Transcript Hepatitis Viruses

Chair of Microbiology, Virology, and Immunology
Hepatitis Viruses
Characteristics of Human Hepatitis Viruses
Virus
Family/ Genus
Size/ Genome
Length of
Incubation
Mechanism of
transmission
HAV
Picornaviridae /
Hepatovirus 72
27-30 nm,
single-stranged
RNA
HBV
Hepadnaviridae
/ hepadnavirus
142 nm, circular 50-180
double-stranged days
DNA
HCV
Flaviviridae
30-50 nm single- 14-28 days Parenteral,
stranged RNA
likely other
sources
No
HDV
Unclassified
35-40 nm single- 50 180
stranged RNA
days*
Parenteral
transmission
No
HEV
Caliciviridae
27 34 nm singlestranged RNA
Oral-fecal
No
15-40 days Mostly oralfecal
6 weeks
Parenteral
Vaccine
Yes
Recombinant
subunit
vaccine
Global Prevalence of Hepatitis A Infection
HAV Prevalence
High
Intermediate
Low
Very Low
HEPATITIS A VIRUS
Virus
Hepatitis A
Family
Picornaviridae
Genus
Hepatovirus
Virion
27 nm icosahedral
Envelope
No
Genome
ssRNA
Genome size
7,5kb
Stability
Heat- and acid-stable
Transmission
Fecal-oral
Prevalence
High
Fulminant disease
Rare
Chronic disease
Never
Oncogenic
No
Hepatitis A virus particles found in fecal extracts by
immunoelectron microscopy. Both full and empty particles are
present. The virus is 27 to 29 nm in diameter. (X 125,000.)
Genome organisation of HAV
Hepatitis A Virus
Life Cycle
Hepatitis A Transmission
Fecal-oral contamination of food or water
Food handlers
For example. An epidemic of
Raw shellfish
HAV that occurred in Shanghai,
Travel to endemic areas
China, in 1988 in which
300,000 people were infected
Close personal contact
with the virus resulted from
Household or sexual contact
eating Anadara subcrenata
Daycare centers
obtained from a polluted river.
Blood-borne (rare)
Injecting drug users
Pathogenesis
Pathogenesis of HAV
HAV replicates slowly in the liver without producing
apparent cytopathological effects (CEPs). In the
absence of cytolysis, the virus readily establishes a
persistent infection.
 Jaundice, resulting from damage to the liver
 Antibody is detected and cell-mediated immune
responses to the virus

