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Viruses Viruses & & Human Health Human Health June 23, 2009 1 SBI3C

Viruses& Human Health Human Health June 23, 20091SBI3C

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VirusesViruses

&&• Human HealthHuman Health

June 23, 2009 1SBI3C

April 19, 2023 SBI3C 2

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

3. some viruses are cause cells

to become cancerous

2

(AIDS)

ex. Human Papiloma Virus (HPV)

(genital warts)(cervical cancer)

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 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 reproduceex. polio vaccine, hepatitis B vaccine

Protection Against Viral Diseases

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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

Viral Uses In Medicine

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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AIDSHIV (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

Semen11,000 Vaginal

Fluid7,000

Blood18,000

Amniotic Fluid4,000 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

CycleAIDS

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HIV positive: virus is in its lysogenic cycle (dormant)patient is not sick, but is a carrier of the viruscan 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

BronchitisPneumonia

TuberculosisLung 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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• 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

Drug Therapy

Homework• Read ‘Sex Slaves for Science’

article• Answer questions 1 – 11

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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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Viral Uses In Medicine

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AIDSHistory

• 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 Immuno- deficiency 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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• 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

History - continued

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Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006

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