Human and Rhesus Macaque Immunologic Responses To Anthrax

Vaccine Adsorbed

CDC Anthrax Vaccine Research Program Conrad P. QuinnChief, MPIR LaboratoryMVPD/DBD/NCIRD

FDA Advisory Committee Meeting16th November 2010

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

National Center for Immunization & Respiratory Diseases

Division of Bacterial Diseases

CDC Anthrax Research

AVRP Anthrax Vaccine Adsorbed

• Phase 4 human clinical trialo Double blind, placebo controlledo Route change, dose reduction

• Non-human primate vaccine correlates of protectiono Inhalation anthrax model in Rhesus macaques

AIGIV Rabbit passive transfer model

o Ambulatory NZW infusion modelo Human anti-AVA serum o Proof of concept; prophylactic intervention for

inhalation anthrax

The CDC Anthrax Vaccine Research Program

Document & assure efficacy of AVA

Minimize doses & optimize schedule

Define the AVA correlate of protection Find an immunologic marker(s) that:

• Endorses Human Clinical Trial endpoint• Confirms human vaccinee protection• Identifies when protection is achieved• Quantifies how long protection lasts

An Integrated Study in Humans & Rhesus macaque NHP

AVA Human Clinical Trial

AVA MacaqueDose Ranging &

Immunogenicity Study

ImmunocompetenceModel

Building

Survival AgainstVirulent Challenge

NHPImmune Correlates

of Protection

Human Surrogate Markers

of Protection

HumanHumoral & Cellular

Immune Profiles

MacaqueHumoral & Cellular

Immune Profiles

Hu-AVA1/5 – 1/40

Challenge vs. Vaccination in Rh. Macaques

StudyGroup

IALabel

Week 0

Week 2

Week 4

Month 6

Month 12

Month 18

Month 30

Month 42

8SQ 4SQ AVA AVA AVA AVA AVA AVA AVA AVA

8IM 4IM AVA AVA AVA AVA AVA AVA AVA AVA

7IM

3IM

AVA S AVA AVA AVA AVA AVA AVA

5IM AVA S AVA AVA S AVA S AVA

4IM AVA S AVA AVA S S S AVA

IM Placebo PLAC S S S S S S S S

SQ Placebo PLAC S S S S S S S S

Rh. macaque challenge time points

Building Immunological Profiles

Modulation of rh. macaque immune response (3IM) Variable schedules in humans Quantification of antibody levels and functional competence (ELISA & TNA) Th1 – Th2 disposition Onset and duration of T cell memory & competence (SI) Onset and duration of B cell memory Data mining and bridging to humans

Correlate of protection in rh. macaques Surrogate of protection in human vaccinees

Antibody Levels and Functional Competence Are Highly Correlated

y = 0.95x + 0.84 R2 = 0.86(n=6875)

Anti-PA IgG (µg/ml)

Leth

al T

oxin

Neu

tral

izat

ion

Tite

r (E

D5

0)

Regression Human– n=4568, Rsqrd=0.8672

• LOGED50=0.7811+0.9774LOGIGG– TNA range ED50 0-40,000– ELISA range 0-5781.7 (0-4585.6 when a

TNA result is present)

Diluted AVA Elicits Long-term Circulating Anti-PA IgG

5.32 µg/ml3.40 µg/ml1.22 µg/ml

Macaque Anti-PA IgG

Time (weeks)

0 50 100 150 200 250

An

ti-P

A Ig

G (

g/m

l)

1

10

100

1000

10000

Hu_AVA1/5_AVA1/10_AVA1/20_AVA1/40_AVA

0 1m 6m

5.32 µg/ml

3.40 µg/ml

1.22 µg/ml

vaccination

Diluted AVA Elicits Potent Anamnestic Responses to infection in Rh. Macaque NHP

Macaque Anti-PA IgG Anamnestic Resposnse To Infection

Time (weeks)

0 50 100 150 200 250

Ant

i-PA

IgG

( g

/ml)

1

10

100

1000

10000

Hu_AVA1/5_AVA1/40_AVA

vaccination

challenge challenge

5.32 µg/ml

3.40 µg/ml

4211 µg/ml

3134 µg/ml

37 µg/ml

25 µg/ml

2714 µg/ml

1009 µg/ml

2669 µg/ml

2.63 µg/ml

PA Specific NHP T Cell Competence isMaintained for 52m

3-IM Human Dose and Diluted AVA Provides Long Term Protection in Rhesus Macaque NHP

3-IM priming series. No booster vaccinations.