Hepatitis A - Clinical Features
Incubation period:
Jaundice by
age group:
Complications:
Chronic sequelae:
Average 30 days
Range 15-50 days
<6 yrs,
<10%
6-14 yrs, 40%-50%
>14 yrs, 70%-80%
Fulminant hepatitis
Cholestatic hepatitis
Relapsing hepatitis
None
Body Fluid
Concentration of Hepatitis A Virus
in Various Body Fluids
Feces
Serum
Saliva
Urine
100
102
104
106
Infectious Doses per ml
108
1010
Clinical Variants of Hepatitis A
Infection
Asymptomatic (anicteric) disease
 Children under 6 years of age, > 90%
 Children from 6-14 years old, 40-50%
Symptomatic (icteric) disease
 Adults and children over 14, 70-80%
Typical Serologic Course of Acute
Hepatitis A Virus Infection
Symptoms
ALT
Total anti-HAV
Fecal
HAV
0
IgM anti-HAV
1
2
3
4
5
Months after exposure
6
12
24
Hepatitis A Vaccine Efficacy Studies
Site/Age
Group
Vaccine
Efficacy
(95% CI)
HAVRIX 
(SKB)
2 doses
360 EL.U.
Thailand
1-16 yrs
94%
(79%-99%)
VAQTA 
(Merck)
1 dose
25 units
New York
2-16 yrs
100%
(85%-100%)
Vaccine
HEPATITIS B VIRUS
About 300 million people world-wide are thought to be
carriers of HBV, and many carriers eventually die of
resultant liver disease. HBV causes acute hepatitis that
can vary from a mild and self limiting form to an aggressive
and destructive disease leading to postnecrotic cirrhosis.
Many HBV infections are asymptomatic (especially in
children).
Prevalence of HBsAg Carrier State
>8%
2-8%
<2%
WHO
HEPATITIS B VIRUS
Virus
Hepatitis B
Family
Hepadnaviridae
Genus
Orthohepadnavirus
Virion
42 nm, spherical
Envelope
Yes (HBsAg)
Genome
dsDNA
Genome size
3,2kb
Stability
Acid-sensitive
Transmission
Parenteral
Prevalence
High
Fulminant disease
Rare
Chronic disease
Often
Oncogenic
Yes
Fraction of the blood scrum from a patient with a severe ease
of hepatitis. The larger spherical particles, or Dane particles,
are 42 nm in diameter and are the complete hepatitis B virus.
Also evident are filaments of capsid protein (HBsAg).
HEPATITIS B VIRUS:
HOW THE VIRUS REPRODUCES ??
1. First the virus attached to
a liver cell membrane.
2. The virus is then transported
into the liver cell
3. The core particle then
releases it’s contents of DNA
and DNA polymerase into the
liver cell nucleus.
4. Once within the cell nucleus the
hepatitis B DNA causes the liver
cell to produce, via messenger
RNA; HBs protein, HBc protein,
DNA polymerase, the HBe
protein, and other undetected
protein and enzymes.
 DNA polymerase causes the liver
cell to make copies of hepatitis B
DNA from messenger RNA.
5. The cell then assembles ’live’ copies of virus.
6. However because of the
excess numbers of surface
proteins produced many of
these stick together to form
small spheres and chains.
These can give a
characteristic “ ground
glass” appearance to blood
samples seen under a
microscope.
7. The copies of the virus and excess
surface antigen are released from the
liver cell membrane into blood stream
and from there can infect other liver
cells.
HBV: Replication
Reverse transcription: one of the mRNAs is
replicated with a reverse transcriptase making the
DNA that will eventually be the core of the progeny
virion
 RNA intermediate: HBV replicates through an
RNA intermediate and produces and release
antigenic decoy particles.
 Integration: Some DNA integrates into host
genome causing carrier state

Genome of HBV virus
Genome: 3.200 nucleotídes
S
P
C
X
Open Reading Frames
There are 4 open reading frames derived from the same strand (the
incomplete + strand)
• S - the 3 polypeptides of the surface antigen (preS1, preS2 and S
- produced from alternative translation start sites.
• C - the core protein
• P - the polymerase
• X - a transactivator of viral transcription (and cellular genes?).
HBx is conserved in all mammalian (but not avian) hepadnaviruses.
Though not essential in transfected cells, it is required for infection
in vivo.
HBV Genome
AgHBs
Pré S1
Pré S2
DNA Polimerase
gene P
AgHBc
gene C
AgHBe
Pré C
gene S
ANTIGEN OF HEPATITIS B VIRUS:
HBsAg = surface (coat) protein ( 4 phenotypes : adw, adr, ayw and ayr)
HBcAg = inner core protein (a single serotype)
HBeAg = secreted protein; function unknown
In HBsAg there are some determinants, which are
responsible for 10 subtypes of this antigen.
“а” determinat is general.
There are “d” and “y”, and two additional - “w” and
“r”.
So, there are four main subtypes:
“adr”, “ayr”.
Other determinants - f, g, j, n, t, x.
“adw”,
“ayw”,
HBV SPREAD MAINLY BY
PARENTERAL ROUTE




DIRECT PERCUTANEOUS INOCULATION OF
INFECTED SERUM OR PLASMA
INDIRECTLY THROUGH CUTS OR ABRASIONS
ABSORPTION THROUGH MUCOSAL SURFACES
ABSORPTION OF OTHER INFECTIOUS
SECRETIONS (SALIVA OR SEMEN DURING SEX)
HBV SPREAD MAINLY BY
PARENTERAL ROUTE



