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