Hepatitis Virus Question And Answers

Hepatitis Virus

 

Question 1. Write a short note on Australian antigen.
Answer:

A scientist named Blumberg and his coworkers in 1965 describe a protein antigen in the serum of an Australian aborigine which gave a positive precipitation reaction with sera from two hemophiliacs who had received multiple transfusions. This antigen was named as Australian Antigen.

HBsAg is known as Australia Antigen and was established to be the surface component of the hepatitis B virus.

Australian antigen consists of two different antigenic determinants:

• A group-specific antigenic determinant – a
• Two pairs of type-specific antigens – d – y and w – r.
• In these only one member of each pair is present at a time.

Australia antigen on the basis of type-specific pairing is divided into four types:

• ADW is worldwide in distribution
• adr in Asia
• ayw in Africa, India, Russia
• ayr in Africa, India, Russia

Read And Learn More: Microbiology Question And Answers

Various additional surface antigens, i.e. q, x, f, t, j, n, and g are described, but their characterization is not done:

• Electron microscopy of the serum of hepatitis B patients shows three types of particles, i.e.
  • Spherical particle: It is most abundant and is 22 nm in diameter.
  • Tubular particle: It is of varying length and is 22 nm in diameter.
  • Dane Particle: It is a double-shielded spherical structure that is 42 nm in diameter. This article is complete hepatitis B virus.
• The spherical and tubular particles are antigenically identical and are surface subunits of the hepatitis B virus Australia antigen (HBsAg).

Question 2. Write the test for detection of hepatitis B antigen.
Answer:

A variety of serological techniques are available for the detection of hepatitis B antigens.

• HBsAg antigen is recognized as a specific marker for infection with the virus.
• It becomes detectable in circulation about a month after exposure to infection with a peak level in the prehistoric phase of the disease.
• Methods for detection of HBsAg antigen are as follows:

Question 3. Write a brief about rapid tests for hepatitis B antigen.
Answer:

Rapid Test for Detection of Hepatitis B Rapid test for HBsAg utilizes the principle of immunochromatography, a unique two-site immunoassay on a membrane.

• As the test sample flows through the membrane assembly of the dipstick the colored anti- HBsAgcolloidal gold conjugate complexes with HBsAg in the sample.
• The complex moves further on the membrane to the test region where it is immobilized by the antiHbsAg antiserum coated on the membrane.
• Leading to the formation of a pink-colored band which confirms a positive test result.
• The absence of this colored band in the test region indicates a negative test result.
• The unreacted conjugate and unbound complex if any move further on the membrane and are subsequently immobilized by the anti-mouse antiserum coated on the membrane.
• At the control region forming a pink band. This control band serves to validate.

Question 4. Write about the pathogenicity of the hepatitis B virus.
Answer:

HBV is a bloodborne virus and the infection is transmitted by parenteral, sexual, and perinatal modes.

• Blood of the carriers, and of patients is the most important source of infection.
• The virus can also be present in various other body fluids and excretions, i.e. saliva, breast milk, semen, vaginal secretions, urine, bile, and feces. Out of all these, semen and saliva mostly transmit the infection.
• Transfusion of the blood of carriers is the most widely known mode of infection.
• Therapeutic and prophylactic preparations from pooled human blood and serum have led to hepatitis.
• HBV is very highly infectious. Any object or procedure that can convey minute traces of infected blood or other material, as little as 0.00001 mL can be infectious.
• These include shared syringes, needles, and other sharp items or endoscopes, personal articles such as razors, nail clippers, or combs and practices such as acupuncture, tattooing, ritual circumcision, ear or nose piercing, and field camps for surgery or disease detection by blood testing where separate sterile articles may not be available.
• Professionals who are using sharp articles like barbers, dentists, and doctors may unwittingly transmit the virus if proper sterilization is not used.
• Infection by direct contact with open skin lesions such as pyoderma, eczema, cuts, and scratches are very common transmission where opportunities exist for contact with blood or saliva among members.
• Congenital or vertical transmission is quite common from carrier mothers. The risk to babies is high if the mother is HBeAg positive.
• Infection is usually acquired during birth by contact of maternal blood with the skin and mucosa of the fetus, or in the immediate postnatal period.
• The risk of transmission of disease by heterosexual and homosexual contact increases as the number of partners and the duration increases.

Question 5. Mention serum markers in hepatitis virus infection and their interpretation
Answer:

Following are the serological markers in hepatitis virus infection

• HBsAg
• IgM anti-HBc
• IgM anti-HAV
• Anti-HDV.

