Virus Notes

Virus Notes

Living or Not?

  • Discussion on what constitutes life and whether viruses fit into that category.

Computer Viruses

  • Entry Points for Computer Viruses:

    • Explain how a computer virus gets into a computer.

  • Post-Entry Effects:

    • Describe what happens once a virus breaches a computer's defenses.

  • Removal Process:

    • Outline steps for extracting the virus from the system.

  • Lasting Effects:

    • Discuss the ongoing impact of the virus on computer performance and security.

  • Contagion Potential:

    • Explain how one infected computer can affect others in a network.

What is a Virus?

  • Historical context regarding diseases thought to be caused by smaller agents than cellular bacteria.

  • Definition:

    • A virus is a non-cellular particle comprised of genetic material (DNA or RNA) and protein.

  • Etymology:

    • The term "virus" translates to "poison" in Latin, reflecting its harmful nature.

Why Study Viruses?

  • Living vs Nonliving:

    • Viruses exist at the boundary of living and nonliving entities.

  • Characteristics:

    • Viruses exhibit properties reminiscent of life such as growth, reproduction, adaptation, and metabolism, although they lack cellular structures.

  • Impact:

    • Viruses influence all forms of life and possess organic characteristics.

Viruses: Structure & Shape

  • Size:

    • Viruses measure about $1/2$ to $1/100$ the size of the smallest bacterial cell.

  • Components:

    • Viruses consist of two primary parts: an inner core of nucleic acid (DNA or RNA) and one or two protein coats.

Types of Viruses

  • Examples of Different Viruses:

    • Influenza, Bacteriophage, Ebolavirus, Hepatitis C, Rotavirus, Papillomavirus, Adenovirus.

Viruses: Nucleic Acid and Protein Coats

  • Genetic Material:

    • Nucleic acid within the virus contains essential genetic information; most viruses have either DNA or RNA but not both simultaneously.

  • Retroviruses:

    • These viruses have RNA and replicate backwards, often associated with severe diseases.

  • Protein Coat:

    • The protein coat, or capsid, may include lipid bilayers depending on the virus type.

Genetic Code of Viruses

  • Code Functionality:

    • The genetic code solely allows for the synthesis of viral components, facilitating replication and protein synthesis for the virus's structure.

Infection Process

  • Capsid Functionality:

    • The arrangement of proteins in the viral coat influences infection processes.

  • Host Cell Recognition:

    • Viruses must attach to specific receptor sites on host cell membranes, utilizing the shape and compatibility of the capsid.

  • Specificity:

    • Many viruses can only infect specific target cells due to the necessary lock-and-key recognition mechanism, exemplified by the interaction of poliovirus with human nerve cells.

Viral Invasion Mechanism

  • Attachment and Entry:

    • Step-by-step mechanism of how a virus identifies, binds to, and enters a host cell.

  • Outcome of Recognition:

    • If the virus cannot correctly bind, infection does not occur.

The Lytic Cycle

  • Definition:

    • A process wherein the host cell is ultimately destroyed while replicating viral components.

  • **Steps in the Lytic Cycle:

    1. Attachment

    2. Entry

    3. Replication

    4. Assembly

    5. Lysis (cell rupture) and release of new virions.

The Lysogenic Cycle

  • Integration:

    • Viral DNA integrates with the host cell’s chromosomes, becoming a provirus or prophage, allowing viral genes to be replicated alongside host DNA.

  • Cycle Transition:

    • Proviruses can revert to active lytic cycles, detailing the switch from lysogenic to lytic forms.

  • Lysogenic Steps:

    1. Attachment and Entry

    2. Provirus Formation

    3. Cell Division

    4. Potential Lytic Cycle Activation.

Proviruses and Related Diseases

  • Cold Sores:

    • Caused by Herpes Simplex 1, which can recur intermittently.

  • HIV/AIDS:

    • Targets and kills helper T- cells, critical for immune response.

  • Influenza:

    • Common flu, with considerations for flu shots.

  • Chickenpox:

    • Can reactivate in adults as shingles.

Future of Viruses

  • Eradication Decisions:

    • Discussion about whether we should execute total eradication of all viruses as was accomplished with smallpox.

  • Biotechnological Applications:

    • Exploration of using viruses for innovative medical technologies, particularly in genetic material delivery.

Global Eradication of Smallpox

  • Historical perspective on smallpox, one of the most lethal diseases in human history, and its eradication process, beginning in 1967.

  • Final Case:

    • The last known cases of smallpox occurred in Bangladesh (1975) and Somalia (1977) with specific details about those individuals and the eradication timeline by country.

COVID Mutations

  • **Types of Mutations:

    • Example strains and their genetic alterations illustrated through detailed sequence data.

  • Gene Mutations:

    • Examination of various mutations in SARS-CoV genomes (e.g., B.1.1.7, B.1.351, P.1) and their implications.

Questions for Further Understanding

  • Question 1:

    • Why does the HIV virus exclusively impact the helper T cells?

  • Question 2:

    • How does a virus "change its coat"? What are the implications for mutation speed?

  • Question 3:

    • What is the rationale behind cultivating vaccines in egg culture?

  • Question 4:

    • Discuss the structural components of a virus and the processes involved in their assembly.