1. Viruses and Immunity

2. What is a virus?
A virus particle, or virion, consists of the following:
Nucleic acid - Set of genetic instructions, either DNA or RNA, either single-stranded or double-stranded
Coat of protein - Surrounds the DNA or RNA to protect it
Lipid membrane - Surrounds the protein coat (found only in some viruses, including influenza; these types of viruses are called enveloped viruses as opposed to naked viruses)

3. Lytic cycle A virus particle attaches to a host cell.
The particle releases its genetic instructions into the host cell.
The injected genetic material recruits the host cell's enzymes.
The enzymes make parts for more new virus particles.
The new particles assemble the parts into new viruses.
The new particles break free from the host cell.

4. Once the new viruses are made, they leave the host cell in one of two ways:
They break the host cell open (lysis) and destroy the host cell.
They pinch out from the cell membrane and break away (budding) with a piece of the cell membrane surrounding them. This is how enveloped viruses leave the cell. In this way, the host cell is not destroyed.

5. How a virus works… An infected person sneezes near you.
You inhale the virus particle, and it attaches to cells lining the sinuses in your nose.
The virus attacks the cells lining the sinuses and rapidly reproduces new viruses.
The host cells break, and new viruses spread into your bloodstream and also into your lungs. Because you have lost cells lining your sinuses, fluid can flow into your nasal passages and give you a runny nose.
Viruses in the fluid that drips down your throat attack the cells lining your throat and give you a sore throat.
Viruses in your bloodstream can attack muscle cells and cause you to have muscle aches.

6. What are some examples of viruses?
Common cold
Influenza and Avian Influenza
Chickenpox
Ebola
AIDS
HPV
SARS
Shingles
Smallpox
Human Immunodeficiency Virus (HIV)
bovine spongiform encephalopathy ("mad cow" disease)
Viruses that have an association to cause human cancers include some genotypes:
human papillomavirus (HPV)
hepatitis B
hepatitis C
Epstein-Barr virus
Kaposi's sarcoma-associated herpesvirus and human T-lymphotropic virus

7. How are viruses classified?
They are classified by:
Shape
Nucleic acid they contain (DNA or RNA)
The kind of organism they infect

8. What do viruses need?
A virus is a type of parasite—it depends on a host organism for survival and reproduction

9. How do viruses behave? A virus may be active
A virus can be dormant or latent

10. Active Virus
ATTACHMENT: A specific virus attaches to the surface of a specific cell
INVADE: The nucleic acid (DNA or RNA) of the virus is injected into the cell.
COPY: The viral nucleic acid takes control of the cell an begins to make new virus particles.
RELEASE: The cell bursts open, hundreds of new virus particles are released from the cell. These virus particles go on to infect other cells.

11. How does our body respond to viruses?
Immunobiology, 5th ed. Janeway

12. Reduction of the spread…
Carrier organisms - mosquitoes, fleas
The air
Direct transfer of body fluids from one person to another - saliva, sweat, nasal mucus, blood, semen, vaginal secretions
Surfaces on which body fluids have dried

13. What are vaccines?
A vaccine is a substance that stimulates the body’s immune response.
The goal of vaccination is to prevent or control an infection.

14. Immunity
Immunity
The ability of the body to fight infection and/or foreign invaders by producing antibodies or killing infected cells.
Immune System
The system in the body responsible for maintaining homeostasis by recognizing harmful from nonharmful organisms and produces an appropriate response.

15. Foreign Invaders Called Pathogens Antigens
Viruses, bacteria or other living thing that causes disease/immune response.
Antigens
Toxins that pathogens produce that cause harm to an organism.

16. Parts of the Immune System
Blood - White Blood Cells in particular.
Lymph nodes
Thymus Gland – Produces T Lymphocytes
Bone Marrow – Produces B Lymphocytes

17. How does the body fight infection/foreign invaders?
The Body’s THREE lines of Defense
First Line of Defense – The Skin
Provides Physical and Chemical barriers
Physical – hard to penetrate, made of indigestible keratin
Chemical – tears, sweat

18. Second Line of Defense – Nonspecific Immune Response
These are defenses the body uses no matter what the invader may be. These defenses include:
Phagocytosis – (WBC) done by Macrophages
Natural Cell Killers
Inflammation - caused by release of Histamine from leukocytes
Fever – caused by histamines. The fever (high temp) kills invaders by denaturing their proteins.
Macrophage: A phagocytic cell found in the liver, spleen, brain and lungs Travels to all areas of the body to find and eat pathogens.