POSSIBLE TRANSFER VIA INANIMATE
ENVIRONMENTAL SURFACES
VERTICAL TRANSMISSION SOON AFTER
CHILDBIRTH (TRANSPLACENTAL TRANSFER
RARE)
CLOSE, INTIMATE CONTACT WITH AN
INFECTED PERSON
Pathogenesis and Immunity






Virus enters hepatocytes via blood
Immune response (cytotoxic T cell) to viral antigens
expressed on hepatocyte cell surface responsible for
clinical syndrome
5 % become chronic carriers (HBsAg> 6 months)
Higher rate of hepatocellular carcinoma in chronic
carriers, especially those who are “e” antigen positive
Hepatitis B surface antibody likely confers lifelong
immunity (IgG anti-HBs)
Hepatitis B e Ab indicates low transmissibility
Determinants or acute and chronic HBV infection
From Murray et. al., Medical
Microbiology 5th edition, 2005, Chapter
66, published by Mosby Philadelphia,,
WHO IS AT GREATEST RISK FOR
HBV INFECTION?
DRUG ABUSERS
 BLOOD PRODUCT
RECIPIENTS
 ACCOUNTS FOR 5-10%
POSTRANSFUSION
HEPATITIS


HEMODIALYSIS
PATIENTS
PEOPLE FROM
SOUTHEAST ASIAN
COUNTRIES (70-80%)




LAB PERSONNEL
WORKING WITH BLOOD
PRODUCTS
SEXUALLY ACTIVE
HOMOSEXUALS
PERSONS WITH
MULTIPLE AND
FREQUENT SEX
CONTACTS
MEDICAL/DENTAL
PERSONNEL
HBV
300,000 NEW CASES IN U.S. PER YEAR
 LIFETIME RISK FOR AVERAGE PERSON
IS 5%
 SEXUAL PROMISCUITY > RISK
 LIFETIME RISK FOR DENTIST IS 13-28%

Jaundice
CHARACTERISTICS OF HBV
INFECTION
INFECTION IS USUALLY SELF LIMITING,
COMPLETE RESOLUTION IN 6 MONTHS
 HOWEVER, WHEN INFECTED

5% ADULTS CHRONIC CARRIERS
 20% CHILDREN CHRONIC CARRIERS
 80-90% NEONATES AND INFANTS BECOME
CHRONIC CARRIERS

HBV - Diagnosis
Acute Infection
HBV DNA
HBeAg
Anti-HBe
Anti-HBs
Anti-HBc
HBsAg
0
Anti-HBc IgM
2
Months
4
6
Years
HBV - Diagnosis
Chronic Infection
HBV DNA
HBeAg
Anti-HBe
HBsAg
Anti-HBc IgG
Anti-HBc IgM
Months
Years
PRACTICE
HBsAG
 HBcAB (TOTAL)
 HBsAB
 HAV-IGM
 HCV


PAST INFECTION.
N.
P.
P.
N.
N.
PRACTICE
HBsAg
 HBcAB (total)
 HBsAB
 HAV-IGM
 HCV


IMMUNIZATION.
N.
N.
P.
N.
N.
PRACTICE
HBsAg
P.
 HBcAB (Total)
P.
 HBsAB
N.
 HAV-IGM
N.
 HCV
N.
 MAY BE ACUTE OR CHRONIC.
 Order Hep. B Core IgM to clarify.
 The IgM will be positive , If Acute.

