Viral envelopes No defined shape Derived from host cell membranes – Intracellular membranes (nuclear, ER) – Plasma membrane Contain viral glycoproteins.

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Viral envelopes No defined shape Derived from host cell membranes – Intracellular membranes (nuclear, ER) – Plasma membrane Contain viral glycoproteins (peplomers) necessary for entry into cells – Attachment proteins – Fusion proteins – Enzymes (Flu neuraminidase) – Host proteins (Mumps)

Examples of viral envelopes EBV Rabies Courtesy S.K. Vernon WHRI, Wyeth-Ayerst Research, Radnor, Pa. Influenza Courtesy Dr. L Stannard Univ of Cape Town HIV-1

PROPERTYNONENVELOPED VIRUSESENVELOPED VIRUSES ComponentsProteinsPhospholipids, proteins, glycoproteins Sensitivity to heat, acid, detergent, drying Resistant (stable)Sensitive (labile) Release from host cellCell lysisBudding (cell survives) and lysis TransmissionFomites, dust, fecal-oral, droplets Droplets, secretions, organ or blood transplant Effect of dryingRetains infectivityLoses infectivity Survival within GI tractYesNo ( except for rotavirus & enterovirus) Host immune responseAntibody responseAntibody and cell-mediated responses (latter contributes to pathogenesis) Adapted from Rapid Reviews Microbiology and Immunology, Table 18-1 (Naked viruses)