Question 6. Classify hepatitis viruses. Describe the laboratory diagnosis of infections caused by the hepatitis B virus.
Answer:

Classifiation of Hepatitis Virus

• Hepatitis A virus (HAV)
• Hepatitis B virus (HBV)
• Hepatitis C virus (HCV)
• Hepatitis D virus (HDV)
• Hepatitis E virus (HEV)
• Hepatitis G virus (HGV).

Laboratory Diagnosis of Infections Caused by Hepatitis B Virus

• Serum bilirubin is raised (5-20 mg%). Conjugated hyperbilirubinemia indicates intrahepatic cholestasis.
• Serum enzymes (SGOT and SGPT) are raised (400-4,000 IU), and serum alkaline phosphatase may or may not be raised depending on cholestasis.
• Plasma albumin may be low but is usually normal.
• Urine may contain excessive urobilinogen but bile salts and bile pigments are absent. The presence of bile salts and bile pigment (bilirubinuria) indicates cholestasis.
• Prothrombin time may be normal, but if prolonged, constitutes a bad prognostic sign.
• Serological tests: See table.

Serological Diagnosis of Hepatitis B Virus Infection

• Positive is indicative of high infectivity
• Negative is indicative of low infectivity

1. Detection of Viral Markers

• HBsAg:
  • HBsAg is a specific marker for HBV infection. This is the first marker to appear in blood after the infection. This is detectable in the blood even before the elevation of transaminases and onset of clinical illness.
  • Peak levels of HBsAg marker are seen in the prehistoric phase of the disease. It remains in circulation during the icteric phase or symptomatic course of the disease. HBsAg disappears with recovery from clinical disease in most patients, however, it persists for years in carriers.
  • Antibody to HBsAg is seen under some weeks after the disappearance of HBsAg and persists for very long periods. Anti-HBs is the protective antibody.
• HBeAg:
  • HBeAg marker appears inside serum at the same time as HBsAg, but in most of cases, it disappears within a few weeks.
  • Sera consisting of HBeAg is highly infectious and those with anti-HBe of little infectivity. HBeAg indicates active intrahepatic viral replication, and the presence in the blood of HBV DNA, virions, and DNA polymerase.
  • The presence of HBeAg is an adverse prognostic sign. The disappearance of HBeAg is followed by the appearance of anti-HBe.
• HBcAg:
  • This marker is not detectable in the serum but can be demonstrated in liver cells by immunofluorescence.
  • Anti-HBc antibody appears in serum a week or two after the appearance
    of HBsAg. This is the earliest antibody to appear inside the blood.
  • It remains till complete life and thus serves as a useful indicator of prior infection with hepatitis B virus even after all the other markers become undetectable.
  • Initially, anti-HBc is predominantly IgM type, but later on, it is mainly IgG type.
  • Hence, the recent or remote infection can be differentiated by selective tests for IgM (recent infection) or IgG (remote infection) anti-HBc antibody.

2. Viral DNA Polymerase: This appears transiently in serum at the time of the prehistoric phase.

3. Polymerase Chain Reaction (PCR): HBV DNA level can be detected in serum by PCR. This is a highly sensitive test. HBV DNA is an indicator of viral replication in the liver and so helps to assess the progress of patients under antiviral chemotherapy.

4. Biochemical Tests: In acute viral hepatitis caused by hepatitis B, transaminase values range between 500 to 2, 000 units (SGPT is always higher than SGOT). Serum bilirubin level indicates the degree of jaundice and may rise up to 25—fold.

Question 7. Mention the virus causing hepatitis. Write in detail about the pathogenicity and clinical features of hepatitis B virus (HBV) infection. Diagnostic marker in the laboratory for diagnosis of hepatitis due to HBV infection.
Answer:

Virus-causing hepatitis are hepatitis viruses A, B, C, D, E, and G. Hepatitis B is a DNA virus, while hepatitis A, C, D, E, and G viruses have RNA genomes.