HBV - Vaccine
Vaccine
Age Group
Dose
Volume
(μg)
Engerix-B
Recombivax HB
(Optional 2-dose)
# Doses
(ml)
0-19 yr
 20 yr
Adults on
hemodialysis
10
20
0.5
1.0
3 (mo 0,1,6)
3 (mo 0,1,6)
40
2.0
4 (mo 0,1,2,6)
0-19 yr
 20 yr
11-15 yr
Adults on
hemodialysis
5
10
10
0.5
1.0
1.0
3 (mo 0,1,6)
3 (mo 0,1,6)
2 (mo 0, 4-6)
40
1.0*
3 (mo 0,1,6)
Combined HAV and HBV - Vaccine
Bivalent HAV and HBV vaccine
1ml contains 720 ELISA Units of inactivated
HAV and 20 ug of recombinant HBsAg protein
Dosage: 1 ml at 0, 1, 6 months
Recommended for all susceptible persons  18
years at risk of exposure to both HAV and HBV,
including travelers to areas of
high/intermediate endemicity for both viruses
Therapeutic Agents
Immune Modulators
Nucleo(s)tide analog
Interferon
Lamivudine
Thymosin
Adefovir dipivoxil
Therapeutic vaccines
Emtricitabine
Entecavir
L-dT/ L-dC
Clevudine
Famciclovir
Characteristics of hepatitis C viruses
Virus
Hepatitis C
Family
Flaviviridae
Genus
Hepacivirus
Virion
60 nm spherical
Envelope
Yes
Genome
ssRNA
Genome size
9,4 kb
Stability
Ether-sensitive, acid-sensitive
Transmission Parenteral
Prevalence
Moderate
Fulminant
disease
Rare
Chronic
disease
Often
Oncogenic
Yes
Model of Human Hepatitis C Virus
Lipid Envelope
Capsid Protein
Nucleic Acid
Envelope Glycoprotein E2
Envelope Glycoprotein E1
HCV RNA Structure
Transcription, Replication
IRES, Translation
Structural
Non-Structural
5' UTR
3' UTR
Structure
C
E1
E2
Nucleocapsid,
Assembly
Envelope Proteins,
Assembly and Entry
Processing
p7
NS2
Protease
Calcium
Channel?
NS3
Replication
NS4A
NS4B
NS3 cofactor
Serine Protease,
Helicase
NS5A
Phosphoprotein,
Replication
Replication?
IRES = internal ribosomal entry site; UTR = untranslated region;
C = nucleocapsid core; E1 = envelope protein 1; E2 = envelope protein 2;
NS = nonstructural
NS5B
RNA-dependent RNA
polymerase
Hepatitis C: A Global Health Problem
170-200 Million (M) Carriers Worldwide
United States
3-4 M
Western
Europe
5M
Eastern
Europe
10 M
Far East Asia
60 M
Southeast Asia
30-35 M
Americas
12-15 M
Africa
30-40 M
Australia
0.2 M
HCV - Epidemiology
Prevalence In Groups at Risk
Recipients of clotting factors before 1987
75 - 90%
Injection drug users
70 - 85%
Long-term hemodialysis patients
10%
Individuals with > 50 sexual partners
10%
Recipients of blood prior to 1990
5%
Infants born to infected mothers
5%
Long-term sexual partners of HCV positive
1 - 5%
Health workers after random needlesticks
1 - 2%
Current Likelihood of Transmission
Transfusion
~ 1 in 1,000,000
Maternal-Infant
Mother HIV-negative
Mother HIV-positive
~ 5%
15 - 20%
Heterosexual partner
~1 in 1,000 per yr
Needlestick injury
HCV-positive source
HCV status unknown
~ 5%
~ 1%
HCV
ACCOUNTS FOR 90-95% OF POST
TRANSFUSION HEPATITIS
 RISK OF SEXUAL TRANSMISSION
LOWER THAN FOR HBV
 RISK THROUGH CASUAL CONTACT LOW

HCV

VERTICAL TRANSMISSION POSSIBLE
RISK INCREASED IF MOTHER IS POSITIVE
FOR HCV RNA
 RISK INCREASED IF MOTHER IS HIV
POSITIVE


OVERALL PREVALENCE ESTIMATED
AT 1.4%
WHO IS AT GREATEST RISK FOR HCV
INFECTION?




