Lecture 16: DNA Viruses PDF

Lecture 16 DNA viruses  Deoxyriboviruses of medical importance Herpesviridae Papillomaviridae Adenoviridae Parvoviridae Hepatitis B virus Polyomaviridae Poxviridae  Herpesviridae Double stranded DNA, linea...

Lecture 16 DNA viruses  Deoxyriboviruses of medical importance Herpesviridae Papillomaviridae Adenoviridae Parvoviridae Hepatitis B virus Polyomaviridae Poxviridae  Herpesviridae Double stranded DNA, linear genome Latent infection: the viral Icosaedric capsid, 150 nm genome is maintained silently Enveloped viruses (fragile viruses) in the infected cell, replicating at each cell cycle Medical Microbiology, Murray- 9th Edition  Virus Primary Target Cell Site of Latency Means of Spread Alphaherpesvirinae Herpes simplex type 1 Mucoepithelial cells Neurons Close contact Herpes simplex type 2 Mucoepithelial cells Neurons Close contact (STD) Mucoepithelial and T Respiratory and close Varicella-zoster virus Neurons cells contact Betaherpesvirinae Several cell types Close contact (STD), including monocytes, Monocytes, myeloid Cytomegalovirus transplants, epithelial cells, stem cells congenital endothelial cells HHV-6 Lymphocytes T cells Saliva HHV-7 Lymphocytes T cells Saliva Gammaherpesvirinae B cells and epithelial Epstein-Barr virus B cells Saliva (kissing disease) cells Human herpesvirus 8 Lymphocytes B cells Close contact (sexual) Medical Microbiology, Murray- 9th Edition  Gene expression in herpesviruses Zabierowski et al. 2005  Viral infection -Herpersviridae  Productive infection: virus infects sensitive and permissive cells with production of viral particles. Expression of immediate early, early and late genes  Abortive infection: cells are sensitive but not permissive -> production of immediate early genes only, but incomplete viral replication  Latent infection: the viral genome is maintained silently in the infected cell, replicating at each cell cycle. Viral genome in episomal form or integrated into the cellular genome. The only region of the genome to be transcribed generates the latency-associated transcripts → these RNAs are not translated into protein but encode micro-RNAs that inhibit expression of immediate early and other genes  VZV Sensory ganglia EBV HSV-1, HSV- 2 B cells Sensory ganglia HHV8 Latency sites B cells CMV Monocytes Bone marrow progenitors Herpes Simplex virus type 1 and type 2 (HSV-1 and HSV-2) Considerable homology between the HSV-1 and HSV-2 genomes - eleven glycoproteins of HSV (gB, gC, gD, gE, gG, gH, gI, gJ, gK, gL, and gM) - antigenic specificity by gG : the resulting antibody response allowing for the distinction between HSV-1 (gG-1) and HSV-2 (gG-2) As an enveloped virus, HSV is very labile and is readily inactivated by drying, detergents Cause characteristic mucocutaneous lesions with clustered vesicles Latency site: the sensory neurons (mainly trigeminal ganglia for HSV-1, sacral ganglia for HSV-2) Transmission route of HSV-1 and HSV-2 HSV-1 and HSV-2 are ubiquitous Exclusive human disease The infected person is a lifelong source of contagion HSV is transmitted by vesicle fluid, saliva, and genital secretions (close contacts, sexual contacts) HSV-1 is spread by oral contact (kissing) or through the sharing of saliva on contaminated items; can be transmitted by sexual contact HSV-2 is spread by sexual contact Pathogenesis of HSV-1 and -2 infection HSV initiates infection through the mucosal surfaces or breaks in the skin (mucocutaneous lesions, primary infection) Retrograde transport from the mucous membranes to the ganglia → establishment of latency A recurrence can be activated by various stimuli (e.g., stress, trauma, fever, sunlight, immunosuppression) Reactivation (recurrent infection): anterograde transport from the ganglia to the initial site of infection and productive infection Clinical signs of HSV-1 and HSV-2 infection HSV-1 and HSV-2 cause painful, but often benign and recurrent lesions HSV-1 - Oral