Il virus dell’epatite BGiovanni RaimondoEpatologia Clinica e BiomolecolarePoliclinico Universitario di Messina

La patogenesi dell’epatite BCarlo FerrariUnità Operativa di Malattie Infettive ed EpatologiaAzienda Ospedaliero-Universitaria di Parma

Il virus dell’epatite BGiovanni RaimondoEpatologia Clinica e BiomolecolarePoliclinico Universitario di Messina

VIROLOGY OF HEPATITIS B VIRUS (HBV)

Modulo 1

Virology of Hepatitis B Virus (HBV)Family: Hepadnaviridae

Genus: HepadnavirusOrthohepadnavirus (Mammalian)Human Hepatitis B-Virus (HBV)Chimpanzee Hepatitis B Virus (ChHBV)Gibbon Hepatitis B-Virus (GiHBV)Orang Utan Hepatitis B Virus (OuHBV)Gorilla Hepatitis B-Virus (GoHBV)Woolly Monkey Hepatitis B-Virus (WMHBV)Woodchuck Hepatitis-Virus (WHV)Ground squirrel Hepatitis-Virus (GSHV)Arctic Ground squirrel Hepatitis-Virus (AGSHV)

AvihepadnavirusDuck Hepatitis B-Virus (DHBV)Heron Hepatitis-Virus (HHV)Ross Goose Hepatitis BVirus (RGHBV)Snow Goose Hepatitis BVirus (SGHBV)Maned Duck Hepatitis BVirus (MDHBV)Grey Teal Hepatitis B Virus (GTHBV)Stork Hepatitis B-Virus (STHBV)

• DNA virus• 3.2 kilobases• partial-double-stranded• enveloped

Mature virus (Dane particle) 42 nm diameter

Target cells: hepatocytesReceptor: unknownLigand: preS1-protein

HEPATITIS B VIRUS

HBV GENOMES gene: pre-S1 (large S), pre-S2 (middle S), S (small S)

X gene: X

Core gene: core, ePol gene: P

C

A

B

HEPATITIS B VIRUS

C

A

B

HEPATITIS B VIRUS Genome Organization

• 3.2 kb pdDNA• 3 promoters = Core, S-, and X• 4 ORF = preC/Core, pre-S1/pre-S2/S,

Polymerase, X-gene

HBsAg and Reverse Transcriptase (RT) Protein Synthesis

Met- ……… Ala - Arg - Phe - Ser - TrpTrp - Leu - Ser - Leu - Leu

Met- ………… Pro - Phe - Leu - Leu - AlaAla Gln - Phe - Thr

GENOMIC REGIONS

ATG..... AGC CCG TTT CTC CTG GCT CAG TTT ACT

ATG ..... GCC CGT TTC TCC TGG CTC AGT TTA CTA

Transcription

RT

HBsAg

mRNA … … … … … … … … … … … … … … … … …

mRNA … … … … … … … … … … … … … … … … … …

Translation

RT

S

HBsAg and RT Protein Syntheses in HBV Strains with A181V aa Change in RT

GENOMIC REGIONS

Transcription

Translation

Met- ……… Ala - Arg - Phe - Ser - STOPSTOP

ATG..... AGC CCG TTT CTC CTG ACT CAG TTT ACT

ATG ..... GCC CGT TTC TCC TGA CTC AGT TTA CTA

Met- ………… Pro - Phe - Leu - Leu - ThrThr Gln - Phe - Thr

… … … … … … … … … … … … … … … … …

… … … … … … … … … … … … … … … … … …

RT

S

RT

HBsAg

mRNA

mRNA

HBV Life Cycle

HBV Life Cycle

RECYCLING

HBV GENETIC HETEROGENEITY

Modulo 1

Geographic Distribution of HBV Genotypes

Genotype A Worldwide

“ “ B Asia

“ “ C Asia

“ “ D South Europe, Americas, Australia

“ “ E Africa

“ “ F Native Americans and Polynesians

“ “ G Europe, USA

“ “ H Native Americans

HBV Genomic Variants…

• Naturally occurring

• Therapeutically induced

…When Are They Clinically Relevant?

