Hepatitis, Lect 42, 43

Front 1

Structure of hepatitis A virus

Back 1

1. Non-enveloped (naked) with a single-stranded, (+)-sense RNA genome.

2. Virions are icosahedral and even more stable than other picornaviruses; resistant to
inactivation by heat, detergent, low pH, and desiccation.

Front 2

Hepatitis A virus replication

Back 2

1. Replicates like other picornaviruses.
a. Binds to a receptor expressed on liver cells and a few other cell types.

2. Is NOT cytolytic, released by exocytosis.

Front 3

Hepatitis A epidemiology
1. How is it transmitted?
2. Where is it found in nature?
3. How is it spread?

Back 3

1. ~40% of acute hepatitis cases caused by HAV.

2. Virus is transmitted by the fecal-oral route and spreads quickly because:
a. most infected people are contagious before symptoms appear.
b. 90% of children and 25-50% of adults have inapparent, but productive
infections.
c. virus is released into stool at high concentrations.

3. Virus can survive in fresh and salt water for many months.
a. Water contaminated with sewage is a source of virus and can contaminate
shellfish, particularly filter-feeders.

4. HAV outbreaks usually due to a “common source” like contaminated water or raw
shellfish, or infected individuals. Infected food handlers, daycare workers, children have the potential to infect many other people.
a. Children are the most frequently infected group (schools, camps)

5. Virus is found worldwide and all year-long.

6. HAV is rarely spread via blood because viremia is low and chronic infections do not
occur.

Front 4

Pathogenesi and immunity of Hepatitis A
1. How does it replicate?
2. How does the immune system respond?

Back 4

1. HAV is ingested and probably replicates in the GI tract (oropharynx or epithelial
lining of the intestines), then enters the bloodstream.

2. HAV replicates in parenchymal cells in the liver, including hepatocytes and Kupffer
cells.

3. Virus is released from cells into bile and then into stool.
a. Virus is shed in high concentration into stool ~10 days before jaundice or
antibody can be detected.

4. HAV replication in liver cells is NOT cytopathic, immune response to HAV is thought
to result in immunopathogenesis. Antibody, complement, ADCC contribute to lysis of
infected cells and liver damage (icterus).

5. HAV IgG antibodies induced by infection provide lifelong protective against re-
infection. There is only 1 serotype.

6. HAV does not produce chronic infections, nor immune complex-related syndromes,
like rash or arthralgia.

Front 5

Describe the clinical manifestations of hepatitis A

Back 5

1. Disease in children is milder that in adults and usually asymptomatic.

2. Incubation period is 3-4 weeks.

3. Initial symptoms include: fever, fatigue, nausea, loss of appetite, abdominal pain.

4. Symptoms occur abruptly 15-50 days after exposure and intensify for 4-6 days
before icteric phase.

5. Symptoms of HAV infection are similar to those of other hepatitis virus infections
resulting from liver damage due to immunopathogenesis, and include: dark urine,
pale feces, and elevated liver enzymes.

6. Virus is shed in stool up to 2 weeks before symptoms appear, but stops before
symptoms disappear.

7. Complete recovery occurs in 99% of cases.

8. Fulminant hepatitis occurs in 1-3 persons per 1000 infected with HAV and is
associated with 80% mortality rate.

Front 6

What is the lab diagnosis of hepatitis A made on the basis of?

Back 6

1. Made on the basis of:
a. time course of the clinical symptoms,
b. identification of a known infected source,
c. specific serologic tests.
i. Detection of anti-HAV IgM indicates acute HAV infection and detection of
anti-HAV IgG indicates a previous HAV infection (or vaccination) and
immunity to re-infection.

Front 7

Treatment and prevention of hepatitis A

Back 7

1. Clinical illness can be prevented with 80-90% effectiveness by prophylaxis with
immune serum globulin (passive immunization) given before or early after exposure
(<2 weeks).

2. A killed (inactivated) HAV vaccine is available and recommended for:
a. people living in or traveling to areas where HAV is endemic,
b. children as part of routine vaccination (1st vaccination at 1 year old, booster at
18 months old),
c. men who have sex with men.
d. Vaccine is given in 2 doses; an initial dose and a booster 6-12 months later.

3. Spread of HAV is prevented by good hygiene and avoidance of potentially
contaminated food and water.

Front 8

Structure of hepatitis C virus

Back 8

1. Enveloped virus with icosahedral capsid and single-stranded, (+)-sense RNA
genome. Virus exists as a quasispecies due to high error rate of viral RNA polymerase.

Front 9

Replication of hepatitis C virus

Back 9

1. Not very well understood.
2. Occurs in the cytoplasm.
3. Viral genome is translated into a single polyprotein that is subsequently cleaved by
viral protease into individual viral proteins.
4. Virions bud from the ER, but release mechanism is unclear.

