Conversation Starters…

1. Describe the steps of viral replication.2. What is an obligate parasite?3. Where did HIV come from?4. What is a retrovirus?

HIV/AIDS AND OTHER INFECTIOUS AGENTS

Modified with permission from a powerpoint originally from Mrs. Jenn Boyd, Westlake High School

I. Viruses:The Human and Animal Impact

A. Virus: comes from Latin for “Poison”B. Can be economically devastating by damaging crops, domesticated

animalsC. Ex. rabies• humans get virus by animal bite (saliva) causes inflammation of CNS

4. Myxomatosis in rabbits• Ex. Australia

Rabbits were introduced to Australia. They increased in numbers and were eating all of the grass. To control their population, Myxoma virus spread by fleas or mosquitoes was used to kill them.

I. Viruses:The Human and Animal Impact

II. Autoimmune DiseasesA. General Mechanism:

1. The immune system MISTAKES its own cells for pathogens,

2. THE IMMUNE SYSTEM ATTACKS THE TISSUE OF THE BODY.

B. Examples:A. RHEUMATOID ARTHRITIS: Destructive inflammation of the

joints. B. MULTIPLE SCLEROSIS: Nerve disease that results from

destruction of myelin sheath of nerve fibers.C. LUPUS: Inflammation of skin, joints, heart, brain, lungs, and

kidneys.

III. HIV and AIDSA. AIDS

1. Acquired Immunodeficiency Syndrome (AIDS)2. Caused by the HUMAN IMMUNODEFICIENCY VIRUS or HIV3. AIDS IS NOT A specific disease, but a condition in which the immune

system CANNOT protect the body against a variety of pathogens.

B. HIV1. Attacks the human immune system and destroys the body’s ability to fight

infection.

A. HIV enters the body and attaches to receptors on the surface of a type of T Cell known as HELPER T CELLS. • T Cells help other Lymphocytes respond to the early stages of an infection.

B. HIV destroys Helper T cells body loses its ability to fight off disease

C. NET: HIV destroys body's ability to defend itself

IV. HIV Mechanism of Infection

QUICK CHECK:

1. What does AIDS stand for?2. What does HIV stand for?

QUICK CHECK:1. What type of cell is destroyed by HIV?2. The process of DNA turning into mRNA is called t__________.3. The process of mRNA being used to make proteins is called

t______________.

C. HIV is a Retrovirus1. RNA genome2. Contains Reverse Transcriptase: turns RNA sequence into a DNA

strand3. Viral DNA is integrated into the host DNA (= provirus)4. It is replicated whenever the host DNA replicates5. New viruses are produced and released

QUICK CHECK

What does reverse transcriptase do?

V. Transmission of HIV

A. HIV can only be spread through direct contact of certain body fluids (eg. blood, semen, breast milk).

1. Transmitted through sexual intercourse, sharing needles, transfusion of contaminated blood.

B. Not spread by:1. Casual contact (eg. holding hands, using dishes previously

used by a person with HIV)2. Insects (mosquitoes, fleas, ticks)

A. No known cure for HIV infectionB. No vaccine (at present) C. Only avoid behaviors that place you at risk of contracting

the virus. D. Recently in the news:

1. Abzyme (antibody + enzyme): found in lupus patients is able to degrade the part on HIV that binds to helper T cells.

2. Attempts to increase mutation rate of the virus3. Bone marrow transplant: • double CCR5 mutation bone marrow transplanted into a person with HIV

1.bone marrow makes RBCs and WBCs2.going to be expensive to do human trials3.risky to do bone marrow transplants (1/3 survival rate)

VI. Treatment of HIV

E. CCR51. Signal receptor on outside of

helper T cells2. 32-bp (base pair) deletion• causes a shift during the making of the

proteins on the surface

Who is Most Likely to Have ΔCCR5?

VII. Stages of HIV Infection

A. HIV infection progresses in stages.1. When first infected by the virus, a person may have flu like symptoms or no

symptoms. 2. Within a few weeks to several months, antibodies to HIV begin to appear in

the blood. 3. Presence of antibodies in the blood used to:

1.diagnose disease

2.screen donated blood

B. HIV POSITIVE = HIV antibodies can be detected in and are present in the blood.

C. Other symptoms of the syndrome may not appear for months or even years.

VII. Stages of HIV Infection

QUICK CHECK

Does HIV follow the lytic or lysogenic cycle? How do you know?

D. AIDS = number of Helper T cells drops below 200/mL • Immune system cannot fight disease

E. May take from a few to 20 years to get to this point

F. People with AIDS may be susceptible to a variety of diseases.• Typically people with AIDS become sick when they are

infected by pathogens that do not normally cause disease in people with healthy immune systems. • These diseases are called OPPORTUNISTIC

INFECTIONS.

VII. Stages of HIV Infection

QUICK CHECK

1. When does somebody have AIDS?2. Can someone have HIV and not have AIDS?

VIII. ViroidA. Short circular pieces of RNA that infect plants.• Do not code for proteins

B. Uses host’s enzymes to replicate and stunts host’s growth. C. Can be transferred by insects.• Ex. Potatoes, tomatoes, avocados

IX. Prion Disease: Mad Cow DiseaseA. Caused by a prion

1. PRION: mis-folded protein that caused other proteins to become mis-folded

B. Characteristics:1. NO nucleic acid2. Long incubation period

C. Examples:1. Mad cow disease: brain wasting disease. Makes holes in

brain tissues.2. Creutzfeldt-Jakob Disease (CJD): brain disease in humans.3. Scrapie: neurodegenerative disease in sheep4. Feline spongiform encephalopathy: in cats

X. Prion Disease: Kuru

A. Rare disease in New GuineaB. Cultural Traditions: Cannibalism--ate the brains of dead people as

part of a funeral ritual• Practice stopped in 1960, but cases of kuru were reported for many

years afterward. • Why?

XI. Immunity & VaccinationA. A person who becomes resistant to a specific pathogen is said to

have acquired immunity.B. Vaccination: contains modified pathogens that can no longer cause

disease. C. The antigens stimulate an immune response, producing memory

cells against it.• Polio, measles, mumps, tetanus

Learning Log:

1. How does a vaccine work? 2. What is an autoimmune disease?3. Describe how a retrovirus replicates.