Hepatitis B – classification and lab diagnosis | microbiology notes

• in Hepatitis Hepatic tissue gets affected
• Heterogeneous group of virus
• Causes acute inflammation of liver
• All are RNA virus except HEP B virus (DNA virus)

Classification

6 virus type

1. Hep A : infectious Hepatitis – Spread by person
2. Hep B : serum hepatitis – blood product
3. Hep C : Past transfusion Hepatitis – Blood transfusion
4. Hep D : Can’t do replication
5. Hep E
6. Hep G

Hepatitis B

• Only dna virus
• Most wide spread
• Most important
• Producing self limiting hepatitis
• Can be subclinical or symptomatic

Complication

• Chronic hepatitis
• Cirrhosis of liver

Morphology

• Spherical – 22nm
• Tubular form – 200 nm
• Dome particle
• Three Antigens on body – surface Antigen – HBsAg

– E Antigen – HBeAg

– C Antigen – HBcAg

1. HBsAg :
   • Has two components
   • “A” epitos
   • 2 pair of specimen Ag – d/y or w/r
   • Has 4 subtypes : ADW, ADR,AYW,AYR

2. HBcAg:

• Forms intracellular core protein
• Not secreted
• Not circulate in blood
• Can be demonstrated in hepatocytes by immunofluorescence

3.HBeAg:

• Non particulate
• Soluble
• Possesses signal protein
• Present in circulation

Viral genome :

1.S gene :

• Has 3 regions : 1) s GENE, 2)pre s1 gene, 3)Pre s2 gene
• S region – Major protein
• S + pre s1 Gene = middle protein
• Pre s1 + pre s2 + s = large protein — present in virion

2. C gene :

• 2 region : 1) pre c region , 2) c region = 2 nucleocapsid protein
• Pre- c = HBeAg
• C region = HBcAg

3. X gene:

• Code for HBxAg – which can activate the transcription of viral gene
• Binds to ps3 – carcinogenesis
• Elevated in patients with severe chronic hep. Carcinogenesis

4. P gene :

• Largest gene
• Codes for polymerase protein
• Has 3 enzymatic prosperity : 1) DNA polymerase, 2) RNAseH, 3) RNA transcriptase

Pathogenesis :

• Parenteral route
• Sexual transmissino
• Direct skin contact
• Vertical transmission

Replication :

Hep. B. virus (P. DS. DNA)

↓

Attachment

↓

Cytoplasm

↓

Uncoating

↓

Nucleus

↓

Partially Double stranded DNA

Converts into complete DNA

↓

Rna Polymerase

↓

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Lab Diagnosis

Can be detected by ELISA , immunochromatography and PCR