VIRUSES

VIRUS: (LATIN) REFERRING TO POISON AND OTHER NOXIOUS THINGS

VIRUS STRUCTURE

• ENVELOPE – OUTER COVERING MADE OF PROTEIN

• CAPSID – CAPSULE MADE OF PROTEIN. ENCLOSES NUCLEIC ACID

See next screen for typical diagram

VIRUS

STRUCTURE

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VIRUSES – Are they alive?Remember your 6 Unifying Principles: An

organism must fully meet all 6 to be considered living.

1. Evolution- Viruses mutate but only within a host

2. Homeostasis- Viruses do not regulate their internal environment

3. Growth & Development- Viruses do neither on their own

4. Continuity- A virus can only reproduce using a host cell

5. Energy, Matter, and Organization- A virus has no enzymes for metabolism

6. Ecology- Viruses depend on other organisms, but other organisms do not depend on viruses

NO!Viruses are not alive!

Viruses DO NOT completely meet ANY of the 6 Unifying Principles of

Biology!

VIRUSES ARE:OBLIGATE INTRACELLULAR

PARASITES(They are incapable of replicating except when inhabiting the

inside of a cell.)

•Viruses are a set of encapsulated genes that can be transmitted between a defined set of host

cells.

•To access a cell, a virus displays a receptor protein on its surface allowing it to be recognized

by the host cell.

•Some viruses may infect just humans, others infect a variety of organisms (what viruses

infect=host range)

• FIRST: A virus must have a means of placing its genetic material into a host cell

• SECOND: Once in, the host cell’s normal processes are hijacked by viral proteins

• THIRD: The host cell’s DNA is reprogrammed to produce new viral proteins and genetic material at a FAST rate!

Viruses use the cell’s:Amino acids, nucleotides, and ATP (for energy)

VIRUS INFECTION

Virus Reproduction ProcessVirus Reproduction Process

a.a. AbsorptionAbsorption

b.b. EntryEntry

c.c. ReplicationReplication

d.d. ReleaseRelease

BACTERIA VIRUSES

• Group of viruses that infect BACTERIA only

• Called BACTERIOPHAGE or PHAGE for short

BACTERIOPHAGE

REPRODUCTION OF A BACTERIOPHAGE

Latent Viruses

• “Latent” or “hidden” viruses may exist in a host

• They are inactive

• They are unrecognizable by the immune system

• They may be triggered and enter the lytic cycle

LYTIC AND LYSOGENIC STAGES OF A VIRAL INFECTION IN BACTERIA

Lysogenic Cycle of a Temperate Virus

Remains in cell Activated to produce new viruses

--Does not cause disease --Does not cause disease immediatelyimmediately

HIV reproductionStep 1:

• The genome enters a special T-cell variant through two cytokine receptors

HIV reproductionSteps 2 and 3:

• The endogenous reverse transcriptase converts the viral RNA genome into a DNA genomes.

HIV reproductionStep 4:

• Special sequences and an integrase enzyme allow the viral DNA to incorporate into the host DNA

HIV reproductionSteps 5 and 6:

• From the viral genome, new viral protein components are made

HIV reproductionStep 7 and 8:

right time, the capsid reforms and the viral RNA genome is re-incorporated. New virus buds from the infected cell.

___________________

* 200 kinds of Viruses

Symptoms include nasal discharge, obstruction of nasal breathing, swelling of the sinus membranes,

sneezing, sore throat, cough, and headache.

Common Cold

__________________

•Poliomyelitis is a crippling disease of spinal nerve cells caused by poliovirus infection.

•The disease can strike non-immune persons of any age but affects mainly children under the age of three, and causes paralysis in one case of every 200 to 1000 infections.   

•Preventable by vaccination. 

Polio

______________

Acquired immunodeficiency syndrome, is caused by the human immunodeficiency virus,

or HIV.

HIV destroys the body's ability to fight infections by attacking cells of the immune

system.

STDSTD

AIDS

______________

The vast majority of cases reported to the Centers for

Disease Control and Prevention (CDC) each

year occur in wild animals like raccoons, skunks,

bats, and foxes.

Infects the central nervous system, causing

encephalopathy and ultimately death.

Rabies

______________

(Herpes simplex )

•Between 50 - 80% of all people possess this virus and is spread through direct contact with an infected individual.

•Once the virus has entered the body, it cannot be removed.

• Only 10% of HSV1 infected people ever develop a sore.

                    

Cold Sore

_____________

It usually occurs durally occurs during adulthood after exposure to chicken pox in childhood. The chicken pox virus remains dormant in the body.

_____________

Most infected children will have a rash, high fever, cough, runny

nose, and watery eyes.

For every 1,000 children who get it, 1 or 2 will die from it

Spreads so easily that any child who is not immunized will

probably get it, either now or later in life.

Measles

___________

Non-cancerous skin growths caused by a

viral infection in the top layer of the skin. Viruses

that cause them are called human

papillomavirus (HPV). STDSTD

Warts

_______________

HSV-2 usually produces only mild symptoms or signs or no symptoms at

all.

However, HSV-2 can cause recurrent painful genital sores in many adults, and HSV-2 infection can be severe in people

with suppressed immune systems.

Regardless of severity of symptoms, genital herpes frequently causes

psychological distress in people who know they are infected.

STDSTD

Herpes

_____________

The most common serious liver infection in the world.

It is caused by the HBV virus that attacks the liver.

HBV is 100 times more infectious than the AIDS virus. Yet, can be prevented with a safe and effective vaccine.

Hepatitis B

C. Virologist

1. Growing cells in a controlled medium: ________________2. Serology

3. _____________is used to separate fragments of molecules based on charge and size.

4.. Studies bacteriophages.

Tissue culture

- study of biological fluids used to determine antibody response

Electrophoresis

The End