1. NAJRAN UNIVERSITY College of Applied Medical Sciences General Microbiology Course Lecture No. 16 By Dr. Ahmed Morad Asaad Associate Professor of Microbiology

2. Cultivation and assays of viruses It requires living cells (viruses are obligate intracellular parasites) 1- Embryonated chicken eggs: Advantages: *- They are sterile *- They have no immunological response *- They are easily available and inexpensive 2- Tissue culture: 3 types: Malignant cell line as human carcinoma of cervix (Hela cells) Human embryonic fibroblast Monkey kidney cells 3- Animal inoculation

3. Detection of viral growth in culture by: 1- Cytopathic effect (CPE) in the form of: *- Cell death *- Production of multinucleated gian cell *- Haemadsorption *- Production of inclusion bodies as: Negri bodies in rabies Guarneiri bodies in small pox Torr’s bodies in yellow fever

4. Development of viral cytopathic effects (CPE): Human embryo skin muscle cells were infected with human cytomegalovirus and stained at selected times to demonstrate (A) uninfected cells, (B) late virus cytopathic effects (nuclear inclusions, cell enlargement), (C) cell degeneration, and (D) a focus of infected cells in a cell monolayer (i.e., a plaque), hematoxylin and eosin stain. (A, X 255; B, X 900; C, X 225; D, X 20.)

5. Replication of viruses 1- Attachment (adsorption) 2- Penetration (engulfment) 3- Uncoating 4- Eclipse phase 5- Synthesis of new viral components 6- Assembly 7- Release (shedding)

6. Viral infection It may be: 1- Superficial 2- Systemic: Acute Chronic (carrier) 3- Persistent: Latent infection (herpesvirus) Slow virus infection (AIDS) Transformation

7. Diagnosis of viral infection 1- Microscopic examination (Electron microscopy) 2- Cultivation of viruses 3- Detection of viral antigens or antibodies (Serological diagnosis) Enzyme-linked immuno-Sorbent Assay (ELISA) Radio-Immuno-Fluorescence (IF) Radio ImmunoAsaay (RIA) 4- Molecular methods: Nucleic acid hybridization Polymerase Chain Reaction (PCR)