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BIOE 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
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, due to proton pump in membrane
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 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.cdc.gov/flu/weekly/usmap.htm
http://students.washington.edu/grant/random/sneeze.jpg
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: Stimulate both cell mediated and
antibody mediated immunity 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 viral debris
Memory Killer T Cells: 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 O2 and CO2 (pH level) Glucose, ions Serum from blood: proteins
Passaging Cells
OrganDissection/
Breakdown…
Add media for growth
Incubate
Divide -> transferred
Primary
Cell Line
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.bt.cdc.gov/agent/smallpox/vaccination/
facts.asp 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/inspiration/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
http://www.npr.org/templates/story/story.php?storyId=3262013http://www.npr.org/templates/story/story.php?storyId=5126636
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 USDisease Max # of
Cases# Cases in
2000%
Diphtheria
206,929 (1921)
2 -99.99
Measles 894,134 (1941)
63 -99.99
Mumps 152,209 (1968)
315 -99.80
Pertussis 265,269 (1952)
6,755 -97.73
Polio 21,269 (1952) 0 -100
Rubella 57,686 (1969) 152 -99.84
Tetanus 1,560 (1923) 26 -98.44
HiB ~20,000 (1984)
1,212 - 93.14
Hep B 26,611 (1985) 6,646 -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
http://www.npr.org/templates/story/story.php?storyId=849775
http://www.npr.org/templates/story/story.php?storyId=3870193
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
HW7