20. Third Line of Defense – Specific Immune Response
This is a specific response to a specific pathogen/antigen.
The response involves the creation of Antibodies.

21. Antibodies Y-shaped protein molecule.
Made up of variable and constant regions.
Made up of Heavy and Light chains.
Produced by B- Lymphocytes
Function: Recognize antigens, bind to and deactivate them.
Note: Variable region recognizes the anitgens.

22. How an antibody operates/works?
Deactivation of a bacterium by an antibody.

23. The Pathway of Specific Immune Response
Pathogens
Pathogens eaten by Macrophage
Displays portion of Pathogen on surface
Helper-T cell recognizes Pathogen
Step 1
Step 2
Step 3

24. Activates B- Cell
Activates Cytotoxic
T- Cell
Memory B-Cell
Memory T-Cell
Kills Infected Cells
Antibodies

25. Cellular Immunity .vs. Antibody Immunity
Cellular Immunity Antibody or Humoral Immunity
Carried out by T-Cells
Infected cells are killed by Cytotoxic T –Cells.
Carried out by B-cells
Antibodies are produced and dumped into blood stream.
Antibodies bind to antigens and deactivate them.

26. Immune Response Explained
Antigen infects cells.
Macrophage ingests antigen and displays portion on its surface.
Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active.
Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells.
Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells.
Active Cytotoxic T-Cells kill infected cells.
At the same time, B-Cells divide into Plasma Cells and Memory B- Cells.
Plasma cells produce antibodies that deactivate pathogen.
Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.
Supressor T-Cells stop the immune response when all antigens have been destroyed.

27. Primary .vs. Secondary Immune Response
Primary Immune Response
This is a response to an invader the First time the invader infects the body.
No measurable immune response for first few days.
Next 10 – 15 days antibody production grows steadily
Secondary Immune Response
A more rapid response to an invader the 2nd time it invades the body.
Antibody production increases dramatically and in a much shorter time period..

28. Primary .vs. Secondary Immune Response

29. Passive .vs. Active Immunity
This is immunity where the body is “actively” producing antibodies to fight infection.
Ex: You have a throat infection and you are actively creating antibodies to fight it.
Vaccination: An injection of a weakened strain or DEAD of an infectious microbe (pathogen) that causes the body to undergo active immunity (produce antibodies).
Passive Immunity
This is immunity where antibodies are given to a person from the blood of another person or animal.
This immunity only lasts for a short period of time.
ex: Breastfeeding mothers pass antibodies to their children through the milk.

30. Autoimmune Disease
Autoimmune diseases are diseases where the immune system begins to attack itself.
Ex:
Rheumatoid Arthritis – crippling disease of the joints.
Lupus – disease of blood and organs.
Multiple Sclerosis – disease of nervous system
Cause(s): unknown
Cures/Treatments: No known cures. Usually treated with drugs.

31. Allergies
Allergy - An exaggerated response by the immune system to an allergen. Allergen: a normally harmless substance that causes an allergic reaction. ex: dust, pollen, mould, food, insect stings Types of Allergic reactions There are two types of allergic reactions. a. Immediate – occurs within seconds and normally lasts for about 30 mins. b. Delayed – takes longer to react and can last for a much longer time.

32. What happens during an allergic reaction?
During an allergic reaction antibodies cause histamines to be released from certain cells.
Histamines cause:
a. Swelling of tissues
b. Release of fluids (runny noses and eyes)
c. muscle spasms (some cases)
Anaphylaxis or anaphylactic shock:
This is the sudden and severe allergic reaction to a substance that can cause death.
Treatments for Allergies
Avoidance of material – especially food.
Epinephrine – “epi – pen”
Antihistamines -- benadryl

33. Epidemiology
Viral epidemiology is the branch of medical science that deals with the transmission and control of virus infections in humans. Transmission of viruses can be vertical, that is from mother to child, or horizontal, which means from person to person

34. Epidemics and Pandemics
When outbreaks cause an unusually high proportion of cases in a population, community or region they are called epidemics.
If outbreaks spread worldwide they are called pandemics

35. Treatment
Because viruses use the machinery of a host cell to reproduce and reside within them, they are difficult to eliminate without killing the host cell.
The most effective medical approaches to viral diseases so far are vaccinations to provide resistance to infection, and antiviral drugs.