Refresher: How Vaccines Work Vaccine Research Today

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Refresher How Vaccines Work Vaccine Research
Today

• Jerald C. Sadoff MD
• AIDS Vaccine 2009 Journalist Scholarship Training
  Overview
• October 18th 2009 Paris, France

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Topics to be covered

• Refresher How Vaccines Work
• Basic principles in developing vaccines
• Vaccine Research Today

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Refresher How Vaccines Work

• The general answer
• The battle between the bugs and us
• Their Genes and our Genes
• Timing and location are everything

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The general answer how vaccines work

• Vaccines work by fooling the body into thinking
  it is infected with a bug so that next time when
  it sees the real thing it will be ready faster
  with a more powerful response
• Sometimes it gets the body to do something
  different and better then if it were naturally
  infected

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The Battle Between Us and the BugsWhat we can do

• We recognize them as something different not
  belonging inside the body
• Once recognized we try and kill them
• We have two systems of doing this
• The Innate system
• The Cognate system

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The Innate System

• Ancient system found in almost all living things
  in some form
• Recognizes patterns in pieces of the bugs rather
  then specific pieces
• Immediate but no memory for next time
• Poisons released quickly that kill everything
  around
• Massive numbers of all kinds of cells called in
  rapidly that eat what they encounter (called
  inflammation)

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Cognate System

• Newer more sophisticated system found in higher
  animals which is dependent on the innate system
• Recognizes very specific parts of the bug called
  antigens or epitopes
• Comes up slower if hasnt seen it before
• It remembers from one time to the next
• Its weapons antibodies and T cells recognize and
  kill very precisely

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• Vaccines induce the cognate system to remember,
  recognize, and kill viruses, bacteria, parasites
  or cancer cells

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• The cognate system has 3 weapons
• Antibodies
• White cells Macs and Polys
• White cells T cells

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Antibodies

• Antibodies are proteins floating in our fluids
  and organs everywhere they can get
• At one end they recognize and stick on the
  surface of the bug
• When they bind bad things happen to the bug

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White cells Macs and Polys

• Recognize the back end of the antibody stuck on
  the surface of the bug
• They use the antibodies like a zipper to close
  around the bug and eat it
• Once the bug is inside the cell its held in a bag
  and poisons are dumped in that kill it

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White cells T cells

• Recognize our cells that have been infected by
  bacteria, viruses or parasites
• They get very close to the infected cell
• They secrete signals to the cell in very high
  concentrations that tell the cell to kill the bug
• Some of these T cells are memory cells that live
  a long time and some are effectors that are out
  in the tissues ready to pounce

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B - cell
Central or Effector Memory
CD 8 T cell
CD 4 T cell
antibodies
TH1
TH2
TH1
TH2
IFN-? IL-2
TNF-a IL-4
DTP, Hib, Pneumococcus, Measles, Polio, Hep B,
Rotavirus, HPV, Malaria
TB, Malaria, HIV
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Battle with the Bugs What they do

• They protect themselves from innate White cell
  engulfment and killing
• Bacteria like Pneumococcus build thick walls of
  sugar on their outsides that white cells cant
  engulf without the zipper of antibody basis of
  the new pneumococcal vaccine
• TB organisms poison the bag they are in inside
  the cell so they cant be killed once inside
• Viruses like varicella hide in the nerves where
  white cells cant go

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Battle with the Bugs What they do

• They move rapidly from one site to another so
  they are gone by the time the cognate system has
  responded
• The malaria parasite is only in the blood for
  less then a minute before it gets to the liver
  and then it changes so adaptive antibody isnt
  made
• It only stays in the liver for 10-14 days so that
  adaptive T cells are too slow
• The new malaria vaccine induces both antibody and
  T cells that are ready for it

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Battle with the Bugs What they do

• They avoid the cognate T cell response by
  changing the ability of the cells they have
  infected to show they are infected
• Measles, CMV and HIV all turn down the ability of
  the infected cells to put pieces of the virus on
  its surface so that a cognate response is dampened

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Battle with the BugsTheir Genes and Our Genes

• They can change their genes rapidly because
• They reproduce so fast
• Sometimes like HIV they dont reproduce very
  accurately
• They are a population attacking us not an
  individual while we tend to be concerned about
  protecting each individual in our population

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Battle with the BugsTheir Genes and Our Genes

• We cant change our genes rapidly
• We have a lot of genes
• We have genes to make antibodies that can
  recognize just about everything including plastic
  that doesnt exist in nature
• We have genes for T cells that can recognize just
  about everything but each individual is unique on
  what pieces of viruses can be presented
• We can slowly change our antibody genes

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Battle with the Bugs What they do

