viral markers

Mohamed Sabry Ass. Lecturer of Internal Medicine

Tanta Faculty of Medicine

Serology for viral hepatitis (HAV, HBV & HCV)

Pathogenesis

Clinical presentation

Life cycle & Modes of transmission

Serology

Serology

Hepatitis B viurs

Serology

Hepatitis B viurs

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Hepatitis A virus:

Anti-hepatitis A virus IgM:

Positive at the time of onset of symptoms.Usually accompany the first rise in the alanine aminotransferase (ALT) level.

This test is sensitive and specific.The results remain positive for 3-6 months after the primary infection and for as long as 12 months in 25% of patients.

Anti-hepatitis A virus IgG:

Anti-HAV immunoglobulin G (IgG) appears soon after IgM and generally persists for many years.

The presence of anti-HAV IgG in the absence of IgM indicates past infection or vaccination rather than acute infection. IgG provides protective immunity.

HBV: Structure

HBV: virus proteins & particles:

HBV: Genomic structure:

Basics:

Deoxyribose nucleic acid (DNA) is the genetic material in all cells.

It is a double helix structure made of nucleotides.

Each nucleotide consists of a deoxyribose sugar, a phosphate group, and one of four bases: adenine, thymine, guanine and cytosine.

Protein products of the four genes

S gene: HBsAg S region: Major proteinS+preS2: Middle proteinS+preS2+preS1:Large protein

P gene: DNA polymerase

Directs replication and repair of HBV DNA

C gene: HBcAg

HBeAg

Translation begins with the C region.Translation begins at the preC region

X gene: HBxAg It can transactivate transcription of cellular and viral genesIt may contribute to carcinogenesis.

Viral proteins & particles:

Serology for HBV:

Antigen AntibodiesHepatitis B Surface Antigen (HBsAg)

Antibody to Hepatitis B Surface Antigen (Anti HBs)

Hepatitis B Core Antigen (HBcAg)

Antibody to Hepatitis B Core Antigen (Anti HBc IgM & Anti HBc)

Hepatitis B ‘e’ Antigen (HBeAg)

Antibody to Hepatitis B ‘e’ Antigen (Anti HBe)

Hepatitis B surface antigen (HBsAg):

It is the envelop protein expressed on the outer surface of the virion and on the small spherical and tubular structures.

It plays a major role in cell membrane attachment to initiate the infection process by binding to the hepatocyte plasma membrane

C Seeger, et al. (2000): Mol Biol Rev.

HBsAgCommon

group reactive antigen (a).

Several subtype specific antigens (d, y,

w & r).

HB isolates fall into at least 8 genotypes (A-H).

Gen

otyp

es v

ary Antigenic subtype

Geographic Destribution

Clinical course

Exam

ples

genotype A (subtype adw) and genotype D (ayd)

Geographic Destribution

Clinical course

Exam

ples


genotype A & D predominate in USA and Europe and genotype B &

C predominate in Asia.

Clinical course

Exam

ples


genotype A & D predominate in USA and Europe and genotype B

& C predominate in Asia.

genotype B is associated with less aggressive liver damage and less HCC as compared to genotype C .

1st virological marker detectable in serum usually between 8th and 12th weeks of

infection

HBsAg


infection

It preceeds elevation of aminotransferase activity and clinical symptoms by 2-6

weeks

HBsAg


infection

It preceeds elevation of aminotransferase activity and clinical symptoms by 2-6

weeks

It remains elevated during the entire

icteric or symptomatic phase of the disease.

HBsAg

1st virological marker detectable in serum

usually between 8th and 12th weeks of infection

It preceeds elevation of aminotransferase

activity and clinical symptoms by 2-6 weeks

It remains elevated during the entire icteric or symptomatic phase

of the disease.

Typically, it disappeares 1-2 months after the onset of jaundice and

rarely persists beyond 6 months.

HBsAg

Strategies for prevention of

HBV is based on providing

susceptible persons with anti

HBs.

The protective antibodies

Anti HBs

Anti HBs

Duration of protection: almost

indefinitely. A single booster may be

required after 5 ys.

