Download No Slide Title

Viral Infections
and asthma
Sebastian L Johnston
Professor of Respiratory Medicine
Department of Respiratory Medicine
National Heart and Lung Institute
Imperial College of Science, Technology &
Medicine
London, UK
Causes of exacerbations
• Poor underlying control
• Environmental factors
–
–
–
–
–
–
–
Virus infections
Allergen exposure
Air pollution
Bacterial infections
Stress
Exercise/cold air
Occupational exposure
The common cold viruses
• rhinoviruses
• enteroviruses
• influenza viruses A & B
• coronaviruses
• parainfluenza viruses
• respiratory syncytial virus
Virus infections and asthma
exacerbations
Johnston BMJ 1995;310:1225
Epidemiology
• Association of viruses with exacerbations
Children
Adults
15%
40%
60%
85%
Positive virus detection
No virus detected
RV infection of the lower airways
• A crucial question in asthma pathogenesis
• Direct vs indirect hypotheses
• Implications in treatment research
Temperature preferences of
rhinoviruses
• RVs can successfully replicate at 37°C and some
strains may even prefer it.
33°C
33° 37°
37°C
8
7
5
a
b
c
d
e
f
g
h
4
3
2
1
70
R
V
41
R
V
16
R
V
14
R
V
9
R
V
7
R
V
2
R
V
1b
0
R
V
titer
6
Papadopoulos et al. J Med Virol. 1999;58:100
•
•
•
•
Increase of viral titres
Increase of viral RNA
New viral protein synthesis
Cytopathic effect
log titre
RV infection of primary bronchial
epithelial cells
RV7
RV2
6
5
4
3
2
1
0
0
24
48
72
Hours post-infection
38kD
28kD
0
6
24
48
Papadopoulos et al. J Infect Dis 2000;181:1875
Localization of RVs in the bronchi
• In-situ hybridization in biopsies of experimentally
infected volunteers
• Co-localization of genomic and replicative RNA
strand
Papadopoulos et al. J Infect Dis 2000;181:1875
Asthmatic vs normal subjects frequency, severity & duration of illness with
rhinovirus infections
• 74 atopic asthmatic & non atopic normal spouses
• Regular NA sampling every 2 wks over 3 months,
daily diary card + PEF
• PCR for rhinoviruses
– frequency of infection not different between groups
– no difference in severity or duration of URT illness
– LRT symptoms more severe and more prolonged in
asthmatics (P<0.0001)
– falls in PEF more severe (P<0.03) Corne, Johnston. Lancet 2002;359:831
The immune response to viruses later
in life
• PBMC from
– 7 atopic asthmatic
– 7 non atopic non-asthmatic subjects
• Incubated with rhinovirus in vitro
• Supernatants assayed for type 1 and type 2
cytokines
The immune response to rhinoviruses
• Type 1 response deficient in asthmatic subjects
1000
800
600
400
200
0
6h
24h
48h
Normal (-)
Asthmatic (-)
Normal + RV
Asthmatic + RV
1000
900
800
700
600
500
400
300
200
100
0
Asthmatic
1200
Normal
IFN-g/IL-4 ratio
IFN-g
Papadopoulos et al (Thorax in press)
Type 1 deficiency in virus induced
asthma
<Picture>
Gern et al AJRCCM 2000;162:2226
Deficient type 1 immune response in
RSV bronchiolitis
•
•
•
•
Birth cohort study through first winter
Proven RSV infections
Nasal lavage day 1-2 & 5-7, PBMCs day 5-7
Divided clinically into URTI alone, or bronchiolitis
IL-4/IFN-g
0.07
0.008
IL-10/IL-12
IL-4/IFN-g
0.07
50
0.06
40
0.05
30
0.04
0.03
0.02
20
P=0.01
10
0.01
0
URTI
P=0.01
Bronchiolitis
0
URTI
Bronchiolitis
Legg et al, AJRCCM in revision
IFN-g mRNA production by PHA stimulated
PBMCs
10000
IFN-g : GAPDH
(Mean&SD)
1000
p=0.006
100
p=0.009
10
1
0
RSV URTI
24h
n=15
VB
24h
n=9
RSV URTI
48h
n=15
VB
48h
n=9
Legg et al, AJRCCM in revision
IL-18 mRNA production by LPS stimulated
PBMCs
10000
(Mean&SD)
IL-18 : GAPDH
1000
p=0.008
p=0.066
100
10
1
RSV URTI
24h
n=15
VB
24h
n=9
RSV URTI
48h
n=15
VB
48h
n=9
Legg et al, AJRCCM in revision
Bronchiolitics cleared virus less
rapidly
100000
F protein Gene Copies
4/19 rose
6/9 rose
10000
1000
100
10
1
0
Day 1-2
URTI
Day 5-7
Day 1-2
Day 5-7
Bronchiolitis
RSV bronchiolitis
•
•
•
•
Deficient type 1 immunity in RSV bronchiolitis
Associated with impaired virus clearance
Not related to age
Not likely to be a result of RSV infection as
already present on days 1-2
• Genetic susceptibility or very early life
environmental factors likely explanation
• Similar mechanisms in virus induced asthma
exacerbation?
Role of IL-8 and neutrophils in virus
induced asthma
• IL-8 produced by epithelium and
monocytes/macrophages after RV infection
IL-8
50
RV 9
Control
Control
pg/ml
ng/ml
40
IL-8
200
30
20
RV 9
100
10
0
0
4
24
48
72
96 120 144 168
Hours after infection
Johnston SL et al. J Infect Dis 1997;175:323
6h
24h
48h
Hours after infection
72h
Johnston SL et al. J Immunol. 1998;160:6172
Correlation between IL-8 and
neutrophilia
Asthmatic subjects
% Neutrophils
• IL-8 correlates with
neutrophilia in virusinduced asthma:
– sputum
– nasal aspirates
• correlation with MPO
• severity of URT symptoms
Sputum IL-8 (pg/ml)
Teran, Johnston et al, AJRCCM 1997;155:1362
Pizzichini, Johnston et al, AJRCCM 1998;158:1178
Inflammation
• Induction of lymphocyte, neutrophil and eosinophil
chemoattractants and activators
• IL-1, IL-6, IL-8, IL-10, IL-11, IL-12, IL-13, IL-16, IL18, interferons, RANTES, MIP-1a ......
Eotaxin
pg/ml
100
75
Eotaxin-2
Control
Infected
50
25
-
+
+
-
+
+
-
+
+
0
24h
48h
Hours after infection
Papadopoulos et al. Clin Exp Allergy 2001;31:1060
Molecular mechanisms of virus-induced
inflammation
• NF-kB: A transcription factor mediating several
virus-mediated responses
Respiratory virus
Cytokines,
LPS, Viruses
?
I-kB degradation
NF-kB / I-kB complex
Increase of transcription
•
•
•
•
•
•
IL-6
IL-8
IL-11
RANTES
ICAM-1
VCAM-1
Conclusions
• Rhinoviruses are major cause of asthma
exacerbations in adults and children
– asthmatics may have deficient type 1 immunity
• Major mechanisms
– IL-8
– NFB
• Lower airway infection and resulting
inflammation likely the major mechanism
• Therapy for rhinovirus induced LRT disease
should ideally reach the lower airway