DRUG ABUSERS
BLOOD PRODUCT
RECIPIENTS (ANTIHCV SCREENING HAS
GREATLY REDUCED
RISK)
HEMODIALYSIS
PATIENTS
LAB PERSONNEL
WORKING WITH
BLOOD PRODUCTS



SEXUALLY ACTIVE
HOMOSEXUALS
PERSONS WITH
MULTIPLE AND
FREQUENT SEXUAL
CONTACTS
MEDICAL/DENTAL
PERSONNEL (3-10%
VIA NEEDLESTICK
FROM INFECTED
PATIENT)
Diagnostic Tests
 Hepatitis C antibody tests
 Qualitative HCV RNA tests
 Quantitative HCV RNA tests
 Genotyping
Acute HCV Infection
1000
HCV RNA positive
800
Anti-HCV
ALT
600
(IU/L)
Symptoms
400
200
Normal
ALT
0
0
2
4
6
8
10
12
24
1
2
3
Weeks
4
5
Months
Time After Exposure
6
7
HCV Antibody Test
 Indicates past or present infection
 Inexpensive, sensitive and specific
 Poor positive predictive value in low
prevalence populations
 Low sensitivity in immunosuppressed patients
Qualitative HCV RNA (PCR)
 Confirms diagnosis of HCV infection
 Useful in the early diagnosis of acute hepatitis C
 Demonstrates the presence of active infection
 “Gold standard” for documenting
response to treatment
Potential HCV Therapies
Phase I
R803
Rigel
HCV/MF59
Chiron
SCH-6
Schering
ANA245
ANADYS
Phase II
ISIS 14803
Isis
E-1
Innogenetics
Phase III
Viramidine
Valeant
Albuferon
VX-950
Human Genome
Vertex
Sciences
JTK 003
AKROS
Oral IFN alpha
Pharma
Amarillo
Biosciences
NM283
Idenix
HepX-C
XTL
IDN-6556
Idun
Infergen/gamma IFN
InterMune
Amantadine
Endo Labs
Solvay
Ceplene
Maxim
VX-497
Vertex
Omega IFN
Biomedicine
Multiferon
Viragen
Civacir
NABI
IP-501
Indevus
Zadaxin
SciClone
REBIF
Ares-Serono
Time to Market
HCV-086
ViroPharma/
Wyeth
Characteristics
of hepatitis D viruses
Virus
Hepatitis D
Family
Unclassified
Genus
Deltavirus
Virion
35 nm spherical
Envelope
Yes (HBsAg)
Genome
ssRNA
Genome size
1,7 kb
Stability
Acid-sensitive
Transmission
Parenteral
Prevalence
Low, regional
Fulminant disease
Frequent
Chronic disease
Often
Oncogenic
?
Hepatitis Delta Virus (HDV)
HDV INFECTION PATTERNS

COINFECTION
ACUTE SIMULTANEOUS INFECTION WITH
HBV AND HDV
 OFTEN RESULTS IN FULMINANT INFECTION

(70% CIRRHOSIS)

SURVIVORS RARELY DEVELOP CHRONIC
INFECTION (< 5%)
HDV INFECTION PATTERNS

SUPERINFECTION
RESULTS IN HDV SUPERINFECTION IN AN
HBsAg CARRIER (CHRONIC HBV)
 CAN OCCUR ANYTIME DURING CHRONIC
DISEASE
 USUALLY RESULTS IN RAPIDLY
PROGRESSIVE SUBACUTE OR CHRONIC
HEPATITIS