lesions (herpetic gingivostomatitis, herpes labialis) - Genital herpes - Rarely: ocular infections (herpetic keratitis) and cerebral infections: herpetic encephalitis - Disseminate infections in immunosuppressed patients Infected people may experience recurrent mucocutaneous HSV infection (herpes labialis, cold sores, fever blisters)  Clinical signs of HSV-1 and HSV-2 infection HSV-2 - Genital herpes - Recurrent genital HSV disease is shorter in duration and less severe than the primary episode - HSV-2 meningitis (Mollaret meningitis) may be a complication of genital HSV-2 infection  HSV infection in neonates Herpes genitalis in pregnant women is the main risk for neonatal herpes Transmission frequently occurs during delivery Primary maternal infection: transmission in 30-50% of cases Reactivated maternal infection: transmission in 1-5% of cases HSV infection in the neonate is a devastating and often fatal disease HSV disseminates to the liver, lung, and other organs, as well as to the central nervous system (CNS) Vesicular lesions may or may not be present Progression of the infection to the CNS results in death, mental retardation, or neurologic disability  Diagnosis of HSV infection Virus isolation (liquid from vesicles, CSF) Genome Detection by PCR (liquid from vesicles, crusted lesions, CSF, blood) - Has replaced culture in diagnosis of active infection - High sensitivity, can differentiate HSV-1 and HSV-2 Serology Cytopatic effect on Vero cells (1-3days) - very limited use - only to identify a primary infection (seroconversion) Treatment of HSV-1 and HSV-2 infection Acyclovir Valacyclovir Famciclovir Nucleoside analogs Inhibit the viral DNA polymerase, an enzyme essential for viral replication The prototype anti-HSV drug is acyclovir (ACV). Valacyclovir (the valyl ester of ACV), and famciclovir are related to ACV in their mechanisms of action but have different pharmacologic properties The drugs are ineffective against latent virus  Varicella Zoster Virus (VZV) Varicella or Herpes Zoster or chickenpox shingles Primary infection Reactivation VZV establishes a latent infection in sensory ganglia Epidemiology and transmission of VZV infection Ubiquitous virus (>90% of individuals in low-resource countries have specific antibodies) VZV is extremely communicable, with rates of infection exceeding 90% among susceptible household contacts Spread principally by the respiratory route, but may also spread through contact with skin vesicles  Pathogenesis of VZV infection VZV spreads predominantly by the respiratory route and, after local replication of the virus in the respiratory tract, it disseminates (viremia) and reaches the skin →skin lesions over the en re body sensory ganglia Zerboni et al. Nature Reviews Microbiology volume 12, 197–210 (2014)  Clinical Syndromes caused by VZV Varicella (chickenpox) - childhood exanthem - fever and a diffuse rash formed by vesicles →pustules →crusts VZV is localized at the skin level VZV infection in immunocompromised patients or neonates can result in disseminated and potentially fatal disease  Clinical Syndromes caused by VZV Herpes zoster or shingles -Recurrence of VZV infection develops in 10% - 20% of the population infected with VZV, and the incidence rises with age - Severe pain in the area innervated by the affected nerve preceed the appearance of lesions (vesicles) -A chronic pain syndrome (postherpetic neuralgia) can persist for months to years in as many as 30% of patients  Rates* of zoster and postherpetic neuralgia (PHN)¶ by age - United States A decline in VZV-specific cell-mediated immunity rather than humoral immunity, is regarded as the major precipitant factor for VZV reactivation 30 to 40 percent of persons above 55 years do not have any detectable VZV-specific T- cells Among those who develop herpes zoster, robust VZV cell-mediated immunity at the onset of rash is correlated with reduced severity of disease and less risk of PHN * Per 1000 person-years. ¶ Defined as ≥30 days of pain.  