BME 301

Lecture Nine

Summary of Lecture 8

  Pathogens: Bacteria and Virus Levels of Immunity:  Barriers  First line of defense   Innate    Inflammation Phagocytes Complement Adaptive     Immunologic memory Antibody mediated immunity Cell mediated immunity  Pathogens within cells Diversity to recognize 100 million antigens

Class Activity 2

The Immune System

Q3: How can technology solve health care problems?

CS1: Prevention of infectious disease

Outline

     Pathogens: How They Cause Disease The Immune System: How We Fight Disease How Vaccines Work The Power of Vaccines: Childhood Illnesses Designing a New Vaccine: HIV/AIDS

Roadmap of CS 1

    Science   Organisms that cause disease Immunity Engineering  How to make a vaccine Vaccines: From idea to product Societal Impact    Health and economics Ethics of clinical trials Developed world/Developing world

Viruses

 Three basic problems each must solve    How to reproduce inside a human cell How to spread from one person to another     Inhale Eat During birth Intimate physical contact How to evade the immune system

Influenza

 Viral Reproduction - 1  Must get inside human cell to use cell’s biosynthetic machinery   Influenza virus binds to cell receptor Induces receptor mediated endocytosis

Influenza

 Viral Reproduction - 2  pH slowly reduced in endosome, virus releases its single stranded RNA and polymerase proteins   RNA segments and polymerase proteins enter nucleus of infected cell Cell begins to make many copies of the viral RNA and viral coat proteins

Influenza

 Viral Reproduction - 3   New viral particles exit nucleus and bud from cell Viral polymerase proteins don’t proofread reproduction  Nearly every virus produced in an influenza infected cell is a mutant



Influenza

Viral Spread   Infected person sneezes or coughs http://students.washington.edu/grant/rand om/sneeze.jpg

Micro-droplets containing viral particles inhaled by another person     Penetrates epithelial cells lining respiratory tract Influenza kills cells that it infects  Can only cause acute infections  Cannot establish latent or chronic infections How does it evade immune extinction?

  Antigenic drift Caused by point mutations Yearly vaccination  http://www.bme.utexas.edu/faculty/richards kortum/BME301/thisweek/archives.htm

Influenza

 How does the virus cause symptoms?

    Cells of respiratory tract are killed by virus or immune system Resulting inflammation triggers cough reflex to clear airways of foreign invaders Influenza infection results in production of large quantities of interferon   Fever Muscle aches   Headaches Fatigue MMR Weekly

Genetic Shift and Flu Pandemics

   Genetic Shift    Animals co-infected by different strains of virus Viral gene segments randomly reassociate Reassortment of virus segments from birds, pigs, etc is source of new strains that infect humans How does this happen?

  Virus shed in bird feces, gets into pigs' drinking water Humans handle and/or cough on the pig   New virus - segments from humans, birds & pigs China:    Breeding ground for new influenzas strains Proximity of humans, pigs, and ducks in China Asian flu, Hong Kong flu, etc. http://www.cdc.gov/flu/avian/facts.htm

Vaccines

How Are They Made?

Vaccination

  Vaccination:  Practice of artificially inducing immunity Goal of vaccination:   Make memory T helper cells, memory killer T cells, and memory B cells that will protect the vaccinated person against future exposure to pathogen Want the vaccine to have:  Maximum realism  Minimum danger

What is needed to make memory cells?

  Memory B Cells & Memory Helper T Cells:  B and T cell receptors must see virus or debris Memory Killer T Cells:  viral Antigen Presenting Cells must be

infected

with virus

Types of Vaccines

    Non-infectious vaccines   DTaP Pneumococcus Live, attenuated bacterial or viral vaccines  Chicken Pox Carrier Vaccines DNA Vaccines

    

Non-infectious vaccines

Killed bacterial or inactivated viral vaccines    Treat pathogen with chemicals (like formaldehyde) Impossible to guarantee that you have killed all the pathogen Salk (inactivated) Polio vaccine, rabies vaccine Subunit vaccines     Use part of pathogen OR Use genetic engineering to manufacture pathogen protein No danger of infection Hepatitis A & B, Haemophilus influenza type b, pneumonoccocal conjugate vaccines Toxoid vaccines   Bacterial toxins that have been made harmless Diphtheria, tetanus and pertussis vaccines This approach will make memory B cells and memory helper T cells, but NOT memory killer T cells Booster vaccines usually required