• They can change so rapidly that they can out run
  the cognate responses
• HIV changes its surface variable regions so that
  it avoids neutralizing antibody that develops
• About 25 of humans eventually develop broad
  neutralizing antibodies
• HIV changes the epitopes that are recognized by T
  cells within 10-20 days of first infecting humans
  thus avoiding that cognate response
• HIV can eventually find something that it human
  host cant respond to

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Battle with the Bugs What they do

• They misdirect the cognate system to
  immunodominant antigens that they can change and
  away from antigens they cant change
• Gonorrhea and E. coli pilus antigens highly
  variable and immunodominant distract from tip
  proteins that are required for attachment and sex
• HIV gp120 variable regions are B cell dominant
  and can vary rapidly
• HIV subdominant T cell antigens protect in the
  few animals that recognize them (Watkins)

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Timing and Location are Everything

• Timing - Vaccines work because the cognate
  response after vaccination is much faster when
  the bug is first seen then what occurs if it has
  to develop from scratch
• Pneumococcal anti sera given within 3 days of
  hospitalization 40 survival after 3 days no
  survival
• Most vaccines have very little effect after the
  infection has progressed since the system is
  already mounting a cognate response due to the
  infection
• Rabies is an exception - following a rabid animal
  bite the virus travels slowly up the nerve to the
  brain immediate immunization can save your life
  if the immunity develops before the virus gets
  there, thats why a bite on the face is worse
  then the arm

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Timing and Location are Everything

• Location is important because the cognate immune
  response has to get to the pathogen rapidly to be
  effective
• Only 4 of 8 sets of T cells directed exactly at
  the same piece of malaria worked to protect mice
  from malaria
• The 4 that worked are the one that got to the
  liver

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Studies with NIH VRC Bob Seder, Mario Roederer
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Timing and Location are Everything

• An example of where timing and location are both
  thought to be critical is the protection induced
  by CMV vaccine against SIV infection to be
  further presented at this meeting by Louis Picker
• The effector T cells induced by this vaccine are
  not only ready to kill at the time of infection
  but they are already located where the virus
  goes.

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Basic Principles

• Use what the disease gives you
• Correlates and Surrogates make everything easy
• When everything else fails Proof of Principle
  studies and bootstrapping
• Manufacturing Vaccines are not iPods
• Assays rule
• Eternal triangle of risk vs time vs resources

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What the disease gives you

• Epidemiology
• Hemophilus type B no disease till 4-6 month
• Rotavirus 2nd infection with different type
• Zoster more disease gt65 years of age
• High Attack rate
• Rotavirus - efficacy in 400 children
• Malaria efficacy in 2000 children

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What the disease gives you

• Animal Model
• Hep B - Non Human Primate
• Pnumococcus, Hemophilus,
• TB (?) low dose NHP challenge
• HIV- (?) SIV low challenge dose

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What the disease gives you

• Possibility of Human Challenge studies
• Shigella
• Cholera
• Malaria
• HIV (?)

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Basic Principles

• Use what the disease gives you
• Correlates and Surrogates make everything easy
• When everything else fails Proof of Principle
  studies and bootstrapping
• Manufacturing Vaccines are not iPods
• Assays rule
• Eternal triangle of risk vs time vs resources

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Basic Principles

• Use what the disease gives you
• Correlates and Surrogates make everything easy
• When everything else fails Proof of Principle
  studies and bootstrapping
• Manufacturing Vaccines are not iPods
• Assays rule
• Eternal triangle of risk vs time vs resources

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RISK
RESOURCES
TIME
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Vaccine Research Today

• Antigens
• Reverse Engineering
• Bioinformatics
• Epitopes
• Vaccine Delivery
• Adjuvants
• Non-replicating vectors
• Replicating vectors

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Reverse Engineering

• Utilizing molecular modeling and immune responses
  in protected volunteers to down select from
  thousands of possible proteins
• Limited number of proteins put in mouse or other
  small animal studies
• Recent promising examples
• Common Group B meningococcal protein
• Common Pneumococcal protein
• Common Staphylococcal protein

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Reverse Engineering Structural studies

• Understanding the detailed molecular structure of
  a target protein and its interaction with
  antibody design an immunogen to induce that
  antibody
• Influenza and HIV tremendous current work
• Identified binding regions of monoclonals that
  neutralize somewhat broadly including new ones
  that bind V3 stem
• So far unsuccessful in designing immunogen

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Bioinformatics

• Using scoring systems with internal validation
  combine all of the information about antigen
  candidates to select promising antigens for
  inclusion in vaccine vector
• Example TB antigens for inclusion in a
  recombinant BCG for over-expression