Pathogenicity of Hepatitis B Virus (HBV) Infection:

• HBV is a bloodborne virus and the infection is transmitted by parenteral, sexual, and perinatal modes.
• Blood of the carriers, and of patients is the most important source of infection.
• The virus can also be present in various other body fluids and excretions, i.e. saliva, breast milk, semen, vaginal secretions, urine, bile and feces.
• Out of all these, semen and saliva mostly transmit the infection.
• Transfusion of the blood of carriers is the most widely known mode of infection.
• Therapeutic and prophylactic preparations from pooled human blood and serum have led to hepatitis.
• HBV is very highly infectious. Any object or procedure that can convey minute traces of infected blood or other material, as little as 0.00001 mL can be infectious.
• These include shared syringes, needles, and other sharp items or endoscopes, personal articles such as razors, nail clippers,or combs and practices such as acupuncture, tattooing,
  ritual circumcision, ear or nose piercing, and field camps for surgery or disease detection by blood testing where separate sterile articles may not be available.
• Professionals who are using sharp articles like barbers, dentists, and doctors may unwittingly transmit the virus if proper sterilization is not used.
• Infection by direct contact with open skin lesions such as pyoderma, eczema, cuts, and scratches is very common among young children, as also through household transmission where opportunities exist for contact with blood or saliva among members.
• Congenital or vertical transmission is quite common from carrier mothers. The risk to babies is high if the mother is HBeAg positive. ‘
• Infection is usually acquired during birth by contact of maternal blood with the skin and mucosa of the fetus, or in the immediate postnatal period.
• The risk of transmission of disease by heterosexual and homosexual contact increases as the number of partners and the duration increases.

Clinical Features of Hepatitis B Virus Infection: Clinical features of HBV infection are divided into three phases, i.e.

• Preicteric phase:
  • In this phase, the majority of patients develop malaise, myalgia, anorexia, nausea, and vomiting.
  • A minority of patients develop arthralgia, serum sickness, polyarteritis nodosa, and glomerulonephritis.
• Icteric phase:
  • In this patient develops jaundice, pale stools, and dark urine.
• Convalescent phase:
  • This phase is long and drawn out along with malaise as well as fatigue.
  • Duration for uncomplicated hepatitis is 8 to 10 weeks.
  • Mild symptoms can present for a year.

Diagnostic Marker in Laboratory for Diagnosis of Hepatitis due to HBV Infection:

• HBsAg: It is also known as surface antigen or envelope antigen. This is the most specific marker for HBV infection. It appears first in the blood and is detected in circulation after a month of exposure to infection. It is also seen before the occurrence of jaundice and elevation of transaminase. This marker is at its peak level in the prehistoric phase. HBsAg disappears as the patient get recovers from the clinical condition.
•  Anti-HbsAg antibody: It is seen as a surface antigen that disappears and persists for a long time. It is a protective antibody.
• HBcAg: It is also known as a core antigen. It does not appear in the serum of the patient. It is only seen in liver cells by immunofluorescence
• Anti-HBc antibody: It is detected during the prehistoric phase. It is seen after the appearance of surface antigens in the blood. It is the earliest antibody to appear in the blood. It remains for a lifetime and acts as an indicator of prior infection with HBV even if all the other HBV markers become undetectable.
• HBeAg: It is the hidden antigenic component of the virus core. It is seen at the time when surface antigen appears and it disappears in some of the weeks.
• Viral DNA polymerase: It is seen in serum at the prehistoric stage of jaundice.

Question 8. Write a short note on the hepatitis B virus.
Answer:

The Hepatitis B virus is a DNA virus that belongs to the Hepadnaviridae family.

• Its size is 42 nm in diameter.
• The outer surface or envelope of the hepatitis B virus consists of a hepatitis B surface antigen (HBsAg) and it surrounds a 27 nm inner dense core which consists of a hepatitis B core antigen (HbcAg).
• The core of the hepatitis B virus which is also called a nucleocapsid shows icosahedral symmetry.
• The core of the virus internally consists of a genome which is a single circular double-stranded DNA with DNA-dependent DNA polymerase.
• Both viral DNA and HBcAg are found in the nucleus and HBsAg is found in the cytoplasm and at the cell membrane
• Complete hepatitis B virion is also called a Dane particle.
• Electron microscopy of sera of hepatitis B virus patients shows three types of particles, i.e.
  • Spherical particle: It is most abundant and is 22 nm in diameter.
  • Tubular particle: It is of varying length and is 22 nm in diameter.
  •  Dane Particle: It is a double-shielded spherical structure that is 42 nm in diameter. This article is complete hepatitis B virus.

The spherical and tubular particles are antigenically identical and are surface subunits of the hepatitis B virus which represents the Australian antigen (HBsAg).

