Plus Sense RNA Viruses

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Daniele Adamo
7 anni fa
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1 Plus Sense RNA Viruses Family Corona Toga/Flavi Picorna Calici Retro Genome < ss (+) RNA > Diploid (+) RNA Capsid symmetry Helical < Icosahedral > Envelope < Yes > < No > Yes e.g. Human corona virus Rubella virus Hepatitis C virus Polio Hepatitis A virus Norwalk agent Hepatitis E virus HIV-1

2 Famiglia Coronaviridae Virus rotondeggianti di nm di diam Formati da: rivestimento esterno glicoproteico formato da unità tozze e ben visibili (aspetto a corona) capside interno elicoidale e flessibile di 20nm di diam un genoma: RNA monocatenario non segmentato (+) infettante di paia di basi

3 Coronaviridae Schema grafico Immagine reale

5 The envelope carries three glycoproteins: S - Spike protein: receptor binding, cell fusion, major antigen E - Envelope protein: small, envelope-associated protein M - Membrane protein: transmembrane - budding & envelope formation In a few types, there is a third glycoprotein: HE - Haemagglutinin-esterase The genome is associated with a basic phosphoprotein, N.

6 Replicazione Entrano per endocitosi Restano nel citoplasma La progenie si assembla nel Golgi Escono per gemmazione Crescono lentamente (24-48 ore)

7 Famiglia Coronaviridae Due Generi che infettano i vertebrati: Coronavirus Torovirus

8 Le infezioni umane da Coronavirus

9 Coronavirus:tre gruppi Gruppo I HCoV-229E diarrea epidemica del maiale gastroenterite trasmissibile del maiale gastroenterite del cane peritonite infettiva del gatto Gruppo II HCoV-OC43 epatite del topo virus bovini Gruppo III Virus della bronchite aviaria (CoV) T CoV (tacchino)

10 These viruses infect a variety of mammals & birds. The exact number of human isolates are not known as many cannot be grown in culture. In humans, they cause: Respiratory infections (common), including Severe Acute Respiratory Syndrome (SARS) Enteric infections (occasional - mostly in infants <12 months) Neurological syndromes (rare)

11 TRASMISSIONE by aerosols of respiratory secretions by the faecal-oral route by mechanical transmission.

12 Epidemiologia Coronavirus infection is very common and occurs worldwide. The incidence of infection is strongly seasonal, with the greatest incidence in children in winter. Adult infections are less common. The number of coronavirus serotypes and the extent of antigenic variation is unknown. Re-infections appear to occur throughout life, implying multiple serotypes (at least four are known) and/or antigenic variation, hence the prospects for immunization appear bleak.

13 Patogenicità Most virus growth occurs in epithelial cells. Occasionally the liver, kidneys, heart or eyes may be infected, as well as other cell types such as macrophages. In cold-type respiratory infections, growth appears to be localized to the epithelium of the upper respiratory tract, but there is no adequate animal model for the human respiratory coronaviruses. Clinically, most infections cause a mild, self-limited disease (classical 'cold' or upset stomach), but there may be rare neurological complications. SARS is a form of viral pneumonia where infection encompasses the lower respiratory tract.

14 SARS SARS is a type of viral pneumonia, with symptoms including fever, a dry cough, dyspnea, headache, and hypoxaemia (low blood oxygen concentration). Typical laboratory findings include lymphopaenia (reduced lymphocyte numbers) and mildly elevated aminotransferase levels (indicating liver damage). Death may result from progressive respiratory failure due to alveolar damage. The estimated case fatality rate is 13 2% for patients younger than 60 years and 43 3% for patients aged 60 years or older

15 DIAGNOSI DI LABORATORIO Serological testing for anti-coronavirus antibodies consists of indirect fluorescent antibody testing and enzyme-linked immunosorbent assays (ELISA) Although some patients have detectable coronavirus antibody within 14 days of illness onset, definitive interpretation of negative coronavirus antibody tests is possible only for specimens obtained >21 days after onset of fever. Molecular testing consists of reverse transcriptasepolymerase chain reaction (RT-PCR) tests specific for the RNA This can detect infection within the first 10 days after the onset of fever in some SARS patients, but the duration of detectable viraemia and virus shedding is unknown, so RT- PCR tests performed too late could give negative results.

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