Viruses & Human Health ‏

1. SBI3C Viruses & • Human Health‏

2. SBI3C Viral diseases are difficult to treat because: 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 some viruses are oncoviruses cause cells to become cancerous onco = tumour (AIDS) (genitalwarts) (cervical cancer) ex.Human Papiloma Virus (HPV) 2

3. SBI3C 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 • antiviral agents: • drugs given after infection to • slow the reproduction of the virus • ex. Valtrex – helps heal and decrease pain • (herpes) SBI3C 3

4. SBI3C 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 SBI3C 4

5. SOME EXTRA INFO ON HIV…

6. SBI3C Worldwide HIV Distribution Note: Total exceeds 100 percent due to rounding. Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006.

7. SBI3C Structure of HIV

8. SBI3C • 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 (membrane picked up as it buds off white • blood cell) • can only be transmitted from 1 bodily fluid to another • ex. 1. blood to blood: needles, transfusions, • toothbrushes • 2. semen & vaginal secretions • breast milk SBI3C 8

9. SBI3C Transmission of AIDS (Worldwide)‏ 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 • HIV in Body Fluids

10. SBI3C Life Cycle of HIV Lysogenic Cycle HIV+ Lytic Cycle AIDS

11. SBI3C 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 11

12. SBI3C 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 SBI3C 12

13. SBI3C 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 SBI3C 13

14. SBI3C The ultimate fate of a patient with AIDS patient dies from other infections due to a lack of immune response ex. pneumonia cancer

15. SBI3C Transmission of AIDS (Worldwide)‏

16. SBI3C “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

18. SBI3C 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

19. Homework • Read ‘Sex Slaves for Science’ article • Answer questions 1 – 11

20. SBI3C Viral Uses In Medicine • 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 20

21. SBI3C 21

22. SBI3C 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 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 SBI3C 22

23. SBI3C 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 23

24. SBI3C 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