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Scoring of Antigens Over-expressed/Up-regulated
in AERAS-427 From List of Top 45
Rv1738
Rv1733c
Rv2029c
Rv1996
Rv2450c
Rv2389c
Rv2623
Rv0685
32/45 top scoring antigens by bioinformatics
analysis directly over-expressed or up-regulated
in AERAS-427
Rv1009
Rv2628
Rv0867c
Rv1980c
Rv3804c
Rv2031c
Rv0079
Rv1886c
Rv3130c
Rv0288
Rv3131
Rv2032
Rv0824c
Rv1908c
Rv2626c
Rv1174c
Rv3873
Rv1349
Rv2005c
Rv1813c
Rv3127
Rv2006
Rv2029c
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Epitopes

• Fundamental problem in B and T cell based
  vaccines is epitope selection to cover the
  variety of pathogens that might be encountered
• Second problem is the virus changing its epitopes
• Third problem is immunodominance of some epitopes
  over others

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Epitope Diversity

• The approach with Pneumococcal, rotavirus and HPV
  vaccines is to make multiple serotypes (up to 16
  for Pneumo) with the broadest epidemiologic
  coverage

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Epitope Diversity- HIV

• Informatics approach to combine all known
  variablility in the data base with natural
  segments and maximize coverage
• Criticism of this is that the variability is
  escape to variants that cant be responded to
• That this does represent incoming virus
• Search for epitopes that cant vary because of
  their function

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Epitope Immunodominance- HIV

• Utilization of subdominant antigens in absence of
  dominant antigens
• Sequential immunization
• Immunization with separate vaccines

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Vaccine Delivery - Adjuvants

• Adjuvants stimulate the innate system mainly
  through toll receptors
• Several new adjuvants in clinical trials
• AS04 with flu vaccines responses in 200-800 range
  compared to 20-60 for most flu vaccine
• AS01-E in malaria and TB vaccines provide very
  high CD4 T cells in humans
• IC-31 in TB vaccines induce CD4 T cells

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Vaccine Delivery Non-replicating vectors

• Vaccinia Based NYVAC, ALVAC, MVA
• HIV- Alvac part of Thai trial
• TB MVA AERAS-485 in a 2800 subject Phase IIB
  efficacy trial in Cape Town S, Africa
• Adeno based Ad5, Ad35, Chimp Adeno
• HIV-
• Ad 5 Merck NIH HIV trial,
• Ad 5 - Current VRC trial
• Malaria -Chimp Adeno prime for MVA boost
• TB Ad35 induced high CD8 T cells

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Ad35 Viral Vector

• Targets CD46 on
• Human Dentritic Cells
• Low African seroprevalence
• (lt2 with neut gt200)
• E1 Part of E3 deleted
• Makes room for TB antigens
• (85A, 85B, 10.4)
• Cant replicate in humans
• Grows to high titer in
• PerC6 cells
• Ad5 E1 in PerC6
• chromosome
• Ad5 E4 Orf6, 6/7
• put in Ad35
• Ad35 pIX put back

Genomic Structure
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BCG immunized Adults St Louis
PRELIMINARY DATA 10 DEC 2008
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Replicating Vectors

• Replicating vectors have the advantage of longer
  antigen production and possibly more effector
  cells
• Recombinant BCG
• Persists for around 40 days
• Appears to be a good prime for protein or viral
  booster
• Yellow Fever
• Being used as a vector for dengue vaccine now in
  phase II trials
• Being explored for HIV with promising NHP data

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Replicating Vectors - CMV

• Persists throughout the life of the animal
• Down regulates the Class I so can re-infect
• Induces subdominant antigens
• Induces primarily effector memory T cells
• Prevents productive SIV infection in low dose NHP
  challenge
• Safety issues as a human vaccine
• Birth defects in new borns
• Liver and potential heart disease

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Vaccines I Have Helped Develop

• Licensed (10)
• Hep A (VAQTA)
• Hemophilis type B (Liquid Pedvax)
• Hemophilus type B Hep B (Comvax)
• Varicella (4 degree Varivax)
• Measles-Mumps-Rubella- Varicella (ProQuad)
• Hib-HepB-DPT-IPV (Hexavac)
• Zoster (ZostaVax)
• Rotavirus (Rota Teq)
• Human Pappiloma Virus (Gardasil)
• Cholera (Dukoral)

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Vaccines I Have Helped Develop

• Phase III
• Malaria (RTS,S) ongoing
• Cholera (Peru 15) beginning
• Phase IIB
• Shigella (John Robbins - Polysaccharide
  conjugate) - successful
• Gonorrhea (Pili vaccine) failed
• Pseudomonas E. Coli Klebsiella (Passive Aby)
  failed
• HIV (Adeno Vectored Gag, Pol, Nef) failed
• TB (MVA85A-AERAS-485) ongoing
• TB (AERAS-402) ongoing
• Phase II
• TB (GSK- M72) - ongoing
• TB (AERAS- 404 HyVac4 SSI/Sanofi) - Ongoing