HDV - Coinfection
ALT
HDV RNA
IgM anti-HDV
IgG anti-HDV
HDAg
IgM anti-HBc
HBsAg
IgG anti-HBc
anti-HBs
Months
HDV - Superinfection
ALT
HDV RNA
IgM anti-HDV
IgG anti-HDV
HDAg
HBV DNA
HBsAg, IgG anti-HBc
Years
HDV
Transmission:
Oral
No
Percutaneous
Common
Sexual
Yes, rare
Perinatal
No
Incubation period
21 - 45 days
Jaundice
Unknown
Fulminant
2 – 7.5%
Diagnostic tests:
Acute infection
IgM anti-HDV
Chronic infection
IgG anti-HDV, HBsAg +
Immunity
Not applicable
Case-fatality rate
1 – 2%
Chronic infection:
Superinfection
80%
Coinfection
< 5%
HEPATITIS E VIRUS
Virus
Hepatitis E
Family
Caliciviridae
Genus
Unnamed
Virion
30-32 nm,
icosahedral
Envelope
No
Genome
ssRNA
Genome size
7,6kb
Stability
Heat-stable
Transmission
Fecal-oral
Prevalence
Regional
Fulminant disease In pregnancy
Chronic disease
Never
Oncogenic
No
Epidemiology
 Suspected from study of waterborne
hepatitis in India in 1980
 Confirmed by transmission to chimp and
human in 1983
 Probably accounts for many historical
outbreaks of hepatitis
 Endemic mainly in Asia, Middle East,
North Africa
Epidemiology
 Fecal-oral transmission (human to human)
 Contaminated water supplies in tropical or
subtropical developing countries
 Mainly young adults
 Can infect primates, swine, sheep, rats
 Swine may be reservoir of infection in North
America (attenuated virus)
 Maternal-infant transmission occurs and is
often fatal
Clinical Characteristics
 Similar to hepatitis A
 Can cause severe acute hepatitis
 Subclinical infection is common
 Attenuated virus from animal reservoirs
 Low-dose infections often asymptomatic
 No chronic infection
 Up to 20% mortality among pregnant women (esp. third trimester)
Course of Acute Infection
Viral Replication
IgM Antibody
IgG Antibody
ALT
Viremia
Symptoms
Virus in Stool
0
10
20
30
40
50
Time After Infection (days)
60
1
2
(years)
Prevention
 Passive (Immune serum globulin)
 Does not prevent infection
 May ameliorate hepatitis
 Active (Vaccine)
 Anti-ORF2 prevents infection in chimps and
humans
 Clinical trials in progress
HEV
Transmission:
Oral
Common No
Percutaneous
Unknown
Sexual
No
Perinatal
Yes, unknown frequency
Incubation period
15 - 60 days
Jaundice
Common
Fulminant
<1%, in pregnancy up to 30%
Diagnostic tests:
Acute infection
IgG anti-HEV (seroconversion)
Chronic infection
Not applicable
Immunity
Not applicable
Case-fatality rate
0,5 – 4 %
1.5 – 21% in pregnant women
Chronic infection
None
HEPATITIS G VIRUS
Virus
Hepatitis G
Family
Flaviviridae
Genus
Unnamed
Virion
60 nm, spherical
Envelope
Yes
Genome
ssRNA
Genome size
9,4 kb
Stability
Ether-sensitive
Transmission
Parenteral
Prevalence
Moderate
Fulminant disease
?
Chronic disease
Yes
Oncogenic
?
HGV AND GVB-C
SHARE 95% AMINO ACID IDENTITY
 THUS REPRESENT DIFFERENT ISOLATES
OF THE SAME HUMAN VIRUS
 “HEPATITIS C-LIKE VIRUS”
 CLASSIFIED IN THE FLAVIVIRIDAE FAMILY

 SAME AS HCV

GENETIC ORGANIZATION
SIMILAR TO HCV
 GENONE CONSISTS OF SINGLE-STRANDED
RNA MOLECULE OF POSITIVE POLARITY

HGV - EPIDEMIOLOGY



TRANSMISSABLE BY BLOOD AND BLOOD PRODUCTS
PRESENT IN ASYMPTOMATIC BLOOD DONORS
WITH NORMAL ALT LEVELS
FOUND IN:
GENERAL POPULATION
1-2 %
HEMOPHILIA PATIENTS
18 %
IV DRUG USERS
33 %
Patients with chronic Hepatitis B
10 %
Patients with chronic Hepatitis C
20%
HGV - CLINICAL SIGNIFICANCE

RECENT DATA SUGGESTS:
 HGV INFECTION DOES NOT CAUSE ACUTE



HEPATITIS
HGV MAY ESTABLISH CHRONIC INFECTIONS
FREQUENTLY OCCURS WITH HBC AND HCV
INFECTIONS
MAY NOTQUALIFY AS A TRUE HEPATITIS
VIRUS
THE END