Virology - 02 DNA Viruses

VIROLOGY VIRUS FAMILIES DNA VIRUSES OUTLINE • DNA Viruses o In General o Virus Families o Adenoviridae o Parvoviridae o Papovaviridae o Poxviridae o Herpesviridae o Hepadnaviridae • DNA VIRUSES Virus Family Envelope Present Capsid Symmetry Hepadnaviridae E Icosahedral Herpesviridae E Icosahedral Poxviridae E Complex Parvoviridae N Icosahedral Papovaviridae N Icosahedral Adenoviridae N Icosahedral IN GENERAL • Viral genomes contain information which: o ensures replication of viral genomes o ensures packaging of genomes into virions o alters the structure and/or function of the host cell to a greater or lesser degree Size Specific Pathogenic Viruses 42 Hepatitis B Virus nm 150- Herpes Simplex 200 Virus (HSV) nm Varicella-Zoster Virus (VZV) Cytomegalovirus Epstein Barr Virus 230- Smallpox 300 Vaccinia nm 18- B19 20 nm 45- Human 55 Papilloma Virus nm (HPV) BK polyomavirus JC polyomavirus 70- Adenovirus 80 nm ADENOVIRIDAE • • • General Rule o All are ds-DNA, Except: Parvovirus o All are icosahedral, Except: Poxvirus(COMPLEX) o All are enveloped, Except: Papovavirus, Adenovirus, Parvovirus o All multiply in nucleus, Except: Poxvirus (cytoplasm) o Largest is Poxvirus while smallest is Parvovirus • • These are naked icosahedral viruses with double stranded linear DNA Can cause a variety of upper and lower respiratory tract diseases like pharyngitis, conjunctivitis and pneumonia May cause gastroenteritis in children MOT - droplets, the fecal-oral route or fomites PARVOVIRIDAE • • • • Very small naked viruses, with single stranded linear DNA B19 virus causes FIFTH DISEASE or ERYTHEMA INFECTIOSUM B19 virus replicates in immature erythroid cell slapped cheek rash PAPOVAVIRIDAE • • • • • • these are naked viruses with double stranded circular supercoiled DNA PAPOVA is an acronym for Papilloma, Polyoma and Vacuolating Viruses Papilloma ( HPV) Polyoma ( BK virus and JC virus ) Vacuolating Virus ( Simian Vacuolating virus ) Human Papillomavirus (HPV) o HPV-1 - Plantar Warts o HPV-2 and 4 - Warts of the Hand o HPV-6 and 11 - Genital Warts o HPV 5 and 8 - Epidermodysplasia verruciformis o HPV 13 and 32 - Hecks’s Disease o HPV-16 and 18 - Cervical Cancer o HPV-16 - Subset cancer of oropharynx and penile cancer in men o HPV 41-42 -Genital Warts o HPV 3, 10 - Flat cutaneous warts o HPV 6,11,42,43,44, 55 and more - Anogenital warts POXVIRIDAE • • • • • These are the largest, brick shaped or ovoid viruses, envelope has an unusual appearance. The most complex of all viruses Small Pox Virus – also called Variola Virus, the agent of small pox Vaccinia Virus Molluscum Contagiosum – causes small , pink, wart like benign tumors of the skin, seen on genitals or body extremities EPSTEIN BARR VIRUS • • • • HERPESVIRIDAE HERPES SIMPLEX VIRUS ( HSV1 & HSV2) • • • • • • • • • these are enveloped viruses with double stranded linear DNA generalities about herpesviridae: o they can develop a latent state o cytopathic effect o herpesviridae are held at bay by the cell mediated immune response Herpes Simplex Virus 1 (HSV-1) – cause acute gingivostomatitis, recurrent herpes labialis/cold sore or fever blisters, keratoconjunctivitis, encephalitis Herpes Simplex Virus 2 (HSV2) – causes genital herpes, neonatal herpes, aseptic meningitis HSV -1 is transmitted via respiratory secretions and saliva while HSV-2 is transmitted thru sexual contact, perinatal infection Specimen for diagnosis: lesions or conjunctival scrapings Direct examination of virus can be made by: EM, PAP’s smear, DFA, Indirect Fluorescence Serologic tests not helpful because antibodies against HSV-1 and 2 cannot be differentiated and uninfected individuals may possess the antibody HHV-6 – known to infect T-lymphocytes; may cause EXANTHEM SUBITUM or ROSEOLA also known as 6th DISEASE VARICELLA –ZOSTER VIRUS • • • • Causes chicken pox Zoster can cause Shingles Transmitted by : a) respiratory droplets b) direct contact with lesions Diagnosis is made based on clinical signs CYTOMEGALOVIRUS (CMV) • • • • • • Causes cytomegalic inclusion disease in neonates It is also the cause of pneumonia in ummunocompromised patients and