refresher: how vaccines work; vaccine research today jerald c. sadoff md aids vaccine 2009...

Refresher: How Vaccines Work; Vaccine Research Today

Jerald C. Sadoff MD

AIDS Vaccine 2009 Journalist Scholarship Training Overview

October 18th 2009 Paris, France

AERAS GLOBAL TB VACCINE FOUNDATION

Topics to be covered

• Refresher: How Vaccines Work

• Basic principles in developing vaccines

• Vaccine Research Today


Refresher: How Vaccines Work

• The general answer

• The battle between the bugs and us

• Their Genes and our Genes

• Timing and location are everything


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


The Battle Between Us and the Bugs:What 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


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)


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 hasn’t seen it before

• It remembers from one time to the next

• Its weapons: antibodies and T cells recognize and kill very precisely


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


The cognate system has 3 weapons:

1. Antibodies

2. White cells: Macs and Polys

3. White cells: T cells


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


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


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


CD 4 T cell

CD 8 T cell

TH1 TH2 TH1 TH2

IFN-γ

IL-2TNF-α

IL-4

B - cell

antibodies

DTP, Hib, Pneumococcus, Measles, Polio, Hep B,

Rotavirus, HPV, Malaria TB, Malaria, HIV

Central or

Effector

Memory


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



• 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



• 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


Battle with the BugsTheir Genes and Our Genes

• They can change their genes rapidly because– They reproduce so fast– Sometimes like HIV they don’t 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


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 doesn’t 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


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


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)


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, that’s why a bite on the face is worse then the arm



• 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


Studies with NIH VRC – Bob Seder, Mario Roederer



• 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.


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


What the disease gives you

• Epidemiology –– Hemophilus type B – no disease till 4-6 month– Rotavirus – 2nd infection with different type– Zoster – more disease >65 years of age

• High Attack rate –– Rotavirus - efficacy in 400 children– Malaria – efficacy in 2000 children



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



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


Basic Principles





• Assays rule



RISK RESOURCES

TIME


Vaccine Research Today

• Antigens– Reverse Engineering– Bioinformatics– Epitopes

• Vaccine Delivery– Adjuvants– Non-replicating vectors– Replicating vectors


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


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


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


Scoring of Antigens Over-expressed/Up-regulated in AERAS-427 – From List of Top 45

Rv

312

7R

v2

005

cR

v3

873

Rv

262

6c

Rv

203

2R

v0

288

Rv

188

6c

Rv

203

1c

Rv

086

7c

Rv

100

9R

v2

623

Rv

245

0c

Rv

173

8

Rv

202

9c

Rv

200

6R

v1

813

cR

v1

349

Rv

117

4c

Rv

190

8c

Rv

082

4c

Rv

313

1R

v3

130

cR

v0

079

Rv

380

4c

Rv

198

0c

Rv

262

8R

v0

685

Rv

238

9c

Rv

199

6R

v1

733

c

Rv

262

9R

v1

793

Rv

116

9c

Rv

113

0R

v0

467

Rv

334

7c

Rv

313

2c

Rv

203

0c

Rv

192

6c

Rv

387

5R

v2

744

cR

v2

620

cR

v1

884

cR

v2

780

Rv

262

7c

32/4

5 to

p s

cori

ng

anti

gen

s b

y b

ioin

form

atic

s an

alys

is

dir

ectl

y ov

er-e

xpre

ssed

or

up

-reg

ula

ted

in A

ER

AS

-427

Rv

202

9c


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


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


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


Epitope Immunodominance- HIV

• Utilization of subdominant antigens in absence of dominant antigens

• Sequential immunization

• Immunization with separate vaccines


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


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


ITRITR E2B E2A E4

E1 L1-L3 E3L4 L5

ITRITR E2B E2A E4

E1 L1-L3 E3L4 L5

Genomic Structure

Ad35 Viral VectorTargets CD46 onHuman Dentritic CellsLow African seroprevalence (<2% with neut >200)E1 & Part of E3 deleted• Makes room for TB antigens (85A, 85B, 10.4)• Can’t replicate in humansGrows to high titer inPerC6 cells• Ad5 E1 in PerC6

chromosome• Ad5 E4 Orf6, 6/7

put in Ad35• Ad35 pIX put back


PR

EL

IMIN

AR

Y D

AT

A –

10

DE

C 2

00

8

Aeras Study C-008-402DSMO subtracted Ag85A/b CD8 Response

BCG/AERAS-402 (3x10^10 vp)

0 84 91 98 112 119 126 140 182

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

BCG 402 402

%C

D8 R

esp

on

se BC

G im

mu

niz

ed

Ad

ult

s S

t L

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is


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


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


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)


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

refresher: how vaccines work; vaccine research today jerald c. sadoff md aids vaccine 2009...

Documents

bug slide

cognate system slide

infected slide

t cells

vaccines work vaccine

memory cells

france slide

inflammation slide