Hepatitis-B : Mode of Transmission, HBV, Pathogenesis, Treatment And MCQs for NEET, GPAT,

INTRODUCTION :-

1.] Hepatitis – B virus [HBV] the cause of ”serum hepatitis” is the most versatile of the hepatotropic viruses.

2.] It has an longer incubation period of about 30 – 180 days and is basically transmitted such as in recipient of blood and blood products.

3.] HBV can produce severe form of illness that includes :-

• acute hepatitis B
• chronic hepatitis
• progression to cirrhosis
• fulminate (severe and sudden in onset) hepatitis
• asymptomatic carrier stage

4.] HBV plays role in the development of hepatocellular carcinoma (most common primary malignant tumor of the liver).

MODE OF TRANSMISSION :-

• HBV is an hardy virus and can withstand extremes of temperature and the humidity.
• HBV can spread primarily through blood and body fluids.
• Virus may also spread through contact with body secretion, such as semen, saliva, sweat, tears, breast milk and pathologic effusions.
• During the active acute chronic hepatitis, HBV is present in all physiologic and pathologic body fluids with the exception of stool.

HEPATITIS – B VIRUS [HBV] :-

1.] HBV shows three forms of viral particles of 2 sizes :-

• Small (spheres and tubules/filaments)
• Large (spheres)

2.] Small particles are numerous and exist in two forms – as 22 nm sphere, and as tubules 22 nm in diameter and 100 nm long.

3.] Large particles, 42 nm in diameter, are double – shelled spherical particles, also called dane particles.

4.] The genomic structure of HBV is quite compact and complex. The HBV DNA consist of 4 overlapping genes which encode for multiply proteins :-

• S gene code for the surface envelope protein, hepatitis B surface antigen (HBsAg) this protein in the major  protein. Pre S -1 and Pre S – 2 region of genome are the upstream of S – gene and code for pre – S gene protein products that include receptor on the HBV surface and for hepatocyte membrane protein.
• P gene is the largest and codes for the DNA polymerase.
• C gene codes for two nucleotide protein HBeAg and a core protein termed as HBcAg.
• X gene codes for HBxAg which is a small non – particulate protein. HBxAg has a role in transactivation of the transcription of both viral and cellular genes.

Expression of HBxAg and its antibodies associated with enhanced HBV DNA replication has been implicated in a hepatocellular carcinoma in patients of chronic hepatitis.

PATHOGENESIS :-

There are certain evidence which links immune pathogenesis with the hepatocellular damage :-

• When HBV is not directly cytopathic (refers to structural change in host cell that are caused by viral invasion) that means a carrier state of hepatitis B without the hepatocellular damage exists.
• It has been observed that individuals with defect or deficiency of the cellular immunity have more persistent, hepatitis B diseases.
• In support of cell mediated mechanism in  hepatocellular damage by HBV comes from the observation that viral antigens are attacked by host cytoxin CD8+T lymphocytes.
• The host response of CD8+T lymphocytes by elaboration of antiviral cytokines is variable in different individuals, that determines whether an HBV – infected person recovers, develops mild or severe disease, or progresses to chronic disease.

TREATMENT :-

A.] Oral Antiviral drugs for Hepatitis – B :

Tenofovir disoproxil (Viread)

Tenofovir alafenamide (Vemlidy)

Entecavir (Baraclude)

Telbivudine (Tyzeka or Sebivo)

Adefovir Dipivoxil (Hepsera)

Lamivudine (Epivir-HBV, Zeffix, or Heptodin)

B.] Immune modulators (Interferon) for Hepatitis – B :

Pegylated Interferon (Pegasys)

Interferon Alpha (Intron A)

MULTIPLE CHOICE QUESTIONS :-

1.] Which of the following hepatitis virus is not RNA virus ?

a. Hepatitis – A virus

b. Hepatitis – B virus

c. Hepatitis – E virus

d. Hepatitis – G virus

2.] Which of the following nucleic acid is present in hepatitis – B virus ?

a. dsDNA

b. ssRNA

c. ssDNA

d. dsRNA

3.] The most serious infection is ?

a. super infection of an HBsAg carrier by HDV

b. infection with HBV and HDV

c. coinfection of HBV and HDV

d. None of the above

4.] Which of the following specimen contains hepatitis B virus in an infected person ?

a. Blood

b. Semen

c. Saliva

d. All of the above

5.] Which of the following antigenic type of hepatitis B virus is present in the envelope ?

a. HbsAg

b. HBcAg

c. HBeAg

d. HBxAg

6.] The development of hepatocellular carcinoma is associated with ?

a. ground squirrel hepatitis virus

b. hepatitis B virus

c. woodchuck hepatitis virus

d. all of the above

7.] Which of the following antigenic type of hepatitis B virus is prevalent in India ?

a. Adw

b. Adr

c. Ayw

d. Ayr

8.] Which of the following virus can be transmitted by parental route ?

a. HBV

b. HCV

c. HDV

d. All of the above

9.] Incubation period of HBV virus ?

a. 30 – 180 days

b. 2 days

c. 1 week

d. 10 days

10.] The tubule of small viral particle has a diameter of about ?

a. 23 nm

b. 30 nm

c. 22 micro meter

d. 22 nm

SOLUTIONS :-

1.] (b) hepatitis – B virus

2.] (a) dsDNA

3.] (a) super infection of an HBsAg carrier by HDV

4.] (d)

5.] (a) HbsAg

6.] (d)

7.] (c) Ayw

8.] (d)

9.] (a) 30 – 180 days

10.] (d) 22 nm

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REFERENCES :-

1.] Textbook Of Pathology By Harsh Mohan; 7th edition; Page no. 591 – 592.

2.] Robbin’s Basic Pathology; 5th edition; Page no. 844 – 846.