Parasitology and Virology: Hepatitis Viruses

Hepatitis B

• HBsAg appears during the incubation period and is detectable in most patients during the prodrome and acute disease.
• Prolonged presence of HBsAg (at least 6 months) indicates carrier state and risk of chronic hepatitis and hepatic carcinoma.
• HBsAb is not detectable in the acute or chronic carrier state because it is bound to the large amount of HBsAg present in the blood.
• In the acute state, when recovered, there is a period of several weeks when HBsAg has disappeared but HBsAb is not yet detectable, known as the window phase.
• HBeAg presence indicates transmissibility, and its presence indicates low transmissibility.

Interpretation of Hepatitis B Serological Test Results

• HBsAg + HBeAg + HBcAb (IgM): active case (acute)
• HBeAb+ HBcAb (IgM): window
• HBsAb + HBeAb + HBcAb (IgG): recovered (immune)
• HBsAg + HBeAb + HBcAb (IgG): chronic carrier
• HBsAb: vaccine (immune)

Treatment and Prevention of Hepatitis B

• Alpha interferon is clinically useful for the treatment of chronic hepatitis B infections.
• Nucleoside analogues, such as lamivudine, are effective in reducing hepatic inflammation and lowering HBV levels in chronic carriers.
• The vaccine (e.g. Recombivax) contains HBsAg produced in yeast by recombinant DNA techniques.
• Indications for vaccination include healthcare personnel, patients receiving multiple transfusions or dialysis, and patients with frequent sexually transmitted diseases.

Hepatitis C

• Leads to chronic liver disease, cirrhosis, and predisposition to hepatocellular carcinoma.
• Mean incubation period is 8 weeks.
• Causes significant autoimmune reactions, including vasculitis, arthralgias, purpura, and membranoproliferative glomerulonephritis.

Laboratory Diagnosis of Hepatitis C

• Diagnosed by detecting antibodies to HCV by ELISA.
• Test does not distinguish between IgM and IgG and does not distinguish between an acute, chronic, or resolved infection.
• Confirmation by PCR to detect viral RNA.

Treatment and Prevention of Hepatitis C

• A combination of alpha interferon and ribavirin is the treatment of choice for chronic hepatitis C.
• New treatments include Sovaldi/Gratisovir (Sofosbuvir), Olysio (Simeprevir), Dactavira (Daclatasvir), Harvoni (Sofosbuvir + Ledipasvir), Epclusa (Sofosbuvir + Velpatasvir), and Mavyret (Pibrentasvir + Glecaprevir).
• No vaccine is available, and hyperimmune globulins are not available.

Hepatitis D

• Defective virus that requires HBV co-infection to replicate.
• Transmitted sexually, through blood, and perinatally.
• Pathogenesis involves cytotoxic T cell damage to infected hepatocytes.
• Disease is more severe in co-infected individuals.

Laboratory Diagnosis of Hepatitis D

• Diagnosis made by detecting either delta antigen or IgM antibody to delta antigen in the patient's serum.

Treatment of Hepatitis D

• Alpha interferon reduces some effects of chronic hepatitis caused by HDV but does not eradicate the chronic carrier state.
• Immunization against HBV prevents HDV infection.

Hepatitis E

• Clinically resembles hepatitis A, but chronic liver disease does not occur.
• No prolonged carrier state exists.
• No antiviral treatment and no vaccine are available.

Hepatitis G (GBV-C, Human pegivirus)

• Discovered in the mid-1990s, causing some sort of chronic liver disease.
• Transmitted by blood and sexual intercourse.