Introduction to Virology Lecture Notes PDF
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AlMaarefa University
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Summary
This document provides a general introduction to virology, covering topics such as viral structure, properties, and replication. Key aspects of viral classification and different types of viruses are also briefly outlined. The document also touches upon antiviral drugs and diagnostic methods.
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### General Properties of Viruses Viral Structure 1. Genome: DNA or RNA. - All the DNA viruses are double stranded except the - All the RNA viruses are single stranded except the Rotavirus. 2. Capsid: protein coat surrounds the genome. - Icosahedral: e.g.,...
### General Properties of Viruses Viral Structure 1. Genome: DNA or RNA. - All the DNA viruses are double stranded except the - All the RNA viruses are single stranded except the Rotavirus. 2. Capsid: protein coat surrounds the genome. - Icosahedral: e.g., Adenoviruses, Hepatitis B virus (HBV). - Helical (filamentous): Influenza viruses, Ebola virus. - Complex: Monkeypox virus. 3- Envelope: - Acquired from the host cell membrane or nuclear membrane. - All helical viruses are enveloped, Most icosahedral viruses are enveloped.   Difference between Envelope & Capsid ------------------------------------ +-----------------------------------+-----------------------------------+ | Envelope viruses | Nonenveloped viruses | +===================================+===================================+ | Envelope: | Capsid: | | | | | - - | - - | +-----------------------------------+-----------------------------------+ | Sensitive to high & low PH | Not sensitive to high & low | | | | | | PH | +-----------------------------------+-----------------------------------+ | Cannot cause infection to the | Can cause infection to the | | gastrointestinal system | gastrointestinal system | +-----------------------------------+-----------------------------------+ | Sensitive to disinfectants. | Less sensitive to disinfectants. | +-----------------------------------+-----------------------------------+ | Can exit the cells without lysing | Lyse the cells for release | | them | | +-----------------------------------+-----------------------------------+ ### Atypical Viruses - Viruses which depend on helper viruses to complete - Example: 2. Prion: - Infectious protein without nucleic acid. - A misfolded protein that can change normal cellular - Accumulation of prions leads to neural cell death and progression to spongiform encephalopathy. Classification of Viruses: - Natural host range - Mode of transmission - Pathogenicity - Tissue tropism. DNA === HBV RNA === - Enveloped viruses: released via budding - Nonenveloped viruses: released via host cell lysis Steps of Viral Replication 1. Adsorption (attachment). 2. Penetration (Entry). 3. Uncoating. 4. Genome transcription and protein synthesis. 5. Assembly. 6. Release. Virus replication: general  Effect of Viruses on Host Cells - Latent infection: virus remains inactive in infected - Chronic infection: viral replication occurs with few or - Malignant transformation. Oncogenic viruses: - HPV→ Cervical carcinoma. - HCV, HBV→ hepatocellular carcinoma #### ¾ Feco-oral transmission: HAV. 1. How do these viruses reach the central nervous - Arboviruses - HIV - HSV - Poliovirus - Rabies virus. 2. Which part of the brain is affected by these viruses? - HSV - Poliovirus - Rabies virus ### Diagnosis of Viral Infections  Antiviral Drugs --------------- - Most viral infections resolve spontaneously in immunocompetent individuals. - Antiviral drugs act by inhibiting the viral replication cycle at various stages. - They do not destroy the viruses but inhibit their replication→ immune mechanisms eliminate the virus. - Currently, antiviral therapy is available only for HIV, - Challenges: - Because viruses are obligate intracellular parasites, antivirals might harm the infected cells. - Rapid viral mutation→ resistance. +-----------------------------------+-----------------------------------+ | Viral Replication Step | | +===================================+===================================+ | | - | +-----------------------------------+-----------------------------------+ | | - | +-----------------------------------+-----------------------------------+ | | - | +-----------------------------------+-----------------------------------+ | | - - - - | +-----------------------------------+-----------------------------------+ | | - | +-----------------------------------+-----------------------------------+ | | - | +-----------------------------------+-----------------------------------+ | | - | +-----------------------------------+-----------------------------------+  +-----------------------------------+-----------------------------------+ | Example | Viral Replication Step | +===================================+===================================+ | | - - - - | +-----------------------------------+-----------------------------------+ | | - - | +-----------------------------------+-----------------------------------+ | | - | +-----------------------------------+-----------------------------------+ | - - | - - | +-----------------------------------+-----------------------------------+   #### Test your knowledge A. HIV B. HAV C. HBV D. HCV A. Penetration B. Uncoating C. Protein synthesis D. Release #### Test your knowledge A. HIV B. HCV C. Herpes viruses D. Influenza viruses A. HCV B. HSV-1 C. Rota viruses D. Monkeypox virus - Lippincott Illustrated Microbiology 4th edition: Chapter 4, 23, 31. - Murray Medical Microbiology 8^th^ edition. - Schaechter\'s Mechanisms of Microbial -
