Upload
gwendoline-oliver
View
216
Download
3
Embed Size (px)
Citation preview
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)
April 19, 2023 SBI3C 3SBI3C 3
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
April 19, 2023 SBI3C 4SBI3C 4
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
SBI3C 6
Worldwide HIV Distribution
Note: Total exceeds 100 percent due to rounding.Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006.
April 19, 2023 SBI3C 8SBI3C 8
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
SBI3C 9
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
April 19, 2023 11
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
SBI3C 11
April 19, 2023 SBI3C 12SBI3C 12
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
April 19, 2023 SBI3C 13SBI3C 13
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
April 19, 2023 SBI3C 14
The ultimate fate of a patient with AIDS
• patient dies from other infections due to a lack of immune response
ex. pneumonia
cancer
SBI3C 16
“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
SBI3C 18
• 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
April 19, 2023 20
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
SBI3C 20
Viral Uses In Medicine
April 19, 2023 SBI3C 22SBI3C 22
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
April 19, 2023 23SBI3C 23
• 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