Number Survived / Number Challenged(Survival Rate)

Challenge Time

Undiluted 1/5 1/10 1/20 1/40

12 Months - -8/10

(80.0%)11/20

(55.0%)13/20

(65.0%)

30 Months10/10

(100.0%)8/8 (100.0%)

6/9(66.7%)

7/8(87.5%)

-

52 Months8/10

(80.0%)9/9

(100.0%)6/10

(60.0%)- -

LO

G10 E

LIS

A A

NT

IBO

DY

CO

NC

EN

TR

AT

ION

1

10

100

1,000

10,000

WEEK

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190

STUDY_ARM TRT-8SQ TRT-8IM TRT-7IMTRT-5IM TRT-4IM CONTROL

Human 3-IM Priming Establishes Long Term Responses

PLAC

433.20

310.02

254.80

320.45

216.83

7IM 47.77 8IM 38.078SQ 35.695IM 21.584IM 6.02PLAC 1.85

3 yrs

6.02(5.28-6.87)

1yr

21.58(18.9-24.7)

PA Specific Human T Cell Competence isMaintained for 43m

T cell SI were detectable by 0.5m, significantly above control levels by 1m, and sustained for 43m irrespective of schedule.

Rabbit Passive Transfer Studies – AIGIV• Human anti-AVA IgG fraction

• Minimum of 4 doses AVA SC• Single intravenous infusion• 24hr prior to aerosol exposure• 3 dose levels human AIGIV• 200 LD50 equivalents B. anthracis Ames• Flebogamma protein control• Ambulatory, minimal invasion, maximum

access• Facilitates long term, multiple infusions,

combination therapies

29log taktf

GMC AIGIV Profiles in Rabbits Challenge

Infusion

608 µg/ml

333 µg/ml

145 µg/ml

292 µg/ml

161 µg/ml

65 µg/ml

AIGIV Passive Transfer Survival

20mg/kg AIGIV10mg/kg AIGIV

5mg/kg AIGIV

Flebogamma ControlsNaïve Controls

292 µg/ml

161 µg/ml

65 µg/ml

GMTTD 3.9dGMTTD 4.9d

GMTTD 5.7d

Correlates of Protection Modeling

Approach: David Madigan, Columbia U, NY

• Least Squares Regression Analyses • LASSO - automatic variable selection and estimation

algorithm via constrained maximum likelihood logistic regression

o Evaluation of NHP data• Bayesian multi-level models

o Bridging between genera Chuck Rose, Lydia Foster, CDC

• Linear Mixed Effects Model (log-log transformed) • Anti-PA IgG longevity and decay in humans and NHPs

Active Immunization Antibody Decay in Humans and NHP fits a Conventional

Power Law Model

-2

-1

0

1

2

3

4

5

6

7

0 1 2 3 4 5

Ln(Week)

Ln

(Ig

G)

Human and NHP1/5_AVA slopes and intercepts are not

statistically significantly different

Human

NHP_1/5_AVA

NHP_1/10_AVA

NHP_Hu_AVA

NHP_1/20_AVA

N = 94 vaccinated animals

29log taktf

29log taktf

From C.Rose & L.Foster

Segregation of NHP Survivors by wk30 Anti-PA IgG Levels and Decay Kinetics

n= 94 vaccinated animals

74µg/ml anti-PA

55/58 survivors 18/36 survivors

= alive = dead

Interpretive Value of the GUP Anti-PA IgG Response

Significant NHP survival at 30 and 52 months post-vaccination

IgG and TNA ED50 are correlated with survival

Other assays (SI) only weakly correlate with survival

IgG and TNA ED50 are highly correlated with each other

NHP anti-PA IgG responses to1/5 diluted 3-IM AVA and human responses to a 3-IM schedule fit the same decay model

Peak response to 3-IM vaccination combined with decay kinetics may be useful in predicting protection in NHP

1. Anti-PA IgG antibodies are an adequate, if not perfect, correlate of protection from which to bridge between animal models and humans

2. Bridging from animals to humans may be achieved from active immunization studies

3. Antibody passive transfer studies comprise only one facet of the protective immune

response are required to overcompensate for the absence of CMI may set unnecessarily high requirements for

measureable circulating antibody from active immunization

4. GUP vaccine efficacy informs PEP Effects of concomitant abx on human immune response

to AVA need to be evaluated

Conclusions