All Aquiver

and

Poised for Action

One Year After the

STEP Vaccine

CD4 T Cells

A quick immunology overview

HIV (or parts of HIV from a vaccine) are

Engulfed by Surveillance Cells

HIV, or vaccine components

Surveillance Cell

HIV (or parts of HIV from a vaccine) are

Engulfed by Surveillance Cells

HIV (or parts of HIV from a vaccine) are

Engulfed by Surveillance Cells

Surveillance Cells Cut Up Virus/Vaccine Parts

into Different Little Bits

Little Bits of Virus (or Vaccine Parts) are Presented

on the Surface of the Surveillance Cells

EPITOPES

(peptides-

15 amino acids long)

CD4 T Cells become Excited (all aquiver and poised for

action) when Presented with their Epitope

CD4

CD4

EPITOPE

(peptide)

EPITOPE

(peptide)

CD4 T Cells are the Conductors of the

Immune Orchestra

CD4

CD4

IL4 cytokine

IL10 cytokine

IL2 cytokine

IFN cytokine

TNF cytokine

(polyfunctional)

CD4 T Cells are the Conductors of the

Immune Orchestra

CD4

CD4

IL4 cytokine

IL10 cytokine

IL2 cytokine

IFN cytokine

TNF cytokine

Killer Antibodies

CD8Killer CD8

T Cell

Rationale

WHY CD4?

CD4 T cells help optimize the killing activity of CD8 T cells

CD4 T cells enhance antibody responses

WHY STEP?

Important to work out what went right with this vaccine

regime

Need to Know Which Parts of the Vaccine

Excited the CD4 T Cells

Identifying CD4 Epitopes Using Gag Peptide Pools

1,2,3,4,5,6,7,8,9,10..............111,112,113,114,115,116,117,118,119,120,121,122

1 2

1&2

24

23

23&24

1.1, 1.2, 1.3, 1.4, 1.5

2.1, 2.2, 2.3, 2.4, 2.5

23.1, 23.2, 23.3, 23.4, 23.5

24.1, 24.2, 24.3, 24.4, 24.5, 24.6, 24.7

Single

15mersoverlapping by 11aa 1. MGARASVLSGGELDR (epitope peptide) 2. ASVLSGGELDRWEKI (epitope peptide)

..............

..............

Minipools

Maxipools

Master pool Gag

Gag gene MGARASVLSGGELDRWEKI LTSLRSLFGNDPSSQ............................................................

A representative example of

identifying the epitope that elicited

a Gag-specific CD4 T cell response one

year post STEP vaccination

(PTID 13837)

Gag-specific CD4

epitope mapping

IFN

-

IL-2

DMSO Gag Master Pool

Gag Maxipool 1&2 Gag Maxipool 9&10

Gag Maxipool 21&22 Gag Maxipool 23&24

Pool Positive?

Gag Master

Maxipool 1&2

3&4

5&6

7&8

9&10

11&12

13&14

15&16

17&18

19&20

21&22

23&24

To Investigate Gag Maxipool 21 & 22

Overlapping

15mer Peptides

Positive?

21.1

21.2

21.3

21.4

21.5

22.1

22.2

22.3

22.4

22.5

We need to test the participant’s CD4 cells with the 10, single 15mer peptides that make up this Maxipool

To Investigate Gag Maxipool 21 & 22

IFN

-

DMSO

Gag single 15mer 22.2

TNF-IL-2

Gag single 15mer peptide, 22.2, elicits no more CD4 response than the DMSO negative control, therefore is negative.

IFN

-

IL-2 TNF-

DMSO

Gag single 15mer 22.3

To Investigate Gag Maxipool 21 & 22

Gag single 15mer peptide, 22.3, elicits a higher, CD4 response than the DMSO negative control, therefore is positive.

To Investigate Gag Maxipool 21 & 22

IFN

-

IL-2 TNF-

DMSO

Gag single 15mer 22.4

Gag single 15mer peptide, 22.4, elicits a higher, CD4 response than the DMSO negative control, therefore is positive.

IFN

-

IL-2 TNF-

DMSO

Gag single 15mer 22.5

To Investigate Gag Maxipool 21 & 22

Gag single 15mer peptide, 22.5, elicits no more CD4 response than the DMSO negative control, therefore is negative.

To Investigate Gag Maxipool 21 & 22

Overlapping

15mer Peptides

Positive?

21.1

21.2

21.3

21.4

21.5

22.1

22.2

22.3

22.4

22.5

PTID 13837’s CD4 T Cell Gag Epitope

R429QANFLGKIWPSHKGRPGN447

Gag gene

Gag 15mer peptide 22.3

Gag 15mer peptide 22.4

Relative Positions of Gag CD4 Epitopes

Gag gene

(293)

(297)

(297)

(261)(73)

(41)

(37)(429)

(477)

(465)

(465)

(477)

(373)

(385)

(481)

Cytokine Profile of Epitope-Specific CD4 T Cells

One Year Post Vaccination

This participant had a vaccine-induced CD4 T cell

response to Gag epitope 24.5 and 24.6

(from maxipool 23 & 24).

This participant then became infected with HIV.

Will this vaccine-induced response still be

dominant after infection?

Vaccinated PTID 9952

Infected, vaccinated PTID 9952

one year post vaccination

9952 CD4 Gag Responses IFN & IL2 & TNF

0.00

0.05

0.10

0.15

0.20

Stimulant

An

tig

en

Sp

ec

ific

CD

4 T

Ce

ll R

es

po

ns

e (

%)

Infected, vaccinated PTID 9952

one year post vaccination

9952 CD4 Gag Responses IFN & IL2 & TNF

0.00

0.05

0.10

0.15

0.20

Stimulant

An

tig

en

Sp

ec

ific

CD

4 T

Ce

ll R

es

po

ns

e (

%)

Conclusion Low, vaccine-induced Gag-specific CD4 T cell responses were

identified, at one year post vaccination, in uninfected participants in the STEP vaccine trial

Two responses in some participants

Epitopes located along entire length of Gag gene

Most common Gag-specific CD4 T cell response at one year post vaccination was the release of two cytokines, IL2 and TNF – degree of polyfunctionality.

Some vaccine-induced CD4 responses dominate after infection

Overall, data suggests utility of these vaccine-induced, CD4 T cell responses.

Acknowledgements

Trial participants and the CAB

Repository technicians

SAL

Endpoints

Evan Thomas and Janice Chen

Nicole Frahm

Steve de Rosa

Julie McElrath

National Health & Medical Research Council (NHMRC), Australia