Relative Replication Yield (RC) of HBV Mutants

0 1 2 3 4 5 6 7 8 9 10L180M+A181V+N236T

A181V+N236TL180M

L180M+T184G+S202I+M204V*A181V

M250V*M204I

L180M+A181V+M204VI169T+V173L+L180M+M204V+M250V*

N236TL180M+M204V*

WTA181T+N236TL180M+A181V

A181TI169T+V173L+L180M+M204V*

V173L+L180M+M204V*

Modified from Edwards R, et al. Global Antiviral Journal 2005;1(Suppl2):77

Secondary Mutations at the RT Level in HBV Isolates from Naïve Patients

aa substitution No. of cases

N94R 1

V173M 1

A181D * 1

T207I 1

V214A/E 2

Q215S/H/P 9

R217L 1

S219A 3

F221Y 3

I233V 3

P237T 2

N238H 4

*Previously unreported aa substitution in a position critical for primary resistance to Lamivudine and Adefovir.

aa substitutions No. of Cases

Q215S/H/P +V173M 1

F221Y 1

P237T 2

N238H 1

L217RF221Y +

N238T

3

2

V214EN238H +

N94R

1

1

S219A + S185I 1

F221Y + I233V + N238D 1

Q215S + R217L + F221Y 1

S202T +L217R + S219A + F221Y 1

Pollicino T, et al. Antivir Ther 2009;14:649-654

Single Mutation Multiple Mutations

MOST COMMON, NATURALLY OCCURING HBV GENETIC VARIANTS

Modulo 1

PreC/C-gene

np 1814-6ATG

TGG

HBcAg

HBeAgPredicted precore protein

np 1896

np 1901-3ATG

np = nucleotide position

PreC/C-gene

np 1814ATG

TGG TAG stop codon

HBcAg

HBeAgPredicted precore protein

np 1896

np 1901ATG

np = nucleotide position

Basal-Core Promoter Mutations

Pre-C C P Enhancer II/basal core promoter

np 1762 1764

X

A T G A

Hepatitis B Virus Genome Organization

PreS/S Gene Transcription and Envelope Proteins (ORFs: Pre-S1/Pre-S2/S)

Pre-S1 RNA (2.4kb)

S

S

Pre-S2/S RNA (2.1kb)

ATG

p r e-S1 p r o t e i n

p r e-S2 p r o t e i n

Pre-S2/S RNA (2.1kb)

Pre-S2Pre-S1ATG

ATG

ATG

S

ATG

ATG SPre-S2

S p r o t e i n

LHBs

MHBs

SHBs

Envelope Gene and Proteins

S-gene

Large protein (390-399 aa)

Middle protein (281 aa)

Small protein (226 aa)

Natural Occurring Pre-S1 HBV Variant

PRE-S2 S

183-bp deletion

PRE-S1ATG

ATG

ATG

Gerken G, et al. Virology 1991;183:555-565

Pre-S2 Minus HBV Variants

SPRE-S1ATG

ATG

AGG

HBV Variants Carrying Deletion in Pre-S2 Region

SPRE-S1ATG

ATG

ATG

PRE-S2

In framedeletion

PreS2-Defective HBV Variants: Evidence of Clinical Impact

- Fulminant hepatitis

- Fibrosing cholestatic hepatitis

- Cirrhosis and HCC

Distribution of pre-S2-defective variants in HBsAg+ patients (pts) with different clinical picturesRaimondo G, et al. J Hepatol 2004;40:515-519

°p=0.002*p=0.02

All pts infected with genotype D.

