Virology Lecture Notes PDF

Course Learning Outcome 1. Explain the unique properties of viruses, their composition, structure and multiplication in host organisms (C2) 2. Distinguish between viruses based on their structure, composition, multiplication in host organisms, diseased caused and transmission (C4) 3. Determine...

Course Learning Outcome 1. Explain the unique properties of viruses, their composition, structure and multiplication in host organisms (C2) 2. Distinguish between viruses based on their structure, composition, multiplication in host organisms, diseased caused and transmission (C4) 3. Determine the suitable method(s) in studying a specific virus (C4) 4. Elaborate on the differences between viruses and acellular agents (C5) 5. Conduct laboratory experiments in virology (P4) LECTURE 1 INTRODUCTION We live and carry viruses all over the place Virus infect ALL living things (e.g. animals, plants, bacteria etc.) Microbiome  We eat and breathe billions of virions regularly (e.g. airborne, waterborne)  We carry virus genomes as part of our own genetic material (e.g. endogenous retrovirus) Learning outcomes…. Define virus, viriods, virions List the characteristics of viruses Recall the history of virology Viriod? Naked nucleic acid that encodes very few viral proteins Small pathogenic RNAs Transmit successfully from plant to plant Doesn’t need a protein shell to protect it Distinguish them from viruses Virions? Virus particle that infect host The size.. Nanoparticles (10nm-300nm) Smallest animal virus poliovirus , biggest poxvirus The biggest animal virus is still smaller than the smallest bacteria cannot be seen under a light microscope and only be seen under an electron microscope so small that they could pass through filters that are used to sterilize solutions by removing bacteria and other contaminants Examples of various sizes of viruses as compared to bacteria E. Coli Quite recently, a more bigger viruses were discovered…up to 200nm  Mimivirus in 2006 – 750 micron meter Pandoravirus in 2013– 200 nm, infact bigger from some bacteria, visible under light microscope!!! The replication… Obligate intracellular parasites require to be inside host in order to multiply as they rely entirely upon the host cell's ability to create the energy necessary to perform all of the manufacturing processes during their replication. Without a host cell, viruses cannot carry out their life- sustaining functions or reproduce. Because they are not able to i) synthesize proteins, because they lack ribosomes and must use the ribosomes of their host cells to translate viral messenger RNA into viral proteins. ii) generate or store energy in the form of adenosine triphosphate (ATP), and so have to derive their energy, and all other metabolic functions, from the host cell. iii) synthesize basic building materials, such as amino acids, nucleotides, and lipids (fats). Not similar to bacteria replication-binary fission ❑ Replication of virus in a host can results in host destruction; this accounts for the fact that some viruses are agents of diseases. ❑ The process whereby they introduce their nucleic acids and replicate or reproduce is known as infection. ❑Infection from one cell to another is called transmission. E.g zoonosis transmission ❑This is property is not exclusive to viruses as two groups of bacteria –rickettsia and chlamydia are also intracellular parasites Exist in two phases ❑extracellular phase: phase in which virus particles or virions are inert ❑intracellular phase: a phase in which virus infect host cells and induce it to synthesize virions components and eventually complete virus particles  Other characteristics… ❑Their genome- is either DNA or RNA but not both ❑Acellular (non-cellular) They are not made up of cells-no cytoplasm and semi- permeable membrane which separates the cell from its outer boundary ❑Lack the characteristics of living things. They DO NOT metabolize, respire, respond to stimuli, grow, require nutrition, reproduce, have movement, excrete waste product  Is virus alive? ❑Because viruses are inert outside of living host cells, in this sense, they are not considered to be living organisms. ❑However, once viruses enter a host cell, the viral nucleic acids become active, and viral multiplication results. ❑ In this sense, viruses are alive when they multiply inside the host cells they infect. ❑clinically viruses can be considered alive because they cause infection and disease, just as pathogenic bacteria, fungi, and protozoa too. How old are viruses? -self-replicating RNA molecules was view as a virus actually present before cellular life began on earth. -Then DNA virus came later -Quite old approximately billions of years ago. Left-inscribed rabid hector in old Greece mythtology 700B.C., probably rabies that we know today. Right- Ancient Egyptian carving on the individual with the typical leg of paralysis polio caused by poliovirus. 1580 – 1350BC - Chinese practice varioation in which a postule from one person infected with small pox was taken and infected another person (11th century) - as kind of protection-30% of the people infected with small pox will die and the remaining 70% will survived - Lady Montagu also did the same thing (17th century)  Leewenhoek – made the 1st. microscope in 17th century to see microorganism. Pasteur- these miroorganisms can grow in broth (culturable), making milk sour to produce cheese, producing wine etc. These microorganisms was bacteria (mid-18th century) Koch-these bacteria could caused disease (mid to end 18th century) No concept of viruses yet!! TMV-1st. Isolated virus Tobacco was a big industry towards the end of 15th century. -grinded tobacco leaves, mix with some buffer then filter it to see if there is any bacterial agents could be found -Then concepts of filterable agents came up -Using centered glass filtered (Burke’s filter) so that the porosity of the filter can be controlled. -leaf extract was introduced at the top and could be filtered it through. -Consistently, researcher found out what passed through the filter when inoculated into new healthy leaves would cause the disease later. -It wasn’t that was retained on the filter. -diameter of filter was roughly 0.2 micron -slimy liquid poison: contagium vivum fluidum in Latin