Viruses & Human Health‏ June 23, 2009 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) (genital warts) (cervical cancer) ex. Human Papiloma Virus (HPV) November 21, 2018 SBI3C 2

Protection Against Viral Diseases  vaccines: only true protection against viral diseases, it is preventative 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) November 21, 2018 SBI3C 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 (Dr. John Bell) OHRI (Ottawa Health Research Institute): University of Ottawa professor success with mice injected cancer cells : also trials in humans that didn’t respond to conventional cancer treatments (chemotherapy & radiation) tumours receded wthin weeks cancer cells give off hormones that inhibit immune response also found that viruses stimulated response & person was immune to that form of cancer for life November 21, 2018 SBI3C SBI3C 4

SOME EXTRA INFO ON HIV… November 21, 2018

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

Structure of HIV 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 November 21, 2018 SBI3C SBI3C 8

Transmission of AIDS (Worldwide)‏ HIV in Body Fluids Semen 11,000 Vaginal Fluid 7,000 Blood 18,000 Amniotic 4,000 Saliva 1 Average number of HIV particles in 1 mL of these body fluids SBI3C

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

virus is in its lysogenic cycle (dormant) 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   November 21, 2018 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 November 21, 2018 SBI3C 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 November 21, 2018 SBI3C 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 November 21, 2018 SBI3C

Transmission of AIDS (Worldwide)‏ Why so may cases of homosexual AIDS cases in US? -1st case of AIDS in US came from a traveling salesman, homosexual; - then spread by homosexual drug users & then to heterosexual drug users etc. became HIV+ in Africa, then went to Jamaica, then west coast US; caused epidemic in the male homosexual population 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 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 SBI3C

Homework Read ‘Sex Slaves for Science’ article Answer questions 1 – 11 November 21, 2018

Viral Uses In Medicine help kill cancer cells 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 Viral Uses In Medicine November 21, 2018 SBI3C 19

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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 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 November 21, 2018 SBI3C SBI3C 21

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 November 21, 2018 SBI3C 22

HIV Prevalence Worldwide Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006 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 SBI3C