evaluation is needed Koilocytes (HPV infected cells) Prevention of viral cancer by vaccination • Successful vaccines against two viruses: HBV and HPV • HBV recombinant subunit (HBsAg) vaccine since 1986 • Protects against hepatitis, cirrhosis and liver cancer • HPV virus-like particle (VLP), a polyvalent empty capsid vaccine • Two successful HPV vaccines were licensed in 2006 • Protects against cervical, anal, oropharyngeal, vulvar, and vaginal and penile cancers 10 antibodies HBV virus-like particles HBV vaccine • 1976 -1986: plasma-derived, contained purified HBsAg (22nm VLPs) from the serum of people with chronic HBV infection - problems with safety (potential transmission of blood infections) and supply • Late 1986: yeast-derived recombinant HBsAg assembled into similar 22nm VLPs: highly immunogenic, safe, easy bulk production • 1988: mammalian cell derived VLP which also contained pre-S recombinant antigens 11 Effectiveness of HBV vaccine • According to the latest WHO estimates, the number of children <5 with chronic HBV infections has declined to below 1% in 2019 from 5% in the period of 1980-2000s. • Intervention strategies could lead to a 90% reduction in incidence of new chronic infections and 65% reduction in worldwide mortality by 2030. 12 Incidence of HBV infection in the United States, 1980 -2015 (Adapted from Schillie et al., 2018) HPV vaccine strategy • Capsid regions are largely conserved between different types • DNA virus – does not mutate much • Capsid proteins could sufficiently stimulate the long lasting humoral immunity • HPV L1 proteins are able to self assemble into VLPs • Used the knowledge from recombinant HBV virus-like particles (VLPs), which stimulated good immune response 13 HPV virus-like particles (VLPs) • VLPs stimulate protective immune response by mimicking the authentic epitopes of virions • Expression of HPV L1 recombinant protein in insect cells / baculovirus (bivalent) and yeast cells (quadrivalent) 14 Assembly of L1 and L2 monomers (Adapted from Schiller and Muller, 2015) 15 Prophylactic HPV vaccine timeline 1991: Jian Zhou & Ian Frazer described the synthesis of “empty” VLPs composed of L1 and L2 capsid proteins of HPV-16. 1992 Doug Lowy & John Schiller showed that recombinant L1 alone can generate VLPs and that they are highly immunogenic. 1993: Lowy and Schiller further showed that the anti-L1 antibodies neutralise HPV. 1998: Lowy and Schiller set up first clinical trial of prototype vaccine containing L1 VLPs composed of HPV16 and HPV-18. 2006 - 2007: Vaccines based on VLPs licensed by FDA: Merck’s Gardasil: HPV-16, -18, -6 & -11 GSK’s Cervarix: HPV-16 & -18 2014: Merck’s 9-valent Gardasil-9 introduced: Added HPV types 31, 33, 45, 52, 58 to achieve cross protection against prevalent cervical HPV types. Impact of screening and HPV vaccination • Elimination of cervical cancer prediction models (from Brisson et al., 2020). Equilibrium occurs 90–100 years after the introduction of HPV vaccination. • HPV vaccination and screening ramp-up in low-income and lower-middle-income countries: (A) average agestandardised cervical cancer incidence per 100 000 women-years, (B) relative reduction in incidence Vaccination coverage = 90% at age 9 years (and at ages 10–14 years in 2020). Vaccine efficacy = 100% against HPV-16, 18, 31, 33, 45, 52, and 58. Vaccine duration = lifetime. Screening = HPV testing. Screening uptake = 45% (2023– 29), 70% (2030–44), and 90% (2045 onwards). Screen and treat efficacy = 100%. Loss to follow-up = 10%. 16 Equilibrium occurs 90–100 years after the introduction of HPV vaccination. Future of tumour virus vaccines 17 • A number of vaccine candidates against EBV. EBV Gp340 envelope glycoprotein (protects B Cell) and gH/gL/gp45 (protects both B cells and epithelial cells in mice and monkeys) - not yet taken up by pharmaceutical industries • HTLV-1 envelope glycoprotein protects macaques and rabbits from challenge: not seen by pharmaceutical industries as a market • HCV and HIV: no efficacious vaccines yet Summary • Therapy for viral tumours involve treating the virus or cancer or both • There isn’t an effective therapy available for all tumour viruses • Vaccines and screening hold great promise to reduce global viral tumour burden • However, vaccines are not available for all tumour viruses 18