Hepatitis B Virus

Sample for Hepatitis B Virus

1. The best sample for the viral hepatitis B markers or profile is serum.
2. A random sample can be taken. No need for a fasting sample.

Purpose of tests (Indications)

1. Viral hepatitis B marker is done for:
   1. The diagnosis of HBV infection.
   2. The diagnosis of the carrier.
   3. The diagnosis of chronic hepatitis.
   4. Screening of blood for transfusion.

Definition of the Hepatitis B Virus

1. HBV is also called serum hepatitis or long incubation hepatitis. The DNA virus causes viral hepatitis B. This is a double-stranded DNA virus, and one strand is incomplete.

Biology of the Hepatitis B Virus

1. This virus belongs to the Hepadnaviridae family.
2. HBV is found in the blood and body secretions.
3. In the HBs antigen-positive serum, there are three types of particles:
   1.  The most common are spherical 20 nm in diameter.
   2. The second particle is 200 nm long and 20 nm in width.
   3. Dane particles, also called virions, 42 nm spherical, are few in the blood.

4. HBsAg particles (sphericle and tubular) are not infectious. While Dane particle is infectious.

Summary of the features of Hepatitis B virus (HBV)

Parameters	HBV features
Family	Hepadnaviridae
Genus	Orthohepadnavirus
Genome	dsDNA
Genome size	3.2 kb
Virus particle (Viron)	42 nm, spherical
Mode of transmission	Parenteral
Prevalence	High
Fulminant disease	Rare
Chronicity	usually seen
Oncogenicity	It is an oncogenic virus
Stability	It is acid-sensitive It is stable at 37 °C for 60 minutes HBsAg is stable at pH 2.4 for 6 hours Sodium hypochlorite destroy within 3 minutes Ultraviolet rays do not destroy HBsAg

The outcome of the disease is:

1. Acute hepatitis.
2. Chronic hepatitis.
3. Cirrhosis.
4. Liver cell carcinoma.
5. This is usually seen in young adults.

Hepatitis B virus (HBV) Transmitted by:

1. Blood and blood products.
2. Contaminated needles can spread it.
   1. In I/V drug abusers, it is seen in about 25% to 30% every year in the USA.
   2. It is also seen in renal dialysis patients.
3. It can spread through sexual contact through the rectum or by sexual intercourse.
   1. It is quite common in male homosexuals.
   2. It is less common in heterosexuals.
4. It can spread through other body fluids like infected blood, saliva, and semen through a small break in the skin or mucous membrane.
   1. There is an increased risk in renal transplantation patients and patients with leukemia and lymphoma.
5. There is transplacental spread.
6. Hospital workers are also at risk, roughly 5% of yearly cases in the USA.
   1. This usually happens by accidental needle prick.
   2. It is also common in dentists and dental workers.

It is Common in (high-risk group):

1. Multiple Blood transfusion recipients.
2. Male homosexuals.
3. Dialysis patients.
4. Transplant patient.
5. I/V drug user.
6. Hospital worker because of needle pricks.
7. Patient with leukemia and lymphoma.
8. During delivery can infect the newborn if the mother is a carrier.
9. A family member with close contact.

Incubation period

1. This has long incubation varying from 5 weeks to 6 months (60 to 90 days).
2. This viral can give acute infection and may develop chronic disease.

Structure of Hepatitis B Virus (HBV)

1. This is a DNA virus called a Dane particle (Virion).
2. It has an inner core surrounded by an outer capsule.
3. The outer capsule contains the antigen called the hepatitis B surface antigen (HBs-Antigen). This is also called as Australian antigen (HBsAg).
4. The inner core contains HBV core antigen one is called HBcAg, and another antigen is incorporated into the Core antigen is called HBeAg.
5. The HBcAg is in a very small amount, so not detectable, but its Antibody is found in circulation.

HBV antigens and antibodies:

1. Dane particle (Virion) has a double-shell structure that contains several different antigens (antigenic material).
   1. The outer envelope is called a surface antigen (HBsAg), also called the Australian antigen.
   2. The inner core contains HBV core antigen (HBcAg), and HBV e antigen (HBeAg).
   3. Within the core is double-stranded DNA (double-stranded viral deoxyribonucleic acid).
   4. There is an enzyme called DNA-polymerase.