Prevalence of pre-S mutants in patients infected with genotype B, C, or mixed genotypes Chen BF, et al. Gastroenterology 2006;130:1153-1168

cc : chronic (inactive) carriersCH : chronic hepatitisLC : liver cirrhosis

DeletionWild-type + deletionWild-type

Diagnosis No. pts No. pS2 variants

Inactive carriers° 15 2

Chronic hepatitis°* 50 25

Cirrhosis°* 26 13

HCC°* 19 16

Infection with HBV PreS2-Defective Variants is associated with HCC

HBV Surface Antigen “a” Determinant

Clinically Relevant Mutations in the “a” Determinant of HBsAg

124137

139 147

Cys

Ile

Cys Ser

Lys

Thr

Gly

Cys Cys

Tyr

8 amino acid insertion)

Asn, Thr

Tyr

Thr

IIe,Glu Met

Arg

145

Hepatits B Virus

…leads to an infection that lasts indefinitely and is referred to as “occult infection” when it is mantained without HBsAg

…replication process takes place through a reverse transcription phase like retroviruses, and like retroviruses it may be integrated into the host genome

…has a compact genomic structure, with partial overlapping of its different genomic regions

…cannot eliminate the viral mutants that develop during each replicative cycle, so that they may accumulate leading to the formation of a complex quasispecies, often influencing the clinical evolution of the liver disease

La patogenesi dell’epatite BCarlo FerrariUnità Operativa di Malattie Infettive ed EpatologiaAzienda Ospedaliero-Universitaria di Parma

INNATE IMMUNE RESPONSES IN HBV INFECTION

Modulo 1

Role of Innate Immunity in Acute Viral Infections

Time (months) after infection1 2 3 4 5 6

Viral load

Innate response T cell response

Antibody response

Early viral containment

Priming and maturation of adaptive immune responses

Kinetics of Virus Replication and Liver Damage in HBV InfectionMajority of viral clearance prior to peak of liver inflammation

non-cytolytic mechanisms likely implicatedWebster GR, et al. Hepatology 2000;32:1395-1406

Thimme R, et al. J Virol 2003;77:68-76Guidotti L, et al. Science 1999;284:825

ALT (U

/L)

0

100

200

300

400

500

ALTLiverHBV DNA

Live

r HB

V-D

NA

(%)

100

10

1

0

2 4 6 8 10 12 14 16 18

1

10

100

HBV

1,000

2,000

ALT

Weeks after infection

242080 4 6 10 12 18 2214 162

Chimpanzee infectionHuman infection

0

Weeks after infection

Intrahepatic CTL Frequency, HBV Replication, and Liver Damage in Acute Hepatitis B

0

100

200

300

400

0 2 4 6 8 10 12 14 16 18 20 22 24

20

40

60

80

100

sAL

T (U

/L)

HBV-DNA ALT %

HB

V-D

NA

liver

Intrahepatic HBV-specific CD8 T cells in chimps

00

1010

55

HBV-specific

CD8 cells

Thimme R, et al. J Virol 2003;77:68

In Vivo Chimpanzee DataLack of IFN-inducible genes in chimpanzee model of HBV infection

HBV seems unable to induce innate responses: a ‘stealth virus’

Genes associated with entry and expansionof the virus, reflecting activation and effector

function of the innate immune responseNo gene

Genes associated with viral clearance(brought into the liver by cells of the adaptive

immune response)110 genes

Wieland S, et al. PNAS 2004;101:6669-6674

HBV Is a Good Inducer of Innate Responses: Proofs in Favor

• Intrahepatic expression of innate immune response genes immediately afterinfection in woodchucks infected with WHV (Guy CS. J Virol 2008;82:8579-8591)

• Induction of IFN-I in HepaRG hepatocytes infected with baculovirus carrying HBVgenome results in non-cytolytic control of HBV (Lucifora J. Hepatology 2009;51:63-72)

• Primary human hepatocytes infected with HBV stimulate Kupffer cells to produceIL-6 with anti-HBV activity (Hösel J. Hepatology 2009;50:1773-1782)

Flaws of These Studies

• In woodchuck infection, activation of innate responses is transient and it isstimulated by inocula with very high viral concentrations; moreover, this animalmodel may only partially reproduce human infection

