Download 4. Viruses & Human Health

Viruses
&
• Human Health
June 23, 2009
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Viral diseases are difficult to treat because:
1. No drug is available to kill viruses in the body
2. Some viruses are lysogenic  can remain dormant
for years (hide inside cells)
ex. a) Herpes Simplex Virus I (HSV I)
(cold sores)
b) HIV
(AIDS)
3. some viruses are cause cells
to become cancerous
(genital warts)
(cervical cancer)
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ex. Human Papiloma Virus (HPV)
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Protection Against Viral Diseases
vaccines: only true protection against viral diseases
people are given a dead or weakened form
of the virus
builds up an army of WBC’s & antibodies to
kill the living virus immediately before it
can reproduce
ex. polio vaccine,
hepatitis B vaccine
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Viral Uses In Medicine
1. Viral Vectors
Viruses can be used for gene
therapy as “carriers”
Viral core is removed &
desired human gene is added
Virus is mixed with living
cells
Virus attaches to human host
cell & injects the human gene
i.e. acts like a microscopic
hypodermic needle
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SOME EXTRA INFO ON HIV…
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Worldwide HIV Distribution
Note: Total exceeds 100 percent due to rounding.
Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006.
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Structure of HIV
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AIDS
HIV (Human Immunodeficiency Virus)
virus that causes AIDS
RNA core (retrovirus)
can only infect helper T cells (type of white blood cell)
cannot survive outside the body because
glycoprotein membrane around its capsid dries
out
can only be transmitted from 1 bodily fluid to another
ex. 1. blood to blood: needles, transfusions,
toothbrushes
2. semen & vaginal secretions
3. breast milk
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Transmission of AIDS (Worldwide)
• HIV in Body Fluids
Blood
18,000
Semen
11,000
Vaginal
Fluid
7,000
Amniotic
Fluid
4,000
Saliva
1
Average number of HIV particles in 1 mL of these body fluids
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Life Cycle of HIV
Lysogenic Cycle
HIV+
Lytic Cycle
AIDS
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HIV positive:
virus is in its lysogenic cycle (dormant)
patient is not sick, but is a carrier of the virus
can infect others
AIDS (Acquired Immunodeficiency Syndrome)
patient has symptoms of the disease
(begins when HIV enters the lytic cycle)
WBC’s are being destroyed
Early symptoms:
night sweats, diarrhea, cold symptoms
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AIDS Associated Disease
Late Symptoms
•
•
•
Gastrointestinal: Cause most of illness
and death of late AIDS
Symptoms:
Wasting (extreme weight loss)
Abdominal pain
Infections of the mouth and esophagus
Respiratory: 70% of AIDS patients
develop serious respiratory problems
Bronchitis
Pneumonia
Tuberculosis
Lung cancer
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More AIDS Associated Disease
• Skin Disorders: 90% of AIDS
patients develop skin or mucous
membrane disorders
•
•
Herpes
Thrush
•
Eye Infections: 50-75% patients
develop eye conditions.
•
Dry eye syndrome
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The ultimate fate
of a patient with AIDS
•
patient dies from other
infections due to a lack of
immune response
ex. pneumonia
cancer
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Transmission of AIDS (Worldwide)
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“When you have sex with someone, you are
having sex with everyone they have ever had
sex with.”
Former US Surgeon General
C. Everett Koop
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Drug Therapy
• Reverse Transcriptase Inhibitors: Competitive
enzyme inhibitors. Example: AZT, ddI, ddC
• Protease Inhibitors: Inhibit the viral proteases.
Prevent viral maturation
• Problem with individual drug treatments: Resistance
• Drug Cocktails: A combination of:
• One or two reverse transcriptase inhibitors
• One or two protease inhibitors
• Drug cocktails have been very effective in
suppressing HIV replication and prolonging the life
of HIV infected individuals, but are not considered
to be a cure
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Homework
• Read ‘Sex Slaves for Science’ article
• Answer questions 1 – 11
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Viral Uses In Medicine
2. Oncolytic viruses used in targeted cancer treatment
Choose a nonpathogenic virus that can infect human
cells is chosen ex. Vaccinia (cowpox)
Allow this virus to attack human tumour cells
After reproducing, viruses released kill host cancer
cell i.e. lytic cycle
New viruses infect neighbouring tumour cells
Also stimulate immune system, bringing WBC’s in to
help kill cancer cells
Note: cancer  is caused by a mutated ‘stop’ gene
 results in uncontrollable cell division
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AIDS
History
•
•
•
•
•
•
•
1950s: Blood samples from Africa have HIV
antibodies
1976: First known AIDS patient died
1980: First human retrovirus isolated (HTLV-1)
1981: First reports of “Acquired Immunodeficiency Syndrome”
1983: Virus first isolated in France (LAV)
1984: Virus isolated in the U.S.
1985: Development and implementation of
antibody test to screen blood donors
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History - continued
• 1986: Consensus name Human Immunodeficiency
Virus (HIV-1)
Related virus (HIV-2) identified
• 1992: AIDS becomes the leading cause of death
among adults ages 25 - 44 in the U.S.
• 1997: Mortality rates of AIDS starts to decline due
to the introduction of new drug cocktails
• 2005: World Health Organization (WHO) predicts
up to 40 million infected individuals
• More than 22 million have already died
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HIV Prevalence Worldwide
Adults Ages 15-49 with HIV
15.01% - 34.0%
5.01% - 15.0%
1.01% - 5.0%
0.51% - 1.0%
0.0% - 0.5%
Not available
Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006
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