Treatment, Prevention, and Control of VZV infection Acyclovir for adults and immunocompromised Valacyclovir patients with VZV infections and for Famciclovir patients with shingles There is no good treatment for the postherpetic neuralgia that follows zoster A live attenuated vaccine for VZV (Oka strain) has been licensed and is administered after 1 years of age - The vaccine induces production of protective antibody and cell-mediated immunity Zoster immunization (with live attenuated or recombinant vaccine) is associated with a boost in VZV-specific T-cell immune responses, contributing to preventing or attenuating disease  Human cytomegalovirus (CMV) CMV is a member of the subfamily Betaherpesvirinae Contains > 200 ORF, but only one- quarter is committed to replication 151 ORF are immunogenic for CD4+ and CD8+ T cells CMV-specific T cell responses are Infects only humans typically robust Fibroblasts, epithelial cells, CMV-specific T cell responses involve endothelial cells, macrophages approximately 10 percent of CD4+ and are permissive for CMV CD8+ memory cells within the replication peripheral blood of CMV-seropositive Latency in myeloid cells individuals Although usually causing mild or asymptomatic disease in children and adults, CMV can cause severe disease in immunocompromised patients and in those with immature immune system (foetuses) CMV is a common human pathogen Seroprevalence studies City Country % Albany USA (New York) 45 Paris France 47 Melbourne Australia 54 Bologna Italy 70 St. Petersburg Russia 78 Buenos Aires Argentina 81 Moscow Russia 81 Jerusalem Israel 85 Punjab India 87 Hong Kong China 94 Esperito Santo Brazil (South-Eastern) 98 Manila Philippines 100 Fajara the Gambia 100 Entebbe Uganda 100  Transmission of CMV Foetus Newborn Intrauterine At birth Vertical transmission Pregnant woman Transplant patients Transplanted CMV organ/Transfusions Sexual Transmission through transmission saliva (children) (adults) Immunopathogenesis of CMV infection Inflammation Inhibits MHC -I ad II expression Inhibit phagocyte function and cell Evade NK cell migration killing Viral homologue of IL-10 Inhibits proliferation Causes polyclonal of T cells activation of B cells Cytomegalovirus infection: different virulence at different age /condition of the immune system CMV Disease Congenital CMV infection Primary infection Vertical or HIV transmission Asymptomatic or mononucleosis Asymptomatic infection Maternal immunity reduce the risk of transmission of infection by 70% Maternal immunity CMV-SERONEGATIVE CMV-SEROPOSITIVE MOTHER MOTHER % transmission to 30 - 50 0.5 – 1.00 foetus % symptomatic new borns 10-115 2 - 55 % sequelae 110 1 - 44  Congenital CMV infection The most common congenital infection in high-income countries Increased incidence in the last 5 decades in the UK (Kadambari et al. Lancet Infect Dis 2020) It develops in 0.3% -2% newborns (0.64% global prevalence) 17–20% chance of serious long-term effects in infected children One of the main causes of hearing loss in children Second only to Down syndrome as a cause of mental retardation Highest risk of symptomatic CMV infection if mother is infected in the first trimester of pregnancy Clinical signs of congenital CMV infection Non-neurological signs: Intrauterine growth retardation preterm delivery hepatosplenomegaly jaundice trombocytopenia anemia Neurological signs: hypotonia lethargy convulsions intracranial calcification hearing loss  Clinical signs of CMV infection in immunocompromised patients (CMV disease) Almost every organ can be affected by CMV: - Liver (hepatitis) - Lungs (pneumonia) - Central nervous system (meningoencephalitis) - Gastrointestinal system (esophagitis, colitis) - Kidneys - Eyes (retinitis)  Does cytomegalovirus play a causative role in the development of various inflammatory diseases and cancer? - Enhancing inflammation - Oncomodulation - Immunosuppressive tumor microenvironment (TME) - Tumor growth is promoted by affecting cellular proliferation and survival, immune evasion and immunosuppression, and giving rise to angiogenic factors - CMV strains isolated from primary breast cancer exhibit a slow growing high risk phenotype that could transform normal mammary epithelial cells (Nehme et al eBioMedicine 2022) Söderberg-Nauclér C Journal of Internal Medicine, Volume: 259, Issue: 3, Pages: 219-246,  Laboratory diagnosis of CMV infection Genome Detection A rapid, sensitive diagnosis can be obtained by detection of the viral genome, using PCR in cells of a biopsy, blood, bronchoalveolar lavage, urine sample, saliva, CSF Useful for diagnosis of congenital CMV infection (urine, saliva) Useful for diagnosis of CMV infection in immunocompromised patients (peripheral blood, viral load is calculated by quantitative PCR) Serology Titers of CMV-specific IgM antibody is high during primary infection However, CMV-specific IgM antibody may also develop during the reactivation of CMV Useful in diagnosis of maternal infection (prenatal screening) Maternal CMV serology should be performed in the first trimester of pregnancy, as congenital CMV sequelae are limited to maternal infection acquired in the first trimester  Epstein-Barr Virus (EBV) Coding for 100-200 proteins replicates in B cells and epithelial cells causes latent infection in memory B cells can stimulate and immortalize B cells (in vitro): oncogenic virus  Epidemiology and transmission of EBV infection EBV is ubiquitous (80-90% seropositive adults) Oral route (saliva) More than 90% of EBV-infected people intermittently shed the virus for life, even when totally asymptomatic  Pathogenesis of EBV infection-1  Oropharyngeal epithelial cells are permissive for viral replication  Infection of B lymphocytes typically results in latent infection  Latent infection is characterized by persistence of the viral genome along with expression of a restricted set of latent gene products (LMP-1, EBNA), which drive cellular proliferation and contribute to the transformation process  Pathogenesis of EBV infection -2 EBV in saliva infects epithelial cells and then naïve resting B cells in the tonsils Viral replication promotes virus shedding into saliva and establishes a viremia to spread the virus to other B cells Latent virus promotes B cell replication EBV-infected latent B cells should be considered oncogenically transformed since they will proliferate indefinitely when cultured in vitro (immortalized cell lines) The B cell outgrowth is controlled by a T-cell response to B-cell proliferation and to EBV antigenic peptides (up to 80% of total white Atypical T-cells characteristic of blood cell count are atypical lymphocytes = infectious mononucleosis mononucleosis) Pathogenesis of EBV infection Primary infection Teenagers / Young In childhood adults Asymptomatic 50% symptomatic infection infection Infectious mononucleosis “ kissing disease” Latent infection  Clinical signs of EBV infection self-limiting lymphoproliferative disorder  Consequences of EBV infection EBV is a recognized oncogenic agent Epstein-Barr Virus–Induced cancers: Endemic Burkitt lymphoma (sub-saharan Africa) B-cell lymphomas in patients with immunodeficiencies Hodgkin’s disease Nasopharyngeal carcinoma (certain regions of Asia) Co-factors are necessary for the development of cancer: - malaria contribute to the development of Burkitt lymphoma (sub- Saharan Africa) - HIV infection/immunosuppression -genetics/food co-factors for development of nasopharyngeal carcinoma in China Endemic Burkitt lymphoma 41 Laboratory course of EBV mononucleosis Comparsa e evoluzione nel tempo dei marker sierologici di EBV EBV – IgM EBV-IgG EBNA IgG EBNA (EBV nuclear antigen) Generation of antibody to EBNA indicates resolution of the active infection Onset Acute Past EBNA, Epstein-Barr nuclear antigen  Laboratory diagnosis of EBV infection