• IFN-I production by HepaRG cells is stimulated by high intracellular HBVreplication levels which likely do not reproduce the early kinetics of HBVreplication in natural infection

HBV Is a Poor Inducer of Innate Responses: Proofs in Favor

Cytokine production in acute HBV infection

is significantly more modest and delayed compared with

acute HIV infection (Stacey AR, et al. J Virol

2009;83:3719-3733)

Low production of type 1 IFN, IL-15 and IFN-1, associated with high serum IL-10 levels,

at the early stages of HBV infection

(Dunn C, et al. Gastroenterology 2009;137:1289-1300)

IFN-α IL-15 IFN-1A B C

-10 -5 0 5 10 15 20 -10 -5 0 5 10 15 20

Time (days since T0) Time (days since T0)Fold

cha

nges

in

grou

p m

ean

cyto

kine

leve

l

HIV infection HBV infection

Healthy DNA

high

Resolution phase

Acute HAV

n.27 n.11 n.17 n.13

p=0.05

p=0.02

pg/m

l

100

200

300

400

Healthy DNA high

Resolution phase

Acute HAV

n.10 n.11 n.16 n.13pg

/ml

2

4

6

8

p=0.03p=0.05

Healthy DNA high

Resolution phase

Acute HAV

n.25 n.11 n.18 n.13

p=0.0001p=0.0002

p=0.0001

pg/m

l

200

400

400

800

Can the lack of IFN-I detection in acute HBV infection be attributable to active suppression rather than a complete

failure of induction?

Regulation of Toll-like Expression by HBV

• HBeAg can suppress TLR-2 expression in chronic hepatitis B (Visvanathan K, et al.Hepatology 2007;45:102-110)

• Low levels of TLR-1, 2, 4, and 6 messenger RNA transcripts in PBMC of CAHpatients (Chen Z, et al. Clin Immunol 2008;128:400-408)

• Hepatitis B virus suppresses Toll-like receptor mediated innate immuneresponses in murine parenchimal and nonparenchimal liver cells (Wu J, et al.Hepatology 2009;49:1132-1140)

VirionsHBsAgHBeAg ISGF3

IFN receptor

Interferon loop

TYK2 JAK1

SOCS1

SOCS3

IRF-9

STA

T1

STA

T2

IFN- IFN-

IFN receptor

IFN

-

PKR, ADAR1, 2-5OAS, IFIT1, Viperin, ISG6-16,

MxA

ISG expression

TLR2 TLR4 TLR3

Extracellular sensing (TLR) Intracellular sensing (RIG-1)

NF-kB

TRIF

IRF-3PP

RIG-1

PP

IRF-3IRF-7

PRDNF-kB target genes

IFN-

Intracellular Host Innate Immune Defences

What Role Do NK Cells Play in Acute HBV Infection?

Hepatocytes express very low levels of MHC Class I, such that any up-

regulation of cellular stress ligands able to engage NK activatory

receptors should be able to induce local NK cell effector function

NK cells are extremely abundant in the liver, constituting 30-40% of

intrahepatic lymphocytes

Kinetics of NK Cell Responses

FUNCTION

HBV-DNA HBV-DNA copies/mL

IFN

Normalized51Cr release

050,000

100,000150,000200,000250,000

0 2 5 7 10

Weeks from HBsAg detection

% IF

N

0 13102 5 70

1234

0

5

10

15

51C

r rel

ease

NK cellsCD56+CD3-

PHENOTYPE%

CD

69+

0

12.5

25

0 2 5 7 100

35

70

NK

G2D

MFI

% CD69

NKG2D MFINK cells

CD56+CD3-

NK IFN

CD8 IFNCD4 IFN

% C

D56

+CD

3-IF

Ng+

00.51

1.52

2.533.5

0 5 7 10 1300.10.20.30.40.50.6

% C

D8/

4+IF

Ng+

Weeks from HBsAg detection

Early induction after infection(Fisicaro P, et al. Gut 2009;58:974-982)

