Introduction to Viruses

• Key Components:

  • Spike (S) Protein

  • Nucleocapsid (N)

  • Membrane (M)

  • Envelope (E)

  • RNA viral genome

• Instructor: Craig McCormick, Ph.D.

  • Professor, Department of Microbiology & Immunology

  • Email: craig.mccormick@dal.ca

Overview of MICI2100 Virology Block

• Course Schedule:

  • Oct. 2: Introduction

  • Oct. 4: Virus Structure

  • Oct. 9: Virus Entry

  • Oct. 11: Virus Genome Replication (Part 1)

  • Oct. 16: Virus Genome Replication (Part 2)

  • Oct. 18: Viral Assembly and Egress

  • Oct. 23: Viral Genetics and Evolution

  • Oct. 25: MIDTERM #2

The Nature of Viruses

• Viruses Defined:

  • Special kinds of entities that can replicate in specific hosts.

  • While often associated with diseases, many viruses are benign or beneficial.

• Potential of Viral Study:

  • Aid in disease prevention

  • Understanding fundamental aspects of host biology

Goals of Virology Study

• Fundamentals:

  • What is a virus?

  • Virus morphology

  • Mechanism of replication within host cells

  • Host defenses against viruses

  • Evolving nature of new viruses

• Drill Down on Specific Viruses:

  • Poliovirus

  • Influenza virus

  • HIV

  • SARS-CoV-2

Learning Resources

• Reliable Sources for Virus Information:

  • NCBI - National Center for Biotechnology Information

    • NCBI Website

  • TWIV: This Week in Virology - Microbiology podcasts collection

• Global Surveillance Resources:

  • ProMEDmail.org - International Society for Infectious Diseases

  • MMWR - Morbidity and Mortality Weekly Report (CDC)

Viral Presence in Our Lives

• Ubiquity of Viruses:

  • Present in our environment; we encounter billions of viruses daily.

  • Air intake averages 6 liters per minute; multiple kilograms of food consumed daily.

  • Millions of viral particles per milliliter of seawater.

  • Viral infections cross species barriers, leading to zoonotic infections.

Marine Viruses & Global Impact

• Impact on Environment:

  • Significant role in the ocean's carbon cycle.

  • Marine microbes are dominant biomass; they host approximately 10^30 viruses.

Ancient Viral Infections

• Evidence of Viruses in Genomes:

  • Retroviruses have been present in vertebrate genomes for about 100 million years.

  • 10% of human genome consists of retrovirus-like sequences.

Viral Integration and Human Evolution

• Syncytin:

  • Viral gene crucial for placental development.

  • Demonstrates how captured viral genes influence mammalian physiology.

Visualizing Viruses

• Techniques for Visualization:

  • Plaque Assays (Indirect Method):

    • Serial dilution, inoculation on susceptible cells, overlay with agar, observe cytopathic effects.

  • Electron Microscopy (Direct Method):

    • Powerful visualization method allowing examination of ultrathin stained samples.

Summary of Virology Basics

• Viruses:

  • Submicroscopic, obligate intracellular parasites.

  • Major impact on ecosystems.

  • Genetic exchange occurs between viruses and hosts.

  • Not all viruses have pathogenic effects; many are neutral or beneficial.

  • Plaque assays and electron microscopy are essential methodologies in virology.

Homework Assignment

• Task:

  • Listen to a podcast on TWIV (This Week in Virology).

  • Share insights in the next class for a prize!