Live, attenuated vaccines

       Grow pathogen in host cells Produces mutations which:  Weaken pathogen so it cannot produce disease in healthy people  Pathogen still produces strong immune response that protects against future infection Sabin Polio vaccine (oral Polio) Measles, mumps, rubella, varicella vaccines This approach makes memory B cells, memory helper T cells, AND memory killer T cells Usually provide life-long immunity Can produce disease in immuno-compromised host

Cell Culture: Live, Attenuated Vaccine

 Grow cells:    Removed from tissue In vitro (in glass) By supplying nutrients and other factors    Specific O 2 and CO 2 Glucose, ions (pH level) Serum from blood: proteins

Organ

Passaging Cells

Dissection/ Breakdown… Primary Cell Line Add media for growth Incubate Divide -> transferred Secondary Cell Line

Carrier Vaccines

      Use virus or bacterium that does not cause disease to carry viral genes to APCs   e.g. vaccinia for Smallpox vaccine http://www.bme.utexas.edu/faculty/richards kortum/BME301/thisweek/thisweek.htm

This approach makes memory B cells, memory helper T cells, AND memory killer T cells Does not pose danger of real infection Immuno-compromised individuals can get infection from carrier Carrier must be one that individuals are not already immune to Cannot make booster vaccines with carrier (must use different carrier for booster)

DNA Vaccines

    DNA injections can produce memory B cells and memory T killer cells Reasons are not fully understood Make a DNA vaccine from a few viral genes No danger that it would cause infection

Types of Vaccines

    Non-infectious vaccines    No danger of infection Does not stimulate cell mediated immunity Usually need booster vaccines Live, attenuated bacterial or viral vaccines    Makes memory B cells, memory helper T cells, AND memory killer T cells Usually provides life-long immunity Can produce disease in immuno-compromised host Carrier Vaccines    Makes memory B cells, memory helper T cells, AND memory killer T cells Does not pose danger of real infection Immuno-compromised individuals can get infection from carrier DNA Vaccines

Effectiveness of Vaccines

  Vaccination Effectiveness  About 1-2 of every 20 people immunized will not have an adequate immune response to a vaccine Herd Immunity   Vaccinated people have antibodies against a pathogen They are much less likely to transmit that germ to other people    Even people that have not been vaccinated are protected About 95% of community must be vaccinated to achieve herd immunity Does not provide protection against non-contagious diseases – eg tetanus

Vaccines

How Are They Tested?

Vaccine Testing

  Laboratory testing Animal Model   Animal must be susceptible to infection by agent against which vaccine is directed Animal should develop same symptoms as humans

Vaccine Testing

 Human Trials  Phase I   Small number of volunteers (20-100) Usually healthy adults     Last few months Determine vaccine dosages that produce levels of memory B or T cells that are likely to be protective Evaluate side effects at these dosages FDA must approve the vaccine as an Investigational New Drug (IND)  NPR Story –  Ebola Vaccine Trials http://www.npr.org/rundowns/segment.php?wfId= 1513230

Vaccine Testing

 Human Trials  Phase II  Larger number of volunteers (several hundred)  Last few months to few years   Controlled study, with some volunteers receiving:   Vaccine Placebo (or existing vaccine) Endpoints: Effectiveness, safety

Vaccine Testing

 Human Trials  Phase III  Large number of volunteers (several hundred to several thousand)    Last years Controlled double blind study, with some volunteers receiving:   Vaccine Placebo (or existing vaccine) Neither patients nor physicians know which was given

 

Vaccine Testing

Role of the FDA:   Licensure by FDA required before a company can market the vaccine (about a decade) Each batch of vaccine must be tested for safety, potency, purity and sample lot must be sent to FDA Post-licensure surveillance  Doctors must report adverse reactions after vaccination to FDA and CDC  Vaccine Adverse Events Reporting System (VAERS)  As many as 12,000 reports per year, 2,000 serious  Most are unrelated to the vaccine

Vaccine Testing

  Recommendations by health departments and expert physician groups  When should vaccine be used   Who should receive it Weigh: risks and benefits of the vaccine, costs of vaccination Legislation:  States determine which vaccines are required by law   All 50 states have school immunization laws Can be exempted based on:    Medical reasons (50 states) Religious reasons (48 states) Philosophical reasons (15 states)