2. There are three antigens:

   1. HBsAg
   2. HBcAg
   3. HBeAg

3. There are three Antibodies:

   1. Anti-HBsAb
   2. Anti-HBcAb
   3. Anti-HBeAb

Hepatitis B surface antigen (HBsAg)

1. HBV surface antigen (HBsAg) is detected by immunoassay or nucleic acid probe.
2. HBsAg appears first in the blood, so its detection in the blood is a very common test.
3. HBsAg rises before clinical signs and symptoms appear and is detectable.
4. The peak is during the first week of symptoms.
5. It returns to a normal level by the time jaundice subsides.
6. If it persists, the patient will be a carrier or develop chronic hepatitis.
7. HBsAg interpretations:
   

   Parameters	Clinical presentation
   Appearance of HBsAg	It appears after 2 to 6 weeks after exposure 5% to 15% of patients are negative at onset of jaundice
   Peak level	1 to 2 weeks before or 1 to 2 weeks after the onset of symptoms
   When it is not detected in the blood	It disappears 1 to 3 months after the peak This range may be 1 week to 5 months

Hepatitis B surface antibody (HBsAb)

1. This antibody appears after roughly 4 weeks, after the disappearance of HBsAg.
2. It indicates the end of the acute phase and the patient’s complete recovery from the infection.
3. The patient will develop immunity to HBV infection.
4. After vaccination, there is the appearance of HBsAb.
5. HBsAb interpretations:
   

   Parameters	Clinical interpretations
   Appearance of HBsAb	2 to 6 weeks of the disappearance of HBsAg Few cases may not produce HBsAb
   Peak level	2 to 8 weeks after the appearance
   When it is not detected	Around 85% of the cases have the presence of HBsAb-total It may persist for many years of life There is a slow decline in the titer HBsAb disappear in 6 months in around 15% of the cases

   

   Hepatitis B virus (HBV) showing HBs antigen and antibody

Hepatitis Core antigen (HBcAg)

1. This is not detectable because of the very small quantity, and it is incorporated with HBeAg.
2. There are no commercial kits available to detect HBcAg.

Hepatitis B Core Antibody (HBcAb )

1. There are kits available for HBc-IgM and total HBcAb (HBc-IgM and IgG)
2. This antibody appears after one month of infection.
3. This will be HBcAb-IgM type in acute infection and later replaced by HBcAb-IgG type.
4. HBc-IgM is detected in active acute or recent acute HBV infection.
   1. HBc-IgM rises during active acute infection of HBV and will remain in the convalescent stage.
   2. It will be seen during the period when HBsAg disappears, and HBsAb appears (window period).
   3. It is also called a “core window” marker.
5. This antibody persists in circulation for several years.
6. This antibody will be present in chronic hepatitis cases.
7. In the window period when HBsAg is negative, and still there are no HBsAb, then this is the antibody present in the patient.
8. It is not detected in the early weeks or months of the recovery phase.
9. HBcAb total been elevated for many years and give positive results in:
   1. Late-stage active acute infection.
   2. Convalescent stage.
   3. Chronic stage (chronic infections).
   4. Recovery early stage.
10. HBcAb total may be found with HBsAg.

HBcAb interpretations:

Parameters	HBcIgM	HBcAb total
Appearance of HBcAb	Around 2 weeks after the appearance of HBsAg	About 3 to 4 weeks after the appearance of HBsAg
Peak level	Around one week after the onset of symptoms	3 to 4 weeks after the detection of HBcIgM
When it is not detected	3 to 6 months after the appearance	It is raised throughout the life It may decline over many years

Hepatitis Be antigen (HBeAg)

1. HBeAg is not usually advised for the diagnosis of HBV infection.
2. HBeAg is a marker of infectivity, continued replication of the HBV infection.
   1. HBeAg without the appearance of the HBeAb will indicate greater potential for spreading the infection to other people.
   2. HBeAg disappeared shortly before the disappearance of the HBsAg.
3. HBeAg appears immediately after the appearance of HBsAg.
4. HBeAg indicates early and acute disease.
5. HBeAg positive in chronic hepatitis patients is a sign of a bad prognosis.
6. The persistence of HBeAg indicates the development of chronic hepatitis.

HBeAg interpretations:

Parameters	HBeAg
The appearance of the HBeAg	Around 3 to 5 days after the appearance of HBsAg
Peak level	It is at the same time as the HBsAg
When it is not detected	Around 2 to 4 weeks before the HBsAg disappears in 70% of the cases Approximately 1 to 7 days after the HBsAg disappears in about 20% of the cases

Hepatitis Be antibody (HBeAb)

1. The appearance of HBeAb is a sign of recovery.
2. HBeAb appears after the disappearance of the HBeAg or in 1 to 2 weeks later.
   1. HBeAb appearance indicates that HBV infection is over and infectivity for other people is less common.
3. This antibody shows the end of the acute phase.
4. The presence of HBeAb indicates less infectivity.