The diagnosis is usually serological -EBV-specific serologic tests Active/Primary EBV infection is indicated by the finding of the following: (1) the presence of anti-EBV IgM antibody ± anti-EBV IgG (2) the absence of EBNA antibody Nucleic acid amplification tests (quantitative PCR) are available to detect EBV infection in immunocompromised patients (peripheral blood)  Oncogenic viruses (oncoviruses) Implicated in A large number of the world’s Viruses that can approximately population harbors oncoviruses, cause cancer 12% of all only a small proportion of these human cancers individuals develop cancer One or more additional Oncogenic viruses do not factors, such as chronic kill their host cell, inflammation, Viral cancers develop instead they establish environmental 15–40 years after long-term persistent mutagens, or establishment of infections that may immunosuppression, are chronic infection cause cancer required for cancer development J Clin Med. 2017 Dec; 6(12): 111 doi: 10.3390/jcm6120111  Oncogenic viruses (oncoviruses) -2 Oncogenic DNA viruses include EBV, hepatitis B virus (HBV), human papillomavirus (HPV), human herpesvirus-8 (HHV-8) Oncogenic RNA viruses include, hepatitis C virus (HCV) and human Viruses are an absolute T-cell lymphotropic virus-1 (HTLV-1) requirement for oncogenesis in Kaposi sarcoma (HHV8) and cervical cancer (HPV) J Clin Med. 2017 Dec; 6(12): 111 doi: 10.3390/jcm6120111  Human Papillomavirus (HPV) Belongs to the Papillomaviridae family Double-stranded circular DNA genome Icosaedric capsid, 50 nm Non-enveloped virus Epitheliotropic viruses: cause of cutaneous and mucosal lesions Some types of HPV are oncogenic → responsible for some cancers (including cancer of the uterine cervix) L1 L2 Papilloma virus: Early and late viral proteins  Epidemiology and transmission of HPV infection  Virus is acquired by - Close direct contact (skin lesion) - Indirect contact, fomites (skin lesions) - Sexual transmission (anogenital lesions)  Ubiquitous viruses, found worldwide: up to 50-80% of sexually active subjects are infected by HPV during lifetime  HPV is likely the most prevalent sexually transmitted infection in the world  Epidemiology of HPV-associated cervical cancer Cervical cancer is the fourth cause of cancer death in women worldwide 300,000 deaths / year Cervical cancer remains the leading cause of cancer death in women in low resource countries, by contrast with being the 19th most common cause in Finland (a high-resource country) The Lancet Global Health 2020 8e191-e203DOI: (10.1016/S2214-109X(19)30482-6)  Geographical distribution of world age- standardized incidence of cervical cancer by country The Lancet Global Health 2020 8e191-e203DOI: (10.1016/S2214-109X(19)30482-6) Ever in lifetime cervical cancer Figure 2 screening coverage in women aged 30–49 years in 2019 by country The Lancet Global Health 2022 10e1115-e1127DOI: (10.1016/S2214-109X(22)00241-8) The Lancet Global Health 2022 10e1115-e1127DOI: (10.1016/S2214-109X(22)00241-8)  Viral infection - Papillomaviridae  Productive infection: virus infects sensitive and permissive cells with production of viral particles. Expression of early and late genes  Abortive infection: cells are sensitive but not permissive with production of early viral products, but incomplete viral replicative cycle https://www.drugs.com/health-guide/human- papillomavirus-hpv.html  Pathogenesis of HPV infection HPV infects the squamous epithelium of Other epithelial cells do not support a skin and mucous membranes and productive infec on→risk of cancer induce epithelial proliferation (warts progression and papilloma)  Carcinogenesis in the uterine cervix It is becoming clear that ectocervical cells are permissive and can support productive infection, whereas cells of the endocervix are non-permissive, leading to abortive but persistent infection and a higher risk of carcinogenesis The longer a high-risk HPV infection persists, the