Kinetics of NK Cell ResponsesDelayed induction after infection

(Dunn C, et al. Gastroenterology 2009;137:1289-1300)

0

510

15

20

25

Perc

ent C

D69

+ N

K c

ells

0

5

10

15

Healthy Resolution phase

n.15 n.6 n.10

DNA highPe

rcen

t CD

69+

NK

cel

ls

0

5

10

15

Healthy Resolution phase

n.27 n.11 n.17

DNA high

P=0.03

0.009

0.003

0.02

Weeks 0 5 10 5 20Pe

rcen

t IFN

+N

K c

ells

510

15

20

25

NK cells

HBV-DNA

NK cells

HBV-DNA

Perc

ent I

FN+

NK

cel

ls

Weeks 0 5 10 5 20

ADAPTIVE IMMUNE RESPONSES IN HBV INFECTION

Modulo 1

Kinetics of Virus Replication and HBV-specific Responses During Acute Infection

Webster GR, et al. Hepatology 2000;32:1395-1406

CD4+ T cells

1

10

100

Weeks after infection2 4 6 8 10 12 14 16 18 20

20

40

0

HBV-DNA% tet.+

CD8+ T cells

nd1

10

100

0.4

0.8

HBsAg - - - - + + + + + + + +

HBV-DNA

nd

CD8 Cells Are the Main Effectors of Viral Clearance and Disease in Acute Hepatitis B(Thimme R, et al. J Virol 2003;77:68-76)

No depletion

sALT (U/L)

0

100

200

300

400

500

sALTLiver

HBV-DNA

Live

r HB

V-D

NA

(%) 100

10

1

0

Control Ab

CD4 Ab

CD8 Ab

00

sALT (U/L)

100

200

300

400

500

sALTLiver

HBV-DNA

Live

r HB

V-D

NA

(%) 100

10

1

CD4 depletion

Weeks after infection242080 4 6 10 12 18 2214 162

sALT (U/L)

0

100

200

300

400

500

sALT

LiverHBV-DNA

Live

r HB

V-D

NA

(%) 100

10

1

0

CD8 depletion

Weeks after infection242080 4 6 10 12 18 2214 162

Role of HBV-specific CTL in Liver Damage and Virus ControlHBV is not directly cythopatic; HBV-specific CD8 cells not only protect, but also damage

CD8 CELLCD8 CELL

CLEARANCE BY CYTOKINESIFNγ/TNFα

CYTOPATHIC NON-CYTOPATHIC

CLEARANCE BY LYSIS OF INFECTED CELLS

CD8 CELLCD8 CELL

HBV Pathogenesis

Cyt

okin

es

IFN/TNFα

FasL

Perforins

Liver cell killing

Chemokines

HBV-specific CTL

Infected liver cell

Cured liver cells

Amplification of liver damage

HBV InfectionSelf-limited

Vigorous, T1-oriented, multispecific acute phase

responses

Long-lasting protective responses

%Lysis

0

10

20

30

0

10

20

30

40

POLIMERASE X CORE ENVELOPE

ACUTE PHASE

RECOVERY PHASE(20 years from recovery)

