Papilloma viruses & Polyoma viruses. Human Papilloma viruses (HPV) DNA virus, double strand, circular, Icosahedral nucleocapsid, small size (45-55nm).
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HumanHuman Papilloma viruses (HPV)Papilloma viruses (HPV)
• DNA virus, double strand, circular, Icosahedral nucleocapsid, small size (45-55nm). No envelope
Human Papilloma virus (HPV) Human Papilloma virus (HPV)
• 70 different types (HPV-1 to HPV-70).
• It replicates only in the nucleus of epithelial cells. Infection occurs in skin and mucosal surfaces.
• HPV are species-specific.
Genital wartsGenital warts
• HPV-6, -11, -16, -18 and- 32
• on penispenis, vulvavulva and perianalperianal regions.
• Can blossom into cauliflower-like protuberances.
• Transmission through sex contacts is increasing.
HPV & Cervical CancerHPV & Cervical Cancer
• The agents: The agents: HPV16 & HPV18 responsible for 70% of all cervical carcinoma.
• Starts with a flat area of dysplasia (visible as a white plaque).
• Cervical and anal-cervical carcinoma is associated with persistent HPV infections.
HPV Pathogenesis (1)HPV Pathogenesis (1)• It infects cells in the basal layers cells in the basal layers of the skin or
mucosa.
• Common period: 1-6 months1-6 months
• Viral antigen and infectious virus is produced when the cells begin to become squamifedsquamifed and keratinizedkeratinized.
• Several months later, the wart the wart may regressregress.
HPV Pathogenesis (2)HPV Pathogenesis (2)
• Cell mediated immunity Cell mediated immunity (CMI) responses are more important in recovery.
• In immunocompromisedimmunocompromised patients (e.g. post transplant), there may be warts as a result of reactivation.
DiagnosisDiagnosis
• Diagnosis is clinicalclinical
• HPV cannot be cultivatedcannot be cultivated in the laboratory
• SerologicalSerological tests are neither useful nor neither useful nor availableavailable
Treatment• Using keratolytic agents: - Salicylic acid (to soften and cause
desquamation of epithelium or horny layer of skin).
• Removing warts by surgery.
• Destruction of wart tissue by freezing with dry ice (solid CO2) or with liquid nitrogen.
• Using Podophyllin (a resinous powder obtained by precipitating an alcoholic tincture of the rhizome of American Mayapple)
ParvovirusesParvoviruses - Unusual requirements for replication: either a
helper virus (a helper adenovirus) or rapidly dividing cells.
- The virus replicates when cell growth cycle is in “S” stage (when host DNA replication produces two identical sets of chromosomes.)
- Virus replication is in nucleus of the cell.
B19B19• A parvovirus replicating in erythroid precursor
cells, so the main place for virus replication is: fetal bone marrow and liver.
• Favorite receptor on erythrocytes: p Ag (Globoside).
• B19 can be found in blood and respiratory secretions.
• It can transmit from mother to embryo.
B19B19• A human virus which cannot pass to animals. • The virus interrupts the production of
erythrocytes in embryo causing sever anemia and abortion.
• Erythema infectiosum, (fifth disease), is the commonest clinical manifestation of B19 virus infection.
• In children (age 5-15) and sometimes adults (up to 30). 40-60% infections are asymptomatic.
Fifth disease Fifth disease (Erythema infectiosum)(Erythema infectiosum)
• First stage: 7-8 days after infection, a prodromal influenza-like
illness, characterized by headache, malaise, chills.
• Second stage: 17 to 18 days after infection, the development of a mild feverish
illness and a maculopapular rash. It starts with erythema of the cheeks (Slapped cheek) followed by a rash (resembling the rash of rubella) on the trunk and limbs. These symptoms disappeared 1-3 weeks.
Anemia Anemia & aplastic crisis aplastic crisis
• The virus infects erythroid precursor cells in the bone marrow and leads to anemia. Sever anemia in blood disorders (e.g. in Sickel cell anemia, Leukemia or hemolytic anemia)
• It leads to erythroid aplasia (Aplastic crisis) in patients with hemolytic anemia or immune deficiency, such as people with transplantation event.
• Anemia and aplastic crisis is self-limiting.
DiagnosisDiagnosis
• Detecting viral DNA in serum (PCR)
• A rise in parvovirus-specific IgM or IgG.• Bone marrow examination shows an absence of
erythroid precursors.
TransmissionTransmission
• B19 is anywhere, all through the year, different ages, sporadic or epidemic.• Spread through respiratory secretions,
vertical transmission from mother• Many cases are subclinical.
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