Virology and Immunology (MICR303) - Introduction PDF

MICR303 Virology and Immunology Welcome to the world of Viruses! Dr. Ebrahim Hassan Why we study viruses?!  1918 Spanish Influenza Pandemic In 1918 a deadly global influenza pandemic started Two y...

MICR303 Virology and Immunology Welcome to the world of Viruses! Dr. Ebrahim Hassan Why we study viruses?!  1918 Spanish Influenza Pandemic In 1918 a deadly global influenza pandemic started Two years later, nearly a third of the global population, had been infected in four successive waves Estimates of deaths range as high as 100 million, making it one of the deadliest pandemics in modern history  Why we study viruses?! 1918 – Spanish Influenza COVID-19 – 2019 100 Years ‫جاهزين‬ ‫؟‬  Goals of the course Basic understanding of virology ➔ What is a virus? ➔ Virus structure ➔ Virus genome ➔ Virus replication cycle Introduction to Immunology ➔ Innate vs Adaptive immunity How do viruses cause disease? How to prevent viral infections? ➔ Antivirals ➔ Vaccines Biotechnology applications using viruses ➔ Therapeutic viruses ??? What is a virus?  Virus Structure A virus particle consists of genetic material (DNA or RNA) surrounded by a protective coat of protein called a capsid  Shapes of virus particles Viruses particles in images take by electron microscopes take different forms: Helical Polyhedral Spherical Electron Complex Microscope  Virus replication cycle Viruses are obligate intracellular parasites: A virus cannot replicate alone; instead, it must infect cells and use components of the cell to make copies of itself  Virus replication cycle Steps of the virus life cycle: 1. Attachment: is the first step in the virus life cycle, in which the virus attaches to the cell surface 2. Penetration: is when the virus enters the cell 3. Uncoating: happens when the viral DNA or RNA is freed released from the capsid 4. Synthesis: occurs when the virus directs the host cell's metabolism to produce the virus's nucleic acid and protein 5. Assembly: new virus particles are created by packaging of the replicated genome into capsid 6. Release: when newly made virus particles leave the host cell The life cycle may repeat several times  Types of cells: Eukaryotic vs Prokaryotic cell The primary difference between prokaryotic and eukaryotic cells is that a nucleus and other membrane-bound organelles are only present in eukaryotic cells  Viruses that infect prokaryotic cells Bacteriophages Bacteriophages (viruses of Bacteria): also known as phages, are viruses that infect and replicate only in bacterial cells Unicellular vs Multicellular hosts Multicellular organisms consist of different organs and each organ consists of different cell types that could be infected by viruses Viruses that infect Eukaryotic cells In multicellular hosts, viruses show specificity towards infecting specific tissues/organs Examples: 1. Respiratory viruses  Infect the respiratory tract 2. Neurotropic viruses  Infect the Nervous system 3. Enteric viruses  Infect the Gastrointestinal tract  e.g. Transmission of respiratory viruses Understanding which type of cells and organs a virus infects, helps understanding how the virus is transmitted For example, viruses infecting the respiratory tract are transmitted through coughing and sneezing  What is a virus? – Definition 1. Viruses are small infectious agents that replicate only inside the living cells of an organisms (i.e. obligate intracellular parasites) 2. Viruses infect all life forms, from animals and plants to microorganisms (including bacteria and archaea) ??? Introduction to Laboratory Methods in Virology  Methods in Virology 1. Cell culture 2. Virus quantification (Plaque assay) 3. Different animal models  In Vitro vs In Vivo In Vitro: “In Vitro” is a Latin word for “within the glass”, describing experiments performed outside of a living organism (i.e. in a glass dish or flask in the laboratory) In Vivo: Experiments performed in a living organism (e.g. animal models) In vitro methods to study viruses Unicellular vs Multicellular hosts In multicellular hosts, viruses show specificity towards infecting specific tissues/organs Examples: 1. Respiratory viruses  Infect the respiratory tract 2. Neurotropic viruses  Infect the Nervous system 3. Enteric viruses  Infect the Gastrointestinal tract  Cell culture Cell culture: is the process of growing cells derived from living tissue in an artificial medium in the laboratory Examples of cell lines Viruses end the replication cycle causing cell death  Cytopathic effects Cytopathic effects (abbreviated CPE): refers to observed structural changes in infected cells that are caused due to viral replication  Virus quantification (Plaque assay) Virus quantification involves counting the number of viruses in a specific volume to determine the virus concentration Plaque assay: a confluent monolayer of host cells is infected with the virus at varying dilutions. Virus plaques are formed when a virus infects and kills cells in the cell culture plate Stained live cells are blue Plaques are the clear spots on the cell monolayer Viruses of bacteria - Bacteriophages Phage plaques  in vivo - Animal models The most widely used animal model is the laboratory mouse  Advantages of laboratory mice as an animal model Advantages:  Low cost  Readily available  Small size  Ease of handling  Mouse-specific reagents are widely available  Availability of transgenic mice In summary  Quizzes Bonus Assignments Each lecture will start with a “Quiz” Bonus assignments will be asked covering the previous lecture’s material … for during the lectures for students who wish to dig deeper Quizzes are also a proof of attendance as well into specific topics of interest to promote discussion