HBsAg prepared by recombinant DNA technology

HBV Vaccine

Not secreted and remains

within hepatocytes

Expressed on the surface of

the nucleocapsid

core

HBcAg

HBcAg

Anti HBc IgM

First antibody

to appear.

Indicates acute HBV

infection.

Anti HBcIgM

Anti HBcIgM

May be the only

marker in CORE

WINDOW

Indicates acute HBV

infection.

Anti HBcIgM

HBeAg

Secreted into the circulation.

HBeAgSecreted into the circulation. HBeAg

Accessory protein of HBV.

HBeAgSecreted into the circulation.

HBeAgAccessory protein of HBV.

HBeAg

Not essential for replication in vivo

An index of viral replication, infectivity, severity of disease, and response to treatment


HBeAg persists longer than 12 weeks: High probability of progression to a chronic carrier state when.


High probability of progression to a chronic carrier state when HBeAg persists longer than 12 weeks.

Pregnant women with HBeAg positive have a risk of transmission of virus to fetus is > 90%.

Anti HBe

Detectable when HBeAg disappears (12 – 16 wks)

Anti HBe

Seroconversion to Anti HBe indicates

resolution of infection.

Anti HBe

Seroconversion may be associated with acute hepatitis like elevation of aminotransferase.

Anti HBe

HBV: Precore mutation:

Basics

Mutations are sudden changes in an organisms genetic material that result from alterations in DNA that can be induced or appear spontaneously.

HBV: Genomic structure:

HBV: Precore mutation:

Patients with precore mutation tend to have severe liver disease that progress more rapidly to cirrhosis.

This is common in Mediteranean region and Europe.

Clusters of fulminant HBV in Israel and Japan have been attributed to a common source of infection with a precore mutant.

HBV DNA

A measure of virus replication in the liver and infectivity.

HBV DNA

Monitoring treatment in patients with chronic HBV infection.

HBV DNA

Loss of detectable HBV DNA is an earlier indicator of response to

antiviral therapy than loss of HBeAg.

HBsAg Anti-HBsAg

Anti-HBc HBeAg Anti-HBe Interpretation

+ - IgM + -

HBsAg Anti-HBsAg


+ - IgM + - Acute HB, High infectivity

HBsAg Anti-HBsAg



+ - IgG + -

HBsAg Anti-HBsAg



+ - IgG + - Chronic HB, high infectivity

HBsAg Anti-HBsAg




+ - IgG - +

HBsAg Anti-HBsAg




+ - IgG - + Chronic HB, low infectivity

HBsAg Anti-HBsAg




+ - IgG - + HBeAg negative precore

mutant HB

HBsAg Anti-HBsAg





HBeAg negative

precore mutant HB

+ + +

HBsAg Anti-HBsAg





HBeAg negative

precore mutant HB

+ + + + + HBsAg of one subtype and

heterotypic antiHBs

HBsAg Anti-HBs Anti-HBc

HBeAg Anti-HBe Interpretation

- - IgM + +



- - IgM + + Acute HB (window)




- - IgG - +




- - IgG - + HB in the remote past





Low level HB carrier

- + IgG - +





- + IgG - + Recovery from HB







- + - - -







- + - - - Immunization with HBsAg

False positive

HCV• HCV antibody:

• Generally used to diagnose hepatitis C infection.

• Not useful in the acute phase as it takes at least 4 weeks after infection before antibody appears.

HCV• HCV-RNA:

• Various techniques are available e.g. PCR. Cut-off: 1000 copies / ml

• May be used to diagnose HCV infection in the acute phase.

• However, its main use is in monitoring the response to antiviral therapy.

HCV RNA (PCR testing)

Not a predictor of disease severity: a high viral load does not mean the liver disease is more severe, and a low viral load does not mean the patient is ok and does not need therapy!

Helps predict response rate to treatment (lower means a higher chance of cure with therapy)

HCV:

Genotyping: genotype 1 and 4 have a worse prognosis overall and respond poorly to interferon therapy.

The END

viral markers

Science

viral proteins particles

virus proteins particles

major proteins

hepatitis b eantigen

geness gene

precregionx gene

middle proteins

repair ofhbv dnac gene