Question 9. Classify hepatitis virus. Write in detail about antigenicity, modes of transmission, and prophylaxis of hepatitis B.
Answer:

Classifiation of Hepatitis Virus:

• Hepatitis A virus (HAV)
• Hepatitis B virus (HBV)
• Hepatitis C virus (HCV)
• Hepatitis D virus (HDV)
• Hepatitis E virus (HEV)
• Hepatitis G virus (HGV).

Antigenicity of Hepatitis B: The Hepatitis B virus consists of two major antigens:

• HBsAg: These are the surface antigens (envelope protein)
• HBcAg: It is the core antigen of the virus. It consists of group-specific protein and is not detectable inside the blood of the patient.
• HBeAg: It is seen in serum along with HBsAg but it gets disappears within a few weeks. This is the hidden antigenic component of the core. HBcAg and HBeAg are immunologically distinct and are coded by the same gene.
• HBsAg: It consists of a group-specific antigen ‘a’ and two types of specific antigens, d or y and w or r. Thus, there are four antigenic types of HBsAg—adw, adr, ayw, ayr. These are the main markers of epidemiology.
  • Type ADW is predominant in Europe and the USA
  • Type adr in Asia.
  • Type ayw is predominant in Africa, Russia, and India.

Viral Genes and Antigens:

• The viral genome consists of two linear strands of DNA which are held inside a circular configuration. One of the strands, i.e. plus strand is incomplete, while the other is complete. This provides the appearance of partially double-stranded and partially single-stranded DNA. A viral DNA polymerase is associated with the plus strand.
• This DNA polymerase can repair the gap inside the incomplete (the plus strand) strand and render the genome fully double-stranded. The genome consists of four genes coding for different antigens, i.e. HBxAg and its antibody are found to be present in patients with severe chronic hepatitis and hepatocellular carcinoma.

Modes of Transmission There are three modes of hepatitis B infection transmission:

• Parenteral transmission: From this route transmission of infection can occur from accidental inoculation of minute amounts of blood, blood products, or fluid having hepatitis B at the time of medical, surgical, or dental procedures.
• Perinatal transmission: It occurs when the carrier’s mother’s blood contaminates the mucous membrane of the newborn at the time of birth.
• Hepatitis B virus: It is present inside the body fluids, i.e. semen, and vaginal secretion, so it is transmitted via sexual contact. Male homosexuals have a high chance of acquiring the infection.

Prophylaxis of Hepatitis B Hepatitis B infection occurs due to blood transfusion, injection of blood products, in drug addicts, male homosexuals, medical laboratory personnel handling infected patients and blood, and in infants of carrier mothers.

Prophylaxis consists of:

1. General preventive measures
2.  Immunization.

1. General Preventive Measures: These are health education, improvement of personal hygiene, and providing strict attention to sterilization. The most important preventive measure is screening for HBsAg and HBeAg in blood donors. Use of unsterile needles, syringes, and other materials must be avoided to prevent hepatitis B infection.

2. Immunization:

• Passive immunization
  • This is given following any accidental exposure to hepatitis B infection.
  • Hepatitis B immunoglobulin (HBIG) is prepared from donors with high titers of anti-HBs.
  • It can be given in doses of 300-500 IU intramuscularly. HBIG is administered as early as
    possible after exposure mainly under 48 hours. A second dose is given at intervals of 4 weeks after the first dose.
  • It may not prevent infection but protects against illness and the development of a carrier state.
• Active immunization: The following vaccines are available.
  • Plasma-derived hepatitis B vaccine: This vaccine is prepared by purifying 22 nm particles of HBsAg from the plasma of healthy carriers.  Particles are separated by ultracentrifugation and get inactivated with formaldehyde. It is immunologically safe.
  • Recombinant yeast hepatitis B vaccine: This is produced by recombinant DNA inside the yeasts in which a plasmid having the gene of HBsAg has been incorporated. HBsAg
    particles are produced and extracted as well as purified to be used as a vaccine. The vaccine is immunogenic. It is safe and is free of side effects.
    Both vaccines are adsorbed with hydroxide as an adjuvant, and stored in cold but should not be frozen. Three doses at 0, 1, and 6 are administered intramuscularly inside the deltoid muscle. Local swelling and reddening can occur in some 20% of cases with slight fever.
• Recombinant Chinese hamster ovary cell (CHO) hepatitis B vaccine: CHO cells have been used for the preparation of the vaccine. This is the first vaccine using a mammalian cell expression system. It is available commercially.
• Synthetic peptide vaccine: These are chemically synthesized polypeptide vaccines and are still in the experimental stage.