1. Viruses

2. What is a Virus?
Viruses are tiny, non-cellular, infectious agents that invade living cells and take over their machinery to make copies of themselves.

3. What is a Virus?
Viruses are NOT considered living based on the characteristics of life, because they:
Do not make/use energy or have any metabolism (they have no organelles)
Cannot reproduce on their own
Are not made of cells
Do not grow/develop on their own

4. Virus Structure Bacteriophage Capsid – made of protein, Tail
Infects bacterial cells
MOST IMPORTANT PART
Capsid – made of protein,
contains the genetic material
(DNA or RNA)
Tail
Tail Fibres- used for
attaching to target cell

5. Virus Structure Influenza HIV ‘The Flu’ Capsid – made of protein,
Human Immunodeficiency
Virus
MOST IMPORTANT PART
Capsid – made of protein,
contains the genetic material
(RNA)
Antigens
- made of lipids/glycoproteins, help the virus to attack and enter their target
Also help the immune system to identify the virus

6. Viruses Vocab
Viruses are obligate parasites – organisms that need to live in/on another being to survive and do not benefit them in any way
Host - The organism/cell that a parasite exploits
Viruses are pathogens – something that causes disease in the host cell/organism

7. How Viruses Work
Step One – Viruses attach to their specific target cell based on their antigens. This works like a lock and key, so viruses will only affect certain cells.

8. How Viruses Work
Step Two – The virus will inject its genetic information into the host

9. How Viruses Work
Step Three – The cell now starts to make copies of the virus proteins and genetic information
Step Four – The different parts of the virus are assembled into full virus copies

10. How Viruses Work
Step Five – The virus causes cell lysis (cell bursting apart) and the virus copies are released

11. How Viruses Work

12. Lytic/Lysogenic Cycles
Viruses can infect cells in two different ways
If a virus enters and immediately causes infection with the 5 steps, it is called the Lytic Cycle

13. Lytic/Lysogenic Cycles
Viruses can infect cells in two different ways
If a virus enters and remains dormant/inactive in the DNA before causing infection, it is called the Lysogenic Cycle

14. Immune Response
Your immune system recognizes viruses and bacteria based on their surface antigens
Every cell in your body has your specific markers, so anything that looks different is marked by your body as an invader
(this is why people need specific organ transplants and also why you can’t receive blood transfusions from everyone)

15. Immune Response The Immune System protects the body in two ways:
Nonspecific Response: Skin, mucus, sweat, tears, and inflammatory response (heat, redness, swelling, and white blood cells)
Specific Response: Body makes antibodies which seek out and kill specific antigens

16. Brace yourself for the next slide!!
Immune Response
The immune system is incredibly complex which is why it has an entire branch of science called immunology
Brace yourself for the next slide!!

17. Specific Response
There are many cells that are responsible for the specific immune response: Macrophages/Phagocytes- Large cells that ‘eat’ the virus/bacteria and show the T Cells and B Cells the antigen to target Helper T Cells – Cells that tell B Cells, Cytotoxic T Cells, and Natural Killer Cells what to do B Cells – Cells that make Plasma Cells and Memory B Cells Plasma Cells – Cells that make antibodies which target the virus/bacteria Memory B Cells- Cells that ‘remember’ the antigen so they can quickly kill the virus/bacteria if it shows up again later Cytotoxic T Cells – Cells that make poison granules to kill the virus/pathogen Natural Killer Cells - Cells that kill any infected or out of control (cancer) cells

18. Specific Response
HIV attacks Helper T Cells which greatly weakens the immune system
This is how HIV (the virus) causes AIDS - Acquired Immunodeficiency Syndrome (the disease)

19. Medication
Viruses are very difficult to target with medications because they are not living by our definition of life
Antibiotics are medications that are designed to kill living cells so they are useless against viruses

20. Vaccines
Vaccines have been developed for a number of viruses/bacterial infections.
A vaccine actually contains weakened or dead viruses that trigger the immune system to start making antibodies which will protect you in the future

21. Vaccines Currently available vaccines: Keep in mind that not all
vaccines are 100% effective
Currently available vaccines:
DTaP
Shingles
Hepatitis A, B
Tdap
HiB Td
HPV
Varicella (Chickenpox)
Influenza (The Flu)
Adenovirus
Measles, Mumps, Rubella, Varicella
Anthrax
Meningococcal
Japanese Encephalitis
MenB
Rabies
Pneumococcal Conjugate Pneumococcal Polysaccharide
Smallpox
Typhoid
Polio
Yellow Fever
Rontavirus