heterophile negative mononucleosis Transmitted by a variety of modes : a) across the placenta and in mother’s milk b) via the saliva in young children c) transmitted sexually d) blood transfusion and organ transplant Repeated contact with the virus is necessary for infection The virus can remain latentin WBC’s, endothelial cells and other organs May reveal the characteristic “ owl eye’s “ appearance Causes infectious mononucleosis, associated with Burkitt’s lymphoma, other B-cell lymphomas and nasopharyngeal carcinomas Infects mainly lymphoid cells Transmitted by exchange of saliva, causes “kissing disease mononucleosis” Diagnosis is based on 2 approaches: o hematologic approach o immunologic approach ▪ heterophile antibody test ▪ monospot test ▪ EBV specific antibody test HEPADNAVIRIDAE VIRAL HEPATITIS • • • • • • RNA Viruses : Hepatitis A Virus ( HAV ) ; Hepatitis C Virus ( HCV ) ; Hepatitis D Virus ( HDV ) ; Hepatitis E Virus ( HEV ) ; Hepatitis E Virus ( HEV ) DNA Virus : Hepatitis B Virus ( HBV ) Transmission : Remember the code “ ABCDE “ Types of Viral Hepatitis : o acute o chronic Disease states caused by HBV: o Acute hepatitis o fulminant hepatitis o Chronic ( asymptomatic carrier ; chronic persistent hepatitis ; chronic active hepatitis) o Co-infection with HEPATITIS DELTA VIRUS ( HDV ) Complication of viral hepatitis : PRIMARY HEPATOCELLULAR CARCINOMA SEROLOGY OF HEPATITIS B HBsAG AntiHBsAG Acute HBV + Chronic HBV + with High Infectivity Chronic HBV + with Low Infectivity Recovery + Immunized + • HBeAG AntiHBeAg + + - AntiHBcAG IgM IgG - + IgG - + - IgG - Prevention and Treatment o serologic test on donor blood o active immunization o anti-viral agents for Tx of chronic or persistent HBV infection o anti-HIV drug Lamivudine o Treatment with interferon alpha HEPATITIS A VIRUS ( HAV ) • • • Has a naked icosahedral capsid with single stranded RNA; belongs to Family PICORNAVIRIDAE Transmitted by the fecal oral route Hepatitis A has a 15-40 days incubation period before the patient develops acute hepatitis • • • • Young children are the most frequently infected but with milder course than adults Death from HAV is very rare HAV capsid is antigenic, so anti-HAV IgM and anti-HAV IgG is often produced by the patient Serology of Hepatitis A Acute Infection Old Infection ( immune to HAV ) Incubation or No Infection IgM anti-HAV + - IgG anti- HAV + - - HEPATITIS C VIRUS ( HCV ) • • • • Transmitted parenterally An enveloped icosahedral RNA virus Causes acute & chronic hepatitis in a similar manner as HBV Should be called HEPATITIS CIRRHOSIS VIRUS HEPATITIS D VIRUS ( HDV ) • • • • • • An RNA virus transmitted parenterally and can replicate only with the help of HBV The delta virus helical nucleocapsid actually uses HBV’s envelope, HBsAG. Infection occurs in 2 ways: Co-infection Superinfection Serology is not very helpful for diagnosis ADDITIONAL NOTES REPLICATION OF DNA VIRUSES PARVOVIRUSES • • • • • • Diameter:18-26nm Cubic symmetry No envelope ss DNA Genome size: 5.6kbs eg.Human parvovirus B 19 POLYOMAVIRUSES • • • • • • Diameter: 40nm Cubic symmetry no envelope ds DNA Genome size:5kbs eg. SV40, may cause tumors PAPILLOMAVIRUS • • • • • Similar to polyomaviruses Diameter: 55nm Genome size: 6.8 - 8.4kbs o (larger than polyomaviruses) In humans: May cause warts and genital cancers. Eg. Human Papaillomavirus (HPV) HERPESVIRUSES • • • • • • Diameter:150-200nm Cubic symmetry enveloped ds DNA Genome size: 125 - 240kbs eg. Varicella-zoster virus (chicken pox and measles), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) ADENOVIRUS • • • • • • • 47 types infect humans Diameter:70-90nm Cubic symmetry no envelope ds DNA, Genome size: 26 - 45kbs Cause acute respiratory disease, conjunctivitis and gastroenteritis HEPADNAVIRUSES • • • • • • Diameter: 40-48nm Icosahedral enveloped ds DNA Genome size:3.2kbs Causes acute chronic hepatitis ~ high risk of developing liver cancer POXVIRUSES • • • • • • • Brick-shaped or ovoid Size: 220-450nm long x 140-260nm wide x 140-260nm thick Enveloped ds DNA Genome size:130-375kbs (large!) Produce skin lesions eg. Small pox and vaccina virus •