CD4-mediated Proliferative Response to HBV Core in Acute HBV Infection

Urbani S, et al. Hepatology 2005;41:826-831

50

Evolution of infection

0

5

10

15

20

25

30

35

40

45

1

Chronic

1 2 3 4 5 6

Self-limited

Stim

ulat

ion

Inde

x

HBV InfectionChronic evolution

Inefficient acute phase immune responses

Progressive impairment of protective responses

CD4 RESPONSES

CD8 RESPONSES

HBVPOL

HBVX

HBVCORE

HBVENV

2 4 6 8 10 12 14 16 18

1

10

100

HBV

1,000

2,000

ALT

0

Poor induction of early

intracellular innate responses

1Efficient and

timely induction of adaptive responses

3

Early HBV-DNA clearance by non-

cytolytic mechanisms

4

Liver damage and elimination of infected

cells by cythopatic mechanisms

5

NK cells activation

2

0

Summary of the Early Immune Events in HBV Infection

Helper T cellsExpansion of

immune response

B cellsAb production

Blocking cell to cell spreadNeutralization of circulating virus

ANTIBODY PRODUCTION IN ACUTE HBV INFECTIONAcute HBV infection

Th1Th2

BB

Antigen excess Partial neutralization

Anti-HBs negative

EARLY

Th1Th2

BB

Antibody excess Complete neutralization

Anti-HBs positive

LATE

Hierarchy of HBV Control

Partial controlChronic inactive infection

Inefficient controlChronic active infection

Efficient controlOccult infection

0

5

10

1 2 3 4 5 6 7 8 9 10 111213 14 1516mea

n %

IFN

/tot

0

5

10

1 2 3 4 5 6 7 8 9 10 111213 14 1516mea

n %

IFN

/tot

02468

10

1 2 3 4 5 6 7 8 9 1011 1213141516mea

n %

IFN+

/tot

HBV-specific T Cell Responses are Stronger in Acute than in Chronic Hepatitis B

Boni C, et al. J Virol 2007;81:4215-4225

050100

12 34 5 67 8910111213141516

Pt. C1Pt. C1

Pt. C2Pt. C2

Pt. C3Pt. C3

050100

1 2345 678910111213141516

050100

1 2345 678910111213141516

050100

1 234 5 67 8 910111213141516

050100

12 34 5 67 8910111213141516

050100

1 234 5 67 8910111213141516

Pt. C4Pt. C4

Pt. C5Pt. C5

050100

1234 5 678910111213141516050100

1 23 456 78 910111213141516

Pt. C6Pt. C6

Pt. C7Pt. C7

050100

123 4567 8 910111213141516

050100

123 4567 8 910111213141516

050100

1234 5 678910111213141516

050100

12 345 67 8910111213141516

050100

1234 5 67 8 910111213141516

050100

1 23 45678 910111213141516

100

12345 67 8 910111213141516050

050100

12 34 56 78 910111213141516

050100

12 345 678 910111213141516

050100

12 34 56 78 910111213141516

100

1234 56 78910111213141516050

050100

12 34 56 78 910111213141516050100

1234 5 67 8910111213141516

xx corecore envenv polpol xx corecore envenv polpol xx corecore envenv polpol

SFU

/2 x

105

PBM

C

Chronic patients

Pt. A3

Pt. A2

Pt. A1

100

Pt. A4

Pt. A6050

250

1 2 3 4 5 6 7 8 9 1011121314 1516

050

100

1 2 3 4 5 6 7 8 9 10111213141516

050

1 2 3 4 5 6 7 8 9 10111213141516

050

100

1 2 3 4 5 6 7 8 9 10111213141516

Pt. A5

050350

1 2 3 4 5 6 7 8 9 10111213141516

050100

1 2 3 4 5 6 7 8 9 10111213141516

x core env pol

Acute patients

SFU

/2 x

105

PBM

C

Ex Vivo Elispot Analysis

Effect of Antigen Stimulation on HBV-specific T Cell Responses and Correlation with Viral Load

