2500_Virology_1_w_2025 (1)

Introduction to the Course

• Course Title: Introduction to Virology I

• Instructor: Dr. J.D. Dikeakos

• Course Code: Microimm 2500

• Department: Schulich School of Medicine & Dentistry, Microbiology and Immunology

• Contact: Jimmy.dikeakos@uwo.ca

General Course Structure

• Resources:

  • No required reading, but complementary texts:

    • Principles of Virology by Flint et al.

    • Fundamentals of Molecular Virology by Acheson

• Class Format:

  • Engage actively. If concepts are unclear, students are encouraged to ask questions.

Lecture Objectives

• Topics Covered:

  • Importance of virology

  • Locations where viruses can be found

  • Positive roles of viruses

  • Major concepts in virology

  • Historical context of virology

  • Methods of observing viruses

Significance of Virology

Global Impact

• Pandemics: Current case study on the global pandemic. Mention of Pro-MED, a program monitoring emerging diseases, citing the warning issued in December 2019 regarding pneumonia in Wuhan.

Current Statistics

• COVID-19 (SARS-CoV-2):

  • Total cases: 247,472,724

  • New cases in last 24 hours: 487,214

  • Cumulative deaths: 5,012,337

Example Cases of Viruses in Society

• Measles Outbreak:

  • Description of a patient traveling from Indiana engaging in a gathering that led to 34 confirmed cases of measles due to an unvaccinated individual.

  • Highlights the historical significance and transmissibility of viruses like measles.

Outbreak Analysis

• Case Study: Indiana measles outbreak costs $168,000 to control; majority of infected were unvaccinated due to vaccine fear.

• Public Health Data:

  • Graphs showing trends of measles incidence over the years in Canada, with introduction of vaccines coinciding with declines in cases.

Historical Overview of Important Outbreaks

• H1N1 Influenza: Discusses the 2013 outbreak in Alberta leading to 10 deaths.

Viruses in the Environment

Ubiquity of Viruses

• Viruses are present everywhere, including in food products (example: insect viruses on vegetables).

  • 1 teaspoon of ocean water contains approximately 2-5 million viruses.

  • Whales excrete large quantities of calicivirus, influencing their health and the ecosystem.

Human Genetics and Viruses

• Human genomes contain remnants of viral genes, with about 10% of DNA derived from ancient retroviruses.

Defense Mechanisms Against Viruses

• Inner Defense: The body has multiple defense mechanisms and most viruses do not cause disease under normal circumstances.

The Dual Role of Viruses

Positive Contributions

• Polydnaviruses in Nature: Describe symbiotic relationships with wasps and caterpillars showing that some viruses can be beneficial.

• Good Viruses:

  • Virus aiding in plant growth in high-temperature environments (Curvularia thermal tolerance virus).

Major Concepts in Virology

Key Themes

• Viruses are obligate molecular parasites, requiring host cells for replication, and must express mRNA to utilize host machinery for protein synthesis.

• Understanding the viral infectious cycle is crucial for their management and treatment.

Historical Context

• Timeline: Virology traces back over 250 million years with evidence of viruses from the age of dinosaurs, starting from Ancient Greek and Roman observations on infectious diseases.

First Documented Animal Virus

• Foot & Mouth Disease: Identified as the first animal virus, filterable and causing significant outbreaks, marking key advances in virology.

Visualizing Viruses

• Microscopy Advances: Electron microscopy allows for the observation of viruses; most are significantly smaller than E. coli.

Key Takeaway

• A virus is defined as an obligate intracellular parasite that requires a living host for its propagation and survival.

Tobacco Mosaic Virus (TMV)

Overview

• TMV is one of the first viruses to be discovered and characterized. It infects a wide range of plants, particularly tobacco and other members of the Solanaceae family.

Structure

• TMV is a rod-shaped virus composed of a single-stranded RNA genome encapsulated by a protein coat (capsid). This structure contributes to its stability and ability to survive in harsh environmental conditions.

Transmission

• TMV is primarily spread through mechanical means, such as handling plants and using contaminated tools. It can also be transmitted by insect vectors and can remain infectious in plant debris.

Symptoms in Infected Plants

• Common symptoms of TMV infection include mottled leaves, stunted growth, and a mosaic pattern of light and dark green areas. Infected plants may exhibit reduced yield and overall vigor.

Economic Impact

• TMV causes significant economic losses in agriculture, particularly in tobacco, tomato, and pepper crops. Control measures include the use of resistant plant varieties and cultural practices to minimize transmission.

Research and Applications

• TMV has been extensively studied in molecular biology and plant virology. It has served as a model organism for understanding viral replication and host-virus interactions. TMV has also been utilized in various biotechnological applications, including vaccine development and as a nanotechnology platform for drug delivery.

Historical Significance

• The discovery of TMV in the late 19th century was a pivotal moment in virology, leading to the eventual identification and study of many other viruses. The work of scientists like Adolf Mayer and Martinus Beijerinck significantly advanced our understanding of viruses as infectious agents.