Front 10

Epidemiology of hepatitis C virus
1. Who is a reservoir?
2. How is it transmitted?

Back 10

1. Humans are the reservoir for HCV.

2. Virus is transmitted primarily through blood.
a. HCV is the most prevalent blood-borne pathogen in the U.S.
i. An estimated 4.9 million people are infected (200 million worldwide).

b. Most cases due to infection by contaminated needles (i.v. drug use).

c. Blood donations are screened for HCV and HCV antibodies.

d. Transmission can occur via:
i. contaminated, pooled immune globulin
ii. organ donations
iii. factors VIII or IX given to hemophiliacs.

e. Almost all HIV-infected individuals who were or are i.v. drug users are infected with HCV.

3. High incidence of chronic asymptomatic infections results in frequent transmission to
others.

Front 11

Pathogenesis and immunity for HCV

Back 11

1. HCV replicates in hepatocytes, but is not cytopathic. Many infections become
chronic (persistent).

2. Hepatocytes are killed by immune attack by CTLs.

3. HCV infection results in higher frequency of hepatocellular carcinoma (HCC), due to
increased cell division and mutation, not a viral oncogene.
a. Alcoholism enhances frequency of HCC in HCV-infected individuals.

4. Antibodies to HCV are made, but are not protective.

5. ~70% of patients are chronically infected and continue to produce virus for at least 1
year.

6. For those individuals who clear HCV infection, it is not known if re-infection can
occur or whether there is lifelong immunity.

Front 12

What are 3 types of disease that HCV causes?

Back 12

a. Acute hepatitis w/ virus clearance and recovery
b.Chronic persistent infection with progression to disease later in life
(~70% of cases).
c. Severe rapid progression to cirrhosis (in 15% of chronic cases).

Front 13

Acute hepatitis with virus clearance and recovery

Back 13

i. Symptoms of acute HCV infection are similar, but milder than seen
with acute HAV and HBV infections, and inflammatory response is
less intense. Symptoms include fever, anorexia, nausea, vomiting
and jaundice.

ii. Most often initial disease is inapparent and leads to chronic
persistent disease.

Front 14

Chronic persistent infection with progression to disease later in life

Back 14

i. Progression to chronic active hepatitis within 10-15 years.
ii. Cirrhosis and liver failure after 20 years = most common indicator
for liver transplantation.
iii. Hepatocellular carcinoma (HCC) after 30 years in < 5% of cases.

Front 15

Describe the lab diagnosis for HCV

Back 15

1. HCV infection is diagnosed by detection of anti-HCV antibodies in an ELISA.
Seroconversion occurs within 7-31 weeks of infection.
a. Antibodies are not always detectable in viremic or immunocompromised
individuals, or individuals on hemodialysis.

2. RT-PCR is used to detect HCV genome in serum, blood supply, etc.

3. Chronic infection is characterized by elevated liver enzymes, detection of HCV
antibodies and HCV RNA for at least 6 months.

Front 16

Treatment and prevention of HCV

Back 16

1. Treatment is with alpha interferon, pegylated interferon (Peg-intron) and ribavirin.
a. These treatments reduce viral replication and liver damage, but do not
eliminate the carrier state.
b. Associated with side effects, which may limit their use in combination.
2. Prevention of transfusion-acquired HCV has been accomplished by screening.

3. No vaccine.

4. Pooled immune serum globulins are not effective for postexposure prophylaxis.

5. HAART (highly active anti-retroviral therapy) may exacerbate hepatitis in patients
coinfected with HIV and HCV

Front 17

Describe the structure, cause, symtpoms, lab tests, and treatment and vaccines for hep E virus

Back 17

A. Non-enveloped virus with a single-stranded, positive-sense RNA genome.
1. Tentatively classified as a member of the Hepeviridae family.

B. Major cause of enterically transmitted hepatitis, especially epidemics in Asia, Africa,
India, and Mexico.

C. Symptoms and disease produced by HEV infection resemble those of HAV.
1. Higher mortality rate in pregnant women than with HAV.
2. Does not cause chronic infection.

D. Laboratory tests for HEV are not readily available; diagnosis typically made by
excluding other hepatitis viruses.

E. No treatment or vaccine

Front 18

Describe the structure, cause, symptoms, lab tests, treatment of hepatitis G virus.

Back 18

A. Member of the Flaviviridae family, like HCV, enveloped, single-stranded, (+)-sense RNA
genome. Also known as GB virus type C (GBV-C).

