Influenza Set

Key Terms and Objectives

Vocabulary to Know:

Term	Definition
Influenza Virus	A virus that infects epithelial cells in the respiratory system, causing influenza. Types include Influenza A, B, C, and D.
Virus	A microscopic infectious agent that requires a host cell to replicate. Composed of genetic material (DNA or RNA) enclosed in a capsid.
Genetic Material	The DNA or RNA that carries a virus's genetic instructions for replication.
Capsid	The protein shell surrounding the genetic material of a virus. Contains proteins that aid in attachment to host cells.
Envelope	A lipid layer derived from the host cell membrane, surrounding some viruses like Influenza. Helps the virus enter new cells.
Spikes	Glycoproteins on the surface of influenza viruses (H and N spikes) that assist with cell attachment and entry.
Giant Viruses	Viruses much larger than typical viruses, almost the size of small bacteria.
Lytic Cycle	The viral replication process where the virus immediately uses host cell machinery to produce new viruses, eventually lysing (bursting) the host cell.
Lysogenic Cycle	The viral replication process where viral DNA integrates into the host genome and remains dormant until triggered.
Epithelial Cells	Cells lining the respiratory system targeted by influenza viruses.
Flu Vaccine	A vaccine designed to protect against multiple influenza strains, made from inactivated viruses or recombinant proteins.
Recombinant Process	A method of producing vaccines using only a specific viral protein, often using insect cells.
Evolution	The process of change in populations over time through genetic variation and natural selection.
Natural Selection	The mechanism where individuals with advantageous traits are more likely to survive and reproduce, spreading those traits.
Stabilizing Selection	Selection that favors average traits, reducing extremes.
Directional Selection	Selection that favors one extreme trait, shifting population characteristics.
Disruptive Selection	Selection that favors both extreme traits over average traits, possibly splitting populations into two groups.
Information Flow	The central dogma of molecular biology: DNA → RNA → Protein.
Fossil Record	Mineralized remains of organisms providing evidence for evolution.
Analogous Structures	Structures that perform similar functions but evolved independently (e.g., bird wings vs insect wings).
Homologous Structures	Structures inherited from a common ancestor (e.g., vertebrate limb bones).
Antigenic Drift	Small mutations in influenza spikes over time, reducing vaccine effectiveness.
Antigenic Shift	Major genetic changes when two viruses infect the same cell, creating a new hybrid virus.
Lymphatic System	A network of tissues and organs that returns fluid to the blood and helps the immune system fight infection.
Immune System	The body’s defense system against pathogens, involving innate and adaptive responses.
Major-Histocompatibility Complexes (MHC)	Self-identification glycoproteins on cells.
Antigen	A molecule, usually a protein, that triggers an immune response.
Macrophages	Immune cells that engulf pathogens and present antigens to T cells.
Dendritic Cells	Immune cells that present antigens to activate T cells.
Innate Defenses	General, non-specific immune defenses like barriers, inflammation, and phagocytosis.
Cytokines	Chemical signals that coordinate immune responses.
Inflammatory Response	A process where tissue damage triggers histamine release, increasing blood flow and white blood cell recruitment.
Neutrophils	White blood cells that engulf pathogens and debris.
Adaptive Immunity	Specific immunity that targets particular pathogens and retains memory of past infections.
Cell-mediated Immunity	Immune response targeting infected cells using T cells.
Targeting Infected Cells	Cytotoxic T cells recognize infected cells displaying antigens and destroy them.
Core Proteins	Internal viral proteins that mutate less and could be used for universal vaccines.

Objectives:

1. Understand what influenza viruses are and how they are named.
Influenza viruses are classified into types A, B, C, and D. Influenza A and B are the most common in humans. Influenza A viruses are named using the WHO system, which includes the host species (if non-human), type (A or B), geographic origin, strain number, and year. For Influenza A, the naming also includes the types of surface spikes: Hemagglutinin (H) and Neuraminidase (N).

2. Explain the general process of how viruses reproduce.
Viruses follow two replication cycles:

Lytic cycle: Virus attaches, injects genetic material, hijacks cell machinery to make new viruses, assembles them, and lyses (bursts) the host cell to release new viruses.
Lysogenic cycle: Virus integrates its genetic material into the host’s genome, staying dormant until triggered to enter the lytic cycle.

Influenza viruses primarily use the lytic cycle in epithelial cells.

3. Describe how the flu affects the respiratory system and other systems of the body.
Influenza targets epithelial cells lining the respiratory tract. It causes:

Damage to the respiratory lining.
Immune response including inflammation, fever, and mucus production.
Systemic effects due to cytokines, affecting muscle (aches), digestive (nausea), and nervous (headache) systems.

4. Explain the contents of a flu vaccine and how these vaccines are produced.
Flu vaccines contain:

Inactivated or recombinant viral proteins.
Stabilizers (gelatin/sorbitol).
Preservatives (formaldehyde).
Adjuvants (aluminum salts) to boost immune response.

Production methods include:

Egg-based: Growing viruses in fertilized eggs.
Cell culture: Growing viruses in mammalian cells.
Recombinant process: Using only the H spike protein, grown in insect cells.

5. Explain how the process of evolution relates to the study of biology.
Evolution is a unifying theory explaining how species change over time due to genetic variation and natural selection. It helps explain viral evolution, antibiotic resistance, and species adaptation.

6. Understand how the process of natural selection represents the mechanism of evolutionary change.
Natural selection favors traits that enhance survival and reproduction. Individuals with advantageous traits pass them on, leading to adaptation and evolutionary change.

7. Summarize the scientific evidence supporting that populations evolve over time.
Evidence includes:

Fossil record showing species change over time.
Comparative anatomy, showing homologous and analogous structures.
Genetics, showing similarities in DNA across species.
Embryology, showing similar development patterns in embryos.

8. Explain the two processes by which the influenza virus evolves.

Antigenic drift: Small mutations in H and N spikes over time, gradually altering the virus.
Antigenic shift: Sudden combination of genetic material from two different influenza viruses in a host, creating a radically new virus.

9. Explain the role of the immune system in protecting the body from pathogens.
The immune system detects and eliminates pathogens using:

Innate defenses (physical barriers, inflammation, phagocytes).
Adaptive immunity (T and B cells targeting specific antigens and remembering past infections).

10. Describe how the immune system responds to an influenza infection.

Innate response: Epithelial barriers, cytokines, macrophages, and neutrophils respond immediately.
Adaptive response:
- Cell-mediated immunity: Cytotoxic T cells destroy infected cells.
- Antibody-mediated immunity: B cells produce antibodies to neutralize free virus particles.

11. Describe developing treatments for influenza.

Antiviral medications (e.g., Tamiflu) block virus release.
Universal flu vaccines are being developed to target core proteins, which mutate less than surface spikes.
Recombinant vaccines allow rapid production, especially in response to new viral strains.