HBeAb interpretations:

Parameters	HBeAb
When it appears	It appears at the same time or within 1 to 2 weeks after HBeAg disappears 2 to 4 weeks before HBsAg disappear
Peak level	During window period
When not detected	It persists for several years

Clinical presentations of Hepatitis B Virus

1. There is variation in the symptoms from mild to severe.
   1. It is fatal in about 1% to 3% of the patients.
   2. 30% to 40% of patients develop acute hepatitis.
2. Most of the children and 50% of the adults are asymptomatic.
   1. Infants are almost always asymptomatic, and most children do not develop jaundice.
3. The symptoms are insidious.
4. The prodromal period often shows :
   1. Fever.
   2. Malaise.
   3. Myalgia.
5. The patient may have nausea and vomiting.
6. There is weight loss.
7. The acute period with jaundice lasts about one month.
8. The patient will have jaundice and dark color urine.
9. <1.5% may develop fulminant hepatitis.
10. Chronicity decreases with age.
    1. 85% seen in the neonates.
    2. 25 to 50% of children.
    3. 6 to 10% of the adult.
11. These patients are at high risk for liver cell carcinoma.
12. Pregnant ladies may get an infection during 3rd trimester or early postpartum or HBV carrier, frequently transmitting HBV infection to their babies after birth.
    1. When a mother is HBsAg and HBeAg positive, it will transmit the infection to babies from 12.5% to 40%, and this may be high as 70% to 90%.
    2. In one of the studies, when PCR is negative but routine HBsAg and HBeAg are positive, fewer infants get infected.
    3. Without treatment, babies 80% to 90% become chronic carriers of HBsAg. These babies are prone to develop a risk of fatal cirrhosis or liver cell carcinoma.
    4. If newborns are given vaccines and immunoglobulin, it will reduce the risk of the chronic carrier state.

Table showing the difference between HAV and HBV:

Presentation	HBV	HAV
Mode of transmission	Parenteral	Feco-oral
Incubation period	60 to 160 days	15 to 40 days
Time of spread	All the year	Fall and winter
Onset	Slow	Sudden
Chronicity	Roughly 5 to 10%	Complete recovery
Mortality	<0.01%	<1%
Prophylaxis	γ-globulin protects	Some pools of γ-globulin

The significance of various hepatitis markers:

1. Acute infection
   1. HBsAg positive.
   2. HbcAb- IgM positive.

Chronic infection (Chronic carrier):

1. Chronic hepatitis is defined when >6 months surface antigen (HBsAg) is present with normal liver function tests and normal microscopic findings on the liver biopsy.
2. 2 to 10 % develop chronic disease.
3. Chronic hepatitis is divided into:
   1. Chronic persistent hepatitis where abnormal liver function tests, relatively normal microscopic findings on liver biopsy. This condition is seen in 6% of the patients.
   2. Chronic active hepatitis where abnormal liver function tests and abnormal microscopic findings on liver biopsy. This condition may be seen in 3% of the patients.
4. These patients may develop cirrhosis.
5. Cirrhotic patients have more chances for cancer, almost increase 500 times.
6. Lab findings are:
   1. HBsAg positive.
   2. HbcAb-IgG (Total) is positive.
7. HBeAg positive indicates a highly infective stage and poor prognosis.

3. Recovery stage parameter
   1. HBsAg is negative.
   2. HBsAb is positive.
4. Window period marker
   1. HBsAg is negative.
   2. HBsAb is negative.
   3. HBcAb-IgM will be positive.
5. For the HB viral load advice PCR.
   1. PCR qualitative for the HBV genome.
   2. PCR quantitative by HBV DNA by RNA probe.

Table showing various HBV antigens and antibodies

HBV Ag/AB	Appears	Disappears	Significance
HBsAg	4 to 12 weeks	1 to 3 months	Acute or chronic infection
HBeAg	1 to 3 weeks	6 to 8 weeks	Acute infection
HbcAg	not detected
HBsAb	3 to 10 months	6 to 10 years	Indicate immunity
HbeAb	4 to 6 weeks	4 to 6 years	End of acute infection
HbcAb IgM	2 to 12 weeks	3 to 6 months	Acute HBV infection
HbcAb total	3 to 12 weeks	Life long	Past HBV infection/recovery stage

Table showing various stages of HBV infection:

Test	Acute	Chronic	Recovery	Carrier	Window period	Vaccination
HBsAg	positive	positive	negative/positive	positive	negative	negative
Anti-IgM HBc	positive	neg/pos	negative	negative	positive	negative
Anti-IgG HBc	negative	positive	positive	positive	neg/pos	positive
HBeAg	positive	neg/pos	negative	negative	negative	negative
Anti-HBeAb	negative	positive	positive	positive	pos/neg	negative
Anti-HBs Ab	negative	negative	positive	negative	negative	positive
PCR	positive	positive	negative	negative	positive	negative

Treatment

1. In the case of fulminant hepatitis, liver transplantation is needed.
2. Treatment of chronic HBV infection is indicated when HBV-DNA  >2000 IU/L and serum SGPT is raised.
3. Antiviral medications are Lamivudine (Epivir), Adefovir (Hepsera), Telbivudine (Tyzeka) and Entecavir (Baraclude).
4. Interferon alpha-2 is used mainly for young patients.

Prevention

1. Vaccination is the method of choice.
2. This should be given at birth to infants born to carrier mothers.

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