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Viruses & • Human Health June 23, 2009 SBI3C 1 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) May 24, 2017 ex. Human Papiloma Virus (HPV) SBI3C 2 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 May 24, 2017 SBI3C 3 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 May 24, 2017 SBI3C 4 SOME EXTRA INFO ON HIV… May 24, 2017 5 Worldwide HIV Distribution Note: Total exceeds 100 percent due to rounding. Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006. SBI3C 6 Structure of HIV SBI3C 7 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 May 24, 2017 SBI3C 8 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 SBI3C 9 Life Cycle of HIV Lysogenic Cycle HIV+ Lytic Cycle AIDS SBI3C 10 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 May 24, 2017 SBI3C 11 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 May 24, 2017 SBI3C 12 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 May 24, 2017 SBI3C 13 The ultimate fate of a patient with AIDS • patient dies from other infections due to a lack of immune response ex. pneumonia cancer May 24, 2017 SBI3C 14 Transmission of AIDS (Worldwide) SBI3C 15 “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 16 May 24, 2017 17 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 SBI3C 18 Homework • Read ‘Sex Slaves for Science’ article • Answer questions 1 – 11 May 24, 2017 19 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 May 24, 2017 SBI3C 20 May 24, 2017 SBI3C 21 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 May 24, 2017 SBI3C 22 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 May 24, 2017 SBI3C 23 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 SBI3C 24