B. Isolated from a patient with post-transfusion hepatitis, but has not been shown to cause
hepatitis.

C. Can cause a chronic infection lasting for decades.

D. ~60-70% of those infected clear the virus and develop antibodies.

E. Transmitted by sexual intercourse and blood.

F. Found in the blood of millions of people worldwide.
1. In the U.S., in blood from 2% random blood donors, 15% of HCV-infected
individuals, and 35% of HIV-infected individuals.
a. May interfere with replication of HIV and increase lifespan of coinfected
individuals.

Front 19

Structure of hepetitis B
1. What is another name for the virion?
2. Describe the genome

Back 19

1. Virion, also called Dane particle, is enveloped. Envelope contains 3 virus-encoded
glycoproteins; HBsAg is the most prevalent and elicits neutralizing antibodies.

2. Viral genome is the smallest DNA human virus genome known (3.2 kb), partially
double-stranded, circular; 4 genes encode multiple proteins.

3. Genome is enclosed by icosahedral nucleocapsid or core particle, composed of
core antigen (HBcAg). Core particle also contains the viral reverse transcriptase
(RT).

Front 20

What kind of protein does the virus encode?

What are 3 types of virus particles found for Hep B virus?

Back 20

4. Virus encodes a protein, HBeAg, that is not a part of the virion, but is secreted and
is an important indicator of transmissibility.

5. In the serum of infected patients, 3 types of virus particles are found:
a. Dane particles: contain core particle with viral genome, are infectious, least
numerous.

b. Small spherical particles: 22 nm diameter, composed of only HBsAg, no viral
genome, no core, are NOT infectious, most numerous (103-106-fold excess over
Danes, 1012/ml).

c. Tubular, filamentous particles: 22 nm diameter, up to 200 nm long, composed
of only HBsAg, no viral genome, no core, are NOT infectious, less numerous
than small spherical particles.

Front 21

Describe the nomenclature of the following:
1. HBsAg
2. HBcAg
3. HBeAg

Back 21

HBsAg is surface Antigen antibodies to HBsAg are named anti HBs or HBsAb
HBcAg is core Antigen antibodies to HBcAg are named anti HBc or HBcAb
HBeAg is secreted from cell antibodies to HBeAg are named anti HBe or HBeAb

Front 22

Replication cycle of Hep B virus

Back 22

a. Viral genome is delivered to the nucleus and "gap" is filled in.

b. ds DNA viral genome converted to covalently-closed, circular (CCC) molecule.

c. Viral CCC DNA is template for transcription of viral mRNAs and viral pregenomic
RNAs. The CCC molecule can persist in the absence of viral replication, and
represents a critical target for antiviral strategies aimed at “curing" chronic
carriers.

d. In the cytoplasm, viral mRNAs are translated into proteins. The pregenomic
RNA is translated into the RT, which remains bound to the RNA.

e. Pregenomic RNA-RT complex is packaged into core particles in the
cytoplasm.

f. In the core particle, RT performs 3 enzymatic activities to make the genomic
DNA molecule from the pregenomic RNA. 1st, it makes a complementary DNA
strand using the pregenomic RNA molecule as template (RNA-dependent, DNA
polymerase activity, aka reverse transcription).

g. 2nd, as the RT makes the cDNA strand, an RNAse H activity dig

Front 23

Epidemiology of Hep B infection
1. What's the incidence?
2. What is the reservoir?
3. How is it transmitted?

Back 23

1. Incidence: worldwide with widely varying prevalence.

2. Reservoir: chronic carriers, 0.1%-0.5% of U.S. population, >250 million worldwide.
Humans are the only host.

3. Transmission via blood and body fluids:
a. Half of infections are sexually transmitted.

b. Neonatal infections are most likely acquired during birth.
c. Every virion is infectious!

Front 24

Pathogenesis and immunity to HBV
1. What is the hepatotropism due to?
2. What does lifelong immunity result after?
3. What is chronic infection correlated with?

Back 24

1. HBV hepatotropism due to virus-specific receptors on liver cells and hepatocyte-
specific transcription factors that enhance HBV replication.

2. HBV is not directly cytopathic for liver cells, much of the pathology in HBV infection is
immune mediated (CTL).

3. Lifelong immunity results after natural infection and is mediated by antibodies to
HBsAg.

4. Chronic infection is correlated with an increased frequency of developing
hepatocellular carcinoma (HCC).

Front 25

Clinical manifeastations of HBV

Back 25

1. Clinical symptoms during acute phase vary considerably, with most individuals
showing no obvious clinical signs of disease.

2. After incubation period of 45-120 days, a short prodromal phase occurs; patients
frequently experience malaise, lethargy, anorexia, pain in the upper right quadrant.
In some, followed by icteric phase (4-8 weeks), then convalescent period.

