Semester 2 - Hepatitis Virus and Retroviruses Flashcards
What are hepatitis viruses?
A group of viruses causing infection and inflammation of the liver (hepatotrophic virus). They have diversity of nucleic acid composition, structure, and families of origin
What are the human pathogens of hepatitis viruses?
Hep A - Picornavirus (+ssRNA) Hep B - Hepadnavirus (+dsDNA-RT) Hep C - flavivirus (+ssRNA) Hep D - deltavirus (-ssRNA) Hep E - hepevirus (+ssRNA)
What are some characteristics of Hepatitis A
(+)ssRNA, nonenveloped picornavirus
Protein synthesis followed by proteolytic cleavage
What are the clinical features of Hep A?
Range from mild to severe
Sudden onset of fever, malaise, anorexia, abdominal discomfort
10% patients have recurrent illness for 6-9 months following infection
How is Hep A transmitted?
Contaminated food/water
Associated with travellers
How long is the incubation period of Hep A?
2-3 weeks
How is Hep A treated?
Treatment supportive
Vaccine preventable (inactivated) - combo A/B
Heat food/water to >85 Celsius for more than 1 minute or chlorinate
What are some characteristics of Hepatitis B?
Hepadnavirus
Class VII - dsDNA genome with an RNA intermediate
Encodes a reverse transcriptase enzyme
What are the clinical features of Hep B?
Mild fever, dark urine, nausea, anorexia
Vomiting, diarrhea, jaundice (hyperbilirubinemia)
Chronic infection may lead to cirrhosis and liver cancer
How is Hep B transmitted?
Blood products and bodily fluid
Sexual transmission
How long is the incubation period for Hep B?
Variable (weeks to months)
How is Hep B treated?
Nucleotide analogs, RT inhibitors, IFN
Vaccine-preventable (subunit) - combo vaccine
What are some characteristics of Hep C?
Non-A, non-B hepatitis
Flavivirus family (+ssRNA, envoloped)
Gene expression via single polyprotein translation followed by proteolytic cleavage
What is the leading cause of liver cancer and liver transplantation woldwide?
Hep C
What are the clinical features of Hep C?
Fever, fatigue, nausea, vomiting
Dark urine, grey coloured feces, jaundice
Chronic infection leads to liver pathology (failure, cancer)
How long is the incubation period of Hep C?
2-6 months
How is Hep C transmitted?
Infected blood products
Sexual transmission
How is Hep C treated?
IFN and ribavarin
There is no vaccination against HCV
What are characteristics of Hep D?
Deltavirus, requires HBV to replicate viral genome
(-)ssRNA, enveloped
It is NOT a virus. Satellite virus, virusoid, subviral particle
What is a viroid?
A subviral pathogen in plants (no proteins expressed)
What is a virusoid?
Expresses viral protein (HDV)
What is a satellite virus?
Requires another virus for its own replication
What is the nuclear antigen often associated with?
HBV patients with severe liver disease
What is the life cycle of Hep D?
Only infects cells that are also infected with HBV: coinfection occurs simultaneously, superinfection occurs following a primary infection
Replication occurs in the nucleus? - uses cellular RNA polyperases I, II and III, utilizes HBV polymerase enzymes
What are the clinical features of a Hep D infection?
Associated with increased severity of HBV disease. Treatment/prophylaxis is to treat/prevent HBV infection
What are some characteristics of Hep E?
(+)ssRNA, non-enveloped
Enteric
How is Hep E trasmitted?
Fecal-oral - contaminated water, pork/deer meat) Blood products (rare)
What are the clinical features of a Hep E infection?
Fever, fatigue, nausea, anorexia, abdominal pain, joint pain, jaundice, dark coloured urine
Generally self-limiting
Pregnant women - mortality rate high during 3rd trimester
Risk of fulminant hepatitis