0

0.2

0.4

0.6

0.8

1

1.2

1.4

17-01-2003 25-03-2003 12-05-20030

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

50

100

150

200

250

ALT

HB

V-D

NA

% IF

Nγ

+ ce

lls/C

D4

Pt. C1

Pt. C2

Pt. C3

Pt. C4

Pt. C5

Pt. C6

Pt. C7

050100

050100

050100

050100

050100

050100

050100

x core env pol x core env pol x core env pol

SFU

/ 2 x

105

PBM

C

Time point 1 Time point 2 Time point 3

Ex vivo

050100

050100

050100

050100

050100

050100

050100

050100

050100

050100

050100

050100

050100

050100

Pt. C1

Pt. C2

Pt. C3

Pt. C4

Pt. C5

Pt. C6

Pt. C7

x coreenv pol x coreenv pol x core env pol

Time point 1 Time point 2 Time point 3

In vitro

250500

250500

0

0250500

0250500

0250500

0250500

0

0250500

250500

250500

0

0250500

0250500

0250500

0250500

0

0250500

250500

250500

0

0250500

0250500

0250500

0250500

0

0250500

SFU

/ 2 x

105

PBM

C

Boni C, et al. J Virol 2007;81:4215-4225

Frequency of Intrahepatic and Circulating HBV-specific CD8 Cells in Chronic HBV Infection

Fisicaro P, et al. Gastroenterology 2010;138:682-93, 693.e1-4

HBV-DNA TITER IU/mL

Mea

n %

TET

+/C

D8+

in

trah

epat

ic c

ells

0

1

2

3

4

5

6

0-104 104-105 >105

p=0.006

p=0.03

% H

BV-

TET+

/CD

8+0

0.020.040.060.080.1

12468

10LIVER BLOOD

p=0.0002

HBV-specific T Cell Dysfunction

Possible causes

Dendritic cellimpairment

T regsuppression

Defective innate responses

DysfunctionalHBV-T cells

Hyper-production of regulatory cytokines

Persistent exposure to high Ag doses

(HBeAg-HBsAg)

HBV-specific T Cell DysfunctionPossible causes

Persistent exposure to high Ag dosesPersistent inflammation

Amplification of negative costimulatory pathways

Impairment of TCR signaling by -chain

down-regulation

Enhanced T cell apoptosis caused by Bim up-

regulation

DysfunctionalHBV-specific T cells

APC

T CELL

B7 FAMILY TNF SUPERFAMILY

B7.1 or B7.2

PD-L1PD-L2

PD-1 CTLA-4 CD28

ICOSL

ICOS

INHIBITION

OX40L 4-1BBL

CD40CD70

OX40 CD27 CD40L 4-1BB

COSTIMULATORY SIGNALS

Costimulatory Pathways in T Cell Activation

PD-1/PD-L1 Pathway

Barber DL, et al. Nature 2006;439:682-687

PD-1PD-L1

Dendritic cellsLiver cells T lymphocyte

Up-regulation in viral infections

Up-regulation - activated T cells

- high antigen doses

T cell inactivation and functional exhaustion

Anti-PD-L1

T cell functional restoration

Effect of Anti-PD-L1 Treatment on HBV-specific CD8 T Cell Function

Boni C, et al. J Virol 2007;81:4215-4225

Anti-PD-L1

T cell functional restorationBarber DL, et al. Nature 2006;439:682-687

EXPANSION IL-2 PRODUCTION

0

0.5

1

1.5

0 1 2 105

0

10

20

30

40

0 1 2 100

5

10

15

20

0 2 5 10

IFN PRODUCTION

g/mL anti-PD-L1

CONCLUSIONS

HBV-DNA negative HBV-DNA <104 HBV-DNA >104

Antigen load

T cell efficiency+++ ++ +

Immune subjects

Asymptomatic carriers

Chronic patients

Chronic HBV infection comprises a wide spectrum of different virological and immunologicalsituations which are the expression of a complex natural history, where levels of virusreplication and levels of T cell reactivity appear to be inversely correlated and where HBVpersistence is likely caused by the synergistic effect of different mechanisms, includingexhaustion by high antigen concentrations.

FUTURE PERSPECTIVES OF ANTI-HBV IMMUNE THERAPY(Ferrari C. Gastroenterology 2008;134:1601-1604)

T CELL DYSFUNCTION

Antiviral treatmentDecline of antigen load

Inhibition of negative costimulatory pathways

RECOVERY OF T CELL RESPONSIVENESS

VACCINATION

CONTROL OF INFECTION

Blocking antibodies

DC CD8

Viru

s/an

tigen

load