3. Chronic active HBV infection occurs in 5-10% of adults infected with HBV, and in
80-90% of neonatal exposures.

Front 26

Describe the acute infection for HBV

Back 26

Occurs in 90-99% adults, 5-20% infants

3 types: subclinical, icteric hepatitis, fulminant heptatis (fatal 1%)

The icteric hepatitis may go on to the convalescent phase

Front 27

Describe the chronic infection for HBV

Back 27

occurs in 1-10% adults
80-95% infants

Can have 3 types
1. asymptomatic
2. chronic persistent hepatitis
3. chornic active hepatitis

Chronic active hepatitis can develop into cirrhosis and heptaocellular carcinoma

Front 28

What is the lab diagnosis of hepatitis B?

Back 28

a. At primary infection, almost all patients will exhibit IgM reactivity to HBcAg.

b. Also look for HBsAg, HBeAg, and elevated liver enzymes: ALT, AST.

c. Anti-HBsAg is the neutralizing antibody which protects against re-infection; its
appearance indicates clearance of virus and is often preceded by the
appearance of anti-HBeAg.

d. “window phase”: HBsAg -, Anti-HBs-, Anti-HBc +. Anti-HBs and anti-HBe may
be obscured by the antigen-antibody complexes.

e. Chronic infection is indicated if HBsAg is in blood beyond 6 months.

Front 29

What are the serological markers present in acute hepatitis?

Back 29

HBsAg, Anti-HBc, HBeA, viral DNA

Front 30

What are the serological markers present in 'window' period?

Back 30

Anti-HBc

Front 31

What serological markers are present in chronic active hepatitis?

Back 31

HBsAg, Anti-HBC, HBeAg, viral DNA

Front 32

What serological markers are found in those with past infection (immunity)

Back 32

Anti-HBs, Anti-HBc

Front 33

Serological markers indicative of past immunization?

Back 33

Anti-HBs

Front 34

Treatment of Hep B?

Back 34

1. None that is 100% effective.
a. α-IFN
b. nucleoside analogue inhibitors: lamivudine, entecavir, and telbivudine
c. nucleotide analogue inhibitors: adefovir and tenofovir
d. only entecavir and tenofovir currently in use

Front 35

Prevention of HBV?

Back 35

1. HBV vaccine based on HBsAg expressed and purified from yeast.
a. For vaccine purposes, 1 serotype based on HBsAg.
b. x3 injections during a six month period.
c. Universal childhood vaccination and vaccination of personnel at occupational
risk.

2. 5-15% of those vaccinated do not respond to single vaccination series.

3. Hepatitis B immune globulin (HBIG) injection soon after exposure may reduce
symptoms.

4. For infants delivered from HBV chronic carrier mothers, vaccine and HBIG can
prevent infection.

Front 36

Describe the structure of Hep D virus (Delta virus)

Back 36

1. The RNA genome is enclosed in a nucleocapsid composed of one protein, HDAg,
and is surrounded by an envelope composed of HBsAg from HBV.

2. Viral genome
a. Single-stranded, negative-sense RNA genome; 1.7 kb.

Front 37

Describe the replication cycle of HDV

Back 37

1. Infectious HDV only produced in cells infected with HBV
2. Complicated mechanism of replication...
3. HDV requires HBsAg to package virions.

Front 38

Describe the epidemiology of HDV

Back 38

1. HDV infections occur worldwide with similar distribution as HBV. Infected humans
are the source.

2. HDV is transmitted by the same means as HBV: via blood, sexually, and perinatally.

Front 39

Describe the pathogenesis and immunity of HDV

Back 39

1. HDV is directly cytopathic.

2. Coinfection with HBV allows production of infectious HDV virions in HBV-infected
cells expressing HBsAg; the outcome of the disease is not appreciably changed.

3. Superinfection of an HBV carrier with HDV is more serious. Many more cells
express HBsAg and HDV spreads more rapidly. HDV is packaged roughly 1000
times more efficiently than HBV. Increases frequency of chronic infection and
development of cirrhosis.

4. HDV infections can become persistent in chronic HBV carriers.

5. Not clear if long-term immunity to HDV exists.

Front 40

Clinical manifestations of HDV

Back 40

1. Incubation period of 3 to 7 weeks.
2. Patient complaints are similar to those for HBV when HBV/HDV coinfection occurs.
3. Clinical symptoms usually more severe with HDV superinfection.

Front 41

Lab diagnosis of HDV

Back 41

1. Detection of anti HDAg antibodies.
2. Detection of delta antigen.
3. Detection of HDV RNA.

Front 42

What's the treatment and prevention of HDV

Back 42

G. Treatment
1. None that are 100% effective.
2. α-IFN may reduce disease symptoms.

H. Prevention
1. HBV vaccination.