greater the risk of pre-cancer and cancer Tumour Virus Research Volume 11, June 2021, 200213 PAPILLOMAVIRUS: ONCOGENIC VIRUS E2 expression leads to virus replication in permissive cells In nonpermissive cells blocking E2 expression in nonpermissive cells leads to inhibition of virus replication and contribute to progression to cancer EPISOMAL DNA MIXED DNA INTEGRATED DNA  Cancer transformation Blocking E2 expression leads to activation of E6 and E7 E6 and E7 are multifunctional proteins that can increase cell survival by interfering with tumour suppressor activity  Role of E6 and E7 in oncogenesis  P53 and retinoblastoma unchecked cellular protein (pRb)=tumor cycling →accumulation suppressors of mutation Inhibition of apoptosis https://doi.org/10.3390/ijms23073483 Carcinogenesis in the uterine cervix HPV infection occurs with a break in the epithelium so that HPV can infect basal cells HPV infection is usually transient (90% infection clear within 3 years) In most women, there is a 10- to 20-year gap between HPV infection and cancer development  Clinical Syndromes Associated with Papillomaviruses Human Papillomavirus Types Syndrome Common Less Common Cutaneous Syndromes Skin Warts Plantar wart 1 2, 4 Common wart 2, 4 1, 7, 26, 29 Flat wart 3, 10 27, 28, 41 Mucosal Syndromes Benign Head and Neck Tumors Low risk types Laryngeal papilloma 6, 11 — Oral papilloma 6, 11 2, 16 Anogenital Warts 6, 11 1, 2, 10, 16, 30, 44, 45 Condyloma acuminatum Cervical intraepithelial High risk types 31, 33, 35, 39, 45, 51, 52, 56, neoplasia, cervical cancer, 16, 18 58, 59, 66, 68, 69, 73, 82 other cancers Clinical signs caused by HPV infection Tissue tropism and disease presentation depend on the HPV type Cutanous syndromes: Warts  A wart is a benign self-limited proliferation of skin  Infects keratinized surfaces, usually on the hands and feet  Caused by low-risk HPV types Diagnosis is clinical Clinical signs caused by HPV infection Mucosal syndromes Anogenital Warts (condylomata acuminata) -occur almost exclusively on the squamous epithelium of the external genitalia and perianal areas and are more common in promiscuous individuals -caused by low risk HPV types (mainly HPV6 and 11) Clinical signs caused by HPV infection  High-risk HPV types (such as HPV16 and 18) associated with - cervical carcinoma - oropharyngeal cancer - penile cancer - anal cancers HPV is present in 99.7% of all cervical cancers, with HPV-16 and HPV-18 in 70% of them  Laboratory diagnosis of HPV infection  Genome detection Real-time PCR tests of cervical swabs and other tissue specimens are the methods of choice for establishing the diagnosis and typing of the HPV infection  Papillomaviruses do not grow in cell cultures and tests for HPV antibodies are not useful endocervical brush  Prevention of cervical cancer: screening strategies Cell samples for cervical cytology and human papillomavirus (HPV) testing are obtained using endocervical brush during the speculum examination HPV molecular test (PCR) disposable vaginal speculum Conventional Pap smear cervical cytology test  Prevention of HPV-related cancer: vaccine Subunit vaccine -HPV vaccines are prepared from virus- like particles (VLPs) produced by recombinant technology - Viral like particles -> combine safety of subunit vaccines with efficacy of live attenuated vaccines - Purified L1 protein self- assembles to form empty shells that resemble HPV virions  Prevention of HPV-related cancer: vaccine Three different vaccines have been developed:  Quadrivalent HPV vaccine (Gardasil) targets HPV types 6, 11, 16, and 18  9-valent vaccine (Gardasil 9) targets the same HPV types as the quadrivalent vaccine (6, 11, 16, and 18) as well as types 31, 33, 45, 52, and 58  Bivalent vaccine (Cervarix) targets HPV types 16 and 18  Routine HPV vaccination should be initiated at age 11 or 12 years for both boys and girls  Continued cervical cancer screening of vaccinated patients is needed