Biology TodayThird Edition

Chapter 16

HIV and AIDS

Copyright © 2004 by Garland Science

Eli Minkoff • Pam Baker

Chapter 16HIV and AIDS

A. Definitions and HistoryAIDSTh cellsclustersKoch’s postulate

B. VirusesWhat are they?How do they reproduce?

C. HIV infectionStagesSymptomsTestsTreatmentPrevention

AIDS

Acquirednot born with it

ImmunoDeficiencyimmune system is weakened

Syndromewide range of symptoms

Th cells

Produce IL-2

•Needed by B-cell to make anitbodies

•Needed by Tc cells

Figure 16.1

Th cells

Destroyed in AIDS

Lose Tc cells and the ability to make antibodies

Vulnerable to infection

History

1981 Pneumocystis carnii cluster1981 Kaposi sarcoma cluster

in homosexual males

History

Kaposi’s sarcoma also seen in kidney transplant patients

(taking immunosupressive drugs)

1982 called AIDS

All patients had low Th cells

History

1983 French group found RT(reverse transcriptase from

retrovirus)

NIH group grew suspect virus

Found antibodies in patients

1986 named HIV(human immunodeficiency virus)

Montagnier

Gallo

Koch’s postulate (late 1800’s)

To prove that a “microorganism” causes a disease you must demonstrate that:

Koch’s postulate (pg. 579, BT3)

1. The microorganism is found in all “people” with the disease.

2. The microorganism is not found in “healthy” people.

3. Microorganism must be isolated and grown in pure culture.

4. Injecting microorganism into a person should cause the disease…

Koch’s postulate

Koch showed that different bacteria caused Anthrax and TB

(Nobel prize)

Proven ?

Koch’s postulate

Does HIV cause AIDS ?

Most agreeSome still doubt

Does HIV cause AIDS ?

Most agree

Gallo’s criteriapg. 581 BT3

1. HIV (or it’s antibody) is found in the vast majority of patients with AIDS.

2. HIV is found in most people with ARC

3. HIV is a new virus, AIDS is a new disease

4. If HIV is found, AIDS is to; no HIV, no AIDS

5. HIV-contaminated blood spreads AIDS

6. Th cells are low in AIDS and are attacked by HIV

7. HIV is found in brains of AIDS patients who die of AIDS (dementia is a symptom)

What is a virus?

Nucleic acid (DNA or RNA)Protein coat (and maybe envelope)

How Small ?

human cell 1 meterbacteria footballvirus M&M

What is a virus?

Nucleic acid (DNA or RNA)Protein coat (and maybe envelope)

Are they alive?

Cannot replicate on their own

Properties of Living Things• Living things are organized• Living things are metabolic• Living things respond to stimuli• Living things are homeostatic• Living things grow (biosynthesis)• Living things contain genetic material• Living things reproduce• Living things form populations

Figure 16.3

Figure 16.4

1. Virus attachment and2. fusion

3. Retrovirus (RNA)

Reverse transcriptase

RNA DNA

4. Insert into host DNA

5. Host transcribes viral mRNA

6. Make viral proteins etc

7. Assemble viruses

8. Release of viruses

Viruses

Can not replicate on their own

Must use another cells machinery to replicate

Are they living?

Stages of Infection with HIV

Initial infectionflu-like symptomsantibodies produced HIV+

Asymptomatic phasemonths to years

AIDSTh cells declineopportunistic infections

Figure 16.7

AIDS

Th cell declineOpportunistic infectionsHigh feversNight sweatsGeneral weaknessMental deterioration (dementia)Weight loss

HIV+ ?

Most tests detect antibody made against HIV (weeks or months)

ELISA testWestern blot

PCR

$$$

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Figure 16.7

What does HIV+ mean?

Can HIV- person be infected?

Can HIV- person pass disease?

Treatments:

Reverse transcription inhibitors

Protease inhibitors

Fusion blockers

Combination therapy

Figure 16.8

Variable disease progression

Will everyone who is infected with HIV get AIDS ?

We don’t know

12 year study in San Francisco

65% with AIDS; 35%, not yet

Prevention (lowering risks)

High risk behavior

•sharing body fluidsBlood, semen, vaginal secretions

•sharing needles

•pregnancy (untreated)

Prevention (lowering risks)

Moderate risk behavior

•using condoms during sex•breast-feeding•receiving blood transfusion•accidental needle stick•infected dental workers•kissing, “deep”

Prevention (lowering risks)

Low risk behavior

•sharing toothbrush/razor•tatoos•receiving saliva or tears•oral sex

Prevention (lowering risks)

No risk behavior

•shaking hands•sharing toilet•sharing eating utensils•being sneezed on•working in same room•handling pets•“shallow” kissing

Figure 16.9

Chapter 16HIV and AIDS

A. Definitions and HistoryAIDSTh cellsclustersKoch’s postulate

B. VirusesWhat are they?How do they reproduce?

C. HIV infectionStagesSymptomsTestsTreatmentPrevention

End of 16