DNA Viruses PDF

DNA VIRUSES  THE DNA VIRUSES 1) Adenoviridae Human Adenovirus over 80 species with about 40 are pathogenic to man non-enveloped, 70-90 nm in size Linear ds DNA genome with core icosahedral with 252 capsomeres  THE DNA VIRUSES Adenovirus- Properties Stable...

DNA VIRUSES  THE DNA VIRUSES 1) Adenoviridae Human Adenovirus over 80 species with about 40 are pathogenic to man non-enveloped, 70-90 nm in size Linear ds DNA genome with core icosahedral with 252 capsomeres  THE DNA VIRUSES Adenovirus- Properties Stable  Pathogenesis Infects mucoepithelial cells of respiratory, GI and GU tracts ( viremia occurs) produces cytopathic changes  DISEASES ( ADENOVIRUSES) 1. Acute Febrile Pharyngitis - common to children - indistinguishable from common colds and flu 2. Pharyngeal-conjunctival Fever - Main adenovirus types: 3, 4, 7, 14 - Contaminated water in swimming pools, fomites 3. Acute Respiratory Disease - common to military recruits - with rashes 4. Pneumonia 5. Gastroenteritis Host Defenses no antibodies produced cytotoxic T-cells kill infected cells early Epidemiology - common to children below 6 - predominant in cold climate DIAGNOSIS: Culture in HeLa, HEK cell lines Shell vial cell culture DFA PCR, nucleic acid probes PREVENTION: Good handwashing Contact precautions Chlorination of water Disinfection or sterilization of ophthalmologic equipment Use of single dose vials Oral vaccine- restricted use 2) Hepadnaviridae Hepatitis B Virus - double stranded and enveloped - virion also referred to as “DANE PARTICLE” - with several antigens 1) HBsAg 2) HBcAg 3) HBeAg PATHOGENESIS: Virus enters hepatocytes via blood Immune response (cytotoxic T cell) to viral antigens expressed on hepatocyte cell surface responsible for clinical syndrome released by exocytosis HEPATITIS inflammatory condition of the liver may be asymptomatic with carrier state may be chronic and may lead to cirrhosis DEFENSES: antibody and cell mediated responses are not protective  Diagnosis - fever, headache, malaise, jaundice - serology Control - screening of blood - vaccine 3) Herpes Viridae - enveloped - replication occurs in the host’s nucleus - may cause recurrent infections - with latency  Neurotropic - latency in nerve cells (HSV 1 &2, VZV) Lymphotropic - latency in lymphocytes (EBV, CMV) - some are associated with cancers - humans are the natural host Pathogenesis commonly infects skin and mucous membranes (HSV, VZV) internal infection (CMV, EBV) produces intranuclear inclusions and multinucleated giant cells DIAGNOSIS 1. characteristic lesion 2. Intranuclear inclusions on smear 3. TZANCK TEST scraping of an ulcer base to look for Tzanck cells (multinucleated giant cells) AKA: Tzanck smear, chickenpox skin test and the herpes skin test Control - avoid contact - vaccines - Acyclovir PATHOGENESIS a. HSV-1 - Gingivostomatitis - recurs as cold sores (herpes labialis) - herpetic keratitis - leads to scarring and blindness - whitlows - lesions on the fingers b. HSV – 2 - genital Herpes may lead to meningitis and encephalitis MOT: sexual intercourse Defenses antibody production is protective recurrent cell mediated response c. Varicella-Zoster Virus (VZV) Varicella may progress to pneumonia centrifugal rashes macules-papules- vesicles-pustules-crusts not prone to scarring Zoster shingles common to older people lesions are found at the thoracic and lumbar regions d. Cytomegalovirus (CMV) - characterized by jaundice, hepatosplenomegaly, CNS disorder - most important infectious agent associated with organ transplantation - the most common cause of congenital infections, occurring in approximately 1 percent of all neonates. e. Epstein-Barr Virus (EBV) Disease 1. Infectious Mononucleosis - characterized by fever, fatigue, malaise and pharyngitis - kisser’s disease 2. Burkitt’s Lymphoma - commonly associated with the infection of B-cell lymphocytes with the Epstein–Barr virus f. Human Herpes Virus 6,7 and 8 HHV 6 (Roseolavirus) - Roseola - rose-colored eruption in spots HHV7 - measles-like rashes in infants HHV8 - Kaposi’s Sarcoma - neoplastic disease of the skin and mucous membranes - reddish-brown or bluish tumorous plaques, macules, papules or nodules especially on the lower extremeties 4) Papovaviridae - non-enveloped and icosahedral a. Human Papilloma Virus (HPV) - on epithelial cells of the skin and mucous membranes Diagnosis - condylomata acuminata (genital warts) are very distinguishable - histology, molecular methods b. JC and BK Polyoma Virus BK Virus- first isolated from the urine of a renal allograft recipient receiving immunosuppressive drugs JC Virus- first isolated from the brain of the patient with progressive multifocal leukoencephalopathy 5) Parvoviridae - only DNA virus pathogenic to man with a single stranded genome - smallest icosahedral DNA virus - endemic zoonotic infection Parvovirus B-19 - Genus Erythrovirus - AKA: fifth disease/ slapped cheek disease - rashes begin on the cheeks (centripetal) 6) Poxviridae - replication occurs in the cytoplasm - largest viruses - complex symmetry - no animal reservoir a. Variola Disease: 1. Variola Major - causes a severe disease (high mortality rate) 2. Variola minor a. Vaccinia Disease: cowpox - used by Jenner to produce a vaccine for smallpox b. Orf Disease: sheep and goat pox c. Molluscipoxvirus Disease: molluscum contagiosum - characterized by smooth, waxy tumorlike Pathogenesis of Variola: - systemic infection with characteristic rash - MOT: inhalation - centrifugal rash formation - rashes form scarring Diagnosis: - characteristic lesions