Vaccine Schedule

    Birth  Hepatitis B 2 Months      DTap #1 Polio #1 Hib #1 Hepatits B #2 Pneumococcus #1 4 months     DTaP #2 Polio #2 Hib #2 Pneumococcus #2 6 months    DTaP #3 Hib #3 Pneumococcus #3     12 months   MMR #1 Varicella 15 months      Hib #4 Polio #3 Hepatitis B #3 Pneumococcus #4 DTap #4 4-6 years    MMR #2 Polio #4 DTaP #5 11-12 years  Tetanus, Diphtheria By age two: 20 shots!!

Single visit: Up to 5 shots!!

http://www.christianpoint.org/inspirati on/images/crying_baby.jpg

Recommended Vaccine Schedule

History of the Rotavirus Vaccine

 Withdrawn from the market after post-licensure surveillance indicated small number of adverse effects

Vaccines

Are They Effective?

History of Vaccination

   Seventh Century  Indian Buddhists drank snake venom to induce immunity (through toxoid effect) Second millennium   Variolation against smallpox Central Asia, China, Turkey 1721  Variolation against smallpox moves from Turkey to England

History of Vaccination

 History: 1798 - Edward Jenner noted:    Smallpox and Cowpox:   Milkmaids frequently contracted cowpox which caused lesions similar to that smallpox Milkmaids who had cowpox almost never got smallpox Jenner’s (unethical) experiment:  Collected pus from cowpox sores    Injected cowpox pus into boy named James Phipps Then injected Phipps with pus from smallpox sores Phipps did not contract smallpox First to introduce large scale, systematic immunization against smallpox

History of Vaccination

     1885: Attenuation  Louis Pasteur - first vaccine against rabies Early 1900s: Toxoids  Diphtheria, tetanus 1936  Influenza 1950s: Tissue Culture  Polio (Nobel Prize for Enders, Robbins, Weller) 1960s:  Measles, Mumps, Rubella

Effects of Vaccination in US

Disease Max # of Cases # Cases in 2000 Diphtheria 206,929 (1921) 2 Measles Mumps 894,134 (1941) 152,209 (1968) 63 315 Pertussis 265,269 (1952) Polio 21,269 (1952) Rubella Tetanus HiB Hep B 57,686 (1969) 1,560 (1923) ~20,000 (1984) 26,611 (1985) 6,755 0 152 26 1,212 6,646 % D -99.99

-99.99

-99.80

-97.73

-100 -99.84

-98.44

- 93.14

-75.03

Effects of Vaccination

   Smallpox  First human disease eradicated from the face of the earth by a global immunization campaign 1974  Only 5% of the world’s children received 6 vaccines recommended by WHO 1994   >80% of the world’s children receive basic vaccines Each year: 3 million lives saved

Smallpox

  One of world’s deadliest diseases   Vaccine available in early 1800s Difficult to keep vaccine viable enough to deliver in developing world Elimination of smallpox      1950: stable, freeze dried vaccine 1950: Goal  Eradicate smallpox from western hemisphere 1967: Goal achieved except for Brazil 1959: Goal   Eradicate smallpox from globe Little progress made until 1967 when resources dedicated, 10-15 million cases per year at this time  Strategies:  Vaccinate 80% of population  Surveillance and containment of outbreaks May 8, 1980: world certified as smallpox free

Childhood Immunization

 1977:  Goal to immunize at least 80% of world’s children against six antigens by 1990

rtsp://audio.npr.org/me/20021120.me.10.smil

Vaccines

What is Still Needed?

What Vaccines are needed?

 The big three:    HIV Malaria Tuberculosis

Summary of Lecture 9

    How do vaccines work?

 Stimulate immunity without causing disease How are vaccines made?

  Non-infectious vaccines Live, attenuated bacterial or viral vaccines   Carrier Vaccines DNA Vaccines How are vaccines tested?

  Lab/Animal testing Phase I-III human testing  Post-licensure surveillance Impact of vaccines

Assignments Due Next Time

 Two reading assignments:   WTIND - p. 147, 172, 182-185, 311-315 CPS - 767-782  WA5 (Vaccines)